Illustrated Medical Dictionary; Essential A-Z Quick Reference to over 5,500 Medical Terms - Dorling Kindersley DK Publishing ( PDFDrive )

The British
Medical Association

ILLUSTRATED

MEDICAL

DICTIONARY

CORONARY ARTERY coronary Any structure that encircles like
a crown. The term usually refers to the
Superior Aorta Left main coronary arteries encircling the heart. It is
vena cava coronary also sometimes used as a nonmedical
artery term for a heart attack (see myocardial
infarction).
Pulmonary Left
veins circumflex coronary artery Either of the 2 main
artery arteries that supply the tissues of the
heart with oxygen-rich blood. These
Right Left arteries, known as the left and right main
main anterior coronary arteries, arise directly from the
coronary descending aorta. The term coronary artery is also
artery artery applied to any of the arteries that branch
off from the main coronary arteries, such
Inferior Coronary as the left circumflex artery and the left
vena cava vein anterior descending artery. Blockage of a
coronary artery as a result of athero-
Descending sclerosis can lead to myocardial infarction.
aorta (See also coronary artery disease.)

Essential A–Z quick reference
to over 5,500 medical terms

The British
Medical Association

ILLUSTRATED

MEDICAL

DICTIONARY

A Dorling Kindersley Book

A ABDOMEN ABDOMINAL SWELLING

A intake, eating unwisely, or an attack of
diarrhoea. Pain in the lower abdomen
abdomen The region of the body be- is common during menstruation but is
tween the chest and the pelvis. The occasionally due to a gynaecological
abdominal cavity is bounded by the ribs disorder such as endometriosis. Cystitis
and diaphragm above, and by the pelvis is a common cause of pain or discom-
below, with the spine and abdominal fort in the abdomen. Bladder distension
muscles forming the back, side, and as a result of urinary obstruction may
front walls. It contains the liver, stom- also cause abdominal pain.
ach, intestines, spleen, pancreas, and
kidneys. In the lower abdomen, enclosed Abdominal colic is pain that occurs
by the pelvis, are the bladder, rectum, every few minutes as one of the internal
and, in women, the uterus and ovaries. organs goes into muscular spasm in an
attempt to overcome an obstruction
ABDOMEN such as a stone or an area of inflamma-
tion. The attacks of colic may become
Stomach more severe and may be associated
with vomiting (see abdomen, acute).
Liver
Peptic ulcer often produces recurrent
Large Area of gnawing pain. Other possible causes of
intestine abdomen abdominal pain are infection, such as
pyelonephritis, and ischaemia (lack of
Small blood supply), as occurs when a volvu-
intestine lus (twisting of the intestine) obstructs
blood vessels. Tumours affecting an
Rectum abdominal organ can cause pain. Abdo-
minal pain can also result from anxiety.
abdomen, acute Persistent, severe ab-
dominal pain of sudden onset, usually For mild pain, a wrapped hot-water
associated with spasm of the abdomi- bottle is often effective. Pain due to
nal muscles, vomiting, and fever. peptic ulcer can be temporarily relieved
The most common cause of an acute by food or by taking antacid drugs.
abdomen is peritonitis. Other causes Abdominal pain that is not relieved by
include appendicitis, abdominal injury, vomiting, persists for more than 6 hours,
perforation of an internal organ due to or is associated with sweating or faint-
disorders such as peptic ulcer or diver- ing requires urgent medical attention.
ticular disease. Acute abdominal pain Urgent attention is also necessary if
commonly begins as a vague pain in the pain is accompanied by persistent vom-
centre but then becomes localized. iting, vomiting of blood, or passing of
An acute abdomen requires urgent bloodstained or black faeces. Unex-
medical investigation that may involve plained weight loss or changes in bowel
a laparoscopy or a laparotomy. Treat- habits should always be investigated.
ment depends on the underlying cause.
Investigation of abdominal pain may
abdominal pain Discomfort in the ab- include the use of imaging tests such as
domen. Mild abdominal pain is common ultrasound scanning, and endoscopic
and is often due to excessive alcohol examination in the form of gastroscopy,
colonoscopy, or laparoscopy.
abdominal swelling Enlargement of
the abdomen. Abdominal swelling is a
natural result of obesity and growth of
the uterus during pregnancy. Wind in the
stomach or intestine may cause uncom-
fortable, bloating distension of the
abdomen. Some women experience ab-
dominal distension due to temporary
water retention just before menstrua-
tion. Other causes may be more serious.

4

ABDOMINAL THRUST ABSCESS A

For instance, ascites (accumulation of ABO blood groups See blood groups.
fluid between organs) may be a symp- abortifacient An agent that causes abor-
tom of cancer or disease of the heart,
kidneys, or liver; swelling may also be tion. In medical practice, abortion is
due to intestinal obstruction (see intes- induced using prostaglandin drugs,
tine, obstruction of) or an ovarian cyst. often given as vaginal pessaries.
abortion In medical terminology, either
Diagnosis of the underlying cause may spontaneous abortion (see miscarriage)
involve abdominal X-rays, ultrasound or medically induced termination of
scanning, laparotomy, or laparoscopy. In pregnancy (see abortion, induced).
ascites, some fluid between organs may abortion, induced Medically induced
be drained for examination. termination of pregnancy. Abortion may
abdominal thrust A first-aid treatment be performed if continuation of the
for choking, in which sharp upward pres- pregnancy would risk the woman’s life,
sure is applied to the upper abdomen if the mental or physical health of the
to dislodge a foreign body obstructing woman or her existing children is at
the airway. The technique is also known risk, or if there is a substantial risk of
as the Heimlich manoeuvre. handicap to the baby.
abdominal X-ray An X-ray examina-
tion of the abdominal contents. X-rays Depending on the stage of pregnancy,
can show whether any organ is enlarged termination may be induced by using
and can detect swallowed foreign bod- drugs or by the surgical technique of
ies in the digestive tract. They also show vacuum suction curettage, under either
patterns of fluid and gas: distended a general or local anaesthetic, during
loops of bowel containing fluid often which the fetal and placental tissues are
indicate an obstruction (see intestine, removed. Complications are rare.
obstruction of); gas outside the intestine abrasion Also called a graze, a wound
indicates intestinal perforation. on the skin surface that is caused by
scraping or rubbing.
Calcium, which is opaque to X-rays, is abrasion, dental The wearing away of
present in most kidney stones (see tooth enamel, often accompanied by the
calculus, urinary tract) and in some erosion of dentine (the layer beneath
gallstones and aortic aneurysms; these the enamel) and cementum (the bone-
can sometimes be detected on an like tissue that covers the tooth root),
abdominal X-ray. usually through too-vigorous brushing.
abducent nerve The 6th cranial nerve. Abraded areas are often sensitive to
It supplies the lateral rectus muscle of cold or hot food or drink, and a desensi-
each eye, which is responsible for mov- tizing toothpaste and/or protection with
ing the eyeball outwards. The nerve a bonding (see bonding, dental) agent or
originates in the pons (part of the brain- filling may be needed.
stem) and passes along the base of the abreaction In psychoanalysis, the pro-
brain, entering the back of the eye socket cess of becoming consciously aware of
through a gap between the skull bones. repressed (buried) thoughts and feelings.
abduction Movement of a limb away In Freudian theory, abreaction ideally
from the central line of the body, or of a occurs by way of catharsis.
digit away from the axis of a limb. Mus- abscess A collection of pus formed as a
cles that carry out this movement are result of infection by microorganisms,
called abductors. (See also adduction.) usually bacteria. Abscesses may develop
ablation Removal or destruction of dis- in any organ and in the soft tissues
eased tissue by excision (cutting away), beneath the skin in any area. Common
cryosurgery (freezing), radiotherapy, dia- sites include the armpit, breast (see
thermy (burning), or laser treatment. breast abscess), groin, and gums (see
abnormality A physical deformity or abscess, dental). Rarer sites include the
malformation, a behavioural or mental liver (see liver abscess) and the brain
problem, or a variation from normal in (see brain abscess).
the structure or function of a cell, tis-
sue, or organ in the body. Common bacteria, such as staphylo-
cocci, are the usual cause of abscesses,

5

A ABSCESS, DENTAL ACANTHOSIS NIGRICANS
although fungal infections can cause
them, and amoebae are an important ABSCESS, DENTAL

cause of liver abscesses (see amoebia- Enamel Decay

sis). Infectious organisms usually reach

internal organs via the bloodstream, or Gum
they penetrate tissues under the skin Dentine

through a wound.

An abscess may cause pain, depending Pulp Blood
on where it occurs. Most larger absces- Nerve vessel
ses cause fever, sweating, and malaise.
Those that are close to the skin often

cause obvious redness and swelling.

Antibiotics, antifungal drugs, or amoe- Jawbone

bicides are usually prescribed as Abscess

appropriate. Most abscesses also need

to be drained (see drain, surgical), and

in some cases a tube may be left in

place to allow continuous drainage.

Some abscesses burst and drain spon- An abscess in a periodontal pocket can

taneously. Occasionally, an abscess usually be treated by the dentist scrap-

within a vital organ damages enough ing away infected material.

surrounding tissue to cause permanent absence In medical terms, a temporary

loss of normal function, or even death. loss or impairment of consciousness

abscess, dental A pus-filled sac in the that occurs in some forms of epilepsy,

tissue around the root of a tooth. An typically generalized absence (petit

abscess may occur when bacteria mal) seizures in childhood.

invade the pulp (the tissues in the cen- absorption The process by which flu-

tral cavity of a tooth) as a result of ids or other substances are taken up by

dental caries, which destroys the tooth’s body tissues. The term is commonly

enamel and dentine, allowing bacteria applied to the uptake of the nutrients

to reach the pulp. Bacteria can also gain from food into blood and lymph from

access to the pulp when a tooth is the digestive tract. The major site of

injured. The infection in the pulp then absorption is the small intestine, which

spreads into the surrounding tissue to is lined with microscopic finger-like

form an abscess. Abscesses can also projections called villi (see villus). The

result from periodontal disease, in which villi greatly increase the surface area of

bacteria accumulate in pockets that the intestine, thereby increasing the

form between the teeth and gums. rate of absorption.

The affected tooth aches or throbs, acanthosis nigricans A rare condition

and biting or chewing is usually in which thickened dark patches of skin

extremely painful. The gum around the appear in the groin, armpits, neck, and

tooth is tender and may be red and other skin folds. The condition may

swollen. An untreated abscess eventu- occur in young people as a genetic dis-

ally erodes a sinus (channel) through order or as the result of an endocrine

the jawbone to the gum surface, where disorder such as Cushing’s syndrome. It

it forms a swelling known as a gumboil. also occurs in people with carcinomas

As the abscess spreads, the glands in of the lung and other organs.

the neck and the side of the face may Pseudoacanthosis nigricans is a much

become swollen, and fever may develop. more common condition, usually seen

Treatment may consist of draining the in dark-complexioned people who are

abscess, followed by root-canal treat- overweight. In this form, the skin in fold

ment of the affected tooth, but in some areas is both thicker and darker than the

cases extraction of the tooth is neces- surrounding skin, and there is usually

sary. Antibiotics are prescribed if the excessive sweating in affected areas. The

infection has spread beyond the tooth. condition may improve with weight loss.

6

ACARBOSE ACETYLCHOLINESTERASE INHIBITORS A

acarbose A drug that is used to treat more difficult and results in a form of
type 2 diabetes mellitus. Acarbose acts longsightedness called presbyopia.
on enzymes in the intestines, inhibiting acebutolol A beta-blocker drug used to
the digestion of starch and therefore treat hypertension, angina pectoris, and
slowing the rise in blood glucose levels certain types of arrhythmia in which the
after a carbohydrate meal. heart beats too rapidly.
ACE inhibitor drugs A group of vaso-
accessory nerve The 11th cranial nerve. dilator drugs used to treat heart failure,
Unlike the other cranial nerves, most of hypertension, and diabetic nephropathy.
the accessory nerve originates from the ACE (angiotensin converting enzyme) in-
spinal cord. The small part of the nerve hibitors are often prescribed with other
that originates from the brain supplies drugs such as diuretic drugs or beta-
many muscles of the palate, pharynx blocker drugs. Possible side effects
(throat), and larynx (voice box). Damage include nausea, loss of taste, headache,
to this part of the nerve may cause diffi- dizziness, and dry cough.
culty in speaking and swallowing. The acetaminophen An analgesic drug
spinal part of the nerve supplies large more commonly known as paracetamol.
muscles of the neck and back, notably acetazolamide A drug that is used in
the sternomastoid and trapezius. Dam- the treatment of glaucoma and, occa-
age to the spinal fibres of the nerve sionally, to prevent or treat symptoms
paralyses these muscles. of mountain sickness. Possible adverse
effects include lethargy, nausea, diar-
accidental death Death that occurs as rhoea, and impotence.
a direct result of an accident. A high pro- acetic acid The colourless, pungent, org-
portion of deaths in young adults, anic acid that gives vinegar its sour
particularly among males, are acciden- taste. In medicine, acetic acid is an
tal. Many of these deaths are due to ingredient of antiseptic gels that are
road traffic accidents, drowning, or drug used for certain vaginal infections.
overdose. Falls in the home and burning acetylcholine A type of neurotransmit-
or asphyxiation due to fire are common ter (a chemical that transmits messages
causes of accidental death in elderly between nerve cells or between nerve
people. Fatal accidents at work have and muscle cells). Acetylcholine is the
become less common with the intro- neurotransmitter found at all nerve-
duction of effective safety measures. muscle junctions and at many other
sites in the nervous system. The actions
accommodation Adjustment, especially of acetylcholine are called cholinergic
the process by which the eye adjusts actions, and these can be blocked by
itself to focus on near objects. At rest, anticholinergic drugs.
the eye is focused for distant vision, acetylcholinesterase inhibitors A
when its lens is thin and flat. To make group of drugs that are used in the
focusing on a nearer object possible, treatment of mild to moderate dementia
the ciliary muscle of the eye contracts, due to Alzheimer’s disease, in which
which reduces the pull on the outer rim there is a deficiency of the neuro-
of the lens, allowing it to become thicker transmitter acetylcholine in the brain.
and more convex.
With age, the lens loses its elasticity.
This makes accommodation more and

ACCOMMODATION

Light rays from Point of Light rays from Point of
near object focus distant object focus

Ciliary NEAR FOCUS Rounded Ciliary Flattened
muscle lens bends muscle lens
the light
DISTANT FOCUS
7

A ACETYLCYSTEINE ACID–BASE BALANCE
Drugs such as donepezil and rivastig-
Violent stretching of the tendon can
mine work by blocking the action of cause it to rupture; in such cases, surgi-
cal repair may be necessary.
acetylcholinesterase, the enzyme in the achlorhydria Absence of stomach acid
secretions. This may be due to chronic
brain responsible for the breakdown of atrophic gastritis or to an absence or
malfunction of acid-producing parietal
acetylcholine. This raises acetylcholine cells in the stomach lining. Achlorhydria
may not produce symptoms but is asso-
levels, and, in half of all patients, the ciated with stomach cancer, however,
and is a feature of pernicious anaemia
drugs slow the rate of progression of (see anaemia, megaloblastic).
achondroplasia A rare genetic disor-
dementia. They have no effect on der of bone growth that leads to short
stature. The condition is caused by a
dementia due to other causes, such as dominant gene (see genetic disorders)
but often arises as a new mutation. The
stroke or head injury, however. Com- long bones of the arms and legs are
affected mainly. The cartilage that links
mon side effects include nausea, each bone to its epiphysis (the growing
area at its tip) is converted to bone too
dizziness, and headache. Rarely, diffi- early, preventing further limb growth.
Those affected have short limbs, a well-
culty in passing urine may occur. developed trunk, and a head of normal
size except for a protruding forehead.
acetylcysteine A drug used in the treat- aciclovir An antiviral drug that can be
taken by mouth, used topically, or given
ment of paracetamol overdose and as a intravenously to reduce the severity of
viral infections including herpes simplex
mucolytic drug to loosen sputum. When and herpes zoster. Local adverse reac-
tions commonly occur after topical use.
the drug is taken in large doses, vomiting Other side effects are uncommon but
can include nausea and vomiting.
or rash may occur as rare side effects. acid A substance defined as a donor of
hydrogen ions (hydrogen atoms with
achalasia A rare condition of unknown positive electrical charges). Acid molec-
ules, when mixed with or dissolved in
cause in which the muscles at the lower water, split up to release their con-
stituent ions; all acids release hydrogen
end of the oesophagus and the sphinc- as the positive ion. (See also acid–base
balance; alkali.)
ter (valve) between the oesophagus and acid–base balance A combination of
mechanisms that ensures that the body’s
the stomach fail to relax to let food into fluids are neither too acid nor too alka-
line (alkalis are also called bases).
the stomach after swallowing. As a
The body has three mechanisms for
result, the lowest part of the oesopha- maintaining normal acid–base balance:
buffers, breathing, and the activities of
gus is narrowed and becomes blocked the kidneys. Buffers are substances in
the blood that neutralize acid or alka-
with food, while the part above widens. line wastes. Rapid breathing results in
the blood becoming less acidic; slow
Symptoms include difficulty and pain breathing has the opposite effect. The
kidneys regulate the amounts of acid or
with swallowing and pain in the lower alkaline wastes in the urine.

chest and upper abdomen.

A barium swallow (a type of barium

X-ray examination) and gastroscopy may

be performed to investigate achalasia.

Oesophageal dila-

ACHILLES TENDON tation allows the

Calf oesophagus to be
muscle widened for long
periods. Surgery to

cut some of the

muscles at the sto-

mach entrance may

be necessary.

Achilles Achilles tendon
tendon The tendon that

raises the heel.

The Achilles ten-

don is formed from

the calf muscles

Heel (gastrocnemius,
soleus, and plan-

tar muscles) and

is attached to the

calcaneus (heel-bone). Minor injuries to

the Achilles tendon are common and

can result in inflammation (tendinitis).

8

ACIDOSIS ACOUSTIC NEUROMA A
Acne develops in areas of skin with a
Disturbances of the body’s acid–base
balance result in either acidosis (exces- high concentration of sebaceous glands,
sive blood acidity) or alkalosis (excessive
blood alkalinity). mainly the face, centre of the chest,
acidosis A disturbance of the body’s
acid–base balance in which there is an upper back, shoulders, and around the
accumulation of acid or loss of alkali
(base). There are 2 types of acidosis: neck. Milia (whiteheads), comedones
metabolic and respiratory.
(blackheads), nod- ACNE
One form of metabolic acidosis is ules (firm swel-
ketoacidosis, which occurs in uncon-
trolled diabetes mellitus and starvation. lings beneath the Sebaceous Inflamed skin
Metabolic acidosis may also be caused skin), and cysts gland
by loss of bicarbonate (an alkali) as a (larger, fluid-filled Plug
result of severe diarrhoea. In kidney fail- swellings) are the Hair Pus
ure, there is insufficient excretion of most commonly
acid in the urine.
occurring spots.
Respiratory acidosis occurs if breathing
fails to remove enough carbon dioxide Some, particularly
from the lungs. The excess carbon di-
oxide remains in the bloodstream, cysts, leave scars
where it dissolves to form carbonic acid.
Impaired breathing leading to respira- after they heal.
tory acidosis may be due to chronic
obstructive pulmonary disease (see pul- There is no inst-
monary disease, chronic obstructive),
bronchial asthma, or airway obstruction. ant cure for acne,
acid reflux Regurgitation of acidic fluid
from the stomach into the oesophagus but washing the
due to inefficiency of the muscular valve
at the lower end of the oesophagus. affected areas at
Also known as gastro-oesophageal
reflux disease (GORD), acid reflux may least twice daily
inflame the oesophagus, resulting in
heartburn due to oesophagitis. It may may help to keep
occur in pregnancy and often affects
overweight people. it under control. ACNE SPOT
acne A chronic skin disorder caused by
inflammation of the hair follicles and Topical drug treat-
sebaceous glands in the skin. The most
common type is acne vulgaris, which ments, such as benzoyl peroxide or
almost always develops during puberty.
retinoic acid, unblock the pores and
Acne spots are caused by the obstruc-
tion of hair follicles by sebum (the oily promote healing. Ultraviolet light can
substance secreted by the sebaceous
glands). Bacteria multiply in the follicle, be beneficial. If topical treatment has
causing inflammation. The change in
sebum secretion at puberty seems to be failed, oral drug treatment with anti-
linked with increased levels of androgen
hormones (male sex hormones). biotics, hormones, or isotretinoin may be

Acne may be brought on or aggravated given. Acne improves slowly over time,
by drugs such as corticosteroids and
androgens. Exposure to certain chemi- often clearing up by the end of the
cals and oils in the workplace can also
cause a type of acne. teenage years.

acoustic nerve The part of the vestibu-

locochlear nerve (the 8th cranial nerve)

that is concerned with hearing. It is also

known as the auditory nerve.

acoustic neuroma A rare, noncancer-

ous tumour arising from supporting

cells that surround the 8th cranial nerve

(see acoustic nerve), usually within the

internal auditory meatus (the canal in

the skull through which the nerve pass-

es from the inner ear to the brain).

