THREADWORM INFESTATION THROMBOPHLEBITIS
to another occurs in hypomania and thrombocytopenia A reduction in the
mania. In depression, thinking becomes number of platelets in the blood, result-
slow, there is a lack of association, and ing in a tendency to bleed. Sometimes
a tendency to dwell in great detail on thrombocytopenic purpura (abnormal
trivial subjects. In obsessive–compulsive bleeding into the skin) develops. The
disorder, recurrent ideas seem to come cause may be a reduced rate of platelet
into a person’s mind involuntarily. Delu- production or fast rate of platelet des-
sions, which occur in schizophrenia and truction. Thrombocytopenia can be a
other psychotic illnesses, may be an feature of leukaemia, lymphoma, systemic
expression of distorted thinking. lupus erythematosus, megaloblastic
threadworm infestation A common anaemia, or hypersplenism. It can also be
infestation with a small worm, ENTERO- caused by exposure to radiation or,
BIUS VERMICULARIS (pinworm), that lives more often, by an adverse reaction to a
in the intestines. Threadworms primarily prescribed drug such as a thiazide
affect children. The female adult thread- diuretic. Idiopathic thrombocytopenic pur-
worms are white and about 1 cm long pura (ITP) is of unknown cause, but it
(large enough to see). They lay eggs in may be an autoimmune disorder.
the skin around the anus, and their Thrombocytopenia is confirmed by a
movements cause tickling or itching in blood count. Any underlying disease is
the anal region, often at night. Eggs are treated if possible. Children with ITP
transferred from the fingers to the mouth may not need treatment, but adults are
to cause reinfestation or are carried on usually given corticosteroid drugs. If
toys or blankets to other children. Swal- thrombocytopenia persists, splenectomy
lowed eggs hatch in the intestine and may be performed. When the cause is
the worms reach maturity after a period known, treatment usually results in an
of 2–6 weeks. Diagnosis is made by see- increase in platelet numbers.
ing the worms or by applying a piece of thromboembolism The blockage of a
sticky tape to the anal area to collect blood vessel by a piece of a blood clot
the worms or eggs. Treatment is with an (embolus) that has broken off from a
anthelmintic drug. thrombus elsewhere in the circulation.
thrill A vibrating sensation felt when (See also thrombosis; embolism).
the flat of the hand is held against an thrombolytic drugs Sometimes called
area of the body. Thrill is caused by tur- fibrinolytic drugs, this group of drugs is
bulent blood flow in an artery or the used to treat thrombosis, embolism, and
heart. The term is also used to describe myocardial infarction. Thrombolytic drugs
the feeling produced by fluid within the act within blood vessels to dissolve clots.
abdominal cavity in ascites. Possible adverse effects include abnor-
throat A popular term for the pharynx. mal bleeding and an allergic reaction.
The term is also sometimes used to thrombophilia A tendency for blood to
refer to the front of the neck. clot too readily due to an inherited ab-
T throat cancer See pharynx, cancer of; normality in proteins such as factor V. It
larynx, cancer of. may not be recognized until specific cir-
thrombectomy The removal of a throm- cumstances such as injury or air travel
bus that is blocking a blood vessel. It is cause symptoms or signs. (See also
performed as an emergency procedure thrombosis, deep vein.)
if a major artery is blocked, or as a pre- thrombophlebitis Inflammation of a
cautionary measure if there is a risk of section of vein, usually just under the
an embolus breaking off. Before surgery, skin, with clot formation in the affected
the site of the thrombus is established part. This can occur after minor injury to
by angiography and the patient may be the vein or as a complication of varicose
given anticoagulant drugs. veins or Buerger’s disease. The affected
thromboangiitis obliterans Another blood vessel is swollen, red, and tender,
name for Buerger’s disease. and feels hard. Fever and malaise may
thrombocyte An alternative name for occur. A blood clot may develop. Treat-
a platelet. ment includes support with a bandage,
548
THROMBOSIS THYROGLOSSAL DISORDERS
nonsteroidal anti-inflammatory drugs, and is not necessarily serious in itself, but T
sometimes antibiotic drugs. The condi- part of the clot may break off and travel
tion usually clears up in 10–14 days. in the bloodstream to the lungs. This is
thrombosis The formation of a thrombus known as a pulmonary embolism.
(blood clot) in an undamaged blood
vessel. A thrombus that forms within an A diagnosis is made by doppler ultra-
artery supplying the heart muscle (coro- sound scanning. Treatment depends on
nary thrombosis) is the usual cause of the site and extent of the clots. Small
myocardial infarction. A thrombus in an clots may not need treatment if they are
artery of the brain (cerebral thrombosis) confined to the calf and the patient is
is a common cause of stroke. Thrombi mobile. Otherwise, anticoagulant drugs
sometimes form in veins, either just or thrombolytic drugs are given. If there
below the skin or in deeper veins (see is a high risk of a pulmonary embolism,
thrombosis, deep vein). thrombectomy may be performed.
thrombus A blood clot that has formed
In arteries, thrombus formation may inside an intact blood vessel. A throm-
be encouraged by atherosclerosis, smok- bus is life-threatening if it obstructs the
ing, hypertension, and damage to blood blood supply to an organ such as the
vessel walls from arteritis and phlebitis. heart or brain. A thrombus may also
An increased clotting tendency may occur lead to gangrene in an organ or extrem-
in pregnancy, when using oral contra- ity, or to embolism. (See also blood
ceptives, or through prolonged immobility. clotting; thrombosis.)
thrush A common name for the fungal
An arterial thrombosis may cause no infection candidiasis.
symptoms until blood flow is impaired. thumb-sucking A common habit in
Then, there is reduced tissue or organ young children, which provides comfort,
function and sometimes severe pain. oral gratification, amusement when
Venous thrombosis may also cause bored, and reassurance. Thumb-sucking
pain and swelling. Diagnosis is made by tends to decrease after age 3, and most
doppler ultrasound. In some cases, ang- children grow out of it by age 7. In most
iography or venography may also be cases, it is not harmful. However, maloc-
used. Treatment may include anticoag- clusion of the permanent teeth may
ulant drugs or thrombolytic drugs, develop if the habit continues past age
nonsteroidal anti-inflammatory drugs, and 7. This is usually temporary; if not, an
antibiotic drugs. In life-threatening cases, orthodontic appliance may be needed.
thrombectomy may be needed. thymoma A rare tumour of the thymus
thrombosis, deep vein The formation gland. The tumour can arise from any of
of a thrombus within deep-lying veins in the cell types in the thymus gland and
the leg. The cause is usually a combina- can be cancerous or noncancerous.
tion of slow blood flow through 1 part thymoxamine See moxisylyte.
of the body (such as when sitting for thymus A gland that forms part of the
long periods or when the tissues are immune system. The thymus lies behind
compressed, as occurs in long-haul air- the sternum and consists of 2 lobes that
craft flights) and an increase in the join in front of the trachea. Each lobe is
clotting tendency of the blood, which made of lymphoid tissue consisting of
occurs with dehydration, after surgery lymphocytes, epithelium, and fat. The
or injury, during pregnancy, and in thymus conditions lymphocytes to
women taking oral contraceptives. Deep become T-cells. It plays a part in the
vein thrombosis may also be caused by immune response until puberty, gradu-
polycythaemia. Deep vein thrombosis is ally enlarging during this time. After
common in people with heart failure puberty, it shrinks, but some glandular
and those who have had a stroke or who tissue remains until middle-age.
have been immobile for long periods. thyroglossal disorders A set of con-
Clots in the leg veins may cause pain, genital defects caused by failure of the
tenderness, swelling, discoloration, and thyroglossal duct to disappear during
ulceration of the skin, but they can be embryonic development. In embryos,
symptomless. A deep vein thrombosis
549
THYROID CANCER THYROID GLAND, DISORDERS OF
this duct runs from the base of the and parafollicular cells (or C cells),
tongue to the thyroid gland. Abnormal which secrete the hormone calcitonin.
development may cause the duct to T4 and T3 are important in controlling
persist in its entirety or partly as a cyst. the body’s metabolism. Calcitonin
A cyst usually becomes infected and helps to regulate calcium balance in
swollen, which may lead to formation of the body. (See also thyroid gland, dis-
a fistula. The cyst and any remaining orders of; thyroid hormones.)
parts of the duct are removed. THYROID GLAND
thyroid cancer Rare tumours of the
thyroid gland. In most cases the cause
is unknown, although exposure to radio-
active fallout increases the risk of
developing the condition. There are sev-
eral types, depending on the type of
cells involved. In all of them, however,
the first sign is a firm nodule in the
neck, which may grow slowly or rapidly. LOCATION
In many cases, the cancer is painless
and symptoms such as difficulty swal- Thyroid cartilage
lowing, and hoarseness or loss of voice,
only develop when the tumour presses Thyroid gland
on other structures. A diagnosis is made Trachea
by thyroid scanning and needle aspiration
or a biopsy. A thyroidectomy is usually
followed by treatment with radioactive
iodine to destroy any residual cancer. thyroid gland, disorders of Disorders
Cure rates depend on the cell type and of the thyroid gland may cause hyperthy-
on the size and spread of the tumour roidism, hypothyroidism, or enlargement
when diagnosed. Patients need to take or distortion of the gland. Myxoedema,
thyroxine for the rest of their lives. Graves’ disease, and Hashimoto’s thy-
thyroidectomy Surgical removal of all roiditis are common disorders. Goitre may
or part of the thyroid gland, performed sometimes occur with no accompanying
to treat thyroid cancer, some cases of abnormality of thyroid function. In rare
hyperthyroidism, goitre, or a noncancer- cases, the gland is absent at birth, pro-
ous tumour of the thyroid gland. ducing severe cretinism. Sometimes it
thyroid-function tests A group of develops in an abnormal position in the
blood tests used to evaluate the func- neck, causing, in rare cases, difficulty in
tion of the thyroid gland and to detect swallowing or breathing.
or confirm any thyroid disorder. The A genetic disorder may impair the thy-
thyroid hormones T3 and T4 are mea- roid’s ability to secrete hormones and
T sured, as well as thyroid-stimulating goitre may result. Thyroid infection is
hormone (TSH), the pituitary gland hor- uncommon and leads to thyroiditis. Viral
mone that stimulates the thyroid gland. infection can cause extreme pain and
thyroid gland One of the main endo- temporary hyperthyroidism. Hormonal
crine glands, which helps to regulate changes during puberty or pregnancy
the rate of all the body’s internal pro- may cause a degree of goitre temporar-
cesses. The thyroid gland is situated in ily. Hyperthyroidism due to excessive
the front of the neck, just below the lar- production of TSH by the pituitary
ynx (voice box). It consists of 2 lobes, gland is rare but can occur as a result of
one on each side of the trachea (wind- a pituitary tumour.
pipe), joined by a portion of tissue Because iodine is necessary for the
called the isthmus. Thyroid tissue is production of thyroid hormone, its defi-
composed of follicular cells, which sec- ciency may lead to goitre. Severe iodine
rete the iodine-containing hormones deficiency in children may cause myx-
thyroxine (T4) and triiodothyronine (T3), oedema. (See also thyroid cancer.)
550
THYROID HORMONES TIETZE’S SYNDROME
thyroid hormones The 3 hormones is widened and protrudes to form a
bony prominence that is known as
produced by the thyroid gland are thy- the medial malleolus.
tibolone A drug used in the treatment
roxine (T4) and triiodothyronine (T3), of menopausal symptoms and to protect
which regulate metabolism, and calci- against osteoporosis. The drug is given
continuously and combines the effects
tonin, which helps to regulate calcium of oestrogens and progestogens. Possi-
ble adverse effects include irregular
levels in the body. vaginal bleeding, changes in body
weight, ankle oedema, dizziness, skin
thyroiditis Inflammation of the thyroid reactions, headache, migraine, growth
of facial hair, depression, and myalgia.
gland. Thyroiditis occurs in several dif- tic A repeated, uncontrolled, purpose-
less contraction of a muscle or group of
ferent forms. The most common is muscles, most commonly in the face,
shoulders, or arms. Typical tics include
Hashimoto’s thyroiditis, an autoimmune blinking, mouth twitching, and shrug-
ging. Tics usually develop in childhood
disorder that results in hypothyroidism. and are often a sign of a minor psycho-
logical disturbance. They usually stop
Less commonly, the inflammation is within a year of onset but in some cases
persist into adult life. (See also Gilles de
associated with a viral infection, or it la Tourette’s syndrome.)
tic douloureux An alternative name for
may occur temporarily soon after child- trigeminal neuralgia.
ticks and disease Small, 8-legged anim-
birth; in both these cases, long-term als that feed on blood and sometimes
transmit diseases to humans via their
damage to the gland is uncommon. bites. Ticks are about 3 mm long before
feeding and become larger when bloated
thyroid scanning Techniques, such as with blood. Ticks may be picked up in
long grass, scrub, woodland, or caves.
radionuclide scanning and ultrasound
In the UK, the only disease known to be
scanning, that are used to provide infor- transmitted to humans by ticks is Lyme
disease. Others transmitted in various
mation about the location, anatomy, parts of the world include relapsing fever,
Rocky Mountain spotted fever, Q fever,
and function of the thyroid gland. tularaemia, and certain types of viral en-
cephalitis. The prolonged bite of certain
thyrotoxicosis Overactivity of the thy- female ticks can cause tick paralysis, in
which a toxin in the tick saliva affects
roid gland, also called hyperthyroidism. the nerves that control movement. In
extreme cases, this can be fatal.
thyroxine The most important thyroid Tietze’s syndrome Chest pain local-
ized to an area on the front of the chest
hormone. Thyroxine is represented by wall, usually made worse by movement
of the arms or trunk or by pressure on
the symbol T4. the chest wall. The syndrome is caused
TIA The abbreviation for transient isch- by inflammation of 1 or several rib carti-
lages and symptoms may persist for
aemic attack. months. Treatment is with analgesics,
nonsteroidal anti-inflammatory drugs, or
tiabendazole A rarely used anthelmintic local injections of corticosteroid drugs
into the cartilage.
drug used to treat worm infestations,
TIBIA including strongy-
loidiasis. It has
Femur been replaced by
newer anthelmin-
Patella tics that have few
side effects.
tibia Also called
the shin, the inner
and thicker of the
2 long bones in
the lower leg. The T
Tibia tibia runs parallel
to the fibula, the
Fibula narrower bone to
which it is attached
by ligaments. The
Medial upper end articu-
malleolus lates with the femur
to form the knee
Talus joint; the lower end
articulates with the
talus to form part
of the ankle joint.