Usually, the cause of an acoustic neuro-

ma is unknown. However, tumours that

affect the nerves on both sides of the

head simultaneously may be part of a

condition known as neurofibromatosis.

Acoustic neuroma can cause deafness,

tinnitus, loss of balance, and pain in the

face and the affected ear.

Diagnosis is made by hearing tests fol-

lowed by X-rays, CT scanning, or MRI.

Surgery may be needed, but treatment

9

A ACROCYANOSIS ACTINOMYCOSIS

with radiotherapy to shrink the tumour acroparaesthesia A medical term used

is also effective. to describe tingling in the fingers or

acrocyanosis A circulatory disorder in toes (see pins-and-needles).

which the hands and feet turn blue, may ACTH The common abbreviation for

become cold, and sweat excessively. adrenocorticotrophic hormone (also

Acrocyanosis is caused by spasm of the called corticotrophin). ACTH is produced

small blood vessels and is often aggra- by the anterior pituitary gland and stim-

vated by cold weather. It is related to ulates the adrenal cortex (outer layer of

Raynaud’s disease. the adrenal glands) to release various

acrodermatitis enteropathica A rare corticosteroid hormones, most impor-

inherited disorder in which areas of the tantly hydrocortisone (cortisol) but also

skin (most commonly the fingers, toes, aldosterone and androgen hormones.

scalp, and the areas around the anus ACTH production is controlled by a

and mouth) are reddened, ulcerated, and feedback mechanism involving both the

covered with pustules. Acrodermatitis hypothalamus and the level of hydro-

enteropathica is due to an inability to cortisone in the blood. ACTH levels

absorb enough zinc from food. Zinc increase in response to stress, emotion,

supplements usually help. injury, infection, burns, surgery, and

acromegaly A rare disease characterized decreased blood pressure.

by abnormal enlargement of the skull, A tumour of the pituitary gland can

jaw, hands, feet, and also of the internal cause excessive ACTH production which

organs. It is caused by excessive secre- leads to overproduction of hydrocorti-

tion of growth hormone from the sone by the adrenal cortex, resulting in

anterior pituitary gland at the base of Cushing’s syndrome. Insufficient ACTH

the brain and is the result of a pituitary production results in decreased produc-

tumour. A tumour that develops before tion of hydrocortisone, causing low

puberty results in gigantism. Acromeg- blood pressure. Synthetic ACTH is occa-

aly is diagnosed by measuring blood sionally given by injection to treat

levels of growth hormone, followed by arthritis or allergy.

CT scanning or MRI. actin A protein involved in muscle con-

acromioclavicular joint The joint that traction, in which microscopic filaments

lies between the outer end of the cla- of actin and another protein, myosin,

vicle (collarbone) and the acromion slide in between each other.

(the bony prominence at the top of the acting out Impulsive actions that may

scapula (shoulderblade). reflect unconscious wishes. The term is

ACROMIOCLAVICULAR JOINT most often used by psychotherapists
to describe behaviour during analysis

Clavicle Acromioclavicular when the patient “acts out” rather than
joint reports fantasies, wishes, or beliefs.
Acting out can also occur as a reaction

Acromion to frustrations encountered in everyday
life, often taking the form of antisocial,

aggressive behaviour.

Scapula actinic Pertaining to changes caused by
the ultraviolet rays in sunlight, as in

actinic dermatitis (inflammation of the

Humerus skin) and actinic keratosis (roughness
and thickening of the skin).

actinomycosis An infection caused by

ACTINOMYCES ISRAELII or related actino-

acromion A bony prominence at the mycete bacteria. The most common

top of the scapula (shoulderblade). The form of actinomycosis affects the jaw

acromion articulates with the end of area. A painful swelling appears and

the clavicle (collarbone) to form the pus discharges through small openings

acromioclavicular joint. that develop in the skin. Another form

10

ACUITY, VISUAL ADENOCARCINOMA A

of actinomycosis affects the pelvis in the corticosteroid hormones hydrocorti-
women, causing lower abdominal pain sone and aldosterone, normally produced
and bleeding between periods. This by the adrenal cortex (the outer part of
form was associated with a type of IUD, the adrenal glands). Excessive amounts
no longer in use, that did not contain of ACTH are secreted by the pituitary
copper. Rarely, forms of the disorder gland in an attempt to increase output
affect the appendix or lung. Actinomy- of the corticosteroid hormones. Secre-
cosis is treated with antibiotics. tion and activity of another hormone,
acuity, visual See visual acuity. melanocyte stimulating hormone (MSH),
acupressure A derivative of acupunc- is also increased.
ture in which pressure is applied
instead of needles. Addison’s disease can be caused by
acupuncture A branch of Chinese med- any disease that destroys the adrenal
icine in which needles are inserted into cortices. The most common cause is an
a patient’s skin as therapy for various autoimmune disorder in which the
disorders or to induce anaesthesia. immune system produces antibodies
that attack the adrenal glands.
Traditional Chinese medicine main-
tains that the chi (life-force) flows Symptoms generally develop gradu-
through the body along channels called ally over months or years, and include
meridians. A blockage in one or more of tiredness, weakness, abdominal pain,
these meridians is thought to cause ill and weight loss. Excess MSH may cause
health. Acupuncturists aim to restore darkening of the skin in the creases of
health by inserting needles at appropri- the palms, pressure areas of the body,
ate sites along the affected meridians. and the mouth. Acute episodes, called
The needles are stimulated by rotation Addisonian crises, brought on by infec-
or by an electric current. Acupuncture tion, injury, or other stresses, can also
has been used successfully as an anaes- occur. The symptoms of these include
thetic for surgical procedures and to extreme muscle weakness, dehydration,
provide pain relief after operations and hypotension (low blood pressure), con-
for chronic conditions. fusion, and coma. Hypoglycaemia (low
acute A term often used to describe a blood glucose) also occurs.
disorder or symptom that develops sud-
denly. Acute conditions may or may not Life-long corticosteroid drug treatment
be severe, and they are usually of short is needed. Treatment of Addisonian
duration. (See also chronic.) crises involves rapid infusion of saline
Adam’s apple A projection at the front and glucose, and supplementary doses
of the neck, just beneath the skin, that of corticosteroid hormones.
is formed by a prominence on the thy- adduction Movement of a limb towards
roid cartilage, which is part of the larynx the central line of the body, or of a digit
(voice box). The Adam’s apple enlarges towards the axis of a limb. Muscles that
in males at puberty. carry out this movement are often called
ADD The abbreviation for attention defi- adductors. (See also abduction.)
cit disorder, more commonly known as adenitis Inflammation of lymph nodes.
attention deficit hyperactivity disorder. Cervical adenitis (swelling and tender-
addiction Dependence on, and craving ness of the lymph nodes in the neck)
for, a particular drug, for example alco- occurs in certain bacterial infections,
hol, diazepam (a tranquillizer), or heroin. especially tonsillitis, and glandular fever
Reducing or stopping intake of the drug (see infectious mononucleosis). Mesen-
may lead to characteristic physiological teric lymphadenitis is inflammation of
or psychological symptoms (see with- the lymph nodes inside the abdomen
drawal syndrome), such as tremor or and is usually caused by viral infection.
anxiety. (See also alcohol dependence; Treatment of adenitis may include anal-
drug dependence.) gesic drugs, and antibiotic drugs if there
Addison’s disease A rare chronic dis- is a bacterial infection.
order in which there is a deficiency of adenocarcinoma The technical name
for a cancer of a gland or glandular tis-
sue, or for a cancer in which the cells

11

A ADENOIDECTOMY ADIPOSE TISSUE

form gland-like structures. An adeno- organs). Adenomas of endocrine glands

carcinoma arises from epithelium (the can cause excessive hormone produc-

layer of cells that lines the inside of tion, leading to disease. For example,

organs). Cancers of the colon, breast, pituitary gland adenomas can result in

pancreas, and kidney are usually adeno- acromegaly or Cushing’s syndrome.

carcinomas, as are some cancers of the adenomatosis An abnormal condition

cervix, oesophagus, salivary glands, and of glands in which they are affected

other organs. (See also intestine, cancer either by hyperplasia (overgrowth) or

of; kidney cancer; pancreas, cancer of.) the development of numerous adenomas

adenoidectomy Surgical removal of the (noncancerous tumours). Adenomato-

adenoids. An adenoidectomy is usually sis may simultaneously affect 2 or more

performed on a child with abnormally different endocrine glands.

large adenoids that are causing recur- ADH The abbreviation for antidiuretic

rent infections of the middle ear or air hormone (also called vasopressin), which

sinuses. The operation may be perfor- is released from the posterior part of

med together with tonsillectomy. the pituitary gland and acts on the kid-

adenoids A mass of glandular tissue at neys to increase their reabsorption of

the back of the nasal passage above the water into the blood. ADH reduces the

tonsils. The adenoids are made up of amount of water lost in the urine and

lymph nodes, which form part of the helps to control the body’s overall water

body’s defences against upper respira- balance. ADH production is controlled

tory tract infections; they tend to by the hypothalamus. Various factors

enlarge during early childhood, a time can affect ADH production and thus dis-

when such infections are common. turb the body’s water balance, including

ADENOIDS drinking alcohol, the disorder diabetes
insipidus, or a major operation.

Adenoids ADHD The abbreviation for attention
deficit hyperactivity disorder.

Nasal cavity adhesion The joining of normally uncon-
nected body parts by bands of fibrous

tissue. Adhesions are sometimes pre-

Opening of sent from birth, but they most often

eustachian develop as a result of scarring after
tube inflammation. Adhesions are most com-

Pharynx mon in the abdomen, where they often

form after peritonitis (inflammation of

Tongue the abdominal lining) or surgery. Some-
times, loops of intestine are bound
Tonsils together by adhesions, causing intesti-

nal obstruction (see intestine, obstruction

In most children, adenoids shrink after of). In such cases, surgery is usually

the age of about 5 years, disappearing required to cut the bands of tissue.

altogether by puberty. In some children, adipose tissue A layer of fat just

however, they enlarge, obstructing beneath the skin and around various

breathing and blocking the eustachian internal organs. Adipose tissue is built

tubes, which connect the middle ear to up from fat deposited as a result of

the throat. This results in recurrent excess food intake, thus acting as an

infections and deafness. Infections usu- energy store; excessive amounts of adi-

ally respond to antibiotic drugs, but if pose tissue produce obesity. The tissue

they recur frequently, adenoidectomy insulates against loss of body heat and

may be recommended. helps absorb shock in areas subject to

adenoma A noncancerous tumour or sudden or frequent pressure, such as

cyst that resembles glandular tissue the buttocks of feet.

and arises from the epithelium (the In men, superficial adipose tissue accu-

layer of cells that lines the inside of mulates around the shoulders, waist,

12

ADJUVANT ADRENAL GLAND DISORDERS A

and abdomen; in women, it occurs on suppress inflammatory reactions and
the breasts, hips, and thighs. some activities of the immune system.
adjuvant A substance that enhances Production of adrenal cortical hor-
the action of another substance in the mones is controlled by ACTH, which is
body. The term is usually used to des- produced in the pituitary gland.
cribe an ingredient added to a vaccine
to increase the production of antibodies The adrenal medulla is part of the
by the immune system, thus enhancing sympathetic autonomic nervous system.
the vaccine’s effect. Adjuvant chemother- In response to stress, it secretes the
apy is the use of anticancer drugs in hormones adrenaline (epinephrine) and
addition to surgical removal of a tumour. noradrenaline (norepinephrine), which
Adlerian theory The psychoanalytical increase heart-rate and blood flow.
ideas set forth by the Austrian psychia-
trist Alfred Adler. Also called individual ADRENAL GLANDS
psychology, Adler’s theories were based
on the idea that everyone is born with Adrenal Adrenal
feelings of inferiority. Life is seen as a gland cortex
constant struggle to overcome these
feelings; failure to do so leads to neuro- Kidney Adrenal
sis. (See also psychoanalytic theory.) medulla
adolescence The period between child-
hood and adulthood, which broadly LOCATION Fat
corresponds to the teenage years. Ado- Blood vessel
lescence commences and overlaps with,
but is not the same as, puberty. Kidney
ADP The abbreviation for adenosine di-
phosphate, the chemical that takes up STRUCTURE OF ADRENAL GLAND
energy released during biochemical reac-
tions to form ATP (adenosine triphos- adrenal gland disorders A range of
phate), the body’s main energy-carrying uncommon but sometimes serious dis-
chemical. When ATP releases its energy, orders due to deficient or excessive
ADP is reformed. (See also metabolism.) production of hormones by one or both
adrenal failure Insufficient production of the adrenal glands.
of hormones by the adrenal cortex (the A genetic defect causes congenital
outer part of the adrenal glands). It can adrenal hyperplasia, in which the ad-
be acute or chronic. Adrenal failure may renal cortex is unable to make sufficient
be caused by a disorder of the adrenal hydrocortisone and aldosterone, and
glands, in which case it is called Addi- androgens are produced in excess. In
son’s disease, or by reduced stimulation adrenal failure, there is also deficient
of the adrenal cortex by ACTH, a hor- production of hormones by the adrenal
mone produced by the pituitary gland. cortex; if due to disease of the adrenal
adrenal glands A pair of small, trian- glands, it is called Addison’s disease.
gular endocrine glands located above Adrenal tumours are rare and generally
the kidneys. Each adrenal gland has lead to excess hormone production.
2 distinct parts: the outer cortex and the In many cases, disturbed activity of
smaller, inner medulla. the adrenal glands is caused, not by
disease of the glands themselves, but
The cortex secretes aldosterone, which, by an increase or decrease in the blood
together with hydrocortisone and cor- level of hormones that influence the
ticosterone and small amounts of action of the adrenal glands. For exam-
androgen hormones helps to maintain ple, hydrocortisone production by the
blood pressure. Hydrocortisone controls adrenal cortex is controlled by ACTH,
the body’s use of fats, proteins, and car- which is secreted by the pituitary gland.
bohydrates and is also important in Pituitary disorders can disrupt produc-
helping the body to cope with stress. tion of hydrocortisone.
Hydrocortisone and corticosterone also

13

A ADRENAL HYPERPLASIA, CONGENITAL AFFECT

adrenal hyperplasia, congenital An phaeochromocytoma and neuroblastoma,

uncommon genetic disorder in which an which affects children. These tumours

enzyme defect blocks the production cause intermittent hypertension and

of corticosteroid hormones from the sweating attacks. Surgical removal of a

adrenal glands. Excessive amounts of tumour usually cures these conditions.

androgens (male sex hormones) are pro- adrenocorticotrophic hormone See

duced, which can result in abnormal ACTH.

genital development in an affected fetus. adrenogenital syndrome See adrenal

Other effects include dehydration, hyperplasia, congenital.

weight loss, low blood pressure, and aerobic Requiring oxygen to live, func-

hypoglycaemia. Hyperplasia (enlarge- tion, and grow. Humans and many

ment) of the adrenal glands occurs and other forms of life are dependent on

there is excessive skin pigmentation in oxygen for “burning” foods to produce

skin creases and around the nipples. energy (see metabolism). In contrast,

In severe cases, the disorder is appar- many bacteria thrive without oxygen

ent soon after birth. In milder cases, and are described as anaerobic.

symptoms appear later, sometimes pro- aerobics Exercises, such as swimming

ducing premature puberty in boys and and cycling, that allow muscles to work

delayed menstruation, hirsutism, and at a steady rate with a constant, ade-

potential infertility in girls. quate supply of oxygen-carrying blood,

Congenital adrenal hyperplasia is con- and that can therefore be sustained for

firmed by measuring corticosteroid long periods. Oxygen is used to release

hormones in blood and urine. Treat- energy from the body’s stores. To fuel

ment is by hormone replacement. If this aerobic exercise, the muscles use fatty

is started early, normal sexual develop- acid, burning it completely to produce

ment and fertility usually follow. energy, carbon dioxide, and water.

adrenaline A hormone, also called When performed regularly, aerobic

epinephrine, released by the adrenal exercises improve stamina and endur-

glands in response to signals from the ance. They encourage the growth of

sympathetic autonomic nervous system. capillaries, improving blood supply to

These signals are triggered by stress, the cells. Aerobic exercises also improve

exercise, or by an emotion such as fear. body cells’ capacity to use oxygen and

Adrenaline increases the speed and increase the amount of oxygen the body

force of the heartbeat. It widens the air- can use in a given time. The condition

ways to improve breathing and narrows of the heart also improves. (See also

blood vessels in the skin and intestine exercise; fitness.)

so that an increased flow of blood aerodontalgia Sudden pain in a tooth

reaches the muscles. brought on by a change in surrounding

Synthetic adrenaline is sometimes air pressure. Flying at a high altitude in

given by injection as an emergency a lowered atmospheric pressure can

treatment for cardiac arrest or anaphy- cause a pocket of air in the dental pulp

lactic shock. Adrenaline eye drops may to expand and irritate the nerve in the

be used to treat glaucoma, but regular root. Aerodontalgia is more likely if

use can cause a burning pain in the eye. there are improperly fitting fillings or

adrenal tumours Cancerous or non- poorly filled root canals.

cancerous tumours in the adrenal aerophagy Excessive swallowing of air,

glands, usually causing excess secretion which may occur during rapid eating or

of hormones. Adrenal tumours are rare. drinking or be caused by anxiety.

Tumours of the adrenal cortex may aetiology The cause of a disease or the

secrete aldosterone, causing primary study of the various factors involved in

aldosteronism, or hydrocortisone, caus- causing a disease.

ing Cushing’s syndrome. Tumours of affect A term used to describe a per-

the medulla may cause excess secretion son’s mood. The 2 extremes of affect are

of adrenaline and noradrenaline. Two elation and depression. A person who

types of tumour affect the medulla: experiences extreme moods or changes

14

AFFECTIVE DISORDERS AGGREGATION, PLATELET A

in moods may have an affective The age of a fetus is measured in terms
disorder. Shallow or reduced affect may of gestational age, which can be
be a sign of schizophrenia or of an assessed accurately by ultrasound scan-
organic brain syndrome. ning. In children, the most useful
affective disorders Mental illnesses measure of physical development is
characterized predominantly by marked bone age (degree of bone maturity as
changes in affect. Mood may vary over a seen on an X-ray) because all healthy
period of time between mania (extreme individuals reach the same adult level
elation) and severe depression. (See of skeletal maturity, and each bone
also manic–depressive illness.) passes through the same sequence of
affinity A term used to describe the growth. Dental age, another measure
attraction between chemicals that causes of physical maturity, can be assessed by
them to bind together, as, for example, the number of teeth that have erupted
between an antigen and an antibody (see eruption of teeth) or by the amount
(see immune response). In microbiology, of dental calcification (as seen on an
affinity describes physical similarity X-ray) compared with standard values.
between organisms. In psychology, it
refers to attraction between 2 people. In adults, physical age is difficult to
aflatoxin A poisonous substance pro- assess other than by physical appear-
duced by ASPERGILLUS FLAVUS moulds, ance. It can be estimated after death by
which contaminate stored foods, espe- the state of certain organs.
cially grains, peanuts, and cassava.
Aflatoxin is believed to be one of the Mental age can be assessed by com-
factors responsible for the high inci- paring scores on intelligence tests with
dence of liver cancer in tropical Africa. standards for chronological age. A young
afterbirth The common name for the child’s age can be expressed in terms of
tissues that are expelled from the uterus the level of developmental skills, man-
after delivery of a baby. The afterbirth ual dexterity, language, and social skills.
includes the placenta and the mem- agenesis The complete absence at birth
branes that surrounded the fetus. of an organ or bodily component, caused
afterpains Contractions of the uterus by failure of development in the embryo.
that continue after childbirth. Afterpains agent Any substance or force capable of
are normal and are experienced by bringing about a biological, chemical, or
many women, especially during breast- physical change. (See also reagent.)
feeding. They usually disappear a few Agent Orange A herbicide of which
days following the birth but may require the major constituent is the phenoxy
treatment with analgesic drugs. acid herbicide 2,4,5 T. This substance
agammaglobulinaemia A type of im- may be contaminated in manufacture
munodeficiency disorder in which there with the highly toxic TCDD, commonly
is almost complete absence of B-lympho- known as dioxin (see defoliant poisoning).
cytes and immunoglobulins in the blood. age spots Blemishes that appear on the
agar An extract of certain seaweeds skin with increasing age. Most common
with similar properties to gelatine. It are seborrhoeic keratoses, which are
can be taken for constipation to soften brown or yellow, slightly raised spots
and give bulk to faeces, and to relieve that can occur at any site. Also common
indigestion and heartburn. Agar is also in elderly people are freckles, solar kera-
used as a gelling agent in media for toses (small blemishes caused by
bacterial cultures. overexposure to the sun), and De Mor-
age The length of time a person has gan’s spots, which are red, pinpoint
existed. Of medical significance in diag- blemishes on the trunk. Treatment is
nosis and in determining treatment, a usually unnecessary for any of these,
person’s age is usually measured apart from solar keratoses, which may
chronologically, but it can also be mea- eventually progress to skin cancer.
sured in terms of physical, mental, or ageusia The lack or an impairment of
developmental maturity. the sense of taste (see taste, loss of).
aggregation, platelet The clumping
together of platelets (small, sticky blood