On the inside of
the ankle, the tibia
551
TIMOLOL TISSUE-TYPING
timolol A beta-blocker drug used to treat a radio, television, cassette player, or
hypertension and angina pectoris. Timolol headphones to block out the noise in
may also be given after a myocardial in- their ears. A tinnitus masker, a hearing-
farction. It is used as eye-drops to treat aid type device that plays white noise (a
glaucoma. Possible side effects, such as random mixture of sounds at a wide
cold hands and feet, are typical of other range of frequencies), may be effective.
beta-blockers. Eye-drops may cause irri- tinzaparin A type of low molecular weight
tation, blurred vision, and headache. heparin that may be injected once daily
tinea Any of a group of common fungal in the treatment of deep vein thrombo-
infections of the skin, hair, or nails. Most sis (see thrombosis, deep vein).
are caused by fungi called dermato- tiredness A common complaint that is
phytes. The infections may be acquired usually the result of overwork or poor
from another person, an animal, soil, quality, or insufficient sleep. Persistent
the floors of showers, or from house- tiredness may be caused by a number of
hold objects, such as chairs or carpets. conditions, including depression, anxi-
The most common type of tinea infec- ety, anaemia, and diabetes.
tion is tinea pedis (athlete’s foot). Tinea tissue A collection of cells specialized to
corporis causes itchy, usually circular, perform a particular function.
patches on the body. Tinea cruris (jock tissue fluid The watery liquid present
itch) produces a reddened, itchy area in the tiny gaps between body cells,
spreading from the genitals over the also known as interstitial fluid.
inside of the thighs. Tinea capitis caus- tissue-plasminogen activator A sub-
es round, itchy, patches of hair loss on stance produced by body tissues that
the scalp; it occurs mainly in children. prevents abnormal blood clotting. Also
Ringworm of the nails (tinea unguium) called TPA, it is produced by the inner
is often accompanied by scaling of the lining of blood vessels. TPA can be pre-
soles or palms. The nails become thick pared artificially for use as a thrombolytic
and turn white or yellow. drug, which is called alteplase. This is
Most types are diagnosed by appear- used in the treatment of myocardial
ance and by culturing the organisms in infarction, severe angina pectoris, and
a laboratory. Treatment is usually with arterial embolism, including pulmonary
either topical or oral antifungal drugs. embolism. Possible side effects include
tingling See pins-and-needles. bleeding or the formation of a haema-
tinidazole An antibacterial drug that is toma at the injection site and an allergic
particularly useful in treating anaerobic reaction. (See also fibrinolysis.)
infections. It is also used, together with tissue-typing The classification of cer-
other drugs, to eradicate HELICOBACTER tain characteristics of the tissues of
PYLORI infection. Side effects may include prospective organ donors and recipients
nausea, vomiting, gastrointestinal dis- (see transplant surgery). This minimizes
turbances, headache, and dizziness. the risk of rejection of a donor organ by
T tinnitus A ringing, buzzing, whistling, the recipient’s immune system.
hissing, or other noise heard in the ear A person’s tissue type is classified in
or ears in the absence of a noise in the terms of their histocompatibility anti-
environment. Tinnitus is almost always gens, the most important of which are
associated with hearing loss, particularly the human leukocyte antigens (HLAs),
that due to presbyacusis and exposure on the surface of cells. A person’s set of
to loud noise. It can also occur as a HLAs is inherited and unique (except
symptom of ear disorders such as laby- for identical twins, who have the same
rinthitis, Ménière’s disease, otitis media, set). Nevertheless, close relatives often
otosclerosis, ototoxicity, and blockage of have closely matching HLA types. A
the ear canal with earwax. It may also be person’s tissue-type is established by
caused by certain drugs, such as aspirin laboratory tests on cells from a blood
or quinine, or may follow a head injury. sample. In one method, an antiserum
Any underlying disorder is treated if containing antibodies to a particular
possible. Many sufferers make use of HLA is added to the test specimen. If
552
TITANIUM DENTAL IMPLANTS TOLNAFTATE
the HLA is present, it is detected by an Todd’s paralysis Weakness in part of T
observable colour or other change. the body following some types of epil-
titanium dental implants See im- eptic seizure (see epilepsy). The weakness
plants, dental. may last for minutes, hours, or even
TMJ syndrome See temporomandibu- days, but there is no lasting effect. The
lar joint syndrome. cause is thought to be temporary dam-
toadstool poisoning See mushroom age to the motor cortex (the area of the
poisoning. brain that controls movement).
tobacco The dried leaf of the plant NICO-
TIANA TABACUM. Tobacco is used for toe One of the digits of the foot. Each
smoking, chewing, or as snuff by bil- toe has 3 phalanges (bones), except for
lions of people. It contains a variable the hallux (big toe), which has 2. The pha-
percentage of nicotine, and several car- langes join at hinge joints. An artery,
cinogenic substances. There is a direct vein, and nerve run down each side of the
proportion between the amount of to- toe, and the whole structure is enclosed
bacco used, the period over which it is in skin with a nail at the top. The main
used, and the likelihood of cancer. function of the toes is to maintain bal-
Smokers are at increased risk of several ance during walking. Congenital disorders
types of cancer, including lung cancer, include toes missing at birth. (See also
bladder cancer, kidney cancer, and pan- polydactyly; syndactyly; and webbing.)
creatic cancer (see pancreas, cancer of).
All tobacco users have an increased risk toenail, ingrowing A painful condi-
of cancers of the oral cavity (see mouth tion of a toe (usually the big toe) in
cancer), pharynx (see pharynx, cancer which 1 or both edges of the nail press
of), larynx (see larynx, cancer of) and into the adjacent skin, leading to infec-
oesophagus (see oesophagus, cancer of). tion and inflammation. The cause is
tobacco-smoking See smoking. usually incorrect cutting of the nail or
tobramycin An antibiotic drug used to wearing tight-fitting shoes. Temporary
treat serious infections such as periton- pain relief can be obtained by bathing
itis, meningitis, and severe infections of the foot once or twice daily in a strong,
the lungs, skin, bones, and joints. In warm, salt solution, then covering the
eye-drop form, it is sometimes used to nail with a dry gauze dressing. Antibiotics
treat conjunctivitis and blepharitis. High may be prescribed. In some cases, the
doses of injected tobramycin may cause edge of the nail is removed and the nail
kidney damage, deafness, nausea, vom- bed obliterated to prevent recurrence.
iting, and headache. Any preparation of
tobramycin may cause rash and itching. toilet-training The process of teaching
tocography An obstetric procedure for a young child to acquire complete bowel
recording muscular contractions of the and bladder control. A child is unlikely to
uterus during childbirth. It is usually be completely toilet-trained before age
combined with fetal heart monitoring 3 and may normally take much longer
(see cardiotocography). to remain dry at night (see enuresis).
tocopherol A constituent of vitamin E.
Four tocopherols (alpha, beta, gamma, tolbutamide An oral hypoglycaemic drug
and delta) and several tocopherol deriv- (see hypoglycaemics, oral) used in the
atives together make up the vitamin. treatment of type 2 diabetes mellitus.
toddler’s diarrhoea A common condi-
tion affecting some children for a period tolerance The need to take increasingly
after the introduction of an adult diet. It higher doses of a drug to obtain the
occurs because the child is unable to same physical or mental effect. Toler-
digest food properly, perhaps because ance develops after taking a drug over a
of inadequate chewing; the diarrhoea period of time and usually results either
contains recognizable pieces of food. from the liver becoming more efficient
This diarrhoea is no cause for concern, at breaking the drug down or from body
and no treatment is needed. tissues becoming less sensitive to it.
tolnaftate An antifungal drug applied
to the skin to treat, and sometimes pre-
vent, recurrent tinea infections, including
athlete’s foot. In rare cases, tolnaftate
may cause skin irritation or a rash.
553
TOMOGRAPHY TONSIL
tomography An imaging technique that tongue plays an essential part in masti-
produces a cross-sectional image (“slice”) cation, swallowing, and speech.
of an organ or part of the body. Most tongue cancer The most serious type of
tomography today is performed using mouth cancer due to its rapid spread. It
CT scanning and MRI, which produce mainly affects people over 40 and is as-
accurate and detailed images. sociated with smoking, heavy alcohol
-tomy A suffix denoting the operation consumption, and poor oral hygiene. The
of cutting or making an incision. edge of the tongue is most commonly
tone, muscle The natural tension in the affected. The first sign may be a small
muscle fibres. At rest, all muscle fibres ulcer with a raised margin, a leukoplakia,
are kept in a state of partial contraction a fissure, or a raised, hard mass.
by nerve impulses from the spinal cord. Diagnosis of tongue cancer is made by
Abnormally high muscle tone causes an a biopsy. Small tumours, especially
increased resistance to movement, spas- those occurring at the tip of the tongue,
ticity, and rigidity. Abnormally low are usually removed surgically. Larger
muscle tone causes floppiness (see tumours or those that have spread
hypotonia; hypotonia in infants). often require radiotherapy.
tongue A muscular, flexible organ in the tongue depressor A flat wooden or
floor of the mouth that is composed of a metal instrument used to hold the
mass of muscles covered by a mucous tongue on the floor of the mouth to
membrane. The muscles are attached to allow examination of the throat.
the mandible (lower jaw) and hyoid bone tongue-tie A minor mouth defect, also
above the larynx. Tiny nodules called known as ankyloglossia, in which the
papillae stick out from the tongue’s frenulum (the band of tissue attaching
upper surface, giving it a rough texture. the underside of the tongue to the floor
Between the papillae at the sides and of the mouth) is too short and extends
base of the tongue are the taste buds. forwards to the tip of the tongue. There
Taste signals are picked up by nerve are usually no symptoms apart from lim-
fibres from 1 of 4 cranial nerves, and ited movement of the tongue. Rarely,
impulses then travel to the brain. The the condition causes a speech defect,
TONGUE and a minor operation is required to
divide the frenulum.
Epiglottis 10th and tonic One of a diverse group of reme-
9th cranial dies intended to relieve symptoms such
nerves as malaise, lethargy, and loss of ap-
petite. Evidence suggests that tonics
Tonsil mainly have a placebo effect. The term
tonic is also used adjectivally to relate
to muscle tone (see tone, muscle), as in
the tonic neck reflex, one of the primi-
T tive reflexes found in newborn infants.
tonometry The procedure for measur-
ing the pressure of the fluid within the
eye, usually performed by an ophthal-
mologist during an eye examination (see
eye, examination of). Tonometry is use-
ful in diagnosing glaucoma.
tonsil One of a pair of oval tissue masses
Bitter Sweet 5th and at the back of the throat on either side.
taste 7th cranial The tonsils are made up of lymphoid
receptor nerves tissue and form part of the lymphatic
system. Along with the adenoids, at the
Sour Sectioned base of the tongue, the tonsils protect
tongue against upper respiratory tract infec-
Salty tions. The tonsils gradually enlarge
554
TONSILLECTOMY TOUCH
TONSIL toothbrushing Cleaning of the teeth
with a brush to remove plaque and food
Adenoid particles from tooth surfaces and to stim-
Opening of ulate the gums. Toothbrushing should
eustachian be carried out twice a day using a fluo-
tube ride dentifrice (usually toothpaste).
Nasal tooth decay See caries, dental.
cavity tooth extraction See extraction, dental.
toothpaste See dentifrice.
Palate tophus A collection of uric acid crystals
Tonsil deposited in tissues, especially around
joints, but occasionally in other places
Tongue such as the ear. It is a sign of hyper-
uricaemia, which accompanies gout.
Pharynx topical A term describing a drug that is
applied to the surface of the body, not
Epiglottis swallowed or injected.
torsion A term that means twisting, often
from birth until the age of 7, after which applied to the intestine or testis. T
time they shrink substantially. Tonsillitis torticollis Twisting of the neck, causing
is a common childhood infection. the head to be tilted and fixed in an ab-
tonsillectomy Surgical removal of the normal position (wry neck). There is
tonsils, which is now performed only if a often neck pain and stiffness. The cause
child suffers frequent, recurrent attacks is usually a minor neck injury that irri-
of severe tonsillitis. The operation is also tates cervical nerves, leading to muscle
carried out to treat quinsy (an abscess spasm. Other causes are sleeping in an
around the tonsil). awkward position, a neck-muscle injury
tonsillitis Inflammation of the tonsils as at birth, and a burn or injury that has
a result of infection. Tonsillitis mainly caused heavy scarring.
occurs in children under age 9. Some-
times the tonsils become repeatedly Torticollis due to muscle spasm may be
infected by the microorganisms they are treated by use of an orthopaedic collar
supposed to protect against. The main (see collar, orthopaedic), heat treatment,
symptoms are a sore throat and diffi- ultrasound treatment, physiotherapy, or
culty in swallowing. The throat is visibly injections of the toxin that causes botu-
inflamed. Other common symptoms are lism. When the cause is an injury arising
fever, headache, earache, enlarged and from birth, the muscle is gently stretched
tender lymph nodes in the neck, and several times each day; occasionally, an
bad breath. Occasionally, there may be operation is required.
temporary deafness or quinsy (an abs- touch The sense by which certain cha-
cess around the tonsil). racteristics of objects, such as their size,
shape, temperature, and surface texture,
Tonsillitis is treated with plenty of flu- can be ascertained by physical contact.
ids and an analgesic drug such as
paracetamol; in some cases antibiotic The skin has many types of touch
drugs may also be prescribed. receptors, including Merkel’s discs and
tooth See teeth. Meissner’s corpuscles to detect light
tooth abscess See abscess, dental. touch, and Pacinian corpuscles to sense
toothache Pain in 1 or more teeth and deep pressure and vibration. Signals
sometimes the gums. Causes include from these receptors pass, via sensory
dental caries, a tooth fracture (see frac- nerves, to the spinal cord, from there to
ture, dental), a deep, unlined filling (see the thalamus in the brain, and on to the
filling, dental), periodontitis, a dental sensory cortex, where touch sensations
abscess (see abscess, dental), a blow to are perceived and interpreted.
a tooth, or referred pain from sinusitis.
Analgesic drugs may provide temporary The various parts of the body differ in
relief. Treatment depends on the cause. their sensitivity to painful stimuli and
in touch discrimination. For example, the
555
TOURETTE’S SYNDROME TOXOPLASMOSIS
TOUCH A high fever, vomiting, diarrhoea, head-
ache, muscle aches and pains, dizziness,
Meissner’s Pacinian Merkel’s Free nerve and disorientation develop suddenly. A
corpuscle corpuscle disc ending widespread skin rash that resembles sun-
burn and also affects the palms and
soles, develops. Blood pressure may fall
dangerously low, and shock may develop.
Other complications include kidney fail-
ure and liver failure. Treatment in an
intensive care unit may be needed.
toxin A poisonous protein produced by
pathogenic (disease-causing) bacteria,
various animals, or some plants. Bacte-
rial toxins are sometimes subdivided into
3 categories: endotoxins, which are
released from dead bacteria; exotoxins,
which are released from live bacteria; and
TOUCH RECEPTORS IN SKIN enterotoxins, which inflame the intestine.
(See also poison; poisoning; toxaemia.)
toxocariasis An infestation of humans,
cornea is several hundred times more usually children, with the larvae of TOXO-
sensitive to painful stimuli than the CARA CANIS: a small, threadlike worm
soles of the feet. (See also sensation.) that lives in the intestines of dogs.
Tourette’s syndrome See Gilles de la Children who play with an infested dog
Tourette’s syndrome. or soil contaminated with dog faeces,
tourniquet A device placed around a and who then put their fingers in their
limb to compress blood vessels. A tour- mouths, may swallow some of the worm
niquet may be used to help locate a eggs. The eggs hatch in the intestines,
vein for an intravenous injection or for and the released larvae migrate to organs
the withdrawal of blood. An inflatable such as the liver, lungs, brain, and eyes.
tourniquet, called an Esmarch’s bandage, Usually, infestation causes mild fever
is used to control blood flow in some and malaise, which soon clears up; but
limb operations. The use of a tourniquet heavy infestation may lead to pneumonia
as a first-aid measure to stop severe and seizures. Loss of vision may occur if
bleeding can cause gangrene. larvae enter the eye and die there.
toxaemia Presence in the bloodstream A diagnosis is made from sputum
of toxins produced by bacteria. (See also analysis, and by a liver biopsy. Severe
preeclampsia; toxic shock syndrome.) cases require treatment in hospital with
toxaemia of pregnancy See pre- tiabendazole and an anticonvulsant drug.
eclampsia. toxoid An inactivated bacterial toxin. Cer-
T toxicity The property of being toxic (pois- tain toxoids are used to immunize against
onous). Toxicity also refers to the severity specific diseases, such as tetanus.
of adverse effects or illness produced by toxoplasmosis An infection caused by
a toxin, a poison, or a drug overdose. the protozoan TOXOPLASMA GONDII that is
toxicology The study of poisons. (See often caused by eating undercooked
also poisoning.) meat from infected animals, or by hand-
toxic shock syndrome An uncommon, ling faeces from infected cats. In most
severe illness caused by a toxin pro- cases there are no symptoms, but some-
duced by the bacterium STAPHYLOCOCCUS times there may be a feverish illness
AUREUS. Many cases occur in women that resembles infectious mononucleosis.
using vaginal tampons. Other cases have Retinitis (inflammation of the retina)
been linked to use of a contraceptive and choroiditis may also develop. In peo-
cap, diaphragm, or sponge (see contra- ple with an immunodeficiency disorder
ception), or to skin wounds or infections toxoplasmosis may cause lung and heart
by the bacterium elsewhere in the body. damage and severe encephalitis.
556
TPA TRACT
Toxoplasmosis contracted by a pregnant which beat the mucus upwards to help
woman is transmitted to the fetus in keep the lungs and airways clear.
about a third of cases. It may result in tracheitis Inflammation of the trachea.
miscarriage or stillbirth, or the infant may Tracheitis is usually caused by a viral
have an enlarged liver and spleen, blind- infection and is aggravated by inhaled
ness, hydrocephalus, learning difficulties, fumes, especially tobacco smoke. It often
or may die during infancy. Infection in occurs with laryngitis and bronchitis in a
late pregnancy usually has no ill effects. condition known as laryngotracheobron-
The diagnosis is made from blood chitis. Symptoms include a painful dry
tests. Treatment (with pyrimethamine cough and hoarseness. In most cases,
and a sulphonamide drug) is necessary no treatment is needed.
only in pregnant women, in children tracheoesophageal fistula A rare birth
with severe symptoms, in people with defect in which an abnormal passage
an immune system deficiency, and in connects the trachea with the oesopha-
cases of retinitis or choroiditis. gus. About 3 babies per 10,000 are born
TPA The abbreviation used for tissue- with this fistula.
plasminogen activator. The condition is often discovered soon
trabeculectomy A surgical procedure after birth; diagnosis may be confirmed
to control glaucoma by allowing the by X-rays. Treatment consists of an oper-
fluid from the front chamber of the eye ation to close the fistula and connect
to drain out under the conjunctiva. the trachea and oesophagus correctly.
trace elements Minerals necessary in tracheostomy An operation in which
minute amounts in the diet to maintain an opening is made in the trachea and a
health. Examples are chromium, copper, tube is inserted to maintain an effective
zinc, and selenium. (See also nutrition.) airway. A tracheostomy is used for the
tracer A radioactive substance that is emergency treatment of airway prob-
introduced into the body so that its dis- lems involving the larynx. A planned
tribution, processing, and elimination tracheostomy is most commonly perfor-
from the body can be monitored. med on a person who has lost the
trachea The air passage, also called the ability to breathe naturally and is under-
windpipe, that runs from immediately going long-term ventilation or is unable
below the larynx to behind the upper to keep saliva and other secretions out
part of the sternum, where it divides to of the trachea. Permanent tracheostomy
form the bronchi. The trachea is made is needed after laryngectomy.
of fibrous and elastic tissue and smooth tracheotomy Cutting of the trachea. (See
muscle. It also contains about 20 rings of also tracheostomy.)
cartilage, which keep it open. The lining trachoma A persistent infectious disease
of the trachea has cells (goblet cells) of the cornea and conjunctiva. Trachoma
that secrete mucus and cells with cilia, is caused by CHLAMYDIA TRACHOMATIS
TRACHEA and is spread by T
direct contact and
Air Muscle Cartilage ring possibly by flies
passage (see chlamydial
infections). It is
Trachea
Bronchus Mucous uncommon in the
membrane UK, but, world-
wide, is the most
common cause of
Layer of blindness .
mucus tract Any one of
a group of organs
that form a com-
mon pathway to
perform a partic-
LOCATION STRUCTURE OF TRACHEA ular function. The
557
TRACTION TRANSIENT ISCHAEMIC ATTACK
term also refers to a bundle of nerve transcutaneous electrical nerve
fibres that have a common function. stimulation See TENS.
traction A procedure in which part of transdermal patch A method of admin-
the body is placed under tension to cor- istering a drug through the skin. The drug
rect the alignment of 2 adjoining is released from the patch over a period
structures or to hold them in position. of time and is absorbed by the skin.
Traction is most commonly used to TRANSDERMAL PATCH
treat a fracture in which muscles around
the bone ends are pulling the bones
out of alignment.
training A programme of exercises that
is undertaken to prepare for a particular
sport. Training may be concentrated on
improving skills or on improving physical
fitness. Fitness training should include Patch
both aerobic and anaerobic exercises, applied
which together build up strength, flexi- to skin
bility, and endurance. Interval training
is a type of fitness programme in which
a particular exercise is repeated several
times with a rest period between. Cir-
cuit training consists of performing a
set number of different exercises.
trait Any characteristic or condition that transference The unconscious displace-
is inherited (determined by 1 or more ment of emotions from people who
genes). Blue or brown eye colour, dark were important during one’s childhood,
or light skin, body proportions, and nose such as parents, to other people during
shape are examples of genetic traits. adulthood. (See also psychoanalysis.)
The term trait is also sometimes used transfusion See blood transfusion.
to describe a mild form of a recessive transfusion, autologous See blood
genetic disorder. transfusion, autologous.
tramadol An opioid drug used to relieve transient ischaemic attack (TIA) A
severe pain following a heart attack, sur- brief interruption of the blood supply to
gery, or serious illness. It is less likely to part of the brain, which causes tem-
cause dependence with long-term use porary impairment of vision, speech,
than most opioids. Possible side effects sensation, or movement. The episode
include nausea, vomiting, drowsiness, typically lasts for several minutes or, at
confusion, and impaired consciousness. the most, for a few hours. TIAs are some-
trance A sleeplike state in which con- times described as mini strokes, and
sciousness is reduced, voluntary actions they can be the prelude to a stroke.
T lessened or absent, and body functions TIAs may be caused by a blood clot
diminished. Trances are claimed to be (see embolism) temporarily blocking an
induced by hypnosis and have been artery that supplies the brain, or by
reported as part of a group experience. narrowing of an artery as a result
Trances may be a feature of catalepsy, of atherosclerosis.
automatism, and petit mal epilepsy. After a TIA, tests such as CT scanning,
tranexamic acid An antifibrinolytic drug blood tests, ultrasound scanning, or
that promotes blood clotting. It is used angiography may be needed to deter-
to treat menorrhagia. Possible side effects mine a cause. In some cases, the heart
include diarrhoea, nausea, and vomiting. is studied as a possible source of blood
tranquillizer drugs Drugs that have a clots. Treatment is aimed at preventing
sedative effect. Tranquillizers are div- stroke, which occurs within 5 years in
ided into 2 types: major tranquillizers up to one third of patients with TIA.
(see antipsychotic drugs) and minor Treatments include endarterectomy, anti-
tranquillizers (see antianxiety drugs). coagulant drugs, or aspirin.
558
TRANSILLUMINATION TRAZODONE
transillumination A procedure that is transvestism Also called cross-dressing, T
sometimes carried out during physical a persistent desire by a man to dress in
examination of a lump or swelling. Light women’s clothing.
from a small torch is shone on 1 side of
the lump; if it can be seen on the other tranylcypromine An antidepressant drug
side, the lump contains clear fluid. that belongs to the monoamine-oxidase
inhibitor (MAOI) group and is used main-
translocation A rearrangement of the ly in patients with severe depression.
chromosomes inside a person’s cells; it
is a type of mutation. Sections of chro- trapezius muscle A large, diamond-
mosomes may be exchanged or the main shaped muscle extending from the back
parts of 2 chromosomes may be joined. of the skull to the lower part of the
A translocation may be inherited or ac- spine in the chest and across the width
quired as the result of a new mutation. of the shoulders. It is attached to the
A translocation often has no obvious top and back of the shoulderblade and
effect, and causes no abnormality. How- to the outermost part of the collarbone.
ever, in some cases, it can mean that The trapezius helps support the neck and
some of the affected person’s egg or spine and is involved in moving the arm.
sperm cells carry too much or too little
chromosomal material, which may cause trapped nerve See nerve, trapped.
a chromosomal abnormality, such as trauma A physical injury or severe emo-
Down’s syndrome, in his or her children.
tional shock. (See also post-traumatic
transmissible A term meaning capable stress disorder.)
of being passed from one person, or trauma surgery See traumatology.
one organism, to another. traumatology Emergency treatment of
patients suffering from acute trauma
transplant surgery Replacement of a (such as severe and/or multiple injuries).
diseased organ or tissue with a healthy, travel immunization Anyone planning
living substitute. The organ is usually to travel abroad may need immuniza-
taken from a person who has just died. tions before departure. Although few
Some kidneys are transplanted from a immunizations are compulsory for inter-
patient’s living relatives (see organ dona- national travel, some are recommended
tion). The results of surgery have also for the traveller’s protection.
been improved by testing for histo-
compatibility antigens and tissue-typing. Travel agents and tour operators often
Rejection is a major problem. However, include information about which immu-
a combination of a corticosteroid drug nizations may be needed, but travellers
and ciclosporin are given in order to should consult a doctor about individ-
suppress this response. ual requirements. Some vaccines must
Every patient who undergoes an organ be given in 2–3 doses several weeks
transplant operation must take immuno- apart. Therefore, a doctor should be
suppressant drugs indefinitely. (See also consulted at least 2–3 months before
heart transplant; heart–lung transplant; departure. Children under 1 year, and
liver transplant; kidney transplant.) people with a compromised immune
system or serious underlying disorder
transposition of the great vessels A may not be able to have some vacci-
serious form of congenital heart disease nations, such as those for yellow fever
in which the aorta and pulmonary artery and tuberculosis (BCG).
are transposed. Open heart surgery is traveller’s diarrhoea A disorder occur-
needed to correct the defect. ring in people who are visiting foreign
countries. Episodes of diarrhoea range
transsexualism A rare disorder in which in severity and are due to gastroenteritis.
a person wishes to live as a member of Attention to hygiene, drinking bottled
the opposite sex. Transsexuals commonly water, and avoiding ice in drinks can
seek hormonal or surgical treatment to prevent a large proportion of episodes.
bring about a physical sex change. A travel sickness See motion sickness.
psychiatric evaluation and a physical trazodone An antidepressant drug with
examination are necessary before such a strong sedative effect that is used to
treatment is undertaken. treat depression accompanied by anxiety
559
TREATMENT TRICHINOSIS
or insomnia. Possible side effects include treatment but usually improves the
drowsiness, constipation, dry mouth, condition within 3–4 months. Possible
dizziness, and, rarely, priapism. side effects include irritation, peeling,
treatment Any measure that is taken to and discoloration of the skin. Exposure
prevent or cure a disease or disorder or of the skin to sunlight while using
to relieve symptoms. tretinoin may aggravate irritation and
trematode The scientific name for any can lead to sunburn.
fluke or schistosome. trial, clinical A test on human volun-
trembling See tremor. teers of the effectiveness and safety of a
tremor An involuntary, rhythmic, oscil- drug. A trial can also involve systematic
lating movement in the muscles of part comparison of alternative forms of medi-
of the body, most commonly those of cal or surgical treatment for a particular
the hands, feet, jaw, tongue, or head. disorder. Patients involved in clinical tri-
Tremor is the result of rapidly alternat- als have to give their consent, and the
ing muscle contraction and relaxation. trials are approved and supervised by
Occasional tremors are experienced by an ethics committee.
most people and are due to increased triamcinolone A corticosteroid drug that
production of the hormone adrenaline is used to treat inflammation of the
(epinephrine). A slight, persistent tre- mouth, gums, skin, and joints; asthma;
mor is common in elderly people. and certain blood disorders, such as
Essential tremor, which runs in fami- thrombocytopenia and leukaemia.
lies, is a slight-to-moderate tremor that triamterene A diuretic drug used to
may be temporarily relieved by consum- treat hypertension and oedema. Pos-
ing a small amount of alcohol or by sible adverse effects include nausea,
taking beta-blocker drugs. vomiting, weakness, and rash.
Coarse tremor (4–5 muscle movements tribavirin see ribavirin.
per second), which is present at rest but triceps muscle The muscle at the back
reduced during movement, is often a of the upper arm. At the upper end of
sign of Parkinson’s disease. An intention the triceps are 3 “heads”; 1 is attached to
tremor (tremor that is worse on move- the outer edge of the scapula (shoul-
ment of the affected part) may be a sign derblade), and the other 2 to either side
of cerebellar ataxia. Tremor may also be of the humerus (upper-arm bone). The
caused by multiple sclerosis, Wilson’s dis- lower part of the triceps is attached to
ease, mercury poisoning, thyrotoxicosis, the olecranon process of the ulna (the
or hepatic encephalopathy; drugs, such bony prominence on the elbow). Con-
as amfetamines and caffeine; and with- traction of the muscle straightens the
drawal from drugs, including alcohol. arm. (See also biceps muscle.)
trench fever An infectious disease that trichiasis An alteration in the direction
is now rare or unknown in most parts of of eyelash growth, in which the lashes
the world. The disease is caused by rick- grow inwards towards the eyeball. They
T ettsiae spread by body lice. Symptoms can rub against the eye, causing severe
include headache, muscle pains, and discomfort and sometimes damage to
fever, which may occur in bouts. Treat- the cornea. Trachoma is a cause.
ment is with antibiotic drugs. trichinosis An infestation with the lar-
trench foot See immersion foot. vae of the TRICHINELLA SPIRALIS worm,
trench mouth See gingivitis, acute usually acquired by eating undercooked
ulcerative. pork. Trichinosis is rare in the UK. Thor-
trephine A hollow, cylindrical instru- ough cooking of all pork products, and
ment with a saw-toothed edge used for freezing meat to a temperature below
cutting a circular hole, usually in bone. –18°C for 24 hours, helps to avoid infec-
tretinoin A topical drug that is chemi- tion. Slight infestation usually causes
cally related to vitamin A and is used to no symptoms. However, heavy infesta-
treat acne and certain skin disorders tion may cause diarrhoea and vomiting
such as ichthyosis. Tretinoin may aggra- within a day or two of eating the infec-
vate acne in the first few weeks of ted meat, followed by fever, swelling
560
TRICHOMONIASIS TRICYCLIC ANTIDEPRESSANTS
around the eyelids, and severe muscle condition, which TRICUSPID VALVE
pains, which may last for several weeks. is also known as
Trichinosis may be suspected from the
symptoms, and the diagnosis is con- tricuspid insuffic- Tricuspid Aortic
firmed by blood tests, or by a muscle iency, reduces the valve valve
biopsy. Treatment of the infestation is
with an anthelmintic drug. pumping effici-
trichomoniasis An infection caused by
the protozoan TRICHOMONAS VAGINALIS. ency of the heart.