15

A AGGRESSION AGUE

particles). Aggregation is the 1st stage alcohol withdrawal. Depression may be

of blood clotting and helps to plug accompanied by agitation.

injured vessels. Inappropriate aggre- agnosia An inability to recognize objects

gation can have adverse effects; for despite adequate sensory information

example, if aggregation occurs in an about them reaching the brain via the

artery, it may result in a thrombosis. eyes or ears or through touch. Agnosia

aggression A general term for a wide is caused by damage to areas of the

variety of acts of hostility. A number of brain that are involved in interpretative

factors, including human evolutionary and recall functions. The most common

survival strategies, are thought to be causes of this kind of damage are stroke

involved in aggression. Androgen hor- or head injury.

mones, the male sex hormones, seem to Agnosia is usually associated with just

promote aggression, whereas oestrogen one of the senses of vision, hearing, or

hormones, the female sex hormones, touch and is described as visual, audit-

actively suppress it. Age is another ory, or tactile respectively. Some people,

factor; aggression is more common after a stroke that damages the right

among teenagers and young adults. cerebral hemisphere, seem unaware of

Sometimes, a brain tumour or head any disability in their affected left limbs.

injury leads to aggressive behaviour. This is called anosognosia or sensory

Psychiatric conditions associated with inattention. There is no specific treat-

aggressive outbursts are schizophrenia, ment for agnosia, but some interpretative

antisocial personality disorder, mania, ability may return eventually.

and abuse of amfetamines or alcohol. agonist Having a stimulating effect. An

Temporal lobe epilepsy, hypoglycaemia, agonist drug, sometimes known as an

and confusion due to physical illnesses activator, is one that binds to a sensory

are other, less common, medical causes. nerve cell (receptor) and triggers or in-

aging The physical and mental changes creases a particular activity in that cell.

that occur with the passing of time. agoraphobia Fear of going into open

Aging is associated with degenerative spaces or public places. Agoraphobia

changes in various organs and tissues, (see phobia) may occur with claustro-

such as loss of elasticity in the skin and phobia. If sufferers do venture out, they

a progressive decline in organ function. may have a panic attack, which may lead

Mechanical wear and tear causes cumu- to further restriction of activities. Peo-

lative damage to the joints, and the ple with agoraphobia may eventually

muscles lose bulk and strength. Wound become housebound. Treatment with

healing and resistance to infection also behaviour therapy is usually successful.

decline. Gradual loss of nerve cells can Antidepressant drugs may be helpful.

lead to reduced sensory acuity and dif- agraphia Loss of, or impaired, ability to

ficulties with learning and memory. write, despite normal functioning of the

However, dementia occurs in only a hand and arm muscles, caused by brain

minority of elderly people. damage. Agraphia can result from dam-

Heredity is an important determinant age to any of the various parts of the

of life expectancy, but physical degener- cerebrum concerned with writing and

ation may be accelerated by factors can therefore be of different types and

such as smoking, excessive alcohol in- degrees of severity. Such damage is most

take, poor diet, and insufficient exercise. commonly due to head injury, stroke, or

agitation Restless inability to keep still, a brain tumour. Agraphia is often accom-

usually as a result of anxiety or tension. panied by alexia (loss of the ability to

Agitated people engage in aimless, read) or may be part of an expressive

repetitive behaviour, such as pacing up aphasia (general disturbance in the

and down or wringing their hands, and expression of language). There is no

they often start tasks without complet- specific treatment for agraphia, but some

ing them. Persistent agitation is seen lost writing skills may return in time.

in anxiety disorders, especially if there is ague An outdated term for malaria or

an underlying physical cause such as other diseases causing fever in which

16

AIDS AIR CONDITIONING A

the sufferer alternately feels excessively candidiasis (thrush), shingles, tuberculo-
hot and shiveringly cold. sis, and shigellosis. HIV may also affect
AIDS Acquired immune deficiency syn- the brain, causing a variety of neurolog-
drome, a deficiency of the immune ical disorders, including dementia.
system due to infection with HIV (human
immunodeficiency virus). In most coun- Certain conditions, known as AIDS-
tries, illness and death from AIDS is a defining illnesses, are characteristic of
growing health problem, and there is, full-blown AIDS. These include cancers
as yet, no cure or vaccine. (Kaposi’s sarcoma and lymphoma of
the brain), and various infections (pneu-
AIDS does not develop in all people mocystis pneumonia, cytomegalovirus
infected with HIV. The interval between infection, toxoplasmosis, diarrhoea due
infection and the development of AIDS to CRYPTOSPORIDIUM or ISOSPORA, candid-
is highly variable. Without treatment, iasis, disseminated strongyloidiasis, and
around half of those people infected cryptococcosis), many of which are
will develop AIDS within 8–9 years. described as opportunistic infections.

HIV is transmitted in body fluids, in- Confirmation of HIV infection involves
cluding semen, blood, vaginal secretions, testing a blood sample for the presence
and breast milk. The major methods of of antibodies to HIV. Diagnosis of full-
transmission are sexual contact (vagi- blown AIDS is based on a positive HIV
nal, anal, or oral), blood to blood (via test along with the presence of an AIDS-
transfusions or needle-sharing in drug defining illness.
users), and mother to fetus. HIV has
also been transmitted through blood The risk of infection with HIV can be
products given to treat haemophilia, arti- reduced by practising safer sex. Intra-
ficial insemination by donated semen, venous drug users should not share
and kidney transplants; but improved needles. There is a small risk to health
screening has greatly reduced these workers handling infected blood prod-
risks. HIV is not spread by everyday con- ucts or needles, but this risk can be
tact, such as hugging or sharing crockery. minimized by safe practices.

The virus enters the bloodstream and Treatment of HIV infection with a com-
infects cells that have a particular recep- bination of antiviral drugs can slow the
tor, known as the CD4 receptor, on their disease’s progress, and may prevent
surface. These cells include a type of the development of full-blown AIDS. The
white blood cell (a CD4 lymphocyte) 2 main types of antiviral drug used are
responsible for fighting infection and protease inhibitors, such as indinavir,
cells in other tissues such as the brain. and reverse transcriptase inhibitors
The virus reproduces within the infected such as zidovudine. Treatment is also
cells, which then die, releasing more available for AIDS-defining illnesses.
virus particles into the blood. If the AIDS-related complex A combination
infection is left untreated, the number of weight loss, fever, and enlarged lymph
of CD4 lymphocytes falls, resulting in nodes in a person who has been infec-
greater susceptibility to certain infec- ted with HIV (the AIDS virus), but does
tions and some types of cancer. not have AIDS itself. Many people with
AIDS-related complex will eventually
Some people experience a short-lived develop the features of AIDS.
illness similar to infectious mononucle- air The colourless, odourless mixture of
osis when they are first infected with gases that forms the Earth’s atmosphere.
HIV. Many individuals have no obvious Air consists of 78 per cent nitrogen, 21
symptoms; some have only vague com- per cent oxygen, small quantities of
plaints, such as weight loss, fevers, carbon dioxide and other gases, and
sweats, or unexplained diarrhoea, des- some water vapour.
cribed as AIDS-related complex. air conditioning A system that controls
the purity, humidity, and temperature
Minor features of HIV infection in- of the air in a building. Contaminated
clude skin disorders such as seborrhoeic air-conditioning systems may cause le-
dermatitis. More severe features include gionnaires’ disease and humidifier fever
persistent herpes simplex infections, oral

17

A AIR EMBOLISM ALCOHOL

(a lung disease causing coughing and albumin The most abundant protein in

breathing difficulty). the blood plasma. Albumin is made in

air embolism Blockage of a small artery the liver from amino acids. It helps to

by an air bubble carried in the blood. retain substances (such as calcium,

Air embolism is rare. In most cases, it is some hormones, and certain drugs) in

caused by air entering the circulation the circulation by binding to them to

through a vein, either due to injury or prevent them from being filtered out by

surgery. Air embolism can also occur the kidneys and excreted. Albumin also

during diving or air travel accidents, in regulates the movement of water bet-

which lung tissue ruptures, releasing ween tissues and the bloodstream by

bubbles into the bloodstream. osmosis. (See also albuminuria.)

air pollution See pollution. albuminuria The presence of the pro-

air swallowing See aerophagy. tein albumin in the urine; a type of

airway A collective term for the pas- proteinuria. Normally, the glomeruli (the

sages through which air enters and filtering units of the kidneys) do not

leaves the lungs (see respiratory sys- allow albumin to pass into the urine.

tem). The term is also applied to a tube Albuminuria therefore usually indicates

inserted into the mouth of an uncon- that there is damage to the kidneys’

scious person to prevent the tongue filtering mechanisms. Such damage

from obstructing breathing. may be due to a kidney disorder, such

airway obstruction Narrowing or block- as glomerulonephritis or nephrotic syn-

age of the respiratory passages. The drome, or may be a sign that the kidneys

obstruction may be due to a foreign have been affected by hypertension.

body, such as a piece of food, that Albuminuria can be detected by a sim-

becomes lodged in part of the upper ple urine test.

airway and may result in choking. Cer- alcohol A colourless liquid produced

tain disorders, such as diphtheria and from the fermentation of carbohydrates

lung cancer, can cause obstruction. by yeast. Also known as ethanol, alco-

Additionally, spasm of the muscular hol is the active constituent of drinks

walls of the airway, as occurs in bron- such as beer and wine. In medicine, it is

chospasm (a feature of asthma), results used as an antiseptic and solvent. Meth-

in breathing difficulty. anol is a related, highly toxic substance.

akathisia An inability to sit still, occa- Alcohol is a drug and produces a wide

sionally occurring as a side effect of an range of mental and physical effects.

antipsychotic drug or, less commonly, as The effect of alcohol on the central

a complication of Parkinson’s disease. nervous system is as a depressant,

akinesia Complete or almost complete decreasing its activity and thereby

loss of movement. It may be a result of reducing anxiety, tension, and inhibi-

damage to part of the brain due, for ex- tions. In moderate amounts, alcohol

ample, to a stroke or Parkinson’s disease. produces a feeling of relaxation, confi-

albinism A rare genetic disorder charac- dence, and sociability. However, alcohol

terized by a lack of the pigment melanin, slows reactions, and the more that is

which gives colour to the skin, hair, and drunk, the greater is the impairment of

eyes. In oculocutaneous albinism (the concentration and judgement. Exces-

most common type), the hair, skin, and sive consumption of alcohol results in

eyes are all affected. Less often, only poisoning or acute alcohol intoxication,

the eyes are affected. In both forms, with effects ranging from euphoria to

skin cannot tan and ages prematurely, unconsciousness.

and skin cancers may develop on areas Short-term physical effects of alcohol

exposed to the sun. Visual problems of include peripheral vasodilation (widen-

people with albinism include photopho- ing of the small blood vessels), which

bia, nystagmus, squint, and myopia. causes the face to flush, and increased

Glasses are usually needed from an flow of gastric juices, which stimulates

early age; and tinted glasses help to the appetite. Alcohol increases sexual

reduce photophobia. confidence, but high levels can cause

18

ALCOHOL DEPENDENCE ALCOHOL INTOXICATION A

impotence. Alcohol also acts as a tingling; weakness in the legs and
diuretic, increasing urine output. hands; irregular pulse; enlarged blood
vessels in the face; unsteadiness; confu-
In the long term, regular excessive sion; memory lapses; and incontinence.
alcohol consumption can cause gastritis After sudden withdrawal from alcohol,
(inflammation and ulceration of the delirium tremens may occur.
stomach lining), and lead to alcohol-
related disorders. Heavy drinking in Alcohol-dependent persons are more
the long term may also lead to alcohol susceptible than others to a variety of
dependence. However, people who drink physical and mental disorders (see
regular, small amounts of alcohol (an alcohol-related disorders).
average of 1–2 units a day) seem to
have lower rates of coronary heart dis- Many alcoholics require detoxification
ease and stroke than total abstainers. followed by long-term treatment. Dif-
alcohol dependence An illness char- ferent methods of treatment may be
acterized by habitual, compulsive, long- combined. Psychological treatments in-
term, heavy consumption of alcohol and volve psychotherapy and are commonly
the development of withdrawal symp- carried out as group therapy. Social
toms when drinking is suddenly stopped. treatments may offer practical help and
tend to include family members in the
Three causative factors interact in the process. Physical treatment generally
development of the illness: personality, includes the use of disulfiram, a drug
environment, and the addictive nature that sensitizes the drinker to alcohol so
of alcohol. Inadequate, insecure, or that he or she experiences unpleasant
immature personalities are more at risk. side effects when drinking. Alcoholics
Environmental factors are important, Anonymous and other self-help organiz-
especially the ready availability, afford- ations can provide support and advice.
ability, and social acceptance of alcohol. Alcoholics Anonymous A worldwide,
Genetic factors may play a part in caus- independent, self-help organization that
ing dependence in some cases, but it is is operated locally by people working
now widely believed that anyone, irre- on a voluntary basis to overcome alco-
spective of personality, environment, or hol dependence. Regular group meetings
genetic background, can become an are held in which members are encour-
alcoholic. Stress is often a major factor aged to help one another stay sober by
in precipitating heavy drinking. sharing their experiences openly and
offering support and advice.
Alcohol dependence usually develops alcohol intoxication The condition that
in 4 main stages that occur over a num- results from consuming an excessive
ber of years. In the 1st phase, tolerance amount of alcohol, often over a relativ-
to alcohol develops in the heavy social ely short period. The effects of a large
drinker. In the 2nd phase, the drinker alcohol intake depend on many factors,
experiences memory lapses relating to including physical and mental state,
events during the drinking episodes. In body size, social situation, and acquired
the 3rd phase, there is loss of control tolerance. The important factor, how-
over alcohol consumption. The final ever, is the blood alcohol level. Mild
phase is characterized by prolonged intoxication promotes relaxation and
binges of intoxication and mental or increases social confidence. Alcohol
physical complications. causes acute poisoning if taken in suf-
ficiently large amounts, however. It
Behavioural symptoms are varied and depresses the activity of the central ner-
can include furtive, aggressive, or grand- vous system, leading to loss of normal
iose behaviour; personality changes mental and physical control. In extreme
(such as irritability, jealousy, or uncon- cases, intoxication may lead to loss of
trolled anger); neglect of food intake consciousness and even death.
and personal appearance; and lengthy
periods of intoxication. In most cases, recovery from alcohol
intoxication takes place naturally as
Physical symptoms may include nau- the alcohol is gradually broken down in
sea, vomiting, or shaking in the morning;
abdominal pain; cramps; numbness or

19

A ALCOHOLISM ALEXIA

the liver. Medical attention is required chemical produced by a series of reac-

if the intoxication has resulted in tions involving the enzymes renin and

coma. For the chronic mental, physical, angiotensin-converting enzyme. Aldos-

and social effects of long-term heavy terone production is also stimulated by

drinking, see alcohol dependence and the action of ACTH, which is produced

alcohol-related disorders. by the pituitary gland.

alcoholism See alcohol dependence. aldosteronism A disorder that results

alcohol-related disorders A wide var- from the excessive production of the

iety of physical and mental disorders hormone aldosterone from one or both

associated with heavy, prolonged con- adrenal glands. Aldosteronism caused

sumption of alcohol. by an adrenal tumour is known as

High alcohol consumption increases Conn’s syndrome. Aldosteronism may

the risk of cancers of the mouth, tongue, also be caused by disorders, such as

pharynx (throat), larynx (voice box), and heart failure or liver damage, that reduce

oesophagus, especially if combined with the flow of blood through the kidneys.

smoking. Incidence of liver cancer, as Reduced blood flow through the kid-

well as the liver diseases alcoholic hep- neys leads to overproduction of renin

atitis and cirrhosis, is higher among and angiotensin, which, in turn, leads to

alcoholics. High alcohol consumption excessive aldosterone production.

increases the risk of cardiomyopathy, Symptoms are directly related to the

hypertension, and stroke. Alcohol irri- actions of aldosterone. Too much sodium

tates the digestive tract and may cause is retained in the body, leading to a rise

gastritis. Heavy drinking in pregnancy in blood pressure, and excess potassium

increases the risk of miscarriage and is lost in the urine. Low potassium cau-

fetal alcohol syndrome. Alcoholics are ses tiredness and muscle weakness and

more likely to suffer from anxiety and impairs kidney function, leading to thirst

depression and to develop dementia. and overproduction of urine.

Many alcoholics have a poor diet and Treatment in all cases includes res-

are prone to diseases caused by nutri- triction of dietary salt and use of the

tional deficiency, particularly of thiamine diuretic drug spironolactone. If the cause

(see vitamin B complex). Severe thia- of aldosteronism is an adrenal tumour,

mine deficiency, called beriberi, disturbs this may be surgically removed.

nerve function, causing cramps, numb- alendronate sodium See alendronic

ness, and weakness in the legs and acid.

hands. Its effects on the brain can cause alendronic acid A bisphosphonate drug

confusion, disturbances of speech and used in the treatment of osteoporosis

gait, and eventual coma (see Wernicke– and Paget’s disease of bone. The most

Korsakoff syndrome). Severe thiamine common side effect is inflammation of

deficiency can also cause heart failure. the oesophagus, which causes heart-

A prolonged high level of alcohol in burn or difficulty in swallowing. Other

the blood and tissues can disturb body side effects can include headache and

chemistry, resulting in hypoglycaemia abdominal pain.

(reduced glucose in the blood) and Alexander technique A therapy that

hyperlipidaemia (increased fat in the aims to improve health by teaching peo-

blood). These may damage the heart, ple to stand and move more efficiently.

liver, blood vessels, and brain; irrevers- The technique is based on the belief

ible damage may cause premature death. that bad patterns of body movement

aldosterone A hormone secreted by interfere with the proper functioning of

the adrenal cortex (the outer part of the the body and contribute to the develop-

adrenal glands). Aldosterone acts on the ment of disease.

kidneys to regulate the concentrations alexia Word blindness; inability to rec-

of sodium and potassium in the blood ognize and name written words. Alexia

and tissues and control blood pressure. is caused by damage to part of the cere-

Production of aldosterone is stimulated brum (the main mass of the brain) by a

mainly by the action of angiotensin II, a stroke, for example. It severely disrupts

20

ALIENATION ALLERGY A

the reading ability of a person who was allele One of 2 or more different forms of
previously literate. (See also dyslexia.) a gene that occupies a specific position
alienation Feeling like a stranger, even on a chromosome (see gene; inheritance).
when among familiar people or places,
and being unable to identify with a cul- allergen A normally harmless substance
ture, family, or peer group. Alienation is that causes an allergic reaction (see
common in adolescents and also occurs allergy) in people who have become
in people who are isolated by cultural sensitized to it. Allergens can include
or language differences. In some people, foods (for example, nuts, eggs, and shell-
it may be an early symptom of schizo- fish); inhaled substances such as pollen,
phrenia or a personality disorder. house dust, and fur; and some drugs.
alignment, dental The movement of
teeth by using either fixed or removable allergy Various conditions caused by
orthodontic appliances (braces) to cor- inappropriate or exaggerated reactions
rect malocclusion (incorrect bite). of the immune system (known as hyper-
alimemazine An antihistamine drug, also sensitivity reactions) to a variety of
known as trimeprazine, that is used substances. Many common illnesses,
mainly to relieve itching in allergic con- such as asthma and allergic rhinitis (hay
ditions such as urticaria and atopic fever), are caused by allergic reactions
eczema. Alimemazine often causes to substances that in the majority of
drowsiness. people cause no symptoms.
alimentary tract The tube-like struc- Allergic reactions occur only on 2nd or
ture that extends from the mouth to the subsequent exposure to the allergen,
anus (see digestive system). once 1st contact has sensitized the body.
alkali Also known as a base, an alkali is The function of the immune system is
chemically defined as a donor of hydroxyl to recognize antigens (foreign proteins)
ions (each of which comprises an atom on the surfaces of microorganisms and
of hydrogen linked to an atom of oxygen to form antibodies (also called immuno-
and has an overall negative electrical globulins) and sensitized lymphocytes
charge). Antacid drugs, such as sodium (white blood cells). When the immune
bicarbonate, are alkalis. Some alkalis, system next encounters the same anti-
such as sodium hydroxide, are corro- gens, the antibodies and sensitized
sive. (See also acid; acid–base balance.) lymphocytes interact with them, leading
alkaloids A group of nitrogen-containing to destruction of the microorganisms.
substances obtained from plants. Mor- A similar immune response occurs in
phine, codeine, nicotine, and strychnine allergies, except that the immune system
(see strychnine poisoning) are examples. forms antibodies or sensitized lymph-
alkalosis A disturbance of the body’s ocytes against harmless substances
acid–base balance in which there is an because these allergens are misidenti-
accumulation of alkali or a loss of acid. fied as potentially harmful antigens.
There are 2 types: metabolic and res- The inappropriate or exaggerated re-
piratory. In metabolic alkalosis, the actions seen in allergies are termed
increase in alkalinity may be caused by
taking too much of an antacid drug or ALLERGY Antibody
by losing a large amount of stomach attaches to
acid as a result of severe vomiting. In Allergen mast cell
respiratory alkalosis, there is a reduc-
tion in the blood level of carbonic acid Mast cell
(derived from carbon dioxide). This
reduction is a consequence of hyper- Histamine
ventilation, which may occur during a
panic attack or at high altitudes due to Allergen
lack of oxygen. (See also acidosis.) binds to
alkylating agents A class of anticancer antibody
drugs.
Nucleus Histamine
released

TYPE I HYPERSENSITIVITY

21

A ALLOPATHY ALOPECIA

hypersensitivity reactions and can have reactions to specific allergens such as

any of four different mechanisms (termed bee stings. Treatment involves gradu-

Types I to IV hypersensitivity reactions). ally increasing doses of the allergen,

Most well known allergies are caused by but it must be carried out under close

Type I (also known as anaphylactic or supervision because a severe allergic

immediate) hypersensitivity in which reaction can result.

allergens cause immediate symptoms allopathy The practice of conventional

by provoking the immune system to medicine. (See also homeopathy.)

produce specific antibodies, belonging allopurinol A drug treatment for gout.

to a type called immunoglobulin E Taken long term, it reduces the frequ-

(IgE), which coat cells (called mast cells ency of attacks by decreasing production

or basophils). When the allergen is of uric acid. Possible adverse reactions

encountered for the second time, it include itching, rashes, and nausea.

binds to the IgE antibodies and causes alopecia Loss or absence of hair, which

the granules in mast cells to release may occur at any hair-bearing site on

various chemicals, which are responsi- the body but which is usually notice-

ble for the symptoms of the allergy. able only on the scalp.

Among the chemicals released is hist- Male-pattern baldness, the most com-

amine, which causes widened blood mon form of alopecia, is hereditary and

vessels, leakage of fluid into tissues, and most often affects men. Normal hair is

muscle spasm. Symptoms can include lost initially from the temples and

itching, swelling, sneezing, and wheez- crown and is replaced by fine, downy

ing. Particular conditions associated hair; the affected area gradually widens.

with Type I reactions include asthma, Other hereditary forms are rare. They

hay fever, urticaria (nettle rash), angio- may be due to an absence of hair roots

edema, anaphylactic shock (a severe, or abnormalities of the hair shaft.

generalized allergic reaction), possibly In generalized alopecia, the hair falls

atopic eczema, and many food allergies. out in large amounts. Causes include

Types II to IV hypersensitivity reac- various forms of stress, such as surgery,

tions are less often implicated in prolonged illness, or childbirth. Many

allergies. However, contact dermatitis, anticancer drugs cause temporary alo-

in which the skin reacts to substances pecia. The hair regrows when the

such as nickel, is due to a Type IV hyper- underlying cause is corrected.

sensitivity reaction. Localized alopecia may be due to per-

It is not known why certain individuals manent skin damage (for example, by

and not others get allergies, but about burns or radiotherapy) or trauma to

1 in 8 people seem to have an inherited the hair roots by styling or, rarely,

predisposition to them (see atopy). trichotillomania (a disorder in which suf-

Whenever possible, the most effective ferers pull out their hair). The most

treatment for allergy of any kind is common type of localized hair loss is

avoidance of the relevant allergen. alopecia areata, which is an autoim-

Drug treatment for allergic reactions mune disorder. There is no specific

includes the use of antihistamine drugs, treatment, but the hair usually regrows

which relieve the symptoms. Some anti- within a few months. Alopecia univer-

histamine drugs have a sedative effect, salis is a rare, permanent form of

which is useful in treating itching at alopecia areata that causes loss of all the

night due to eczema. Many antihista- hair on the scalp and body, including

mines do not cause drowsiness, making the eyelashes and eyebrows. Skin dis-

them more suitable for daytime use. eases such as scalp ringworm (see

Other drugs, such as sodium cromogli- tinea), lichen planus, lupus erythemato-

cate and corticosteroid drugs, can be sus, and skin tumours may also cause

used regularly to prevent symptoms localized hair loss.

from developing. Treatments for male-pattern baldness

Hyposensitization can be valuable for a include hair transplants or drug treat-

minority of people who suffer allergic ments with minoxidil or finasteride.

22

ALPHA1-ANTITRYPSIN DEFICIENCY A LV E O L I T I S A

alpha1-antitrypsin deficiency A rare may indicate tumour recurrence. How-
genetic disorder in which a person is ever, AFP levels are also raised in some
missing the enzyme alpha1-antitrypsin, noncancerous conditions, including viral
which protects the body from damage and alcoholic hepatitis and cirrhosis.
by other enzymes. The disease mainly alprazolam A benzodiazepine drug used
affects tissues in the lungs, resulting in in the treatment of anxiety, panic attacks,
emphysema, and the liver, causing cir- and phobias.
rhosis. The effects of alpha1-antitrypsin alprostadil A prostaglandin drug used,
deficiency may not become apparent prior to surgery, to minimize the effects
until after the age of 30. There is no of congenital heart defects in newborn
cure, but symptoms can be relieved by babies. Alprostadil is also used as a
drug treatment. In severe cases, a liver treatment for impotence. It is adminis-
transplant may be a possibility. tered by self-injection into the penis or
as a gel introduced into the urethra to
alpha-blocker drugs A group of drugs produce an erection.
used to treat hypertension (high blood alternative medicine Any medical sys-
pressure) and urinary symptoms due to tem based on a theory of disease or
enlargement of the prostate gland. method of treatment other than the
Alpha-blockers are also used to treat orthodox science of Western medicine.
urinary retention caused by an enlarged (See also complementary medicine.)
prostate gland (see prostate, enlarged). altitude sickness See mountain sickness.
Side effects of the drugs may include aluminium A light, metallic element
dizziness and fatigue due to a sudden found in bauxite and various other min-
drop in blood pressure, nausea, dry erals. Aluminium compounds are used
mouth, and drowsiness. in antacid medications and in antiper-
spirants. Most of the aluminium taken
alpha-fetoprotein A protein that is into the body is excreted. Excessive
produced in the liver and gastrointes- amounts are toxic and are stored in the
tinal tract of the fetus and by some lungs, brain, liver, and thyroid gland,
abnormal tissues in adults. where they may result in organ damage.
Alpha-fetoprotein (AFP) can be meas-
ured in the maternal blood from the Certain industrial processes give off
latter part of the 1st trimester of preg- fumes containing aluminium into the
nancy, and its concentration rises air. These fumes can cause fibrosis of
between the 15th and 20th weeks. lung tissue. Drugs that contain alumin-
Raised levels of AFP are associated with ium may interfere with the absorption
fetal neural tube defects, such as spina of other drugs and, therefore, should
bifida or anencephaly, and certain kid- not be taken at the same time.
ney abnormalities. High levels of AFP alveolectomy See alveoloplasty.
also occur in multiple pregnancies (see alveolitis Inflammation and thickening
pregnancy, multiple) and threatened or of the walls of the alveoli (tiny air sacs)
actual miscarriage. AFP levels may be in the lungs. Alveolitis reduces the elas-
unusually low if the fetus has Down’s ticity, and therefore the efficiency, of the
syndrome. For this reason, measure- lungs. It is most commonly due to an
ment of blood AFP is included in blood allergic reaction to inhaled dust of ani-
tests, which are used to screen preg- mal or plant origin, as in farmer’s lung,
nant women for an increased risk of bagassosis, and pigeon fancier’s lung
Down’s syndrome. (due to particles from bird droppings).
AFP levels are commonly raised in
adults with hepatoma (see liver cancer), Fibrosing alveolitis is an autoimmune
cancerous teratoma of the testes or disorder. In some cases, it occurs with
ovaries, or cancer of the pancreas, other autoimmune disorders such as
stomach, or lung. For this reason, AFP rheumatoid arthritis or systemic lupus
is known as a tumour marker. AFP levels erythematosus. Radiation alveolitis is
can be used to monitor the results of caused by irradiation of the lungs and
treatment of certain cancers; increasing may occur as a rare complication of
levels after surgery or chemotherapy radiotherapy for lung or breast cancer.

23

A ALVEOLOPLASTY AMAUROSIS FUGAX
Alveolitis usually causes a dry cough
and breathing difficulty on exertion. A are responsible for the production of
chest X-ray, blood tests, pulmonary the blood protein apolipoprotein E.
function tests, or a lung biopsy may be These genes also result in the depo-
needed to diagnose alveolitis. sition of a protein called beta amyloid
For most types of alveolitis, a short in the brain. Other chemical abnorm-
course of corticosteroid drugs relieves alities may include deficiency of the
symptoms, but for fibrosing alveolitis neurotransmitter acetylcholine.
these may need to be taken indefinitely.
If the cause of allergic alveolitis is rec- The features of Alzheimer’s disease
ognized and avoided before lung damage vary, but there are 3 broad stages. At
occurs, the effects are not permanent. first, the person becomes increasingly
In fibrosing alveolitis, damage progresses forgetful, and problems with memory
despite treatment, causing increasing may cause anxiety and depression. In
breathing difficulty and, sometimes, the 2nd stage, loss of memory, par-
respiratory failure. ticularly for recent events, gradually
alveoloplasty Dental surgery to remove becomes more severe, and there may
protuberances and smooth out uneven be disorientation as to time or place.
areas from tooth-bearing bone in the The person’s concentration and num-
jaw before the fitting of dentures. erical ability decline, and there is
alveolus, dental The bony cavity or noticeable dysphasia (inability to find
socket supporting each tooth in the jaw. the right word). Anxiety increases,
alveolus, pulmonary One of a large mood changes are unpredictable, and
number of tiny, balloon-like sacs at the personality changes may occur. Finally,
end of a bronchiole (one of many small confusion becomes profound. There
air passages in the lungs) where gases may be symptoms of psychosis, such as
are exchanged during respiration. hallucinations and delusions. Signs of
nervous system disease, such as abnor-
ALVEOLUS, PULMONARY mal reflexes and faecal or urinary
incontinence, begin to develop.
Trachea Thin wall
Pleura of alveolus Alzheimer’s disease is usually diag-
nosed from the symptoms, but tests
Air space including blood tests and CT scanning
or MRI of the brain may be needed to
Blood exclude treatable causes of dementia.
vessel
The most important aspect of treat-
ALVEOLI ment for Alzheimer’s disease is the
Bronchus provision of suitable nursing and social
care for sufferers and support for their
LUNGS Bronchiole relatives. Tranquillizer drugs can often
improve difficult behaviour and help
Alzheimer’s disease A progressive con- with sleep. Treatment with drugs such
dition in which nerve cells in the brain as donepezil and rivastigmine may slow
degenerate and the brain shrinks. Alz- the progress of the disease for a time,
heimer’s disease is the most common but side effects such as nausea and
cause of dementia. Onset is uncommon dizziness may occur.
before the age of 60. amalgam, dental A material, consist-
Early onset Alzheimer's disease, in ing of an alloy of mercury with other
which symptoms develop before age 60, metals, that is used as fillings for teeth
is inherited as a dominant disorder. Late (see filling, dental).
onset Alzheimer's disease is associated amantadine An antiviral drug used in
with a number of genes, including 3 that the prevention and treatment of influ-
enza A and to help relieve symptoms of
Parkinson’s disease.
amaurosis fugax Brief loss of vision,
lasting for seconds or minutes, usually
affecting one eye only and caused by

24

AMBIDEXTERITY AMFETAMINE DRUGS A

the temporary blockage of a small the electrical activity of the heart by
blood vessel in the eye by emboli (parti- means of electrodes attached to the
cles of solid matter such as cholesterol chest. The monitor is usually worn for
or clotted blood). These are carried in 24 hours or longer and detects intermit-
the bloodstream from diseased arteries tent arrhythmias (abnormal heart rates
in the neck or, rarely, the heart. Attacks and rhythms). The wearer can press a
may be infrequent or they may occur button on the monitor to mark the
many times a day. This symptom indi- recording whenever symptoms occur.
cates an increased risk of stroke and The recording can later be analysed
requires medical investigation. to see if the periods of arrhythmia
ambidexterity The ability to perform coincide with the symptoms.
manual skills equally well with either amelogenesis imperfecta An inherited
hand because there is no definite hand- condition of the teeth in which the
edness. Ambidexterity is an uncommon enamel is either abnormally thin or is
and often familial trait. deficient in calcium. Affected teeth may
amblyopia A permanent defect of vis- be pitted and discoloured (see dis-
ual acuity in which there is usually no coloured teeth) and more susceptible to
structural abnormality in the eye. In dental caries (tooth decay) and wear.
many cases, there is a disturbance of amenorrhoea The absence of mens-
the visual pathway between the retina trual periods. Primary amenorrhoea is
and the brain. The term is also some- defined as failure to start menstruating
times applied to toxic or nutritional by the age of 16. Secondary amenor-
causes of decreased visual acuity, as in rhoea is the temporary or permanent
tobacco–alcohol amblyopia. cessation of periods in a woman who
has menstruated regularly in the past.
Amblyopia will develop if there is a
marked discrepancy between the images The main cause of primary amenor-
received by the brain from each eye rhoea is delayed puberty. The delay may
while vision is developing during early not indicate a disorder, but, rarely, it may
childhood. The most common cause is result from a disorder of the endocrine
squint. Failure to form normal retinal system, such as a pituitary tumour,
images may also result from congenital hypothyroidism, an adrenal tumour, or
cataract, and severe, or unequal, focus- adrenal hyperplasia. Another rare cause
ing errors, such as when one eye is of delayed puberty is Turner’s syndrome.
normal and there is an uncorrected In some cases, menstruation fails to
large degree of astigmatism in the other. take place because the vagina or the
Toxic and nutritional amblyopia may uterus has been absent from birth, or
result from damage to the retina and/or because there is no perforation in the
the optic nerve. hymen to allow blood to escape.

To prevent amblyopia due to squint, The most common cause of temporary
patching (covering up the good eye to secondary amenorrhoea is pregnancy.
force the deviating eye to function prop- Periods may also cease temporarily after
erly) is the usual treatment. Surgery to a woman has stopped taking oral con-
place the deviating eye in the correct traceptives. Secondary amenorrhoea may
position may be necessary. Glasses may also result from hormonal changes due
be needed to correct severe focusing to stress, depression, anorexia nervosa,
errors. Cataracts may be removed surgi- or certain drugs. Another possible
cally. After the age of 8, amblyopia cause is a disorder of the ovary such as
cannot usually be remedied. polycystic ovary (see ovary, polycystic)
ambulance A vehicle for transporting or an ovarian tumour. Amenorrhoea
sick or injured people that is staffed by occurs permanently following the meno-
trained personnel who can provide emer- pause or after a hysterectomy.
gency treatment during the journey. amfetamine drugs A group of stimu-
ambulatory ECG In ambulatory ECG lant drugs used mainly in the treatment
(electrocardiography), a wearable device of narcolepsy (a rare disorder character-
called a Holter monitor is used to record ized by excessive sleepiness).

25

A AMILORIDE AMNIOCENTESIS

In high doses, amfetamines can cause amiodarone An antiarrhythmic drug used

tremor, sweating, anxiety, and sleeping in the treatment of various types of

problems. Delusions, hallucinations, high arrhythmia (irregular heartbeat). Long-

blood pressure, and seizures may also term use of amiodarone may result in

occur. Prolonged use may produce tol- inflammation of the liver, thyroid prob-

erance and drug dependence. lems, and eye and lung damage.

Amfetamines are often abused for amitriptyline A tricyclic antidepressant

their stimulant effect. drug with a sedative effect. It is useful

amiloride A potassium-sparing diuretic in the treatment of depression accom-

drug. Combined with loop or thiazide panied by anxiety or insomnia. Possible

diuretics, amiloride is used to treat adverse effects include blurred vision,

hypertension and fluid retention due to dizziness, and drowsiness.

heart failure or cirrhosis of the liver. amlodipine A calcium channel blocker

amino acids A group of chemical com- drug used to prevent angina and to treat

pounds that form the basic structural hypertension. Possible side effects are

units of all proteins. Each amino acid headaches and dizziness.

molecule consists of amino and carboxyl ammonia A colourless, pungent gas that

groups of atoms linked to a variable dissolves in water to form ammonium

chain or ring of carbon atoms. hydroxide, an alkaline solution (see alk-

Individual amino acid molecules are ali). Ammonia is produced in the body

linked together by chemical bonds and helps to maintain the acid–base bal-

called peptide bonds to form short ance. In severe liver damage, the ability

chains of molecules called polypeptides. of the liver to convert ammonia to urea

Hundreds of polypeptides are, in turn, is reduced. This leads to a high level of

linked together, also by peptide bonds, ammonia in the blood, which is thought

to form a protein molecule. What differ- to be a cause of the impaired con-

entiates one protein from another is the sciousness that occurs in liver failure.

sequence of the amino acids. amnesia Loss of ability to memorize

There are 20 different amino acids that information and/or to recall information

make up all the proteins in the body. Of stored in memory. Possible causes of

these, 12 can be made by the body; they amnesia are head injury; degenerative

are known as nonessential amino acids disorders such as Alzheimer’s disease

because they do not need to be ob- and other forms of dementia; infections

tained from the diet. The other 8, known such as encephalitis; thiamine defici-

as the essential amino acids, cannot be ency in alcoholics, leading to Wernicke–

made by the body and must therefore Korsakoff syndrome; brain tumours;

be obtained from the diet. strokes; and subarachnoid haemorrhage.

aminoglutethimide An anticancer drug Amnesia can also occur in some forms

used to treat certain types of breast of psychiatric illness.

cancer, prostate cancer, and some en- In retrograde amnesia, the loss of

docrine gland tumours. memory extends back for some time

aminoglycoside drugs A type of anti- before the onset of the disorder. In

biotic drug. Aminoglycoside drugs are anterograde amnesia, there is an inabil-

given by injection and are generally ity to store new information in the

reserved for the treatment of serious period following the onset of illness.

infections because their use can dam- amniocentesis A diagnostic procedure

age the inner ear or kidneys. Important in which a small amount of amniotic

examples are gentamicin and strepto- fluid is withdrawn, using a syringe and

mycin, which are also used topically for guided by ultrasound scanning, from

eye and ear infections. the amniotic sac that surrounds the

aminophylline A bronchodilator drug fetus in the uterus. This fluid contains

used to treat chronic bronchitis, asthma, fetal cells that can be subjected to

and, occasionally, heart failure. Nausea, chromosome analysis to identify chromo-

vomiting, headache, dizziness, and pal- somal defects such as Down’s syndrome

pitations are possible side effects. or genetic analysis to look for genetic

26

AMNION AMOXICILLIN A

AMNIOCENTESIS Occasionally, excessive fluid is formed
(see polyhydramnios); less frequently,
Syringe Ultrasound insufficient amniotic fluid is formed
probe (see oligohydramnios).
amniotic sac The membranous bag that
Amniotic Ultrasound surrounds the fetus and is filled with
fluid beam amniotic fluid as pregnancy advances.
The sac is made up of 2 membranes, the
Bladder inner amnion and the outer chorion.
amniotomy Artificial rupture of the am-
Fetus niotic membranes (breaking the “waters”)
performed for induction of labour.
Cervix Placenta amoeba A type of protozoon (see proto-
Uterus zoa). An amoeba is a microscopic
single-celled organism with an irregular,
disorders such as haemophilia, cystic changeable shape. Amoebae live in
fibrosis, and Tay–Sachs disease. Chemi- moist environments, such as fresh
cal analysis of amniotic fluid can help water and soil. Some types of amoebae
to diagnose developmental abnorm- are parasites of humans, causing dis-
alities such as spina bifida. Rhesus eases such as amoebiasis.
incompatibility and maturity of the fetal amoebiasis An infection caused by the
lungs can also be checked. amoeba ENTAMOEBA HISTOLYTICA, a tiny
single-celled parasite that lives in the
Amniocentesis is usually performed in human large intestine. Amoebiasis is
the 14th–18th week of pregnancy. It spread through drinking water or eating
slightly increases the risk of miscarriage food contaminated by human excreta
or early rupture of the membranes and is containing cysts of the amoeba.
therefore recommended only when the
fetus is thought to be at increased risk Some people carry the amoeba in their
of an abnormality. (See also antenatal intestines and excrete cysts but have no
care, chorionic villus sampling.) symptoms. However, some strains in-
amnion One of the membranes that vade and ulcerate the intestinal wall,
surrounds the fetus in the uterus. The causing diarrhoea and abdominal pain,
outside of the amnion is covered by which may develop into full-blown
another membrane called the chorion. dysentery. The amoebae may spread via
amniotic fluid The clear, watery fluid the bloodstream to the liver, or, rarely,
(popularly called the “waters”) that sur- the brain or lung, where they cause
rounds the fetus in the uterus. The fluid abscesses. Symptoms of an amoebic
is contained within the amniotic sac. It liver abscess are chills, fever, weight
cushions the fetus, allowing movement. loss, and painful enlargement of the liver.