Trichomoniasis is a common cause of
vaginitis. In some cases, the infection is The usual cause is
sexually transmitted.
pulmonary hyper-
In women, the causative organism
may inhabit the vagina for years without tension, but more
causing symptoms. If symptoms occur,
they include painful inflammation of rarely, it follows
the vagina and vulva, and a greenish,
frothy, offensive-smelling discharge. Men rheumatic fever,
usually have no symptoms.
or, in intravenous
The diagnosis is made from exami-
nation of a sample of the discharge. drug users, a bac-
Diagnosis usually difficult in men. Treat-
ment is with metronidazole. The sexual terial infection of
partner or partners of an infected per-
son should be treated at the same time the heart. Right
to prevent reinfection. Tricuspid incom- ventricle
trichotillomania The habit of cons-
tantly pulling out one’s hair. It can be petence results in STRUCTURE OF HEART
associated with severe mental handicap
or with a psychotic illness. It may also symptoms of right-
occur in psychologically disturbed chil-
dren. The sufferer typically pulls, twists, sided heart failure, notably oedema of
and breaks off chunks of hair from the
scalp, leaving bald patches; occasionally, the ankles and abdomen. The liver is
pubic hair is pulled out. Children some-
times eat the removed hair, which may swollen and tender, and veins in the
form a hairball in the stomach, known
medically as a trichobezoar (see bezoar). neck are distended.
Treatment depends on the cause, and
may consist of psychotherapy or anti- A diagnosis is made from the symp-
psychotic drugs.
trichuriasis A parasitic infestation with toms, from hearing a heart murmur
the tropical worm TRICHURIS TRICHURIA
(whipworm). Children are most com- through a stethoscope, and by tests that
monly affected. Infestation occurs when
eggs are ingested and develop into may include an ECG, chest X-rays, echo-
adult worms in the intestines. Severe
infestation may cause bloody diarrhoea, cardiography, and cardiac catheterization.
abdominal pain, and weight loss. Treat-
ment is with anthelmintic drugs. Treatment with diuretic drugs and ACE
triclosan An antiseptic.
tricuspid incompetence Failure of the inhibitors often relieves the symptoms.
tricuspid valve to close fully, allowing
blood to leak back into the right atrium tricuspid stenosis Narrowing of the
when the right ventricle contracts. The
opening of the tricuspid valve, usually
caused by a previous attack of rheumatic
fever. Tricuspid stenosis is uncommon
and often occurs with another heart-
valve disorder. For example, tricuspid
incompetence may also occur in intra-
venous drug users who have a bacterial
infection of the heart. Tricuspid stenosis
causes enlargement of the right atrium.
The symptoms and diagnosis are simi-
lar to those of tricuspid incompetence. T
Treatment is with diuretic drugs and
sometimes a digitalis drug. Heart-valve
surgery is sometimes needed.
tricuspid valve A valve in the heart
consisting of 3 flaps that lies between
the right atrium and the right ventricle.
It ensures that blood flow from the atri-
um to the ventricle is in 1 direction only.
tricyclic antidepressants A type of
antidepressant drug. Tricyclic antidepres-
sants prevent neurotransmitters in the
brain from being reabsorbed, thereby
increasing their level. Examples are ami-
triptyline, clomipramine, and imipramine.
561
TRIFLUOPERAZINE TROCHLEAR NERVE
trifluoperazine An antipsychotic drug triprolidine An antihistamine drug that
used to treat schizophrenia. is used to treat allergy, as an ingredient
trigeminal nerve The 5th cranial nerve. of cough and cold remedies, and to
A trigeminal nerve arises from the brain- treat or prevent allergic reactions to
stem. Both nerves divide into 3 branches certain foods or blood transfusions. Pos-
that supply sensation to the face, scalp, sible side effects of triprolidine include
nose, teeth, lining of the mouth, upper dry mouth, dizziness, difficulty in pass-
eyelid, sinuses, and the front portion of ing urine, and hyperactivity.
the tongue. They stimulate saliva and trismus Involuntary contraction of the
tear production and contraction of jaw jaw muscles, which causes the mouth to
muscles for chewing. become tightly closed. Commonly known
trigeminal neuralgia A disorder of the as lockjaw, it may occur as a symptom
trigeminal nerve in which brief episodes of tetanus, tonsillitis, mumps, or acute
of severe, stabbing pain affect the ulcerative gingivitis and other dental
cheek, lips, gums, or chin on 1 side of problems affecting the back teeth. Treat-
the face. The disorder usually occurs ment is of the underlying cause.
over age 50. Pain may come in bouts trisomy The presence of an extra chro-
that last for weeks at a time. The cause mosome within a person’s cells, making
is uncertain, and pain is often brought 3 of a particular chromosome instead of
on by touching the face, eating, drink- the usual 2. A fault during meiosis to
ing, or talking. Analgesic drugs may be form egg or sperm cells leaves an egg or
tried, but often, carbamazepine is more sperm with an extra chromosome. When
effective. If this fails, surgery may help. the egg or sperm takes part in fertiliza-
trigger finger Locking of 1 or several tion, the resulting embryo inherits an
fingers in a bent position due to inflam- extra chromosome in each of its cells.
mation of the sheath enclosing the tendon The most common trisomy is of
of the affected finger. The finger is usually chromosome 21 (Down’s syndrome).
tender at the base and slightly swollen Trisomy 18 (Edward’s syndrome) and
over the tendon. Treatment involves trisomy 13 (Patau’s syndrome) are less
local injection of a corticosteroid drug common; trisomy 8 and trisomy 22 are
or, if this is unsuccessful, surgery. very rare. Partial trisomy, with only part
triglyceride A type of simple fat (see of a chromosome in triplicate, also
fats and oils) made up of a molecule of occurs. Full trisomies cause abnorma-
glycerol and 3 molecules of fatty acids. lities such as skeletal and heart defects
Triglycerides are the main type of fat and learning difficulties. Except in
found in stores of body fat. Down’s syndrome, babies usually die in
trimeprazine Also called alimemazine. early infancy. The effects of partial tri-
An antihistamine drug used to relieve somies depend on the amount of extra
itching in allergic conditions, and as a chromosomal material present.
premedication in children. Side effects Diagnosis is made by chromosome
T are typical of antihistamines. analysis of cells, which may be obtained
trimester A period of 3 months; human from the fetus by amniocentesis or after
pregnancy is conventionally divided into the birth. There is no specific treatment.
3 trimesters. Parents of an affected child should seek
trimethoprim An antibacterial drug used genetic counselling.
to treat a range of infections, most com- trisomy 21 syndrome Another name
monly those of the urinary tract. Possible for Down’s syndrome.
side effects include rash, itching, nausea, trochlear nerve The 4th cranial nerve.
vomiting, diarrhoea, and a sore tongue. The 2 trochlear nerves arise in the
trimipramine A tricyclic antidepressant brainstem, 1 on each side of the mid-
drug used to treat depression accompa- brain, and enter the eye sockets
nied by anxiety or insomnia. Possible side through gaps in the skull bones. Each
effects include dry mouth, blurred vision, trochlear nerve controls 1 of the 2 sup-
dizziness, constipation, and nausea. erior oblique muscles, which rotate the
triple vaccine See DPT vaccination. eyes downwards and outwards.
562
TROPHOBLASTIC TUMOUR TUBERCULOSIS
trophoblastic tumour A growth aris- tubal pregnancy See ectopic pregnancy. T
ing from the tissues that develop into tubercle A grey, nodular mass found in
the placenta. The most common type of
trophoblastic tumour is a hydatidiform tissues affected by tuberculosis. The
mole. (See also choriocarcinoma.) term also refers to a small rounded pro-
trusion on the surface of a bone.
tropical diseases Diseases prevalent tuberculin tests Skin tests used to
in the tropics because of living condi- determine whether or not a person has
tions and diet include malnutrition, been exposed to the bacterium that
measles, diphtheria, tuberculosis, typhoid causes tuberculosis. Tuberculin tests are
fever, shigellosis, cholera, amoebiasis, carried out for diagnosis of tuberculosis,
and tapeworm infestation. Diseases and before BCG vaccination. A small
spread through the tropics by insects amount of tuberculin (purified protein
include malaria, yellow fever, sleeping from the bacteria) is injected into the
sickness, and leishmaniasis. Exposure to skin. A few days later, the skin reaction,
strong sunlight in the tropics causes an if any, is noted. A reaction indicates
increased tendency to skin cancer, and previous exposure.
may lead to pinguecula and pterygium. tuberculosis An infectious disease, com-
monly called TB, caused in humans by
tropical ulcer An area of persistent skin the bacterium MYCOBACTERIUM TUBER-
and tissue loss caused by infection with CULOSIS. TB is usually transmitted in
1 or more organisms. The condition is airborne droplets expelled when an infec-
most common in malnourished people ted person coughs or sneezes. An
living in the tropics. Treatment is clean- inhaled droplet enters the lungs and
ing and dressing of the ulcer, a course of the bacteria begin multiplying. The
antibiotic drugs, and a high protein diet. immune system usually seals off the
The ulcer usually heals but may scar. infection at this point, but in about 5 per
cent of cases the infection spreads to the
tropicamide A drug used to dilate the lymph nodes. It may also spread to
pupil. Adverse effects of the drug include other organs through the bloodstream,
blurred vision, increased sensitivity to which may lead to miliary tuberculosis,
light, stinging, and, rarely, dry mouth, a potentially fatal form of the disease.
flushing, and glaucoma.
In about another 5 per cent of cases,
trunk The central part of the body, com- bacteria held in a dormant state by the
prising the chest and abdomen. The immune system become reactivated
term also refers to any large blood ves- months, or even years, later. The infec-
sel or nerve, from which smaller vessels tion may then progressively damage the
or nerves branch off. lungs, forming cavities.
truss An elastic, canvas, or padded metal The primary infection is usually with-
appliance used to hold an abdominal out symptoms. Progressive infection in
hernia in place. Trusses are only used if the lungs causes coughing (sometimes
corrective surgery cannot be undertaken. bringing up blood), chest pain, short-
ness of breath, fever and sweating, poor
trypanosomiasis A tropical disease cau- appetite, and weight loss. Pleural effu-
sed by TRYPANOSOMA parasites. (See also sion or pneumothorax may develop. The
sleeping sickness; Chagas’ disease.) lung damage may be fatal.
tsetse fly bites The bites of tsetse flies, A diagnosis is made from the symp-
which are found in Africa, can be painful. toms and signs, from a chest X-ray, and
The flies, resembling brown houseflies, from tests on the sputum. Alternatively,
spread sleeping sickness. a bronchoscopy may also be carried out
to obtain samples for culture.
T-tube cholangiography An imaging
technique performed to check that there Treatment is usually with a course of 3
are no gallstones left in the bile duct or 4 drugs, taken daily for 2 months, fol-
after a cholecystectomy. A T-shaped rub- lowed by daily doses of isoniazid and
ber tube is inserted into the bile duct rifampicin for 4–6 months. However, TB
during the surgery. A week or so later, bacteria are increasingly resistant to the
contrast medium is inserted into the
tube and X-rays are taken.
tubal ligation See sterilization, female.
563
TUBEROSITY TWINS
drugs used in treatment, and others may Rinne test, a vibrating tuning fork is
have to be used and treatment carried held first near the ear, and then against
out for a longer period. If the full course the bone behind it. If it sounds louder
of drugs is taken, most patients recover. when held against the bone, there is
TB can be prevented by BCG vaccina- conductive hearing loss.
tion, which is offered routinely at birth tunnel vision Loss of the peripheral
or age 10–14. Any contacts of an infected visual field to the extent that only
person are traced and examined, and, if objects straight ahead can be seen
infected, are treated early to reduce the clearly. Tunnel vision is most commonly
risk of the infection spreading. caused by chronic glaucoma. Retinitis
tuberosity A prominent area on a bone pigmentosa is another possible cause.
to which tendons are attached. Turner’s syndrome A disorder caused
tuberous sclerosis An inherited disor- by a chromosomal abnormality that only
der that affects the skin and nervous affects females. The abnormality may
system. An acne-like condition of the arise in 1 of 3 ways: affected females
face, epilepsy, and learning difficulties may have only 1 X chromosome instead
often occur. Noncancerous tumours of of 2; they may have 1 normal and 1
the brain, kidney, retina, and heart may defective X chromosome; or they may
also develop. There is no cure, and have a mixture of cells (see mosaicism),
treatment aims only to relieve symp- in which some of the cells are missing
toms. In serious cases, death occurs an X chromosome, some have extra
before the age of 30. Genetic counselling chromosomes, and others have the
is recommended for affected families. normal complement of chromosomes.
tuboplasty Surgery in which a damaged Turner’s syndrome causes short stature;
fallopian tube is repaired to treat infertility. webbing of the skin of the neck; absence
It may be performed by microsurgery. or retarded development of sexual char-
tularaemia A bacterial infection of wild acteristics; amenorrhea, coarctation of
animals that is sometimes transmitted the aorta, and abnormalities of the eyes
to humans. Tularaemia does not occur and bones.
in the UK but is seen in North America. Treatment with growth hormone from
It may result from contact with an infancy helps girls with Turner’s syn-
infected animal or carcass, or a tick, flea, drome to achieve near normal height.
fly, or louse bite. A diagnosis is made by Coarctation of the aorta is treated sur-
blood tests. Treatment is with antibiotic gically. Treatment with oestrogen drugs
drugs. Tularaemia is fatal in 5 per cent induces menstruation, but it does not
of untreated cases. make affected girls fertile.
tumbu fly bites A cause of myiasis. TURP The abbreviation for transurethral
tumour A term that describes any swel- resection of the prostate. TURP is a sur-
ling but which is generally used to refer gical procedure in which the central
to an abnormal mass of tissue that forms part of an enlarged prostate gland is
T when cells in a specific area reproduce at removed (see prostate, enlarged). A
an increased rate. Tumours can be can- viewing instrument called a resecto-
cerous or noncancerous. scope is passed along the urethra until
tumour-specific antigen A substance it reaches the prostate. A heated wire
secreted by a specific type of tumour loop, or sometimes a cutting edge, is
that can be detected in the blood and inserted through the resectoscope and
may be used to help monitor a patient’s used to cut away excess prostate tissue.
response to therapy. Alpha-fetoprotein is twins Two offspring resulting from one
an example of a tumour-specific antigen. pregnancy. Monozygotic, or identical,
tuning fork tests Hearing tests carried twins develop when a single fertilized
out to diagnose conductive deafness. In egg divides at an early stage of develop-
the Weber test, a vibrating tuning fork is ment. Incomplete division of the egg
held against the forehead. If there is results in conjoined twins (see Siamese
conductive hearing loss, the sound twins). Monozygotic twins share the
seems louder in the affected ear. In the same placenta. Dizygotic twins develop
564
TWINS, CONJOINED TYPING
TWINS with sewage, by
flies carrying the
Placenta Placenta Shared bacteria from fae-
placenta ces to food, or by
infected people
handling food.