Amniotic fluid is produced by cells lin- Treatment of all forms of amoebiasis
ing the amniotic sac and is constantly is with drugs such as metronidazole or
circulated. It appears in the 1st week diloxanide, which kill the parasite with-
after conception and gradually in- in a few weeks, leading to full recovery.
creases in volume until the 10th week, amoebic dysentery See amoebiasis.
when the increase becomes very rapid. amoebicides A group of drugs used to
treat amoebiasis. Examples are dilox-
anide, and metronidazole.
amoxapine An antidepressant drug re-
lated to the tricyclics. Possible adverse
effects include blurred vision, dizziness,
drowsiness, abnormal muscular move-
ments, menstrual irregularities, and
breast enlargement.
amoxicillin A penicillin drug commonly
used to treat a variety of infections,

27

A AMOXYCILLIN AMYLOIDOSIS
including bronchitis, cystitis, and ear and
skin infections. Allergy to amoxicillin development of gangrene. Amputation
causes a blotchy rash and, rarely, fever, may also be needed if a limb has been
swelling of the mouth and tongue, itch- irreparably damaged in an accident.
ing, and breathing difficulty.
amoxycillin See amoxicillin. For some time after amputation, there
amphetamine drugs See amfetamine may be an unpleasant sensation that the
drugs. limb is still present, a phenomenon
amphotericin B A drug used to treat known as “phantom limb”. A prosthesis
fungal infections. Lozenges are used for (see limb, artificial) is usually fitted
candidiasis of the mouth. Life-threaten- when the stump has healed.
ing infections, such as cryptococcosis amputation, congenital The separa-
and histoplasmosis, are treated by injec- tion of a body part (usually a limb,
tion. Adverse effects may occur with finger, or toe) from the rest of the body,
injection and include vomiting, fever, as a result of the part’s blood supply
headache, and, rarely, seizures. being blocked by a band of amnion
ampicillin A penicillin drug commonly (fetal membrane) in the uterus. The
used to treat cystitis, bronchitis, and ear affected part may be completely separ-
infections. Diarrhoea is a common ated or show the marks of the “amniotic
adverse effect of ampicillin. Some peo- band” after birth. (See also limb defects.)
ple are allergic to it and suffer from amputation, traumatic Loss of a fin-
rash, fever, swelling of the mouth and ger, toe, or limb through injury. (See
tongue, itching, and breathing difficulty. also microsurgery.)
ampulla An enlarged, flask-shaped area amylase An enzyme found in saliva and
at the end of a tubular structure or pancreatic secretions (see pancreas). It
canal. There are several ampullae in the helps to digest dietary starch, breaking
body, including at the end of the fallo- it down into smaller components such
pian tubes, at the opening of the bile as the sugars glucose and maltose.
duct into the intestine, and on each of amyl nitrite A nitrate drug formerly pre-
the semicircular canals of the inner ear. scribed to relieve angina. Because amyl
nitrite frequently causes adverse effects,
AMPULLA Cochlea it has been superseded by other drugs. It
is sometimes abused for its effect of
Semicircular canal intensifying pleasure during orgasm.
Ampulla amyloidosis An uncommon disease in
which a substance called amyloid, com-
Outer Middle Inner posed of fibrous protein, accumulates
ear ear ear in tissues and organs, including the
liver, kidneys, tongue, spleen, and heart.
INNER EAR Amyloidosis may occur for no known
Cochlea reason, in which case it is called primary;
more commonly, it is a complication of
LOCATION some other disease, and in such cases
it is called secondary. Conditions that
amputation Surgical removal of part or may lead to amyloidosis include multi-
all of a limb. Amputation is necessary if ple myeloma (a cancer of bone marrow),
peripheral vascular disease as a result of rheumatoid arthritis, tuberculosis, and
atherosclerosis or diabetes mellitus has some other longstanding infections,
impaired the blood supply to a limb. If such as chronic osteomyelitis.
blood supply cannot be restored, ampu-
tation is carried out to prevent the The symptoms of amyloidosis vary,
depending on the organs affected and
the duration of the condition. Deposits
of amyloid in the kidneys may cause
kidney failure, which may be fatal.

There is no treatment, but secondary
amyloidosis can be halted if the under-
lying disorder is treated.

28

AMYOTROPHIC LATERAL SCLEROSIS ANAEMIA, HAEMOLYTIC A

amyotrophic lateral sclerosis See are all reduced in number. Aplastic
motor neuron disease. anaemia is caused by a failure of the
bone marrow to produce stem cells, the
amyotrophy Shrinkage or wasting away initial form of all blood cells.
of a muscle, leading to weakness. Amy-
otrophy is usually due to poor nutrition, Treatment of cancer with radiotherapy
reduced use of the muscle (as when a or anticancer drugs can temporarily
limb is immobilized for a long period), interfere with the cell-producing ability
or disruption of the blood or nerve sup- of bone marrow, as can certain viral
ply to the muscle (as can occur in infections and other drugs. Long-term
diabetes mellitus or poliomyelitis). exposure to insecticides or benzene
fumes may cause more persistent aplas-
anabolic steroids See steroids, anabolic. tic anaemia, and a moderate to high
anabolism The manufacture of complex dose of nuclear radiation is another
recognized cause. An autoimmune dis-
molecules, such as fats and proteins, order is responsible in about half of
from simpler molecules by metabolic all cases. Aplastic anaemia sometimes
processes in living cells. (See also develops for no known reason.
catabolism; metabolism.)
anaemia A condition in which the con- A low level of red blood cells may
centration of the oxygen-carrying pigment cause symptoms common to all types
haemoglobin in the blood is below nor- of anaemia, such as fatigue and breath-
mal. Haemoglobin molecules are carried lessness. White-cell deficiency increases
inside red blood cells and transport susceptibility to infections; platelet defi-
oxygen from the lungs to the tissues. ciency may lead to a tendency to bruise
Normally, stable haemoglobin concen- easily, bleeding gums, and nosebleeds.
trations in the blood are maintained by
a balance between red-cell production The disorder is usually suspected from
in the bone marrow and red-cell des- blood-test results, particularly a blood
truction in the spleen. Anaemia may count, and is confirmed by a bone marrow
result if this balance is upset. biopsy. Blood and platelet transfusions
can control symptoms. Immunosuppres-
Anaemia is not a disease but a feature sion is used to treat anaemia due to an
of many different disorders. There are autoimmune process. Severe persistent
various types, which can be classified aplastic anaemia may be fatal unless a
into those due to decreased or defective bone marrow transplant is carried out.
red-cell production by bone marrow (see anaemia, haemolytic A form of anaemia
anaemia, aplastic; anaemia, megaloblastic; caused by premature destruction of red
anaemia, iron-deficiency) and those due cells in the bloodstream (haemolysis).
to decreased survival of the red cells in Haemolytic anaemias can be classified
the blood (see anaemia, haemolytic). according to whether the cause of haem-
olysis is inside or outside the red cells.
The severity of symptoms depends on
how low the haemoglobin concentra- When haemolysis is due to a defect
tion has become. Slightly reduced inside the red cells, the underlying
levels can cause headaches, tiredness, problem is abnormal rigidity of the cell
and lethargy. Severely reduced levels membrane. This causes the cells to
can cause breathing difficulty on exer- become trapped, at an early stage of
cise, dizziness, angina, and palpitations. their life-span, in the small blood vessels
General signs include pallor, particular- of the spleen, where they are destroyed
ly of the skin creases, the lining of the by macrophages (cells that ingest for-
mouth, and the inside of the eyelids. eign particles). Abnormal rigidity may
result from an inherited defect of the
Anaemia is diagnosed from the symp- cell membrane (as in hereditary sphero-
toms and by blood tests (see blood cytosis), a defect of the haemoglobin in
count; blood film). A bone marrow biop- the cell (as in sickle-cell anaemia), or a
sy may be needed if the problem is with defect of one of the cell’s enzymes. An
red blood cell production. inherited deficiency of the glucose-6-
anaemia, aplastic A rare but serious phosphate dehydrogenase enzyme (see
type of anaemia in which the red cells,
white cells, and platelets in the blood

29

A ANAEMIA, IRON-DEFICIENCY ANAEMIA, MEGALOBLASTIC

G6PD deficiency) may result in episodes drugs (NSAIDs) can cause gastrointes-

of haemolytic anaemia since the red tinal bleeding. In some countries, hook-

cells are prone to damage by infectious worm infestation of the digestive tract is

illness or certain drugs or foods. an important cause of anaemia. Rarely,

Haemolytic anaemias due to defects bleeding may also occur as a result of

outside the red cells fall into 3 main disorders of the urinary tract (such as

groups. First are disorders in which red kidney tumours or bladder tumours).

cells are destroyed by buffeting (by arti- Iron deficiency may also be caused or

ficial surfaces such as replacement heart worsened by lack of iron in, or its poor

valves, abnormal blood-vessel linings, or absorption from, the diet.

a blood clot in a vessel, for example). In The symptoms are those of the under-

the 2nd group, the red cells are des- lying cause, along with a sore mouth or

troyed by the immune system. Immune tongue, and those common to all forms

haemolytic anaemias may occur if for- of anaemia, such as fatigue and breath-

eign blood cells enter the bloodstream, lessness. The diagnosis is made from

as occurs in an incompatible blood blood tests and tests to look for an

transfusion, or they may be due to an underlying cause. Treatment is given for

autoimmune disorder. In haemolytic dis- the cause, along with a course of iron

ease of the newborn, the baby’s red cells tablets or, very rarely, injections.

are destroyed by the mother’s antibodies anaemia, megaloblastic An important

crossing the placenta. Thirdly, the red type of anaemia caused by a deficiency

cells may be destroyed by microorgan- of vitamin B12 or another vitamin, folic
isms; the most common cause is malaria. acid. Either of these deficiencies seri-

People with haemolytic anaemia may ously interferes with production of red

have symptoms common to all types of blood cells in the bone marrow. An

anaemia, such as fatigue and breathless- excess of cells called megaloblasts ap-

ness, or symptoms specifically due to pears in the marrow. Megaloblasts give

haemolysis, such as jaundice. rise to enlarged and deformed red

Diagnosis is made by examination of blood cells known as macrocytes.

the blood (see blood film). Some inher- Vitamin B12 is found only in foods of
ited anaemias can be controlled by animal origin, such as meat and dairy

removing the spleen (see splenectomy). products. It is absorbed from the small

Others, such as G6PD deficiency, can intestine after first combining with

be prevented by avoiding the drugs intrinsic factor, a chemical produced by

or foods that precipitate haemolysis. the stomach lining. The most common

Anaemias due to immune processes cause of vitamin B12 deficiency is failure
can often be controlled by immunosup- of the stomach lining to produce intrin-

pressant drugs. Transfusions of red cells sic factor, usually due to an autoimmune

are sometimes needed for emergency disorder; this is called pernicious anae-

treatment of life-threatening anaemia. mia. Total gastrectomy (removal of the

anaemia, iron-deficiency The most stomach) prevents production of intrin-

common form of anaemia caused by a sic factor, and removal of part of the

deficiency of iron, an essential constit- small intestine prevents B12 absorption,
uent of haemoglobin. The main cause of as does the intestinal disorder Crohn’s

iron-deficiency anaemia is iron loss due disease. In a minority of cases, vitamin

to heavy or persistent bleeding; the most B12 deficiency is due to a vegan diet.
common cause in women of childbear- Folic acid is found mainly in green

ing age is menstruation. Other causes vegetables and liver. The usual cause of

include blood loss from the digestive deficiency is a poor diet. Deficiency can

tract due to disorders such as erosive also be caused by anything that inter-

gastritis, peptic ulcer, stomach cancer, feres with the absorption of folic acid

inflammatory bowel disease, haemor- from the small intestine (for example

rhoids, and bowel tumours (see colon, Crohn’s disease or coeliac disease). Folic

cancer of). Prolonged use of aspirin acid requirements are greater than nor-

and other nonsteroidal anti-inflammatory mal in pregnancy.

30

ANAEMIA, PERNICIOUS ANAESTHESIA, GENERAL A

Many people with mild megaloblastic waste (instead of the carbon dioxide
anaemia have no symptoms. Others from aerobic activity), sometimes causing
may experience tiredness, headaches, a muscle fatigue and pain.
sore mouth and tongue, and mild jaun- anaesthesia Absence of all sensation;
dice. If B12 deficiency continues for a insensibility. The term most commonly
long time, additional symptoms due to refers to anaesthesia that is induced
nerve damage, including numbness and artificially for medical purposes. Two
tingling in the feet, may develop. types of anaesthesia are used: local
(see anaesthesia, local) and general (see
Megaloblastic anaemia is diagnosed anaesthesia, general).
by blood tests and a bone marrow biopsy.
Megaloblastic anaemia due to poor diet Damage to nerve tissues by injury or
can be remedied with a short course of disease can produce anaesthesia in a
vitamin B12 injections or folic acid tab- localized area.
lets and the introduction of a normal anaesthesia, dental Loss of sensation
diet. A lifelong course of vitamin B12 induced in a patient to prevent pain
injections or folic acid tablets is during dental treatment.
required if the underlying cause of mal-
absorption is untreatable. For minor procedures, a local anaes-
anaemia, pernicious See anaemia, meg- thetic (see anaesthesia, local) is injected
aloblastic. either into the gum at the site being
anaerobic Capable of living, function- treated or into the nerve a short dis-
ing, and growing without oxygen. Many tance away (called a peripheral nerve
bacteria are anaerobic. Some human block). In addition, topical anaesthetics
body cells are capable of limited anaer- are often used on the gums. For more
obic activity. When muscular exertion is complicated procedures, such as perio-
so strenuous that oxygen is used faster dontal (gum) surgery and multiple
than the blood circulation can supply it, tooth extractions, general anaesthesia
such as during sprinting, muscle cells is carried out (see anaesthesia, general).
temporarily work anaerobically. When anaesthesia, general Loss of sensation
this happens, lactic acid is produced as and consciousness induced to prevent
the perception of pain throughout the

ANAESTHESIA, GENERAL Monitor displays heart-
rate, blood pressure, and
Flow, concentration, and oxygen levels in blood
mixture of gases are regulated
by anaesthetic machine

Endotracheal tube Anaesthetist
delivers gases to patient records vital signs
and drugs used
ECG leads on the
chest connect to monitor

31

A ANAESTHESIA, LOCAL ANALGESIC DRUGS

body during surgery. General anaesth- Reflex anal dilatation, in which the anus

esia is usually induced by intravenous dilates in response to local contact,

injection of a barbiturate drug and may occur in certain anal disorders or

maintained by inhalation of anaesthetic after repeated anal penetration.

gases such as halothane, which may be anal discharge The loss of mucus, pus,

introduced into the lungs via an endo- or blood from the anus. Haemorrhoids,

tracheal tube. During the anaesthetic, anal fissures, and proctitis (inflam-

the pulse, blood pressure, and other mation of the rectum) can all cause

vital signs are continuously monitored. anal discharge.

General anaesthetics have become analeptic drugs Drugs that stimulate

much safer, and serious complications breathing. Replaced by ventilation, they

are rare. However, severe pre-existing are seldom used now.

diseases such as lung or heart disorders anal fissure A common anal disorder

increase the risks. Minor after effects such caused by an elongated ulcer or tear

as nausea and vomiting are usually con- that extends upwards into the anal

trolled effectively with antiemetic drugs. canal from the anal sphincter. A fissure

anaesthesia, local Loss of sensation may be caused by the passage of hard,

induced in a limited region of the body dry faeces. There is usually pain during

to prevent pain during examinations, defaecation and the muscles of the

diagnostic or treatment procedures, and anus may go into spasm. There may be

surgical operations. Local anaesthesia a small amount of bright red blood on

is produced by the administration of faeces or toilet paper.

drugs that temporarily interrupt the The tear often heals naturally over a

action of pain-carrying nerve fibres. few days. Treatment of recurrent or per-

Local anaesthetics applied topically sistent fissures is by anal dilatation and

before injections or blood tests include a high-fibre diet, which helps soften the

sprays and skin creams and ointments. faeces. Surgery to remove the fissure is

These are often used for children. For occasionally necessary.

minor surgical procedures, such as anal fistula An abnormal channel con-

stitching of small wounds, local anaes- necting the inside of the anal canal with

thesia is usually produced by direct the skin surrounding the anus.

injection into the area to be treated. To An anal fistula may be an indication of

anaesthetize a large area, or when local Crohn’s disease, colitis, or cancer of the

injection would not penetrate deeply colon or rectum (see colon, cancer of;

enough into body tissues, a nerve block rectum, cancer of). In most cases, it

may be used. Nerves can also be results from an abscess that develops

blocked where they branch off from the for unknown reasons in the anal wall.

spinal cord, as in epidural anaesthesia, The abscess discharges pus into the anus

which is widely used in childbirth, and and out on to the surrounding skin.

spinal anaesthesia, which is used for An anal fistula is treated surgically

surgery on the lower limbs and abdomen. by opening the abnormal channel and

Serious reactions to local anaesthetics removing the lining. The wound is then

are uncommon. Repeated use of topical left to heal naturally.

preparations may cause allergic rashes. analgesia Loss or reduction of pain

anaesthetics A term for the group of sensation. Analgesia differs from anaes-

drugs that produce anaesthesia and for thesia in that sensitivity to touch is still

the medical discipline concerned with preserved. (See also analgesic drugs.)

their administration. analgesic drugs Drugs used to relieve

anal dilatation A procedure for enlarg- pain. The 2 main types are nonopioid

ing the anus. Anal dilatation is used to and opioid. Nonopioid analgesics,

treat conditions in which the anus be- which include aspirin, paracetamol, and

comes too tight, such as anal stenosis nonsteroidal anti-inflammatory drugs

and anal fissure. It is also used to treat (NSAIDs), are useful in the treatment of

haemorrhoids. Anal dilatation is usually mild to moderate pain (for example,

performed under general anaesthesia. headache or toothache). Combinations

32

ANAL STENOSIS ANDROGEN DRUGS A

of a weak opioid analgesic, such as adrenaline may be life-saving. Antihis-
codeine, with a nonopioid analgesic tamine drugs and corticosteroid drugs
relieve more severe pain. Potent opioids may also be given.
such as morphine are used only when anastomosis A natural or artificial
other preparations would be ineffective communication between 2 blood ves-
because they can produce tolerance sels or tubular cavities that may or may
and drug dependence. not normally be joined. Natural anasto-
moses usually occur when small arteries
Adverse effects are uncommon with are attached directly to veins without
paracetamol. Aspirin and NSAIDs may passing through capillaries. They occur
irritate the stomach lining and cause in the skin and are used to help control
nausea, abdominal pain, and, rarely, a temperature regulation. Surgical anas-
peptic ulcer. Nausea, drowsiness, con- tomoses are used to create a bypass
stipation, and breathing difficulties may around a blockage in an artery or in the
occur with opioid analgesics. intestine. They are also used to rejoin
anal stenosis A tightness of the anus, cut ends of the bowel or blood vessels.
sometimes referred to as anal stricture. (See also bypass surgery.)
Anal stenosis prevents the normal pas- anatomy The structure of the body of
sage of faeces, causing constipation and any living thing, and its scientific study.
pain during defaecation. The condition Human anatomy, together with physiol-
may be present from birth, or may be ogy (the study of the functioning of the
caused by a number of conditions in body), forms the foundation of medical
which scarring has occurred, such as science. Anatomy is subdivided into
anal fissure, colitis, or cancer of the anus. many branches. These include compara-
Anal stenosis sometimes occurs after tive anatomy (the study of the differences
surgery on the anus (for example, to between human and animal bodies),
treat haemorrhoids). The condition is surgical anatomy (the practical know-
treated by anal dilatation. ledge required by surgeons), embryology
anal stricture See anal stenosis. (the study of structural changes that
anal tag A type of skin tag. occur during the development of the
analysis, chemical Determination of embryo and fetus), systematic anatomy
the identity of a substance or of the (the study of the structure of particular
individual chemical constituents of a body systems), and cytology and histol-
mixture. Analysis may be qualitative, as ogy (the microscopic study of cells and
in determining whether a particular tissues respectively).
substance is present, or it may be quan- ancylostomiasis See hookworm infes-
titative, that is, measuring the amount tation.
or concentration of one or more consti- androgen drugs Natural or synthetic
tuents. (See also assay.) androgen hormones used as drugs; one
analysis, psychological See psycho- of the most important is testosterone.
analysis. These drugs are used in the treatment
anaphylactic shock A rare, life-threat- of male hypogonadism (underactivity of
ening allergic reaction that occurs in the testes) to stimulate the development
people with an extreme sensitivity to a of sexual characteristics.
particular substance (allergen), often in-
sect venom, a food item, or a drug (see Androgen drugs are occasionally used
allergy). When the allergen enters the to treat certain types of breast cancer.
bloodstream, massive amounts of hista- They have been widely used by sports-
mine and other chemicals are released, men wishing to increase muscle bulk
causing sudden, severe lowering of and strength, a practice that is danger-
blood pressure and constriction of the ous to health (see steroids, anabolic).
airways. Other symptoms may include
abdominal pain, diarrhoea, swelling of Adverse effects include fluid retention,
the tongue and throat, and itchy rash. weight gain, increased blood cholesterol,
and, rarely, liver damage. When taken by
Anaphylactic shock requires emerg- women, the drugs can cause male char-
ency medical treatment. An injection of acteristics, such as facial hair, to develop.

33

A ANDROGEN HORMONES ANEURYSM

androgen hormones A group of hor- alpha-fetoprotein, by ultrasound scan-

mones that stimulate the development ning, by amniocentesis, or by fetoscopy;

of male sexual characteristics. if anencephaly is detected, termination

Androgens are produced by special- of the pregnancy may be considered.

ized cells in the testes in males and in Anencephaly is due to a failure in the

the adrenal glands in both sexes. The development of the neural tube, which

ovaries secrete very small quantities of is the nerve tissue in the embryo that

androgens until the menopause. The normally develops into the spinal cord

most active androgen is testosterone, and brain. (See also neural tube defects.)

which is produced in the testes. The aneurysm Abnormal dilation (balloon-

production of androgens by the testes ing) of an artery caused by the pressure

is controlled by certain pituitary hor- of blood flowing through a weakened

mones, called gonadotrophins. Adrenal area. Aneurysms most commonly affect

androgens are controlled by ACTH, the aorta and arteries supplying the brain.

another pituitary hormone. The most common cause of an aneu-

Androgens stimulate male secondary rysm is atherosclerosis, a condition in

sexual characteristics at puberty, such which fatty deposits weaken the artery

as the growth of facial hair and deepen- wall. The aorta is the usual site of

ing of the voice. They have an anabolic atherosclerotic aneurysms.

effect (they raise the rate of protein syn- Less commonly, aneurysms may be

thesis and lower the rate at which it is due to a congenital weakness of the

broken down). This increases muscle artery walls. Most cerebral aneurysms,

bulk and accelerates growth. At the end known as berry aneurysms because of

of puberty, androgens cause the long their appearance, are congenital. Mar-

bones to stop growing. They stimulate fan’s syndrome, an inherited disorder in

sebum secretion, which, if excessive, which the muscular layer of the aorta

causes acne. In early adult life, andro- is defective, is often associated with

gens promote male-pattern baldness. aneurysms just above the heart. The

Androgen deficiency may occur if the arterial wall can ANEURYSM
testes are diseased or if the pituitary also be weakened

gland fails to secrete gonadotrophins. by inflammation, Weakened, bulging
Typical effects include decreased body as occurs in poly- artery wall
and facial hair, a high-pitched voice, arteritis nodosa.

underdevelopment of the genitalia, and Most aneurysms

poor muscle development. are symptomless

Overproduction of androgens may be and remain un-

the result of adrenal disorders (see detected, but if

adrenal tumours; adrenal hyperplasia, the aneurysm ex-

congenital), of testicular tumours (see pands rapidly and

testis, cancer of), or, rarely, of androgen- causes pain, or it

secreting ovarian tumours (see ovary, is very large, the

cancer of). In men, excess androgens symptoms are due

accentuate male characteristics; in boys, to pressure on Fatty
they cause premature sexual develop- nearby structures. deposit

ment. In women, excess androgens cause Aneurysms may

virilization, the development of mascu- eventually rupture, cause fatal blood

line features such as an increase in loss, or, in the case of a cerebral

body hair, deepening of the voice, cli- aneurysm, loss of consciousness (see

toral enlargement, and amenorrhoea. subarachnoid haemorrhage).

anencephaly Absence of the brain and In some cases, only the inner layer of

cranial vault (top of the skull) at birth. the artery wall ruptures, which allows

Most infants with anencephaly are still- blood to track along the length of the

born or survive only a few hours. artery and block any branching arteries.

Anencephaly is detectable early in preg- There is usually severe pain and high

nancy by measurement of the maternal risk of rupture occurring.

34

ANGINA ANGIOGRAPHY A

Aneurysms sometimes develop in the To help control the symptoms, it is
heart wall due to weakening of an area important to stop smoking and to lose
of heart muscle as a result of myocar- weight if necessary. Attacks of angina
dial infarction. Such aneurysms seldom pectoris may be prevented and treated
rupture but interfere with the pumping by nitrate drugs. However, if nitrates are
action of the heart. not effective or are causing side effects,
beta-blocker drugs or calcium channel
Aneurysms of the aorta may be detec- blockers may be used.
ted by ultrasound scanning, and cerebral
aneurysms by CT scanning or MRI. Angi- Drug treatment can control the symp-
ography provides information on all toms for many years. If attacks become
types of aneurysm. Ruptured or enlarged more severe or more frequent, despite
aneurysms require immediate surgery treatment, coronary artery bypass sur-
(see arterial reconstructive surgery). gery or angioplasty may be necessary.
angina A strangling or constrictive pain. angioedema A type of reaction caused
Angina has become synonymous with by allergy. Angioedema is characterized
the heart disorder angina pectoris. Other by large, well-defined swellings, of sud-
types of angina include abdominal angi- den onset, in the skin, larynx (voice-
na (abdominal pain after eating caused box), and other areas.
by poor blood supply to the intestines)
and Vincent’s angina, pain caused by The most common cause is a sudden
inflammation of the mouth (see Vin- allergic reaction to a food. Less common-
cent’s disease). ly, it results from allergy to a drug (such
angina pectoris Pain in the chest due as penicillin), a reaction to an insect bite
to insufficient oxygen being carried to the or sting, or from infection, emotional
heart muscle in the blood. stress, or exposure to animals, moulds,
pollens, or cold conditions. There is
Inadequate blood supply to the heart also a hereditary form of the disease.
is usually due to coronary artery dis-
ease. Other causes include coronary Angioedema may cause sudden diffi-
artery spasm, in which the blood ves- culty in breathing, swallowing, and
sels narrow suddenly for a short time, speaking, accompanied by swelling of
aortic stenosis, in which the aortic valve the lips, face, and neck, depending on
in the heart is narrowed, and arrhyth- the area of the body affected. Angio-
mias. If the pain of angina pectoris edema that affects the throat and the
continues, it may be due to myocardial larynx is potentially life-threatening
infarction. Rare causes include severe because the swelling can block the air-
anaemia and polycythaemia, which thick- way, causing asphyxia.
ens the blood, causing its flow through
the heart muscle to slow. Severe cases are treated with injections
of adrenaline (epinephrine) and may re-
The pain usually starts in the centre of quire intubation (passage of a breathing
the chest but can spread to the throat, tube via the mouth into the windpipe)
upper jaw, back, and arms (usually the or tracheostomy (surgical creation of a
left one) or between the shoulder- hole in the windpipe) to prevent suffo-
blades. The pain usually comes on cation. Corticosteroid drugs may also be
when the heart is working harder and given. In less severe cases, antihistamine
requires more oxygen, for example dur- drugs may relieve symptoms.
ing exercise. Angina developing during angiogenesis The growth of new blood
sleep or without provocation is known vessels. Angiogenesis is the process
as unstable angina. Other symptoms that enables tumours to grow; cancer-
may include nausea, sweating, dizzi- ous cells produce chemicals (called
ness, and breathing difficulty. growth factors) that stimulate new
blood vessels to form near the tumour,
Diagnostic tests usually include an supplying it with nutrients.
ECG, which may register normal be- angiography An imaging procedure
tween attacks, and a cardiac stress test. that enables blood vessels to be seen
Blood tests and coronary angiography clearly on X-ray film following the injec-
may also be performed. tion of a contrast medium (a substance

35

A ANGIOMA ANHEDONIA

that is opaque to X-rays). Angiography in the affected vessel, requiring repeat

is used to detect conditions that alter treatment. Angioplasty of peripheral ves-

the appearance of blood vessels, such sels is most successful in treating the

as aneurysm, and narrowing or blockage iliac and femoral arteries in the legs.

of blood vessels by atherosclerosis, or by angiotensin The name of 2 related pro-

a thrombus or embolus. It is also used to teins involved in regulating blood

detect changes in the pattern of blood pressure. The 1st, angiotensin I, is inac-

vessels that supply organs injured or tive and is formed when renin, which is

affected by a tumour. produced by the kidneys, acts on the

Carotid angiography (of the arteries in substance angiotensinogen. Angioten-

the neck) may be used to investigate sin I is then converted to the second,

transient ischaemic attacks. Cerebral ang- active, form, angiotensin II, by angio-

iography can be used to detect an tensin-converting enzyme. Angiotensin II

aneurysm in the brain or pinpoint the causes narrowing of the small blood

position of a brain tumour. Coronary vessels in tissues, resulting in increased

angiography, often combined with car- blood pressure. It also stimulates re-

diac catheterization, can identify the lease (from the adrenal cortex, the outer

sites of narrowing or blockage in coron- part of each adrenal gland) of the hor-

ary artery disease. Digital subtraction mone aldosterone, which also increases

angiography uses computer techniques blood pressure.

to process images and remove unwant- Certain kidney disorders can increase

ed background information. the production of angiotensin II, caus-

Angiographic techniques have been ing hypertension. Whatever the cause of

adapted to allow certain treatments that, hypertension, it may be treated with

in some cases, eliminate the need for drugs called ACE inhibitors, which work

surgery (see angioplasty, balloon; embol- by reducing angiotensin II formation.

ization). (See also aortography.) angiotensin converting enzyme A

angioma A noncancerous tumour made substance that converts angiotensin I to

up of blood vessels (see haemangioma) its active form, angiotensin II. Drugs

or lymph vessels (see lymphangioma). that reduce the action of this enzyme

angioplasty, balloon A technique for are known as ACE inhibitor drugs and

treating a narrowed or blocked section are used in the treatment of hyperten-

of blood vessel by introducing a catheter sion and heart failure.

with a balloon into the constricted area. angiotensin II antagonists A group

The balloon is inflated to widen the nar- of drugs used in the treatment of hyper-

rowed area, deflated again, and then tension (high blood pressure). They

removed. Balloon angioplasty is used to have a similar action to ACE inhibitors

restore blood flow in peripheral vascular but do not cause a dry cough. Examples

disease and coronary artery disease. are losartan and valsartan.

Coronary balloon angioplasty is usually anhedonia Total loss of the feeling

successful, but the narrowing may recur of pleasure from activities that would

ANGIOPLASTY, BALLOON

Artery wall Deflated Narrowed Inflated balloon Compressed
Catheter balloon area fatty deposit

BALLOON IN POSITION BALLOON INFLATED

36

ANHIDROSIS ANOREXIA NERVOSA A

normally give pleasure. Anhedonia is The cause of ankylosing spondylitis is
usually unknown, but in some cases the
often a symptom of depression. disease may be associated with colitis
(inflammation of the colon) or psoriasis
anhidrosis Complete absence of sweat- (a skin disease). Ankylosing spondylitis
may run in families; and about 90 per-
ing. (See also hypohidrosis.) cent of people with the condition have
the genetically determined histocompat-
animal experimentation The use of ibility antigen (HLA-B27).

animals in research to provide informa- Ankylosing spondylitis usually starts
with pain and stiffness in the hips and
tion about animal biology or, by infer- lower back, which are worse after rest-
ing and are especially noticeable in the
ence, human physiology or behaviour. early morning Other, less common, symp-
toms include chest pain, painful heels
Animal research has contributed to the due to additional bone formation, and
redness and pain in the eyes due to iri-
development of drugs, such as vaccines, tis. In time, inflammation in the spine
can lead to ankylosis (permanent stiff-
and surgical techniques, such as trans- ness and limited movement) and kyphosis
(curvature of the spine).
plant surgery. However, because of
The condition is diagnosed by X-rays
ethical concerns, alternative practices, and blood tests. There is no cure but
treatment with exercises, physiotherapy,
such as cell cultures, are now used and anti-inflammatory drugs can reduce
the pain and limitation of movement.
wherever possible. ankylosis Complete loss of movement
in a joint caused by fusion of the bony
animals, diseases from See zoonosis. surfaces. Ankylosis may be due to de-
generation as a result of inflammation,
anisometropia Unequal focusing power infection, or injury, or be produced sur-
gically by surgery to fuse a diseased
in the 2 eyes, usually due to a difference joint to correct deformity or to alleviate
persistent pain (see arthrodesis).
in size and/or shape of the eyes, that anodontia Failure of some or all of the
teeth to develop. It may be due to
causes visual discomfort. For example, absence of tooth buds at birth or the
result of damage to developing tooth
one eye may be normal and the other buds by infection or other widespread
disease. If only a few teeth are missing,
affected by myopia (shortsightedness), a bridge can fill the gap; if all the teeth
are missing, a denture is needed.
hypermetropia (longsightedness), or anomaly A deviation from what is ac-
cepted as normal, especially a birth
astigmatism (uneven curvature of the defect such as a limb malformation.
anorexia The medical term for loss of
cornea). Glasses or contact lenses cor- appetite (see appetite, loss of).
anorexia nervosa An eating disorder
rect the problem in most cases. characterized by severe weight loss and
altered self-image that leads sufferers
ankle joint The hinge joint between the to believe they are fat when they are,
in fact, dangerously underweight. Anor-
foot and the leg. The talus (uppermost exia nervosa most often affects teenage
girls and young women, but the inci-
bone in the foot) fits between the 2 bony dence in young men is rising.

protuberances formed by the lower ends

ANKLE JOINT of the tibia (the
shinbone) and the

fibula (the outer

Tibia bone of the lower
Fibula leg). Strong liga-
ments on either

Ankle joint side of the ankle

Talus joint give it sup-

port. The ankle

Calcaneous allows for up-and-

down movement

of the foot.

An ankle sprain is

one of the most

common injuries. It is usually caused by

twisting the foot over on to its outside

edge, causing overstretching and bruis-

ing of the ligaments. Violent twisting of

the ankle can cause a combined fracture

and dislocation known as Pott’s fracture.

ankylosing spondylitis An uncommon

inflammatory disease affecting joints

between the vertebrae of the spine and

the sacroiliac joints (joints between the

spine and pelvis).

37

A ANORGASMIA ANTHRACOSIS

The causes of anorexia are unclear, but but these effects may be avoided if a

the condition may be linked to a lack of preparation contains both ingredients.

self-worth that leads to excessive con- Antacids interfere with the absorption

cern over physical appearance. Normal of many drugs and should not be taken

dieting may develop into starvation. at the same time as other drugs.

In the early stages, sufferers may be antagonist Having an opposing effect.

overactive and exercise excessively. For example, antagonist drugs counter-

They are obsessed with food, and often act the effects of naturally occurring

make complicated meals for their fami- chemicals in the body. (see also agonist.)

lies, but are reluctant to eat socially and antenatal care The care of a pregnant

manage to avoid eating the meals woman and her unborn baby through-

themselves. As weight loss continues, out a pregnancy. Such care involves

they become tired and weak, the skin regular visits to a doctor or midwife,

becomes dry, lanugo hair (fine, downy who performs abdominal examinations,

hair) grows on the body, and normal blood and urine tests, and monitoring

hair becomes thinner. Starvation leads of blood pressure and fetal growth to

to amenorrhoea in many women. Some detect disease or potential problems.

anorexics sometimes make themselves Ultrasound scanning is carried out to

vomit or take laxative drugs or diuretic identify abnormalities in the fetus. Chori-

drugs to promote weight loss (see onic villus sampling or amniocentesis

bulimia). Chemical imbalances as a may be performed if the baby is thought

result of starvation with or without to be at increased risk of a chromosomal

vomiting can cause potentially fatal car- abnormality or a genetic disorder. The

diac arrhythmias. woman is also advised on general asp-

Hospital treatment is often necessary ects of pregnancy, such as diet, exercise,

and is usually based on a closely con- techniques to help her with childbirth.

trolled feeding programme, combined (See also childbirth, natural.)

with psychotherapy or family therapy. antepartum haemorrhage Bleeding

For some people, antidepressant drugs from the vagina after the 28th week of

may be helpful. Many sufferers relapse pregnancy. Antepartum haemorrhage is

after treatment, and long-term psycho- most commonly due to a problem with

therapy is required. the placenta, such as placenta praevia

anorgasmia Inability to achieve orgasm or placental abruption. Bleeding can

(see orgasm, lack of). also be caused by cervical erosion or

anosmia Loss of the sense of smell. other disorders of the cervix or vagina.

anoxia A complete absence of oxygen Admission to hospital is necessary for

in a body tissue. Anoxia causes disrup- investigation and treatment. Ultrasound

tion of cell metabolism and cell death scanning is used to diagnose problems

unless corrected within a few minutes. with the placenta. If the bleeding is

Anoxia occurs during cardiopulmonary severe, the woman is given a blood

arrest or asphyxiation and will cause transfusion, and the baby is delivered

permanent organ damage or even death immediately by caesarean section.

if not corrected. (See also hypoxia.) anterior Relating to the front of the

antacid drugs Drugs taken to relieve body. In human anatomy, the term is

the symptoms of indigestion, heartburn, synonymous with ventral.

oesophagitis, acid reflux, and peptic ulcer. anthelmintic drugs A group of drugs

Antacids usually contain compounds of that are used to eradicate worm infes-

magnesium or aluminium, which neutra- tations. Possible side effects include

lize stomach acid. Some also contain nausea, abdominal pain, rash, head-

alginates, which protect the lining of ache, and dizziness.

the oesophagus from stomach acid, or anthracosis An outdated term for coal

dimeticone, an antifoaming agent, which worker’s pneumoconiosis. Anthracosis is

helps to relieve flatulence. a lung disease caused by the inhalation

Aluminium may cause constipation of large amounts of coal dust over a

and magnesium may cause diarrhoea; period of many years.

38

ANTHRAX ANTIBODY A

anthrax A serious bacterial infection of A number of drugs are used to prevent
livestock that occasionally spreads to intermittent arrhythmias or to slow the
humans. In humans, the most common rate if an arrhythmia is persistent. These
form of the infection is cutaneous include amiodarone, beta-blocker drugs,
anthrax, which affects the skin. Another calcium channel blockers, digitalis drugs,
form, pulmonary anthrax, affects the disopyramide, flecainide, lidocaine (ligno-
lungs. Anthrax is caused by BACILLUS caine), mexiletine, and procainamide.
ANTHRACIS. This microorganism produ- Side effects are common and often
ces spores that can remain dormant for include nausea and rash. Some antiar-
years in soil and animal products and rhythmics can result in tiredness or
are capable of reactivation. Animals breathlessness because they reduce the
become infected by grazing on contamin- heart’s pumping ability.
ated land. People may become infected antibacterial drugs A group of drugs
via a scratch or sore if they handle used to treat infections caused by bac-
materials from infected animals. Pulm- teria. The term antibacterial was once
onary anthrax occurs as a result of used to describe antibiotics that had
inhaling spores from animal fibres. been produced synthetically rather than
In cutaneous anthrax, a raised, itchy, naturally. The terms are now used inter-
area develops at the site of entry of the changeably. (See also antibiotic drugs.)
spores, progressing to a large blister antibiotic drugs A group of drugs used
and finally a black scab, with swelling of to treat infections caused by bacteria
the surrounding tissues. This is treat- and to prevent bacterial infection in
able with penicillin in its early stages. cases of immune system impairment.
Without treatment, the infection may
spread to lymph nodes and the blood- Most of the commonly used antibiotic
stream, and may be fatal. Pulmonary drugs belong to one of the following
anthrax causes severe breathing diffi- classes: penicillins, quinolones, amino-
culty and is fatal in most cases. glycosides, cephalosporins, macrolides,
and tetracyclines. Some antibiotics are
antiallergy drugs Drugs that are used effective against only certain types of
to treat or prevent allergic reactions bacteria; others, which are known as
(see allergy). There are several groups, broad-spectrum antibiotics, are effec-
including corticosteroids, antihistamines, tive against a wide range.
leukotriene receptor antagonists, and
sodium cromoglicate. Some bacteria develop resistance to a
previously effective antibiotic drug. This
antianxiety drugs A group of drugs is most likely to occur during long-term
used to relieve the symptoms of anxiety. treatment. Some alternative antibiotics
Benzodiazepine drugs and beta-blocker are available to treat bacteria that have
drugs are the 2 main types, although become resistant to the more com-
antidepressant drugs may occasionally monly prescribed drugs.
be used. Benzodiazepine drugs promote
mental and physical relaxation; they Most antibiotic drugs can cause nau-
can also be used to treat insomnia, but sea, diarrhoea, or a rash. Antibiotics
their use for this purpose is avoided be- may disturb the normal balance be-
cause they are addictive. Beta-blockers tween certain types of bacteria and
reduce only the physical symptoms of fungi in the body, leading to prolifera-
anxiety, such as shaking and palpi- tion of the fungi that cause candidiasis
tations, and are not addictive. (thrush). Some people experience a
severe allergic reaction to the drugs,
antiarrhythmic drugs A group of drugs resulting in facial swelling, itching, or
used to prevent or treat arrhythmia breathing difficulty.
(irregular heartbeat). This group includes antibody A protein that is made by cer-
those given intravenously in hospital to tain lymphocytes (white blood cells) to
treat arrhythmias that are causing symp- neutralize an antigen (foreign protein)
toms such as breathlessness or chest in the body. Bacteria, viruses, and other
pain. Adenosine and bretyllium are microorganisms contain many antigens;
examples of drugs used only in hospital. antibodies that are formed against