The 1st symptom,
severe headache,
occurs 7–14 days
after infection and
is followed by fever,
loss of appetite,
malaise, abdominal
tenderness, consti-
Uterus Uterus pation, and often
Cervix Cervix delirium. Diarrhoea
NONIDENTICAL TWINS soon develops. In
IDENTICAL TWINS
the 2nd week of ill-
ness, pink spots
when 2 eggs are fertilized at the same develop on the chest and abdomen,
time. They each have a placenta and and the liver and spleen enlarge. Diag-
may be of different sexes. Twins occur in nosis is confirmed by a blood test or by
about 1 in 80 pregnancies. (See also obtaining a culture of typhoid bacteria
pregnancy, multiple.) from blood, faeces, or urine. Treatment
twins, conjoined Identical twins physi- is with antibiotic drugs. In rare cases,
cally joined due to a failure to separate the bacterium continues to be excreted
during development from a single fertil- after recovery has taken place.
ized egg. Also called Siamese twins. typhus Any of a group of infectious dis-
twitch See fasciculation; tic. eases with similar symptoms that are
tympanic membrane The medical term caused by rickettsiae and are spread by
for the eardrum. insects or similar animals.
tympanometry A type of hearing test Except in some highland areas of
used to establish the cause of conduc- tropical Africa and South America, epi-
tive deafness. During the test, a probe demic typhus is rare today. Endemic
that contains a tone generator, a micro- typhus, also called murine typhus, is a
phone, and an air pump is introduced disease of rats that is occasionally
into the outer-ear canal. The air pres- spread to humans by fleas; sporadic
sure in the ear is varied and tones are cases occur in North and Central Amer-
played into it. The tone pattern reflect- ica. Scrub typhus is spread by mites and
ed from the eardrum and received by occurs in India and Southeast Asia.
the microphone sreveals whether the The symptoms and complications of T
eardrum is moving normally. The test is all types of typhus are similar. Severe
particularly useful in children because it headache, back and limb pain, cough-
does not rely on a response from the ing, and constipation develop suddenly
person being tested. and are followed by high fever, a
tympanoplasty An operation on the measles-like rash, confusion, and pros-
ear to treat conductive deafness by tration. Left untreated, the condition
repairing a hole in the eardrum (see may be fatal, especially in elderly or
myringoplasty) or by repositioning or debilitated people.
reconstructing diseased ossicles. A diagnosis is made by blood tests,
typhoid fever An infectious disease and treatment is with antibiotic drugs
contracted by eating food or drinking and supportive treatment.
water contaminated with the bacterium typing A general term for procedures by
SALMONELLA TYPHI. Typhoid fever is which blood or tissues are classified
spread by drinking water contaminated (see blood groups; tissue-typing).
565
ULCER ULCERATIVE COLITIS
U (such as at an injection site or from a
toothbrush), acute stress, or allergies
(such as allergic rhinitis). In women,
aphthous ulcers are most common dur-
ing the premenstrual period. They may
also be more likely if other family mem-
bers suffer from recurrent ulceration.
Analgesic mouth gels or mouthwashes
may ease the pain of an aphthous ulcer.
ulcer An open sore appearing on the Some ointments form a waterproof cov-
skin or on a mucous membrane that ering that protects the ulcer while it is
results from the destruction of surface healing. Ulcers heal by themselves, but
tissue. Ulcers may be shallow, or deep a doctor may prescribe a paste contain-
and crater-shaped, and they are usually ing a corticosteroid drug or a mouthwash
inflamed and painful. containing an antibiotic drug to speed
Skin ulcers most commonly occur on up the healing process.
the leg (see leg ulcer), usually as the ulceration The formation or presence
result of inadequate blood supply to, or of 1 or more ulcers.
drainage from, the limb. In some cases ulcerative colitis Chronic inflammation
skin cancers, particularly basal cell car- and ulceration of the lining of the colon
cinomas or squamous cell carcinomas, and rectum, or, especially at the start of
may be ulcerated. Rarely, a cancer may the condition, of the rectum alone. The
develop in the skin at the edge of a cause of ulcerative colitis is unknown,
longstanding ulcer. but the condition is most common in
The most common types of ulcers of young and middle-aged adults.
the mucous membranes are mouth ul- The main symptom of ulcerative coli-
cers, peptic ulcers, and those that occur tis is bloody diarrhoea; and the faeces
in ulcerative colitis. may also contain mucus. In severe
Ulcers may also affect the skin or cases, the diarrhoea and bleeding are
mucous membranes of the genitalia extensive, and there may be abdominal
(see genital ulcer). Most genital ulcers are pain and tenderness, fever, and general
caused by sexually transmitted infec- malaise. The incidence of attacks varies
tions. Examples of this type of ulcer are considerably. Most commonly, the at-
hard chancres (see chancre, hard), which tacks occur at intervals of a few months.
develop during the first stage of syph- However, in some cases, there may be
ilis, and soft chancres (see chancroid). only a single episode.
In addition, ulcers may develop on the Ulcerative colitis may lead to anaemia,
cornea (see corneal ulcers). caused by blood loss. Other complica-
ulcer, aphthous A small, painful ulcer tions include a toxic form of megacolon,
that occurs, alone or in a group, on the which may become life-threatening;
inside of the cheek or lip or underneath rashes; aphthous ulcers; arthritis; con-
the tongue. Aphthous ulcers are most junctivitis; or uveitis. There is also an
U common between the ages of 10 and 40 increased risk of cancer of the colon
and affect more women than men. The developing (see colon, cancer of).
most severely affected people have con- A diagnosis is based on examination
tinuously recurring ulcers; others have of the rectum and lower colon (see
just 1 or 2 ulcers each year. sigmoidoscopy) or the entire colon (see
Each ulcer is usually small and oval, colonoscopy), or is made by a barium
with a grey centre and a surrounding enema (see barium X-ray examination).
red, inflamed halo. The ulcer, which During sigmoidoscopy or colonoscopy,
usually lasts for 1–2 weeks, may be a a biopsy may be performed. Samples of
hypersensitive reaction to haemolytic faeces may be taken for laboratory anal-
streptococcus bacteria. Other factors ysis in order to exclude the possibility
commonly associated with the occur- of infection by bacteria or parasites.
rence of these ulcers are minor injuries Blood tests may also be needed.
566
ULCER-HEALING DRUGS ULTRASOUND SCANNING
Medical treatments of ulcerative colitis A fracture to the shaft usually results U
include corticosteroid drugs and sulfa- from a blow to the forearm or a fall onto
salazine and its derivatives. Colectomy the hand. Sometimes the radius is frac-
may be required for a severe attack that tured at the same time (see radius,
fails to respond to other treatments, or fracture of). Surgery is usually needed
to avoid colonic cancer in those people to reposition the broken bone ends and
who are at high risk. fix them together using either a plate
ulcer-healing drugs A group of drugs and screws or a long nail down the cen-
that are used to treat or prevent peptic tre of the bone. The arm is immobilized
ulcers. The eradication of HELICOBACTER in a cast, with the elbow at a right-
PYLORI infection by treatment with anti- angle, until the fracture heals.
biotic drugs and a drug to reduce acid
secretion is now the preferred treat- A fracture of the olecranon process is
ment for peptic ulceration. usually the result of a fall onto the
elbow. If the bone ends are not dis-
Ulcer-healing drugs work in several placed, the arm is immobilized in a
ways. H2-receptor antagonists function cast that holds the elbow at a right-
by blocking the effects of histamine, angle. If the bone ends are displaced,
an action that reduces acid secretion in however, they are fitted together and
the stomach, thereby promoting the fixed with a metal screw.
healing of ulcers. Taking antacid drugs ulnar nerve One of the principal nerves
regularly may be effective in healing of the arm. The ulnar nerve, a branch of
duodenal ulcers because the drugs the brachial plexus, runs down the full
neutralize excess acid. Omeprazole and length of the arm and into the hand.
misoprostol work by reducing acid The ulnar nerve controls muscles that
secretion. Other ulcer-healing drugs, move the thumb and fingers. It also
such as sucralfate, are believed to form conveys sensation from the 5th finger,
a protective barrier over the ulcer, part of the 4th finger, and the palm.
allowing healing of the underlying tis-
sues to take place. A blow to the olecranon process, over
which the ulnar nerve passes, causes a
The choice of ulcer-healing drug dep- pins-and-needles sensation and pain in
ends on the length of time symptoms the forearm and 4th and 5th fingers.
have been present and the appearance Persistent numbness and weakness in
of the ulcer during endoscopy. In many areas controlled by the ulnar nerve may
cases of recent onset, a course of acid- be caused by an abnormal bony out-
blocking drugs or antacids will give growth from the humerus. This may be
rapid relief. Recurrent ulcers usually due to osteoarthritis or a fracture of the
require treatment with antibiotic drugs. humerus, and surgery is needed to
ulna The longer of the 2 bones of the relieve the pressure on the nerve. Per-
forearm; the other is the radius. With manent damage to the ulnar nerve can
the arms straight at the sides, palm for- result in claw-hand.
wards, the ulna is the inner bone (that ultrasound Sound with a frequency that
is, nearer the trunk) running down the is greater than the human ear’s upper
forearm on the side of the little finger. limit of perception: that is, higher than
20,000 hertz (cycles per second). Ultra-
The upper end of the ulna articulates sound used in medicine for diagnosis or
with the radius and extends into a treatment is typically in the range of
rounded projection (known as the olec- 1–15 million hertz (see ultrasound scan-
ranon process) that fits around the ning; ultrasound treatment).
lower end of the humerus to form part ultrasound scanning A diagnostic tech-
of the elbow joint. The lower end of the nique in which very high frequency sound
ulna articulates with the carpals (wrist waves are passed into the body and the
bones) and lower part of the radius. reflected echoes analysed to build a
ulna, fracture of A fracture of the ulna, picture of the internal organs or of a
1 of the 2 bones of the forearm. Ulnar fetus in the uterus. The procedure is
fractures typically occur across the shaft painless and considered safe.
or at the olecranon process.
567
ULTRASOUND TREATMENT UMBILICAL HERNIA
Ultrasonic waves are emitted by a trans- ultrasound treatment The use of ultra-
ducer, which is placed on the skin over sound to treat soft-tissue injuries (such
the part of the body to be viewed. The as injuries to ligaments, muscles, and
transducer contains a crystal that con- tendons). Ultrasound treatment reduces
verts an electric current into sound waves. inflammation and speeds up healing. It
These pass readily through soft tissues is thought to work by improving blood
and fluids, making this procedure useful flow in tissues under the skin.
for examining fluid-filled or soft organs. ultraviolet light Invisible light from the
One of the most common uses of ultra- part of the electromagnetic spectrum
sound is to view the uterus and fetus, at immediately beyond the violet end of
any time during pregnancy, but often at the visible light spectrum. Long wave-
18–20 weeks. The age, size, and growth length ultraviolet light is termed UVA,
rate of the fetus can be determined; intermediate UVB, and short UVC.
multiple pregnancies detected; and Ultraviolet light occurs in sunlight, but
certain problems, such as neural tube much of it is absorbed by the ozone
defects, diagnosed. Scans may be taken layer. The ultraviolet light (mainly UVA)
early in pregnancy if problems, such as that reaches the earth’s surface causes
an ectopic pregnancy, are suspected. the tanning effects of sunlight and the
Ultrasound scanning can also be used production of vitamin D in the skin. It
in newborn babies to examine the brain can have harmful effects, such as skin
through a gap in the skull (for example, cancer (see sunlight, adverse effects of).
to investigate hydrocephalus). Ultra- Ultraviolet light is sometimes used in
sound can help to diagnose disorders phototherapy. A mercury-vapour lamp
such as cirrhosis, gallstones, hydroneph- (Wood’s light) can also produce ultravi-
rosis, and pancreatitis, as well as olet light. This is used to diagnose skin
problems in the thyroid gland, breasts, conditions such as tinea because it
bladder, testes, ovaries, spleen, and causes the infected area to fluoresce.
eyes. The technique is also used during umbilical cord The ropelike structure
needle biopsy to help guide the needle. connecting the fetus to the placenta that
Doppler ultrasound is a modified form supplies the fetus with oxygen and
of ultrasound that uses the Doppler nutrients from the mother’s circulation.
effect to investigate moving objects. The umbilical cord is usually 40–60 cm
This can be used to examine the fetal long and contains 2 arteries and a vein.
heartbeat and to obtain information umbilical hernia A soft swelling at the
about the rate of blood flow in vessels. umbilicus due to protrusion of the ab-
ULTRASOUND SCANNING dominal contents
through a weak area
Radiographer Gel of abdominal wall.
Umbilical hernias
Monitor are quite common
Ultrasound in newborn babies
transducer and occur twice
U as often in boys as
in girls. The swel-
ling increases in
size when the baby
cries, and it may
cause discomfort.
Umbilical hernias
usually disappear
without treatment
by age 2. If a her-
nia is still present
at age 4, surgery
ULTRASOUND SCANNING IN PREGNANCY may be needed.
568
UMBILICUS URETHRITIS
Umbilical hernias sometimes develop outer layer; muscular middle layer; and U
in adults, especially in women after inner watertight layer. Each ureter is sup-
childbirth. Surgery may be necessary for plied by blood vessels and nerves. Urine
a large, persistent, or disfiguring hernia. flows down the ureters partly from grav-
umbilicus The scar on the abdomen ity but mainly as a result of peristalsis.
that marks the site of attachment of the
umbilical cord to the fetus. It is com- Some people are born with double
monly called the navel. ureters, on 1 or both sides of the body.
unconscious A specific part of the mind This sometimes causes reflux of urine,
in which ideas, memories, perceptions, incontinence, or infection.
or feelings that a person is not currently ureteric colic See renal colic.
aware of are stored and processed. The ureterolithotomy The surgical removal
contents of the unconscious mind are of a stone (see calculus, urinary tract)
not easily retrieved, in contrast to those stuck in a ureter. It is not commonly
of the subconscious. (See also Freudian needed because lithotripsy and cysto-
theory; Jungian theory.) scopy can be used to deal with stones.
unconsciousness An abnormal loss of urethra The tube through which urine is
awareness of self and one’s surroundings excreted from the bladder. In females, it
due to a reduced level of activity in the is short and opens to the outside in
reticular formation of the brainstem. An front of the vagina. In males, it is much
unconscious person can be roused only longer, is surrounded by the prostate
with difficulty or not at all. Unconscious- gland at its upper end, and forms a
ness may be brief and light, as in fainting, channel through the length of the penis.
or deep and prolonged (see coma). urethral dilatation The procedure in
underbite See prognathism. which a urethral stricture in a male is
unsaturated fats See fats and oils. widened by inserting a slim, round-
unstable bladder Another name for tipped instrument through the opening
irritable bladder. of the urethra at the tip of the penis.
uraemia The presence of excess urea urethral discharge A fluid that flows
and other chemical waste products in from the urethra in some cases of ure-
the blood, caused by kidney failure. thritis caused by infection.
uranium A radioactive metallic element urethral stricture A rare condition in
that does not occur naturally in its pure which the male urethra becomes nar-
form but is widely found in ores such as rowed and sometimes shortened as a
pitchblende, carnotite, and uraninite. result of shrinkage of scar tissue within
Radioactive decay of uranium yields a its walls. Scar tissue may form after
series of radioactive products, including injury to the urethra or after persistent
radium and radon. During the various urethritis. The stricture may make passing
decay stages, radiation is emitted. Ura- urine or ejaculation difficult or painful,
nium is also poisonous. and it may cause some deformation of
urea A waste product of the breakdown the penis when erect. Treatment is usu-
of proteins by the liver that is transpor- ally by urethral dilatation.
ted to the kidneys and eliminated in the urethral syndrome, acute A set of
urine. Urea is also formed in the body symptoms, usually affecting women,
from the breakdown of cell proteins. Kid- that are very similar to cystitis but which
ney failure impairs the kidneys’ ability occur in the absence of infection.
to eliminate urea and leads to uraemia; urethritis Inflammation of the urethra,
measurement of blood levels of urea is a usually due to an infection but some-
routine kidney function test. Urea is times having other causes.
used in various creams and ointments
to treat skin disorders such as psoriasis. Urethritis may be caused by various
ureter One of the 2 tubes that carry urine infectious organisms, including the bac-
from the kidneys to the bladder. Each terium that causes gonorrhoea. Non-
ureter is 25–30 cm long. There are 3 lay- gonococcal urethritis may be caused by
ers in the walls of the ureters: a fibrous any of a large number of different types
of microorganisms. Urethritis may also
be caused by damage from an accident
569
URETHROCELE URINARY RETENTION
or from a catheter or cystoscope. Other function, and to help detect and diag-
possible causes include irritant chemi- nose urinary tract and other disorders.
cals, such as antiseptics and some urinary diversion Any surgical proced-
spermicidal preparations. Treatment of ure (temporary or permanent) that allows
infection is with antibiotic drugs. urine flow when the outlet channel of the
urethrocele An anatomical abnormality urinary tract, via the bladder and urethra,
in females caused by a weakness in the is obstructed or cannot be used, or the
tissues in the front wall of the vagina. bladder has been surgically removed.
The urethra bulges backwards and down-
wards into the vagina. A urethrocele may Temporary urinary diversion is some-
be congenital but more commonly devel- times needed when urine passage is
ops after childbirth. blocked by prostate gland enlargement
-uria A suffix relating to urine. or by urethral stricture. A tube is passed
uric acid A waste product of the break- directly into the bladder through a
down of nucleic acids in body cells. A small opening in the abdomen (see
small amount is also produced by the catheterization, urinary). Temporary div-
digestion of foods rich in nucleic acids, ersion is also required after some urinary
such as liver, kidney, and other offal. tract operations; a small tube is intro-
Most uric acid produced in the body duced into the kidney and brought to
passes to the kidneys, which excrete it the abdominal surface.
in the urine, but some passes into the
intestine, where it is broken down into Permanent diversion is needed when
chemicals excreted in the faeces. the bladder has been surgically removed,
when neurological bladder control is
When uric acid excretion is disrupted, severely disturbed, such as after severe
for example by kidney disease, it may spinal injury, or if there is an irreparable
result in hyperuricaemia. fistula between a female patient’s bladder
urinal A container for urine, useful for or urethra and her vagina. A section of
bedridden men (women use a bedpan). the ileum is removed to create a substi-
urinalysis Tests on urine, including mea- tute bladder, into one end of which the
surements of its physical characteristics surgeon implants the ureters. The other
(such as colour, cloudiness, and concen- end of the substitute bladder is then
tration), microscopic examination, and brought out through an incision in the
chemical testing such as dipstick urinaly- abdominal wall. The patient wears a bag
sis. This involves dipping a test stick into attached to the skin to collect urine.
a urine sample; chemically impregnated urinary retention Inability to empty the
squares on the stick change colour in the bladder or difficulty in doing so. Urinary
presence of test substances. The inten- retention may be complete (urine can-
sity of colour change shows the amount not be passed voluntarily at all) or
of the substance present in the urine. incomplete (the bladder fails to empty
Urinalysis can be used to check kidney completely). In males, causes include
phimosis, urethral stricture, prostatitis, a
URINALYSIS
U Test stick Colour
is dipped chart
in urine
sample
Urine
sample
Squares on
test stick are
matched to
colour chart
DIPSTICK-URINALYSIS
570
URINARY SYSTEM URINARY TRACT INFECTION
Aorta URINARY TRACT
Kidney Adrenal gland
(whole) (cross section)
Kidney (cross section)
Renal Renal vein
artery
Ureter
Prostate Peritoneum folded back
gland Bladder
Ureter Urethra Bladder
Urethra
MALE FEMALE
stone in the bladder (see calculus, urin- urinary tract The part of the body con- U
ary tract), and enlargement or tumour cerned with the formation and excretion
of the prostate (see prostate, enlarged; of urine. The urinary tract consists of
prostate, cancer of). In females, causes the kidneys (with their blood and nerve
include pressure on the urethra from supplies), the renal pelvises (funnel-
uterine fibroids or from a fetus. In either shaped ducts that channel urine from
sex, the cause may be a bladder tumour. the kidneys), the ureters, the bladder,
and the urethra.
Retention may also be due to defective The kidneys make urine by filtering
functioning of the nerve pathways sup- blood. The urine collects in the renal
plying the bladder as a result of general pelvises and is then passed down the
or spinal anaesthesia, drugs affecting ureters into the bladder by the actions
the bladder, surgery, injury to the nerve of gravity and peristalsis. Urine is stored
pathways, or disease of the spinal cord. in the bladder until there is a sufficient
amount present to stimulate micturi-
Complete retention causes discomfort tion. When the bladder contracts, the
and lower abdominal pain, except when urine is expelled through the urethra.
nerve pathways are defective. The full
bladder can be felt above the pubic bone. urinary tract infection An infection
However, chronic or partial retention anywhere in the urinary tract. It has
may not cause any serious symptoms. differing symptoms, depending on the
Retention can lead to kidney damage area affected. Urethritis causes a burn-
and, often, a urinary tract infection. ing sensation when urine is being
passed. Cystitis causes a frequent urge
Treatment of retention is by catheteri- to pass urine, lower abdominal pain,
zation (see catheterization, urinary). The haematuria, and, often, general malaise
cause is then investigated. Obstruction with a mild fever. Pyelonephritis causes
can usually be treated; if nerve damage fever and pain in the back under the
is the cause, permanent or intermittent ribs. Cystitis and pyelonephritis are
catheterization is sometimes necessary.
urinary system See urinary tract.
571
URINATION, EXCESSIVE URINE, ABNORMAL
almost always the result of a bacterial kidney failure pass urine more frequent-
infection. Urethritis is often due to a ly, especially during the night. Treatment
sexually transmitted infection, such as of frequent urination is always of the
gonorrhoea, but may have other causes. underlying cause.
Urethral infections are more common urination, painful Pain or discomfort
in men. Infections further up the urinary that occurs when urine is being passed.
tract are more common in women. In Painful urination is known medically as
men, there is often a predisposing fac- dysuria. The pain is often described
tor, such as an enlarged prostate gland as burning; sometimes it is preceded by
(see prostate, enlarged). In women, preg- difficulty in starting urine flow. Pain
nancy is a risk factor. after the flow has ceased, with a strong
In both sexes, causes of urinary tract desire to continue, is called strangury.
infections include stones (see calculus, The most common cause, especially in
urinary tract), bladder tumours, congeni- women, is cystitis. Other causes include
tal abnormalities of the urinary tract, or a bladder tumour, bladder stone (see cal-
defective bladder emptying as a result culus, urinary tract), urethritis, balanitis,
of spina bifida or a spinal injury. The prostatitis, vaginal candidiasis (thrush),
risks of developing a urinary tract infec- or allergy to vaginal deodorants. Strang-
tion can be reduced by strict personal ury is usually caused by spasm of an
hygiene, drinking lots of fluids, and reg- inflamed bladder wall, but it may be
ularly emptying the bladder. due to bladder stones. Mild discomfort
Urethritis can lead to the formation of when passing urine may be caused by
a urethral stricture. Cystitis usually only highly concentrated urine.
causes complications if the infection Dysuria may be investigated by phys-
spreads to the kidneys. Pyelonephritis, ical examination, urinalysis, urography,
if it is left untreated, can lead to perm- or cystoscopy. (See also urethral syn-
anent kidney damage, septicaemia, and drome, acute.)
septic shock. urine The pale yellow fluid produced by
The infection is diagnosed by the the kidneys and excreted from the body
examination of a urine culture. Further via the ureters, bladder, and urethra.
investigations using urography or ultra- Urine is produced when blood is filtered
sound scanning may be necessary. Most through the kidneys to remove waste
infections of the urinary tract are treated products and excess water or chemical
with antibiotic drugs. substances. The main component is urea.
urination, excessive The production of A healthy adult produces between 0.5
more than 2.5 litres of urine per day. and 2 litres of urine per day. The mini-
The medical term is polyuria. mum volume of urine needed to remove
Causes include psychiatric problems, all waste products is about 0.5 litres. A
which may cause a person to drink com- high fluid intake increases the amount
pulsively; diabetes mellitus; disorders of of urine produced; high fluid loss from
the kidney known as salt-losing states; sweating, vomiting, or diarrhoea leads
and central diabetes insipidus. Any per- to reduced production.
U son who passes large quantities of urine, abnormal Urine may be pro-
urine should consult a doctor. duced in abnormal amounts or have an
urination, frequent Also known as uri- abnormal appearance or composition.
nary “frequency”, the passing of urine Conditions of abnormal production of
more often than the average of 4–6 urine include excessive production (see
times daily. Causes of frequent urina- urination, excessive), oliguria, and anuria.
tion include excessive production of Abnormal appearances of urine include
urine (see urination, excessive), cystitis, cloudiness (which may be caused by a
anxiety, stones in the bladder (see cal- urinary tract infection, a calculus, or the
culus, urinary tract), enlargement of the presence of salts); haematuria; discol-
prostate gland (see prostate, enlarged) oration from certain foods or drugs; and
in men, and, rarely, a bladder tumour. frothiness (which may be caused by an
Some people who are suffering from excess of protein).
572
URINE TESTS URTICARIA
Abnormal composition of the urine may the patient has stress incontinence (see
occur in diabetes mellitus, kidney failure, incontinence, urinary).
and sometimes glomerulonephritis and urography See intravenous urography.
nephrotic syndrome, as well as in other urology A branch of medicine concerned
kidney disorders such as Fanconi’s syn- with the structure, functioning, and dis-
drome and renal tubular acidosis. orders of the urinary tract in males and
urine tests See urinalysis. females, and of the reproductive system
urodynamics A group of tests carried in males. Investigative techniques that
out to investigate problems with bladder are used in urology include urography,
control, such as incontinence. Urodyna- cystoscopy, ultrasound scanning, cysto-
mic studies involve the insertion of metry, and urinalysis.
probes into the urethra, bladder, and ursodeoxycholic acid A drug used to
rectum or vagina in order to monitor dissolve gallstones. It is only suitable if
pressure changes while the bladder is the stones are made exclusively of
being filled and emptied. cholesterol and if the gallbladder is
functioning normally. Side effects of the
In X-ray monitoring, the patient stands drug are rare but can include diarrhoea,
against an upright table while his or her indigestion, and a rash. Drug treatment
bladder is filled with a contrast medium is less commonly used since the intro-
through a catheter and is then emptied duction of minimally invasive surgery.
again. The shape and functioning of the urticaria A skin condition, also known
bladder, and the functioning of the ure- as nettle rash or hives, that is character-
thra, can then be viewed on an X-ray ized by the development of itchy weals,
monitor. At the same time, a continu- usually on the limbs and trunk. Large
ous recording of pressure changes within weals may merge to form irregular,
the bladder is made on a paper trace. raised patches.
As the bladder is being filled, the
patient is asked to cough. This action Urticaria is generally harmless and usu-
increases the pressure in and around ally lasts only a few hours. Sometimes a
the bladder, and if it causes leakage of persistent or recurrent form develops.
urine onto an electronic absorbent pad, Dermographism is a less common form
URODYNAMICS
X-ray table Uterus Ureter Rectum
Urethra
Solution Radiographer
containing
contrast X-ray
medium monitor
X-ray machine
Probe Probe in U
in bladder vagina
Catheter SITE OF PROBES
to bladder
Monitor
controls
Lead from
vaginal probe
Lead from Lead from
bladder probe electronic pad
X-RAY MONITORING Pressure trace
573
URTICARIA, NEONATAL UTERUS, CANCER OF
of urticaria in which weals form after UTERUS
the skin is stroked. Urticaria sometimes
occurs with angioedema. Uterus Fallopian tube Ovary
The cause of urticaria is often un-
known. The most common known cause
is an allergic reaction (see allergy),
often to a particular food, food additive,
or drug. Urticaria may also be caused by
exposure to heat, cold, or sunlight. Less
commonly, it may be associated with Bladder
another disorder, such as vasculitis, sys-
temic lupus erythematosus, or cancer.
Itching can be relieved by applying Cervix
calamine lotion or by taking antihis-
tamine drugs. More severe cases may
require corticosteroid drugs. Identifying Vagina
and avoiding known trigger factors can
help prevent future reactions. A tend- the cervix; the upper part opens into the
ency to urticaria often disappears in fallopian tubes. The inside is lined with
time without treatment. endometrium. The uterus expands in size
urticaria, neonatal A very common, during pregnancy to accommodate the
harmless skin condition, also known as growing baby. At full-term, the powerful
erythema neonatorum or toxic eryth- uterine muscles expel the baby via the
ema, that affects newborn infants. A birth canal (see childbirth). After the
blotchy rash, in which raised white or menopause, the endometrium atrophies
yellow lumps are surrounded by ill- (becomes thinner) and the uterine mus-
defined red areas of inflammation, cle and connective tissue are reduced.
forms, mainly affecting the face, chest, Conditions that affect the uterus include
arms, and thighs. The cause of neonatal congenital disorders, such as malform-
urticaria is unknown. The rash usually ation or absence of the uterus; tumours,
clears up without treatment. including polyps, fibroids, and cancer
uterine muscle relaxants Drugs that of the endometrium (see uterus, cancer
are used to delay the premature del- of); infections, causing endometritis; and
ivery of a fetus. Beta2-adrenoceptor hormonal disorders. (See also uterus,
stimulants, such as salbutamol, relax prolapse of; uterus, retroverted.)
the muscle of the uterus and may post- uterus, cancer of A malignant growth
pone labour for days or weeks in at-risk in the tissues of the uterus. Cancer of
pregnancies of 24–33 weeks’ gestation. the uterus mainly affects the cervix (see
Delay of premature labour for up to 48 cervix, cancer of) and endometrium. In
hours allows time for corticosteroid rare cases, the uterine muscle is affected
drugs to be given to the mother to help by a type of cancer called a leiomyosar-
the fetal lungs to mature. coma. The term uterine cancer usually
U uterovaginal prolapse See uterus, refers to cancer of the endometrium.
prolapse of. Risk factors for endometrial cancer
uterus The hollow, muscular organ of include anything that may raise oestro-
the female reproductive system in which gen levels in the body, such as obesity, a
the fertilized ovum (egg) normally be- history of failure to ovulate, or taking
comes embedded and in which the oestrogen hormones long term if these
embryo and fetus develop. The uterus are not balanced with progestogen drugs.
is commonly known as the womb. It is It is also more common in women who
situated in the pelvic cavity, behind the have had few or no children.
bladder and in front of the intestines. Before the menopause, the first symp-
In a nonpregnant woman, the uterus tom of cancer of the uterus may be
is 7.5–10 cm long and weighs 60–90 g. menorrhagia or bleeding between per-
The lower part opens into the vagina at iods or after sexual intercourse; after
574
UTERUS, PROLAPSE OF UVULA
the menopause, it is usually a blood- uvea Part of the eye, comprising the iris,
stained vaginal discharge. Diagnosis is the ciliary body and its muscle that
made by hysteroscopy or biopsy. focuses the lens, and the choroid.