39

A ANTIBODY, MONOCLONAL ANTIDEPRESSANT DRUGS

these antigens help the body to neu- endings in the parasympathetic auto-

tralize or destroy the invading micro- nomic nervous system. Acetylcholine

organisms. Antibodies may be formed stimulates muscle contraction, increases

in response to vaccines, thereby giving secretions in the mouth and lungs, and

immunity. Antibodies are also known as slows the heartbeat.

immunoglobulins. Anticholinergic drugs are used in the

Inappropriate or excessive formation treatment of irritable bowel syndrome,

of antibodies may lead to illness, as in urinary incontinence, Parkinson’s disease,

an allergy. Antibodies against antigens asthma, and bradycardia (abnormally

in organ transplants may result in rej- slow heartbeat). They are also used to

ection of the transplanted organ. In dilate the pupil before eye examination

some disorders, antibodies are formed or surgery. Anticholinergic drugs are

against the body’s own tissues, result- used as a premedication before general

ing in an autoimmune disorder. anaesthesia and to treat motion sickness.

antibody, monoclonal An artificially They may cause dry mouth, blurred

produced antibody that neutralizes only vision, urinary retention, and confusion.

one specific antigen (foreign protein). anticoagulant drugs A group of drugs

Monoclonal antibodies are produced used to treat and prevent abnormal

in a laboratory by stimulating the growth blood clotting, to treat thrombosis, and

of a large number of antibody-producing to prevent and treat stroke and transient

cells that are genetically identical. In ischaemic attack. Anticoagulant drugs

effect, this process enables antibodies are also given to prevent abnormal

to be tailor-made so that they will react blood clotting after major surgery (esp-

with a particular antigen. ecially heart-valve replacement) or

Monoclonal antibodies are used in during haemodialysis (see dialysis). The

the study of human cells, hormones, most common anticoagulants are hep-

microorganisms, and in the develop- arin and the newer heparin-derived

ment of vaccines. They are also being drugs, such as tinzaparin, all of which

used in the diagnosis and treatment of have to be given by injection, and warf-

some forms of cancer. arin, which is taken orally.

anticancer drugs Drugs that are used Excessive doses of anticoagulant drugs

to treat many forms of cancer. They are increase the risk of unwanted bleeding,

particularly useful in the treatment of and regular monitoring is needed.

lymphomas, leukaemias, breast cancer, anticonvulsant drugs A group of drugs

cancer of the testis (see testis, cancer of), used to treat or prevent seizures. They

and prostate cancer and are often used are used mainly in the treatment of epi-

together with surgery or radiotherapy. lepsy but are also given to prevent

Most anticancer drugs are cytotoxic seizures following serious head injury or

(kill or damage rapidly dividing cells), some types of brain surgery. They may

but some act by slowing the growth of be needed to control seizures in children

hormone-sensitive tumours. Anticancer with a high fever (see convulsions, febrile).

drugs are often prescribed in combina- Anticonvulsants may produce various

tion to maximize their effects. side effects, including impaired memory,

Treatment with cytotoxic drugs is often reduced concentration, poor coordina-

given by injection in short courses tion, and fatigue. If the side effects are

repeated at intervals. Some drugs cause severe, they can often be minimized by

nausea and vomiting and may result in use of an alternative anticonvulsant.

hair loss and increased susceptibility to antidepressant drugs Drugs used in

infection. Others, such as tamoxifen, the treatment of depression .Most of the

which is used for breast cancer, are commonly used antidepressant drugs

given continuously by mouth for months belong to one of the following groups:

or years and cause few side effects. tricyclic drugs, selective serotonin reup-

anticholinergic drugs A group of take inhibitors (SSRIs), and monoamine

drugs that block the effects of acetyl- oxidase inhibitors (MAOIs). These drugs

choline, a chemical released from nerve are usually successful at relieving the

40

ANTIDIABETIC DRUGS ANTIFUNGAL DRUGS A

symptoms of depression but often take antidiuretic hormone See ADH.
2–3 weeks before benefit is felt. Treat- antidote A substance that neutralizes
ment usually lasts for at least 6 months,
and the dosage is reduced gradually or counteracts the effects of a poison.
before being stopped altogether. anti-D(Rh0) immunoglobulin An anti-

Tricyclics may cause drowsiness, dry serum that contains antibodies against
mouth, constipation, blurred vision, uri- Rhesus (Rh) D factor (a substance pre-
nary difficulty, and irregular heartbeat. sent on the red blood cells of people
SSRIs may cause nausea, indigestion, with Rh-positive blood). Anti-D(Rh0)
and loss of appetite, or allergic reactions immunoglobulin is given routinely at
but are less dangerous in overdose than intervals during normal pregnancy and
other antidepressants. MAOIs may inter- at delivery. An additional dose is also
act with foods containing tyramine (for given after an amniocentesis, miscar-
example, cheese) and other drugs to riage, or any event in which the baby’s
cause a dangerous rise in blood pressure, blood may enter the mother’s circula-
although one MAOI, moclobemide, is less tion. The injected antibodies prevent
likely to cause problems. Antidepressants the woman from forming her own anti-
are not addictive, but abrupt withdrawal bodies against Rh-positive blood, which
of some types can result in physical might adversely affect a subsequent
symptoms and should be avoided. pregnancy. (See also haemolytic disease
antidiabetic drugs A group of drugs of the newborn; Rhesus incompatibility.)
used to treat diabetes mellitus, in which antiemetic drugs A group of drugs
a lack of insulin, or resistance to its used to treat nausea and vomiting.
actions, results in raised blood glucose Antihistamine drugs and anticholinergic
levels. A wide range of antidiabetics are drugs reduce vomiting in motion sick-
used to keep the blood glucose level as ness, vertigo, and Ménière’s disease. The
close to normal as possible, and conse- most powerful antiemetics are used to
quently reduce the risk of complications control nausea and vomiting associated
such as vascular (blood vessel) disease. with radiotherapy or anticancer drugs.
These drugs include serotonin antago-
Antidiabetic drugs include insulin, nists such as ondansetron and nabilone.
which must be administered by injec- Antiemetics are not normally used in
tion, and oral hypoglycaemics such as the treatment of food poisoning be-
glibenclamide and metformin. Acarbose cause the body needs to rid itself of
and guar gum reduce or slow absorp- harmful substances. Only certain anti-
tion of carbohydrate from the intestines emetics can be used to treat vomiting
after meals. Repaglinide stimulates insu- in early pregnancy because damage to
lin release from the pancreas for a short the developing fetus may occur. Many
time and may be taken directly before antiemetics cause drowsiness.
meals. Rosiglitazone reduces resistance antifreeze poisoning Most antifreeze
to the effects of insulin in the tissues in the UK contains ethylene glycol,
and may be used together with other which is poisonous. Drinking antifreeze
hypoglycaemics. initially produces effects similar to alco-
antidiarrhoeal drugs Drugs used to hol intoxication, but vomiting, stupor,
reduce or stop diarrhoea and to help seizures, and coma may follow; acute
regulate bowel action in people with a kidney failure may occur within 24–36
colostomy or ileostomy. In most acute hours. Antifreeze poisoning requires
cases of diarrhoea, the only treatment immediate medical attention.
recommended is oral rehydration therapy. antifungal drugs A group of drugs
Antidiarrhoeal drugs include adsorb- used to treat infections caused by fungi.
ents, bulk-forming agents such as Antifungal drugs are commonly used to
kaolin, and antimotility drugs (includ- treat different types of tinea, including
ing the opioid drugs, morphine and athlete’s foot and scalp ringworm. They
codeine, and loperamide), which slow are also used for candidiasis (thrush)
movement through the intestine. None and rare fungal infections, such as cryp-
of these drugs are suitable for children. tococcosis, that affect internal organs.

41

A ANTIGEN ANTIPSYCHOTIC DRUGS

Antifungal preparations are available in antimalarial drugs Drugs used to treat

various forms including tablets, injec- malaria. One antimalarial drug, chloro-

tion, creams, and pessaries. Prolonged quine, is also used to treat arthritis.

treatment of serious fungal infections antioxidant A type of chemical that

can result in side effects that include neutralizes potentially damaging oxidiz-

liver or kidney damage. ing molecules known as free radicals.

antigen A substance that can trigger an Some antioxidants occur naturally in

immune response, resulting in produc- the body; others (vitamin C, vitamin E,

tion of an antibody as part of the body’s and beta-carotene, for example) are

defence against infection and disease. obtained through food intake or from

Many antigens are foreign proteins (not dietary supplements.

found naturally in the body) such as antiperspirant A substance applied to

parts of microorganisms and toxins or the skin in the form of a lotion, cream,

tissues from another person that have or spray to reduce sweating. High con-

been used in organ transplants. Some- centrations are sometimes used to treat

times, harmless substances (pollen, for hyperhidrosis (abnormally heavy sweat-

example) are misidentified by the ing). Antiperspirants may cause skin

immune system as potentially harmful irritation, particularly if they are used

antigens, which results in an allergic on broken skin. (See also deodorants.)

response (see allergy). antiplatelet drugs Drugs that reduce

antihistamine drugs A group of drugs the tendency of platelets to stick to-

that block the effects of histamine, a gether to form blood clots when blood

chemical released in allergic reactions flow in the arteries is disrupted. This

(see allergy). Antihistamines are used action reduces the risk of thrombo-

to treat rashes such as urticaria and to embolism, which can cause potentially

relieve sneezing and a runny nose in fatal disorders such as a myocardial

allergic rhinitis. They are also some- infarction or stroke. Aspirin and dipyri-

times included in cough remedies and damole are commonly used antiplatelet

cold remedies and are used as antiem- drugs. Others, such as ticlopidine, are

etic drugs. Antihistamines are usually used specifically to protect against clots

taken by mouth but may be given by forming in the coronary arteries of peo-

injection for anaphylactic shock. Many ple with angina.

antihistamines cause drowsiness, but antipruritic drugs Drugs that are used

newer drugs have little sedative effect. to relieve persistent itching (pruritus).

Other possible side effects include loss Antipruritics may be applied as creams

of appetite, nausea, dry mouth, blurred and emollients and may contain corti-

vision, and difficulty in passing urine. costeroid drugs, antihistamine drugs, or

antihypertensive drugs A group of local anaesthetics. Oral antihistamines

drugs used in the treatment of hyper- may also be used to relieve itching.

tension to prevent complications such antipsychotic drugs A group of drugs

as stroke, myocardial infarction, heart used to treat psychoses (mental disor-

failure, and kidney damage. There are ders involving loss of contact with

several types, including angiotensin II reality), particularly schizophrenia and

antagonists, beta-blocker drugs, ACE mania in bipolar disorder (see manic–

inhibitor drugs, calcium channel block- depressive illness). Antipsychotic drugs

ers, alpha-blocker drugs, vasodilator may also be used to sedate people who

drugs, and diuretic drugs. Side effects have other mental disorders (such as

depend on the type of antihypertensive dementia) and who are very agitated or

drugs used, but all can cause dizziness aggressive. Antipsychotics include phe-

if the blood pressure falls excessively. nothiazine drugs, butyrophenones, such

anti-inflammatory drugs Drugs that as haloperidol, and several new drugs

reduce inflammation. The main groups including risperidone, which is used to

of these drugs are nonsteroidal anti- treat the symptoms of mania.

inflammatory drugs and corticosteroid Antipsychotics can cause drowsiness,

drugs. (See also analgesic drugs.) lethargy, dyskinesia, and parkinsonism.

42

ANTIPYRETIC DRUGS ANTIVIRAL DRUGS A

Other possible side effects include dry antisocial personality disorder Imp-
mouth, blurred vision, and difficulty in ulsive, destructive behaviour that often
passing urine. However, newer drugs disregards the feelings and rights of
may have fewer side effects when used others. People who have an antisocial
in the long term. personality lack a sense of guilt and
antipyretic drugs Drugs that reduce cannot tolerate frustration. They may
fever. Examples of antipyretic drugs have problems with relationships and
include paracetamol, aspirin, and other are frequently in trouble with the law.
non-steroidal anti-inflammatory drugs Behaviour therapy, and various forms of
antiretroviral drugs Drugs that are psychotherapy, may help to improve
used to slow or halt the spread of integration. In general, the effects of
viruses in people with HIV infection this disorder decrease with age.
and AIDS. There are 3 main groups:
reverse transcriptase inhibitors, pro- antispasmodic drugs A group of drugs
tease inhibitors, and non-nucleoside that relax spasm in smooth muscle in
reverse transcriptase inhibitors. Drugs the wall of the intestine or bladder.
from different groups are often used in These drugs are used to treat irritable
combination. Antiretroviral drugs can bowel syndrome and irritable bladder.
have a range of side effects, including Possible side effects include dry mouth,
nausea, vomiting, diarrhoea, tiredness, blurred vision, and difficulty in passing
and a range of effects on blood chem- urine. (See also anticholinergic drugs.)
istry, particularly involving fats.
antirheumatic drugs A group of drugs antithyroid drugs Drugs used to treat
used to treat rheumatoid arthritis and hyperthyroidism, in which the thyroid
types of arthritis that are caused by gland is overactive. They may be used
other autoimmune disorders such as as the sole treatment or before thyroid
systemic lupus erythematosus. Antirheu- surgery. Carbimazole and propylthiour-
matic drugs affect the disease process acil interfere with the production of
and may limit joint damage, unlike non- thyroid hormone by the gland.
steroidal anti-inflammatory drugs, which
only relieve pain and stiffness. The antitoxin Any of a variety of commer-
main antirheumatic drugs are cortico- cially prepared substances containing
steroid drugs, immunosuppressant drugs, antibodies that can combine with and
chloroquine, gold, penicillamine, and sul- neutralize the effect of a specific toxin
fasalazine. Many of these drugs can have released into the bloodstream by par-
serious side effects, and treatment must ticular bacteria. Antitoxins are usually
be under specialist supervision. given by injection into a muscle. Occa-
antiseptics Chemicals applied to the sionally, an antitoxin may cause an
skin in order to destroy bacteria and allergic reaction (see allergy).
other microorganisms, thereby prevent-
ing infection. Common antiseptics are antitussive drugs Drugs that suppress
chlorhexidine, cetrimide, hexachloroph- or relieve a cough (see cough remedies).
ene, and compounds containing iodine.
(See also disinfectants; aseptic technique.) antivenom A specific treatment for bites
antiserum A preparation containing anti- or stings inflicted by venomous animals
bodies (also known as immunoglobulins) such as snakes, spiders, and scorpions.
that combine with specific antigens (for- Antivenoms are given by intravenous in-
eign proteins), usually components of jection and may cause allergic reactions.
microorganisms, leading to deactivation
or destruction of the microorganisms. antiviral drugs Drugs used in the
Antiserum is usually used, along with treatment of infection by viruses. No
immunization, as an emergency treat- drugs have been developed that can
ment when someone has been exposed eradicate viruses, and at present immu-
to a dangerous infection such as rabies nization is the most effective way of
and has not previously been immunized. preventing serious viral infections.
However, antiviral drugs can reduce
the severity of some viral infections
(most notably herpes, influenza, viral
hepatitis, and cytomegalovirus infec-
tions), particularly in people who have
reduced immunity. Advances have also

43

A ANTRAL IRRIGATION ANXIETY DISORDERS

been made in the treatment of HIV with the skin surrounding the anus.

infection (see antiretroviral drugs). Itching of the anus is common and may

antral irrigation Irrigation of the max- be due to haemorrhoids or other disor-

illary antrum, one of the nasal sinuses. ders such as threadworm infestation.

More commonly known as sinus wash- anus, imperforate A rare congenital

out, this procedure is used to diagnose abnormality in which the anal opening

and treat persistent sinusitis. Antral irri- is missing or covered over. The severity

gation is performed less often since the of the condition varies from complete

introduction of nasal endoscopy. absence of the anal canal to only a layer

anuria Complete cessation of urine out- of skin covering the anal opening.

put. Anuria may be caused by a severe Treatment involves surgery. A colos-

malfunction of the kidneys, but a more tomy may be needed initially before

common cause is a complete blockage definitive surgery to construct an anus.

of urine flow, due to enlargement of the anxiety An unpleasant emotional state

prostate gland (see prostate, enlarged), ranging from mild unease to intense

a bladder tumour, or a stone (see calcu- fear. Various physical symptoms are

lus, urinary tract). Failure of the kidneys associated with anxiety; the most com-

to produce urine may be due to oxygen mon include palpitations, chest pains, a

depletion as a result of reduced blood feeling of tightness in the chest, and

flow through the kidneys, as occurs in a tendency to overbreathe (see hyper-

shock, or to severe kidney damage ventilation). Muscle tension leads to

caused by a disease such as glomer- headaches and back pains. Gastroin-

ulonephritis. Anuria requires urgent testinal symptoms include dry mouth,

investigation. Treatment of the cause bloating, diarrhoea, nausea, and diffi-

may restore urine production, but any culty in swallowing. Other symptoms

delay can result in permanent kidney include sweating, blushing, pallor, light-

damage, leading to uraemia. headedness, and a frequent need to

anus The end of the alimentary tract urinate or defaecate. Anxiety is a nor-

through which faeces are expelled from mal response to stressful situations and

the body. The orifice at the end of the prepares the mind and body to respond

anal canal is open only during defaeca- effectively. However, anxiety that occurs

tion; at other times it is kept closed by without reason may be a symptom of an

the muscles of the anal sphincter. (See anxiety disorder or another psychologi-

also digestive system.) cal disorder such as depression.

anus, cancer of A rare cancer of the People suffering from anxiety may be

skin of the anus. Possible early signs helped by counselling or psychotherapy.

are development of swelling or an ulcer If there is an underlying disorder such

at the anus accompanied by bleeding as depression, treatment with antianx-

and discomfort. Treatment is by surgical iety drugs can help. Antianxiety drugs

removal and/or radiotherapy. are used for short-term control of symp-

anus, disorders of Most anal disor- toms but are avoided for long-term

ders affect adults and are minor, but treatment because they are addictive.

they may cause discomfort. Rarely, the anxiety disorders A group of mental

anus may fail to develop normally and illnesses, including several specific syn-

surgical treatment is needed (see anus, dromes, in which symptoms of anxiety

imperforate). In anal stenosis, the anus are the main feature. These disorders are

is too narrow to allow the passage of common and mainly affect young adults.

faeces. Anal fissures originate from In generalized anxiety disorder, there

tears in the lining of the anus, usually is persistent tension and apprehension

as a result of straining to pass faeces. that has no specific focus or cause,

Cancer of the skin around the anus is together with physical or psychological

rare (see anus, cancer of). Haemorrhoids symptoms that disrupt normal activity.

are enlarged blood vessels under the Panic disorders are characterized by

anal lining. An anal fistula is an abnor- sudden attacks of extreme, unreason-

mal channel connecting the anal canal able anxiety. Phobias are irrational fears,

44

A N X I O LY T I C S AORTIC STENOSIS A

such as the fear of open spaces or spi- can be destroyed by infective endocardi-
ders, that lead to avoidance of certain tis. Aortic incompetence is associated
situations or objects. with ankylosing spondylitis, and Marfan’s
syndrome. Atherosclerosis may damage
Counselling, psychotherapy, and group the valve, causing a combination of aor-
or individual cognitive–behaviour ther- tic stenosis and incompetence. Aortic
apy are used to treat anxiety disorders. incompetence is also found in untreat-
Antianxiety drugs (especially benzodi- ed syphilis, which is now rare.
azepine drugs) may be used for short-
term treatment but are addictive. Aortic incompetence may not cause
anxiolytics See antianxiety drugs. symptoms and is sometimes found dur-
aorta The body’s main artery, which ing a routine medical examination. The
supplies oxygenated blood to all other heart compensates for the backflow of
parts. The aorta arises from the left ven- blood into the left ventricle by working
tricle (the main pumping chamber of harder, which may eventually lead to
the heart) and arches up over the heart heart failure; this causes breathing diffi-
culty and oedema (fluid accumulation).
AORTA
Chest X-ray, ECG, and echocardiogra-
Aorta phy may be carried out to diagnose
aortic incompetence. A cardiac catheter
Vena cava is sometimes used to demonstrate the
degree of incompetence (see catheter-
Heart ization, cardiac). Heart failure resulting
from aortic incompetence can be treated
Descending with diuretic drugs. Heart-valve surgery
aorta to replace the damaged valve may
eventually be necessary.
Descending aortic stenosis Narrowing of the open-
vena cava ing of the aortic valve (one of the heart
valves), causing obstruction of blood flow
before descending, behind it, through into the circulation. This makes the heart
the chest cavity. It terminates in the work harder and causes the muscle in
abdomen by dividing into the 2 com- the wall of the left ventricle (the main
mon iliac arteries of the legs. pumping chamber) to thicken. Narrowing
of the valve also reduces the amount of
The aorta is thick-walled and has a blood flowing into the coronary arteries.
large diameter in order to cope with the
high pressure and large volume of blood The most common cause of aortic
passing through it. (See also arteries, stenosis is deposition of calcium on the
disorders of; circulatory system.) aortic valve, usually associated with
aortic incompetence Leakage of blood atherosclerosis. Aortic stenosis may also
through the aortic valve (one of the be caused by a congenital abnormality.
heart valves), resulting in a backflow of
blood from the aorta into the left ventri- Aortic stenosis may not cause symp-
cle (the heart’s main pumping chamber). toms. When symptoms do occur, they