Very early endometrial cancer is usu- uveitis Inflammation of the uvea, which
ally treated by hysterectomy and removal may seriously affect vision. Uveitis may
of the fallopian tubes and ovaries. If the affect any part of the uvea, including the
cancer has spread, radiotherapy and anti- iris (when it is called iritis), the 0 (when
cancer drug treatment may also be used. it is known as cyclitis), or the choroid
uterus, prolapse of A condition in which (when it is called choroiditis). The most
the uterus descends from its normal common cause is an autoimmune disor-
position into the vagina. The degree of der. Other causes include infections
prolapse varies from 1st-degree prolapse, such as tuberculosis and syphilis. Treat-
in which there is only slight displacement ment is with corticosteroid drugs and
of the uterus, to 3rd-degree prolapse eye-drops containing an atropine-relat-
(procidentia), in which the uterus can be ed substance. The inflammation is
seen outside the vulva. monitored with a slit-lamp. Various
other drugs may be prescribed if the
Stretching of the ligaments supporting cause is an infection.
the uterus (during childbirth, for exam-
ple) is the most common cause. Prolapse uvula The small, fleshy protuberance
is aggravated by obesity. that hangs from the middle of the lower
edge of the soft palate.
There are often no symptoms, but
sometimes there is a dragging feeling
in the pelvis. Diagnosis is made by
physical examination.
Pelvic floor exercises strengthen the
muscles of the vagina and thus reduce
the risk of a prolapse, especially follow-
ing childbirth. Treatment usually involves
surgery (hysterectomy). Rarely, if surgery
is not wanted or is not recommended, a
plastic ring-shaped pessary may be
inserted into the vagina to hold the
uterus in position. (See also cystocele;
rectocele; urethrocele.)
uterus, retroverted A normal variation
in which the uterus inclines backwards
rather than forwards. A retroverted uterus
rarely causes problems unless it is com-
bined with a pelvic infection.
UTERUS, RETROVERTED
Bladder Usual position Retroverted
of uterus uterus
U
575
VACCINATION VAGINAL DISCHARGE
V sexual intercourse and childbirth and are
richly supplied with blood vessels.
vaginal bleeding Bleeding, via the vagi-
na, that may come from the uterus, the
cervix, or from the vagina itself.
The most common source of bleeding
is the uterus and the most likely reason
for it is menstruation. From puberty to
the menopause, menstrual bleeding
vaccination A form of immunization in usually occurs at regular intervals. How-
which killed or weakened microorg- ever, problems may occur with either
anisms, or inactivated bacterial toxins, the character or the timing of the bleed-
are introduced into the body, usually by ing (see menstruation, disorders of).
injection, to sensitize the immune sys- Nonmenstrual bleeding from the uterus
tem (see vaccine). If disease-causing may be due to a variety of causes. Hor-
organisms or toxins of the same type monal drugs, such as oral contraceptives,
later enter the body, the sensitized can cause spotting. Other possible causes
immune system rapidly produces anti- include endometritis, endometrial can-
bodies that destroy them. cer (see uterus, cancer of), and fibroids.
vaccine A preparation given to induce In early pregnancy, bleeding may be a
immunity against an infectious disease. sign of threatened miscarriage. Later in
Most vaccines contain the organisms pregnancy, it may indicate placenta
(or parts of the organisms) against praevia or placental abruption (see
which protection is sought. antepartum haemorrhage).
Vaccines are usually given by injection Bleeding from the cervix may be due
into the upper arm, but some, such as to cervical erosion, in which case it may
the poliomyelitis vaccine, may be given occur after intercourse. Cervicitis and
orally. Some vaccines require several polyps may also cause bleeding. More
doses, spaced some weeks apart; others seriously, bleeding may be a sign of cer-
require only 1 dose. vical cancer (see cervix, cancer of).
vacuum extraction An obstetric pro- A possible cause of bleeding from the
cedure to facilitate the delivery of a vagina is injury during intercourse,
baby. It may be used if the second stage especially following the menopause,
of labour (see childbirth) is prolonged, when the walls of the vagina become
if the mother becomes exhausted, or if thinner and more fragile. Occasionally,
the baby shows signs of fetal distress. severe vaginitis causes bleeding. Rarely,
Vacuum suction techniques are also vaginal bleeding is caused by cancer
used to perform early abortions. of the vagina.
The vacuum extraction instrument vaginal discharge The emission of se-
consists of a suction cup connected to cretions from the vagina. Some mucous
a vacuum bottle. The suction cup is secretion from the vaginal walls and
placed on the baby’s head in the birth from the cervix is normal in the repro-
canal, and the vacuum machine sucks ductive years; its amount and nature
the baby’s scalp into the cup. The ob- vary from woman to woman and at dif-
V stetrician draws the baby out of the ferent times in the menstrual cycle (see
mother’s vagina by gently pulling on the menstruation). Oral contraceptives can
cup with each uterine contraction. increase or decrease the discharge.
The baby is born with a swelling on Secretions tend to be greater during
the scalp, but this disappears after a pregnancy. Sexual stimulation also pro-
few days, usually without treatment. duces increased vaginal discharge.
vagina The muscular passage, forming Discharge may be abnormal if it is
part of the female reproductive system, excessive, offensive-smelling, yellow or
between the cervix and the external green, or if it causes itching. Abnormal
genitalia. The vagina has muscular discharge often accompanies vaginitis,
walls, which are highly elastic to allow and may be the result of infection, as in
576
VAGINAL ITCHING VA LV U L O P L A S T Y
candidiasis or trichomoniasis, or may be valgus The medical term for outward
due to a foreign body, such as a forgot- displacement of a part of the body.
ten tampon, in the vagina.
vaginal itching Irritation in the vagina, valproate See sodium valproate.
often associated with vulval itching. In Valsalva’s manoeuvre A forcible at-
many cases, it is a symptom of vaginitis,
which may be caused by infection or an tempt to breathe out when the airway is
allergic reaction to hygiene or spermici- closed. The manoeuvre occurs naturally
dal products. Vaginal itching is common when an attempt is made to breathe out
after the menopause, when it is caused while holding the vocal cords tightly
by low oestrogen levels. Depending on together. This happens, for example, at
the cause, treatment may be with anti- the beginning of a sneeze. When per-
biotic drugs or hormones. formed deliberately by pinching the
vaginal repair An operation to correct nose and holding the mouth closed, the
prolapse of the vaginal wall. This may manoeuvre can prevent pressure dam-
be accompanied by a vaginal hysterec- age to the eardrums (see barotrauma).
tomy if the uterus is also prolapsed (see valve A structure that allows fluid or
uterus, prolapse of). semi-fluid material to flow in 1 direc-
vaginismus Painful, involuntary spasm of tion through a tube or passageway but
the muscles surrounding the entrance closes to prevent reflux in the opposite
to the vagina, interfering with sexual direction. The valves at the exits from
intercourse and sometimes also medical the heart chambers and in the veins are
vaginal examinations. (See also inter- essential to the circulatory system. There
course, painful; psychosexual dysfunction.) are also small valves in the vessels of
vaginitis Inflammation of the vagina the lymphatic system.
that may be caused by infection, com-
monly by the fungus CANDIDA ALBICANS Blood at low VALVE
(see candidiasis), the parasite TRICHO- pressure
MONAS VAGINALIS (see trichomoniasis), or Blood at high pressure
bacteria. After the menopause the vagi- closes valve
nal lining becomes fragile and prone to
inflammation. This is called atrophic Valve Valve
vaginitis and is due to a reduction in cusp cusp
the production of oestrogen hormones. (flap)
Infections are treated with antibiotics Blood Low-
or antifungal drugs. In cases of allergy, at high pressure
irritants should be avoided. Any foreign pressure blood
body is removed. Atrophic vaginitis is opens
treated with oestrogen drugs. (See also valve CLOSED VALVE
vulvitis; vulvovaginitis.)
vagotomy An operation in which the OPEN VALVE
vagus nerve, which controls production
of digestive acid by the stomach wall, is valve replacement A surgical operation V
cut. Once widely used to treat some to replace a defective or diseased heart
cases of peptic ulcer, it has now largely valve. (See also heart-valve surgery.)
been replaced by drug treatment.
vagus nerve The 10th cranial nerve and valvotomy An operation that is per-
principal component of the parasympa- formed to correct a narrowed heart
thetic division of the autonomic nervous valve. Cuts are made, or pressure is
system. The vagus nerve passes from applied, to separate the flaps of the
the medulla oblongata (in the brainstem) valve where they have joined, thereby
through the neck and chest to the abdo- reducing the degree of narrowing. Valvo-
men, and has branches to most major tomy is performed either by opening the
organs, including the larynx, pharynx, tra- heart up (see heart-valve surgery) or by
chea, lungs, heart, and digestive system. balloon valvuloplasty.
valvular heart disease A defect of 1
or more of the heart valves.
valvuloplasty Reconstructive or repair
surgery on a defective heart valve (see
heart-valve surgery). Valvuloplasty may
577
VAPORIZER VASECTOMY
be performed as open heart surgery. Varicose veins may not cause any prob-
However, the technique of balloon lems but may ache severely; swollen
valvuloplasty makes it possible to treat feet and ankles and persistent itching
a narrowed valve without opening the may occur. These symptoms may wors-
chest. A balloon catheter is passed en during the day and can be relieved
through the skin into a blood vessel only by sitting with the legs raised. In
and from there to the heart. Inflation of women, symptoms are often worse just
the balloon via the catheter then sepa- before menstruation. In severe cases,
rates the flaps of a narrowed valve. leg ulcers may occur. Thrombophlebitis
vaporizer A device for converting a may be associated with varicose veins.
drug or water into a fine spray so that Usually, support stockings, regular walk-
medication can be taken by inhalation ing, and sitting with the feet up as
or so that inhaled air can be moistened. much as possible are the only measures
variant angina A form of angina that required. In more severe cases, scle-
causes chest pain at rest, often during rotherapy may be carried out. Varicose
sleep. The pain may occur with breath- veins may require surgical removal if
lessness and palpitations. The cause is they become painful or ulcerated, but
thought to be narrowing of the coronary they may later develop elsewhere.
arteries by muscular spasm in their variola Another name for smallpox.
walls. Treatment with calcium channel varus The medical term for an inward
blockers or nitrates is usually effective. displacement of part of the body.
varicella Another name for chickenpox. vascular Relating to the blood vessels
varicella–zoster The virus that causes (see circulatory system).
chickenpox and shingles. vasculitis Inflammation of blood ves-
varices Enlarged, tortuous, or twisted sels. Vasculitis usually leads to damage
sections of vessels, usually veins. Varices to the lining of vessels, with narrowing
is the plural of varix. A vein affected by or blockage, that restricts or stops
varices is called a varicose vein. blood flow. As a result, the body tissues
varicocele Varicose veins surrounding a supplied by the affected vessels are
testis. Varicocele is a common condi- damaged or destroyed by ischaemia.
tion. It almost exclusively affects the left Vasculitis is thought to be caused in
testis and is usually harmless, although most cases by the presence of minute
there may be aching in the scrotum or bodies, called immune complexes, in the
an abnormally low sperm count (see circulating blood. Immune complexes
infertility). Aching may be relieved by (consisting of antigens bound to anti-
supportive underwear. Surgery to divide bodies) are normally destroyed by white
and tie off the swollen veins may be blood cells, but sometimes adhere to
performed if the sperm count is low. the walls of blood vessels, where they
varicose veins Enlarged, tortuous veins cause inflammation. In some cases, the
just beneath the skin. Varicose veins antigens are viruses. Vasculitis is the
most often occur in the legs but can basic disease process in a number of
also occur in the anus (see haemor- disorders, including polyarteritis nodosa,
rhoids), oesophagus (see oesophageal erythema nodosum, Henoch–Schönlein
varices), and scrotum (see varicocele). purpura, serum sickness, temporal arter-
V A defect of the valves in the leg veins itis, and Buerger’s disease.
causes blood to pool in the veins near vas deferens Either of a pair of tubes
the surface of the skin, causing them to that convey sperm from each testis and
become varicose. Contributing factors epididymis to the urethra. The plural
include obesity, hormonal changes and form is vasa deferentia.
pressure on the pelvic veins during vasectomy The operation of male ster-
pregnancy, hormonal changes occurring ilization. Vasectomy is a minor surgical
at the menopause, and standing for long procedure, performed under local
periods of time. Varicose veins are com- anaesthetic (see anaesthesia, local), that
mon, tend to run in families, and affect consists of cutting out a short length of
more women than men. each vas deferens. After vasectomy, the
578
VASOCONSTRICTION VEGETARIANISM
VASECTOMY Bladder
Vas
SITES OF Bladder deferens
INCISIONS Vas Secured
deferens ends
Area to be
removed Penis
Penis Testis
Testis
BEFORE THE PROCEDURE AFTER THE PROCEDURE
man continues to achieve orgasm and vasovagal attack Temporary loss of V
ejaculate as normal, but the semen no consciousness due to sudden slowing
longer contains sperm, which are reab- of the heartbeat, usually brought on by
sorbed in the testes. Male sterilization severe pain, stress, shock, or fear. A
is a safe and effective method of contra- vasovagal attack, a common cause of
ception. However, rarely, the severed fainting in healthy people, results from
ends of a vas deferens reunite, and overstimulation of the vagus nerve.
sperm appear in the ejaculate. If this
occurs, the man can safely undergo VD The abbreviation for venereal dis-
another vasectomy. Some operations to ease, an outdated term for sexually
restore fertility after vasectomy are suc- transmitted infections.
cessful, but the process should be
regarded as irreversible. vector An animal that transmits a par-
vasoconstriction Narrowing of blood ticular infectious disease. A vector picks
vessels, causing reduced blood flow to a up disease-causing organisms from a
part of the body. Vasoconstriction under source of infection (such as an infected
the skin occurs in response to the cold person’s or animal’s blood or faeces),
and reduces heat loss from the body. carries them in or on its body, and later
vasodilation Widening of blood ves- deposits them where they infect a new
sels, causing increased blood flow to a host, directly or indirectly. Mosquitoes,
part of the body. Vasodilation under the fleas, lice, ticks, and flies are the most
skin occurs in response to hot weather important vectors of disease to humans.
and increases heat loss from the body.
vasodilator drugs A group of drugs veganism The adoption of a diet that
that widen blood vessels. Vasodilator excludes all meat and fish and all ani-
drugs include ACE inhibitors, alpha- mal products, including milk and eggs.
blockers, calcium channel blockers, nitrate A vegan diet is likely to result in vitamin
drugs, and sympatholytic drugs. They B12 deficiency. Supplements are essen-
are used to treat disorders in which tial during pregnancy.
abnormal narrowing of blood vessels
reduces blood flow through tissues, vegetarianism Eating a diet that ex-
impairing the supply of oxygen. Such cludes meat and fish, and sometimes
disorders include angina pectoris and all other animal products. Humans do
peripheral vascular disease. Vasodilators not need to eat meat or animal prod-
are also used to treat hypertension and ucts to maintain health as long as the
heart failure. All vasodilator drugs may nutrients supplied by plant foods pro-
cause flushing, headaches, dizziness, vide a balanced diet (see nutrition).
fainting, and swollen ankles. However, people who exclude all animal
vasopressin Another name for ADH. products (vegans) need to plan their
diet carefully or take supplements to
avoid vitamin B12 or calcium deficiency.