Failure of the aortic valve to close AORTIC STENOSIS
properly may be due to a congenital
abnormality in which the valve has 2 Normal Restricted
flaps rather than 3. The valve leaflets blood blood
flow flow

Cusp Abnormal
cusp

NORMAL AORTA STENOSED AORTA

45

A AORTITIS APHRODISIAC

include fainting, lack of energy, chest Five features are scored 1 minute and

pain on exertion due to angina, and again 5 minutes after birth. These are

breathing difficulty. breathing, heart-rate, colour, muscle

Chest X-ray, ECG, and echocardiogra- tone, and response to stimulation.

phy may be carried out to diagnose aphakia The absence of the lens from

aortic stenosis. A cardiac catheter can the eye. Aphakia may be congenital,

be used to demonstrate the degree of may result from surgery (for example,

stenosis (see catheterization, cardiac). cataract surgery), or may be due to a

Heart-valve surgery may be needed to penetrating injury. Aphakia causes sev-

widen or replace the damaged valve. ere loss of focusing in the affected eye

aortitis Inflammation of the aorta (the and requires correction by implanting a

main artery of the body). Aortitis is a lens or with contact lenses or glasses.

rare condition that occurs in people aphasia A complete absence of previ-

with arteritis or untreated syphilis and in ously acquired language skills, caused

some people with ankylosing spondylitis. by a brain disorder that affects the abil-

Aortitis may cause part of the aorta to ity to speak and write, and/or the ability

widen and its walls to become thinner. to comprehend and read. Related dis-

This may lead to an aneurysm (balloon- abilities that may occur in aphasia are

ing of the artery). Aortitis may damage alexia (word blindness) and agraphia

the ring around the aortic valve in the (writing difficulty).

heart, leading to aortic incompetence. Language function in the brain lies in

aortography An imaging technique that the dominant cerebral hemisphere (see

enables the aorta (the main artery of the cerebrum). Two particular areas in this

body) and its branches to be seen clear- hemisphere, Broca’s and Wernicke’s

ly on X-ray film following injection of a areas, and the pathways connecting the

contrast medium (a substance that is two, are important in language skills.

opaque to X-rays). Aortography is used Damage to these areas, which most

if surgery is needed to treat an aneu- commonly occurs as a result of stroke

rysm (ballooning of the aorta). or head injury, can lead to aphasia.

aperient A mild laxative drug. Some recovery from aphasia is usual

apex The uppermost surface of a struc- following a stroke or head injury,

ture, for example the top, end, or tip of although the more severe the aphasia,

an organ such as a lung or the heart. the less the chances of recovery. Speech

apex beat A normal hearbeat felt therapy is the main treatment. (See also

through the chest wall. As the heart con- dysphasia; speech; speech disorders.)

tracts, its tip hits the chest wall and can apheresis A procedure in which blood

be felt between the 5th and 6th ribs on is withdrawn from a donor and is re-

the left side of the chest. The apex beat infused after one or more selected

is displaced when the heart is enlarged. components have been separated and

Apgar score A system designed to removed. In plasmapheresis, antibodies

assess the condition of a newborn baby. that are causing a disease are removed;

APGAR SCORE and in leukapher-
esis, white blood

SIGN SCORE 0 SCORE 1 SCORE 2 cells are removed.
Heart-rate None aphonia Complete
Below 100 beats Over 100 beats loss of the voice,
Breathing None per minute per minute which may result
from surgery to the
Weak cry; irregular Strong cry; regular larynx, or it may
breathing breathing

Muscle tone Limp Some muscle Active be sudden in onset
tone movement and due to emo-

Response to None Grimace or Cry, sneeze tional stress. (See

stimulation whimpering or cough also dysphonia.)

Colour Pale; blue Blue extremities Pink aphrodisiac Any
substance that is

46

APHTHOUS ULCER APPENDIX A

thought to stimulate erotic desire and apolipoprotein A group of proteins
enhance sexual performance. For cent- that are constituents of lipoproteins, the
uries, various substances (most notably carriers of fat in the bloodstream. Apo-
oysters and rhinoceros horn) have been lipoproteins are also involved in the
used as aphrodisiacs. In fact, no sub- growth and repair of nerve tissues.
stance has a proven aphrodisiac effect.
aphthous ulcer See ulcer, aphthous. aponeurosis A wide sheet of tough,
apicectomy Surgical removal of the tip fibrous tissue that acts as a tendon,
of a tooth root. Apicectomy may be per- attaching a muscle to a bone or a joint.
formed as part of root-canal treatment.
aplasia Absent or severely reduced apophysis An outgrowth of bone at the
growth and development of any organ site of attachment of a tendon to bone.
or tissue. For example, in bone marrow Inflammation may also occur, as in
aplasia, the rate of cell division in the Osgood–Schlatter disease.
bone marrow is reduced, leading to in-
sufficient blood-cell production (see apoplexy An outdated term for a stroke.
anaemia, aplastic). Some birth defects, apoptosis The natural process of pro-
such as stunted limbs (see phocomelia),
occur as a result of incomplete tissue grammed cell death. Apoptosis occurs
formation during prenatal development. in embryonic development, when the
aplastic anaemia See anaemia, aplastic. shaping of body parts is taking place
apnoea Cessation of breathing, either and continues throughout life in the
temporarily or for a prolonged period. constant cycle of death and renewal of
body cells. Failure of apoptosis is impli-
Breathing is an automatic process cated in the development of cancers.
controlled by the respiratory centre in apothecary An old term for a pharmacist.
the brainstem. Failure of this centre to appendicectomy Surgical removal of the
maintain normal breathing is known as appendix to treat acute appendicitis.
central apnoea. It may occur in babies, appendicitis Acute inflammation of the
particularly those who are premature, appendix. The cause is usually not
and can be detected by an apnoea known, but appendicitis is sometimes
alarm. Central apnoea can also result caused by obstruction of the appendix
from brainstem damage, for example by a lump of faeces. The 1st symptom is
following a stroke or head injury. usually vague discomfort around the
navel. Within a few hours, this develops
In obstructive apnoea, breathing is pre- into severe, more localized pain, which is
vented by a blockage in the airway. The usually most intense in the lower right-
most common type is sleep apnoea, in hand side of the abdomen. Symptoms
which blockage of the upper airway may differ if the appendix is not in the
occurs repeatedly during sleep. most common position. For example, if
the appendix impinges on the ureter,
Deliberate temporary apnoea occurs the urine may become bloodstained.
in breath-holding attacks. Another type
of apnoea occurs in Cheyne–Stokes res- The usual treatment for appendicitis
piration, in which cycles of deep, rapid is appendicectomy, which is often per-
breathing alternate with episodes of formed endoscopically (see minimally
breathing stoppage. invasive surgery). If the treatment is
delayed, an inflamed appendix may
Treatment of apnoea depends on the burst, releasing its contents into the
cause. In newborn babies, it resolves as abdomen. This leads to peritonitis and,
they mature. In stroke or head injury, in some cases, an abscess.
artificial ventilation may be needed appendix A small, narrow tube that
temporarily until recovery occurs. projects out of the caecum (the 1st part
apocrine gland A gland that dis- of the colon) at the lower right-hand
charges cellular material in addition to side of the abdomen. It may lie behind
the fluid it secretes. The term is usually or below the caecum, or in front of or
applied to the type of sweat glands that behind the ileum (part of the small
appear in hairy body areas after puberty. intestine). The appendix has no known
(See also eccrine gland.) function, but it contains a large amount
of lymphoid tissue which provides a

47

A APPETITE ARBOVIRUS

defence against local infection. The brain) that translate the idea for a move-

position of an individual’s appendix ment into an actual movement. Damage

partly determines the set of symptoms to the cerebrum may be caused by a head

produced by acute appendicitis (inflam- injury, infection, stroke, or brain tumour.

mation of the appendix). There are various forms of apraxia,

APPENDIX each related to damage in different
parts of the brain. A person with ideo-

motor apraxia is unable to carry out a

spoken command to make a particular

Colon movement, but at other times can make

Ileum the same movement unconsciously. In
sensory apraxia, a person may not be

Caecum able to use an object due to loss of abil-
ity to recognize its purpose.

Appendix APUD cell tumour A growth composed
of cells that produce various hormones.

These cells, amine precursor uptake

Rectum and decarboxylation (APUD) cells, occur

in different parts of the body. Some tu-

mours of the thyroid gland, pancreas,

appetite A desire for food; a pleasant and lungs are APUD cell tumours, as are

sensation felt in anticipation of eating. a carcinoid tumour (see carcinoid syn-

Appetite, which is regulated by 2 parts drome) and phaeochromocytoma (a type

of the brain (the hypothalamus and the of adrenal tumour).

cerebral cortex), is learned by enjoying aqueous cream An emollient prepara-

a variety of foods that smell, taste, and tion that is commonly used to treat

look good. It combines with hunger to dry, scaly, or itchy skin in conditions

ensure that the right amount of a wide such as eczema.

range of foods is eaten to stay healthy. aqueous humour A watery fluid that

(See also appetite, loss of.) fills the front chamber of the eye,

appetite, loss of Loss of appetite is behind the cornea.

usually temporary and due to an emo- arachidonic acid One of the fatty acids

tional upset or minor illness. Persistent in the body that are essential for growth.

loss of appetite may have a more seri- arachis oil Peanut oil, mostly used in

ous underlying cause, such as chronic enemas, to soften faeces and make

infection or cancer. bowel movements easier. It may also be

appetite stimulants Various tonics and applied to the scalp, followed by sham-

remedies traditionally prescribed to pooing, in the treatment of cradle cap.

stimulate the appetite. None are proven arachnodactyly Long, thin, spider-like

to be effective. Some drugs such as cor- fingers and toes that sometimes occur

ticosteroids may stimulate the appetite spontaneously but are characteristic of

when used to treat unrelated disorders. Marfan’s syndrome, an inherited con-

appetite suppressants A group of drugs nective tissue disease.

that reduce the desire to eat. Appetite arachnoiditis A rare condition that is

suppressants may be used in the treat- characterized by chronic inflammation

ment of severe obesity, along with diet and thickening of the arachnoid mater,

and exercise. Their use is limited to a which is the middle of the 3 meninges

maximum of 12 weeks due to the risk of (the membranes that cover the brain

serious effects on the blood supply to and spinal cord).

the lungs and on heart valves. arachnoid mater The middle of the 3

apraxia An inability to carry out pur- layers of membrane (meninges) that

poseful movements despite normal cover the brain.

muscle power and coordination. Aprax- arbovirus Any of the many viruses trans-

ia is caused by damage to nerve tracts mitted by a member of the arthropod

in the cerebrum (the main mass of the group of animals, including insects,

48

ARC ARRHYTHMIA, CARDIAC A

mites, and ticks. (See also insects and dis- circulate continuously in the heart and
ease; mites and disease; ticks and disease). take over from the sinoatrial node.
ARC An abbreviation for AIDS-related Rapid, irregular beats that originate in
complex. (See also AIDS.) the ventricles are called ventricular
arcus senilis A grey-white ring near the tachycardia. In atrial flutter, the atria
edge of the cornea overlying the iris (see atrium) beat regularly and very
(the coloured part of the eye). Arcus rapidly, but not every impulse reaches
senilis is caused by degeneration of the ventricles, which beat at a slower
fatty material in the cornea and devel- rate. Uncoordinated, fast beating of the
ops gradually during adult life. The ring atria is called atrial fibrillation and pro-
does not affect eyesight. Development duces totally irregular ventricular beats.
of the condition in early adult life may Ventricular fibrillation is a form of car-
be associated with an abnormality of diac arrest in which the ventricles twitch
fats in the blood (see hyperlipidaemia). very rapidly in a disorganized manner.
areola The pigmented circular area sur-
rounding the nipple. The term is also Sinus bradycardia is a slow, regular
used to describe an inflamed area beat. In heart block, the conduction
around a pimple (see pustule). of electrical impulses through the
aromatherapy A form of complemen- heart muscle is partially or completely
tary medicine that uses aromatic oils blocked, leading to a slow, irregular
extracted from plants. The oil is applied heartbeat. Periods of bradycardia may
in small quantities through massage; or alternate with periods of tachycardia
it is inhaled, incorporated into creams due to a fault in impulse generation
or lotions, or, very occasionally, taken (see sick sinus syndrome).
internally. There is no conclusive scien-
tific evidence of the benefits. ARRHYTHMIA, CARDIAC
arousal The awakening of a person from
unconsciousness or semiconsciousness. Sinoatrial node (pacemaker)
The term is also used to describe any
state of heightened awareness, such as Electrical pathway
that caused by sexual stimulation or to left atrium
fear. Arousal is regulated by the reticu-
lar formation in the brainstem. Atrioventricular
arrhenoblastoma A rare tumour of the node
ovary that occurs in young women. The
tumour is noncancerous but secretes Atria
androgen hormones (male sex hormones)
that cause virilization (the development Ventricles
of male characteristics). Treatment is by
surgical removal of the affected ovary. Normal
arrhythmia, cardiac An abnormality electrical
of the rhythm or rate of the heartbeat. pathway
Arrhythmias, which are caused by a dis-
turbance in the electrical impulses in Abnormal
the heart, can be divided into 2 main electrical
groups: tachycardias, in which the rate pathway
is faster than normal, and bradycardias,
in which the rate is slower. SUPRAVENTRICULAR TACHYCARDIA

In sinus tachycardia, the rate is raised, A common cause of arrhythmia is
the rhythm is regular, and the beat coronary artery disease, particularly
originates in the sinoatrial node (see after myocardial infarction. Some tachy-
pacemaker). Supraventricular tachycar- cardias are due to a congenital defect in
dia is faster and the rhythm is regular. It the heart's conducting system. Caffeine
may be caused by an abnormal electri- can cause tachycardia in some people.
cal pathway that allows an impulse to Amitriptyline and some other antidepres-
sant drugs can cause serious arrhythmias
if they are taken in high doses.

An arrhythmia may be felt as palpita-
tions, but in some cases arrhythmias

49

A ARSENIC ARTERITIS

can cause fainting, dizziness, chest common cause of thickening and nar-

pain, and breathlessness, which may be rowing of arteries, and it increases the

the 1st symptoms. risk of a stroke or kidney failure. Arteritis

Arrhythmias are diagnosed by an ECG. is inflammation of artery walls that

If they are intermittent, a continuous causes narrowing and sometimes block-

recording may need to be made using age. Aneurysm is ballooning of an

an ambulatory ECG. artery wall caused by the pressure of

Treatments for arrhythmias include anti- blood flowing through a weakened area.

arrhythmic drugs, which prevent or slow Thrombosis occurs when a blood clot

tachycardias. With an arrhythmia that forms in a blood vessel, causing obs-

has developed suddenly, it may be pos- truction of the blood flow. Blockage of

sible to restore normal heart rhythm by an artery by a fragment of blood clot or

using electric shock to the heart (see other material travelling in the circula-

defibrillation). Abnormal conduction path- tion is called an embolism. Raynaud’s

ways in the heart can be treated using disease is a disorder involving intermit-

radio frequency ablation during cardiac tent spasm of small arteries in the

catheterization (see catheterization, car- hands and feet, usually due to cold.

diac). In some cases, a pacemaker can arteriography An alternative name for

be fitted to restore normal heartbeat by angiography, an X-ray technique for

overriding the heart’s abnormal rhythm. imaging arteries.

arsenic A poisonous metallic element arteriole A blood vessel that branches

that occurs naturally in its pure form off an artery. Arterioles branch to form

and in various compounds. Arsenic poi- capillaries. They have muscular walls,

soning, which is now rare, used to occur and their nerve supply enables them to

as a result of continuous exposure to be narrowed or widened to meet the

industrial pesticides. blood-flow needs of tissues they supply.

arterial reconstructive surgery An arteriopathy Any disorder of an artery

operation to repair arteries that are nar- (see arteries, disorders of).

rowed, blocked, or weakened. Arterial arterioplasty Surgical repair of an art-

reconstructive surgery is most often ery (see arterial reconstructive surgery).

performed to repair arteries that have arteriosclerosis A group of disorders

been narrowed by atherosclerosis. It is that cause thickening and loss of elas-

also used to repair aneurysms and ticity of artery walls. Atherosclerosis is

arteries damaged as a result of injury. the most common type , and the 2 terms

(See also angioplasty, balloon; coronary are often used synonymously. Other

artery bypass; endarterectomy.) types are medial arteriosclerosis (in

arteries, disorders of Disorders of which muscle and elastic fibres in larger

the arteries may take the form of abnor- arteries are replaced by fibrous tissue)

mal narrowing (which reduces blood and Monckeberg’s arteriosclerosis (in

flow and may cause tissue damage), which there are calcium deposits in the

complete obstruction (which may cause arterial lining).

tissue death), or abnormal widening arteriovenous fistula An abnormal

and thinning of an artery wall (which communication directly between an art-

may cause rupture of the blood vessel). ery and a vein. An arteriovenous fistula

Atherosclerosis, in which fat deposits may be present at birth or result from

build up on artery walls, is the most injury. A fistula can also be created

common arterial disease. It can involve surgically for easy access to the blood-

arteries throughout the body, including stream in dialysis.

the brain (see cerebrovascular disease), arteritis Inflammation of an artery wall,

heart (see coronary artery disease), and causing narrowing or complete block-

legs (see peripheral vascular disease). age of the affected artery, reduced

Atherosclerosis is the main type of art- blood flow, and, in some cases, throm-

eriosclerosis, a group of disorders that bosis and tissue damage. There are

cause thickening and loss of elasticity several types, including Buerger’s dis-

of artery walls. Hypertension is another ease, an arteritis that affects the limbs,

50

ARTERY ARTHROPLASTY A

causing pain, numbness, and, in severe condition that causes inflammation in
cases, gangrene. Polyarteritis nodosa, a the joints and other body tissues such
serious autoimmune disorder, can affect as the membranous heart covering,
arteries in any part of the body, espe- lungs, and eyes. The disorder has dif-
cially the heart and kidneys. Temporal ferent effects in children (see juvenile
arteritis affects arteries in the scalp and chronic arthritis). Ankylosing spondylitis
may affect the eyes. A rare type of arter- is another persistent form of arthritis
itis is Takayasu’s arteritis, which is that initially affects the spine and the
thought to be an autoimmune disorder. joints between the base of the spine
This usually affects young women and and the pelvis. Other tissues, such as the
involves the arteries that branch from eyes, may also be affected. Eventually,
the aorta into the neck and arms. the disorder may cause the vertebrae
artery A blood vessel that carries blood (bones of the spine) to fuse. Reactive
away from the heart. Systemic arteries arthritis typically develops in suscepti-
carry blood pumped from the left ventri- ble people following an infection, most
cle of the heart to all parts of the body commonly of the genital tract or intes-
except the lungs. The largest systemic tines. Gout and pseudogout are types of
artery is the aorta, which emerges from arthritis in which crystals are deposited
the left ventricle; other major systemic in a joint, causing swelling and pain.
arteries branch off from the aorta. The Septic arthritis is a relatively rare condi-
pulmonary arteries carry blood from the tion that can develop when infection
right ventricle to the lungs. enters a joint either through a wound or
from the bloodstream.
ARTERY
Diagnosis of particular types of arthri-
Outer layer tis is made from blood tests and, in
some cases, microscopic examination
Muscle of fluid from the affected joint. X-rays or
layer MRI can indicate the type and extent
of joint damage.
Elastic
layer Physiotherapy and exercises can help
to minimize the effects of arthritis, and
Inner there are specific treatments for some
lining types, such as antibiotic drugs for septic
arthritis. In severe cases, one or more
Arteries are tubes with thick, elastic, joints may need arthroplasty (replace-
muscular walls able to withstand the ment with an artificial substitute) or
high pressure of blood flow. The structure arthrodesis (fusion of the bones).
of arteries helps to even out the peaks arthrodesis A surgical procedure in
and troughs of blood pressure caused which the 2 bones in a diseased joint are
by the heartbeat, so that the blood is fused to prevent the joint from moving,
kept flowing at a relatively constant pres- which relieves pain. Arthrodesis is perfor-
sure. (See also arteries, disorders of.) med if a joint is painful or unstable and
arthralgia Pain in the joints or a single other treatments such as drugs or arthro-
joint. (See also arthritis; joint.) plasty have failed or are inappropriate.
arthritis Inflammation of one or more arthrography A diagnostic technique
joints, with pain, swelling, and stiffness. in which the interior of a damaged joint
is X-rayed after injection of a radiopaque
There are several different types of solution. It is being replaced by MRI,
arthritis, each having different charac- ultrasound scanning, and arthroscopy.
teristics. The most common form is arthrogryposis See contracture.
osteoarthritis, which most often involves arthropathy Disease of the joints.
the knees, hips, and hands and usually arthroplasty Replacement of a joint or
affects middle-aged and older people. part of a joint by metal or plastic com-
Cervical osteoarthritis is a form of osteo- ponents. A hip replacement is one of the
arthritis that affects the joints in the most common operations of this type,
neck. Rheumatoid arthritis is a damaging

51