Vegetarian diets are relatively rich in
fibre, which may help protect against
579
VEGETATIVE STATE VENEPUNCTURE
diverticular disease and cancer of the veins, disorders of Common disorders
intestine (see colon, cancer of; rectum, affecting veins include varicose veins,
cancer of). Vegetarian diets are low in deep vein thrombosis (see thrombosis,
fats, especially saturated fats (which may deep vein), and thrombophlebitis.
contribute to coronary artery disease vena cava Either of 2 large veins into
and possibly some forms of cancer). which all circulating (deoxygenated) blood
These diets are also likely to contain drains. The venae cavae (superior and
less sodium and more potassium, and inferior) deliver blood to the right atrium
vegetarians tend to have lower blood of the heart for pumping to the lungs.
pressure than people who eat meat. VENA CAVA
vegetative state A term that is some-
times used to describe a type of Carotid artery
indefinite deep coma. Although the
eyes may be open and occasional ran-
dom movements of the head and limbs
may occur, there are no other signs of Jugular vein Subclavian
consciousness, and there is no respon- vein
siveness to stimuli. Only the basic
functions, such as breathing and heart- Subclavian
beat, are maintained. artery
vein A vessel that returns blood towards Superior
the heart from the various organs and vena cava
tissues of the body. The walls of veins,
like those of arteries, consist of a Heart
smooth inner lining, a muscular middle Inferior
layer, and a fibrous outer covering. vena cava
However, blood pressure in veins is
lower than in arteries, and the walls of Aorta
veins are thinner, less elastic, less mus-
cular, and weaker than those of arteries.
The linings of many veins contain folds,
which act as valves, ensuring that blood The superior vena cava starts at the top
flows only towards the heart. Blood is of the chest, close to the sternum, and
helped on its way through the veins by passes down through the pericardium
pressure on the vessel walls from the before connecting to the right atrium. It
contraction of surrounding muscles. collects blood from the upper trunk,
(See also circulatory system.) head, neck, and arms. The inferior vena
VEIN cava starts in the lower abdomen and
travels upwards in front of the spine,
Outer layer behind the liver, and through the dia-
phragm before joining the right atrium.
Inner lining It collects blood from the legs, pelvic
organs, liver, and kidneys.
venepuncture A common procedure in
V Muscle layer which a vein, usually in the forearm, is
pierced with a needle to inject fluid or
withdraw blood. A tourniquet is used to
swell the veins, and a sterile needle is
inserted. A syringe is attached to the
Valve flap needle if blood is to be taken or medica-
tion injected. For intravenous infusion, a
cannula (tube) is inserted via the needle.
After the fluid has been injected or
withdrawn, the needle or cannula is
STRUCTURE OF A VEIN removed. The area is then covered and
580
VENEREAL DISEASES VENTILATORY FAILURE
VENEPUNCTURE
Skin Needle
Vein
Tourniquet Fatty
tissue
Syringe
Wall of vein Muscle
INSIDE THE VEIN
pressure applied to stop any bleeding. are available to treat many, though not V
The procedure is not usually painful but all, types of animal venom. (See also
may cause some discomfort. insect stings; jellyfish stings; scorpion
venereal diseases See sexually trans- stings; snake bites; spider bites.)
mitted infections. ventilation The use of a machine called a
venereology The medical discipline ventilator to take over or assist breathing.
concerned with the study and treatment Arrested or severely impaired breathing
of sexually transmitted infections. may be due to head injury, brain dis-
venesection The process of withdrawing ease, an overdose of opioid drugs, chest
blood from a vein for blood donation or injury, respiratory disease, a nerve or
therapeutic bloodletting. Regular blood- muscle disorder, or major chest or ab-
letting is performed in the treatment of dominal surgery. Ventilation may be
polycythaemia and haemochromatosis. needed if a muscle relaxant has been
venlafaxine A serotonin and noradren- given during an operation as part of
aline reuptake inhibitor (SNRI) drug general anaesthesia. Premature babies
used in the treatment of depression. with respiratory distress syndrome may
Venlafaxine combines the effects of sel- also need ventilation for a period until
ective serotonin reuptake inhibitors and their lungs develop sufficiently. Positive
tricyclic antidepressants to produce fewer pressure ventilation (continuous pump-
side effects than other types of anti- ing of air under high pressure) may be
depressant. Side effects may include used in the home in the treatment
nausea, dry mouth, and constipation. of sleep apnoea.
venography A diagnostic procedure that ventilator A device used for the artifi-
enables veins to be seen on an X-ray cial ventilation of a person who is
film after they have been injected with a unable to breathe naturally. A ventilator
substance opaque to X-rays. It is used is an electrical pump connected to an
to detect abnormalities or diseases of air supply that works like bellows. Air is
the veins, such as narrowing or blockage directed through a tube passed down
from thrombosis. the windpipe to inflate the lungs. The air
venomous bites and stings The injec- is then expelled by the natural elasticity
tion of venom by certain animals via of the lungs and ribcage. A valve on the
their mouthparts (bites) or other inject- ventilator prevents the expelled air from
ing apparatus (stings). Venoms are often re-entering the lungs.
carried to discourage predators, and are ventilatory failure A life-threatening
sometimes used to kill or immobilize condition in which the amount of car-
prey. It is rare for a venomous animal to bon dioxide in the blood rises, and the
attack a person unless it has been pro- amount of oxygen falls, due to disrup-
voked or disturbed. Specific antivenoms tion of the normal exchange of gases
581
VENTOUSE VERTEBRA
between the air in the lungs and the VENTRICULAR SEPTAL DEFECT
blood. Ventilatory failure may be due to
brain damage or to depression of the Ventricular septal Left
respiratory centres by excessive doses of defect ventricle
drugs such as morphine. Treatment may of heart
involve artificial ventilation or, in some
cases, the use of respiratory stimulant
drugs. (See also respiratory failure.)
ventouse See vacuum extraction.
ventral Relating to the front of the
body, or describing the lowermost part Septum
of a body structure when a person is
lying face-down. The opposite is dorsal. Right
ventricle A cavity or chamber. Both the ventricle
of heart
heart and brain have anatomical parts
known as ventricles.
The brain has 4 ventricles: 1 in each of
the 2 cerebral hemispheres; a 3rd at the
centre of the brain, above the brain-
stem; and a 4th between the brainstem is small and closes without treatment.
and cerebellum. These cavities are filled Surgery may be performed for larger
with cerebrospinal fluid. defects, usually with good results.
The ventricles of the heart are its 2 ventricular tachycardia A serious car-
lower chambers, which receive blood diac arrhythmia in which each heartbeat
from each atrium and pump it to the is initiated from electrical activity in the
lungs and to the rest of the body. ventricles rather than from the sinoatrial
ventricular ectopic beat A type of node in the right atrium. It is caused by
cardiac arrhythmia in which abnormal an abnormally fast heart-rate due to
heartbeats are initiated from electrical serious heart disease, such as myocar-
impulses in the ventricles of the heart. dial infarction or cardiomyopathy. It may
In a normal heart, beats are initiated by last for a few seconds or for several
the sinoatrial node in the right atrium. days. Diagnosis is confirmed by ECG.
Ventricular ectopic beats may be de- Emergency treatment is with defibril-
tected on an ECG. If there are frequent lation and an antiarrhythmic drug.
abnormal beats that cause symptoms, verapamil A drug that acts as a calcium
or beats that arise from more than 1 channel blocker to treat hypertension,
site in the ventricles, treatment with an angina pectoris, and certain arrhythmias.
antiarrhythmic drug may be required. Possible side effects include headache,
ventricular fibrillation One of the 2 flushing, dizziness, and ankle swelling.
life-threatening cardiac arrhythmias that vernix The white, cheese-like substance
occur in cardiac arrest. The heart has covering a newborn baby. Vernix com-
rapid, uncoordinated, ineffective con- prises fatty secretions and dead cells. It
tractions and does not pump blood. The protects the skin, insulates against heat
problem is due to abnormal heartbeats loss before birth, and lubricates the
V initiated by electrical activity in the ven- baby’s passage down the birth canal.
tricles. It is a common complication of verruca The Latin name for a wart, com-
myocardial infarction and may also be monly applied to warts on the soles.
caused by electrocution or drowning. version A change in the direction in
The diagnosis is confirmed by ECG. which a fetus lies so that a malpresenta-
Emergency treatment is with defibrilla- tion, most often a breech (bottom-down)
tion and antiarrhythmic drugs. presentation, replaces the normal head-
ventricular septal defect The medical down presentation.
term meaning a hole between the lower vertebra Any of the 33 approximately
2 chambers of the heart. The abnormality cylindrical bones that form the spine.
is present from birth and in many cases There are 7 vertebrae in the cervical
582
VERTEBROBASILAR INSUFFICIENCY VILLUS
VERTEBRA vesicle A small blister, usually filled with
clear fluid, that forms at a site of skin
Cervical damage. The term is also used to refer to
vertebrae any small sac-like structure in the body.
Thoracic CERVICAL VERTEBRA vestibule A chamber. The vestibule in
vertebrae the inner ear is a hollow chamber that
connects the 3 semicircular canals.
Lumbar
vertebrae vestibulitis Inflammation of the nasal
vestibule (the part of the nasal cavity
THORACIC VERTEBRA just inside the nostril), usually as a
result of bacterial infection.
Sacrum
Coccyx vestibulocochlear nerve The 8th cran-
ial nerve. It consists of 2 branches: the
SPINE vestibular nerve (concerned with balance)
and the cochlear nerve (concerned with
LUMBAR VERTEBRA hearing). Each vestibulocochlear nerve V
(1 on each side) carries sensory im-
spine; 12 vertebrae in the thoracic spine; pulses from the inner ear to the brain,
5 vertebrae in the lumbar spine; 5 fused which it enters between the pons and
vertebrae in the sacrum; and 4 fused ver- medulla oblongata (in the brainstem).
tebrae in the coccyx. The top 24 vertebrae A tumour of the cells that surround
are separated by discs of cartilage (see the vestibulocochlear nerve (see acous-
disc, intervertebral). Each vertebra has a tic neuroma) may cause loss of balance,
hole in the centre through which the tinnitus, and deafness. Deafness may
spinal cord runs, and processes to also result from damage to the nerve,
which muscles are attached. which may be due to an infection, such
vertebrobasilar insufficiency Inter- as meningitis or encephalitis, or to a
mittent episodes of dizziness, double reaction to a drug such as streptomycin.
vision, weakness, and difficulty in speak-
ing caused by reduced blood flow to viability The capability of independent
parts of the brain. It is usually due to ath- survival and development.
erosclerosis of the basilar and vertebral
arteries and other arteries in the base of villus A minute finger-like projection from
the brain. Vertebrobasilar insufficiency a membranous surface. Millions of villi
sometimes precedes a stroke. are present on the mucous lining of the
vertigo An illusion that one or one’s small intestine. Each intestinal villus con-
surroundings are spinning. Vertigo is tains a small lymph vessel and a network
due to a disturbance of the semicircular
canals in the inner ear or the nerve VILLUS
tracts leading from them. Sudden-onset
vertigo is treated with rest and antihis- Capillary network
tamine drugs, which, in some cases, are
also given to prevent recurrent attacks. Villus
Mucus-
producing cell
Lymph vessel
Artery
Vein
VILLI OF SMALL INTESTINE
583
VINCA ALKALOIDS VIRUSES
of capillaries. Its surface is covered with caused by excessive levels of androgen
hundreds of hairlike structures (micro- hormones. Androgens are male sex hor-
villi). The villi and microvilli provide a mones which, in women, are normally
large surface area for absorption of food secreted in small amounts by the
molecules from the intestine into the adrenal glands and ovaries. Raised levels
blood and the lymphatic system. induce various changes in women, in-
vinca alkaloids A group of substances cluding hirsutism; male-pattern baldness;
derived from the periwinkle plant (VINCA disruption or cessation of menstruation;
ROSEA) that are used to treat leukaemias, enlargement of the clitoris; loss of nor-
lymphomas, and some solid tumours, mal fat deposits around the hips;
such as breast cancer and lung cancer. development of the arm and shoulder
All vinca alkaloids can cause neurological muscles; and deepening of the voice.
toxicity, which appears as neuropathy. virility A term used to describe the
Other side effects may include abdomi- quality of maleness, especially in sexual
nal pain, constipation, and reversible characteristics and performance.
alopecia. Common vinca alkaloids are virilization The development in a woman
vinblastine, vindesine, and vincristine. of male characteristics as a result of
Vincent’s disease A severe form of overproduction of androgen hormones
gingivitis in which bacterial infection by the adrenal glands and/or ovaries.
causes painful ulceration of the gums. This may be due to various conditions
(See also gingivitis, acute ulcerative.) such as certain adrenal tumours, poly-
vincristine A vinca alkaloid used to treat cystic ovary (see ovary, polycystic) and
certain cancers. One particular side effect some other ovarian cysts, or congenital
of vincristine is peripheral or autonomic adrenal hyperplasia.
neuropathy; but, unlike the other vinca virion A single, complete, virus particle.
alkaloids, it causes very little reduction virology The study of viruses and the
in blood-cell production by the bone epidemiology and treatment of diseases
marrow. Other side effects may include caused by viruses. In a more restricted
abdominal pain, constipation, and re- sense, virology also refers to the isola-
versible alopecia. tion and identification of viruses to
viraemia The presence of virus particles diagnose specific viral infections. Depend-
in the blood. Viraemia can occur at cer- ing on the type of virus, this may involve
tain stages in a variety of viral infections. growing viruses in cultures of human or
Some viruses, such as those responsi- animal cells, staining or microscopic
ble for viral hepatitis, yellow fever, and examination of specimens containing
poliomyelitis, are transported in the viruses, or immunoassay techniques.
bloodstream. Others, such as the rubella virulence The ability of a microorganism
virus and HIV, multiply in, and spread to cause disease. This can be assessed
via, certain white blood cells. If viraemia by measuring what proportion of the
is a feature of a viral infection, there is a population exposed to the microorgan-
risk that the infection may be transmitted ism develops symptoms of disease, how
to other people in blood or blood prod- rapidly the infection spreads through the
ucts, or by insects that feed on blood. body, or the mortality from the infection.
viral haemorrhagic fever Diseases viruses The smallest known types of
V that are prevalent in Africa and cause infectious agent. It is debatable whether
severe bleeding. There are several types, viruses are truly living organisms or just
including Ebola fever, Lassa fever, Han- collections of molecules capable of self-
tavirus, and Marburg fever. The diseases replication under specific conditions.
are fatal in a large percentage of cases, Their sole activity is to invade the cells
but Lassa fever may respond to antiviral of other organisms, which they then
drugs if given in the 1st week. take over to make copies of themselves.
virginity The physical state of not hav- Outside living cells, viruses are inert.
ing experienced sexual intercourse. A single virus particle (virion) consists
virilism The presence in a woman of of an inner core of nucleic acid, which
masculine characteristics. Virilism is may be either DNA or RNA, surrounded
584
VISCERA VIRUSES VISION, LOSS OF
Surface Protein shell cones are concentrated more at the
protein centre of the retina (see colour vision).
Nucleic acid Viral The brain coordinates the motor nerve
(genetic material) envelope impulses to the 6 tiny muscles that
move each eye to achieve alignment of
STRUCTURE OF A VIRUS the eyes. Accurate alignment allows the
brain to fuse the images from each eye,
by 1 or 2 protective protein shells (cap- but because each eye has a slightly dif- V
sids). Surrounding the outer capsid may ferent view of a given object, the brain
be another layer, the viral envelope, obtains information that is interpreted
which consists mainly of protein. The as solidity or depth. This stereoscopic
nucleic acid consists of a string of genes vision is important in judging distance.
that contain coded instructions for vision, disorders of The most com-
making copies of the virus. mon visual disorders are refractive
errors, such as myopia, hypermetropia,
Common viral diseases include the and astigmatism, which can almost
common cold, influenza, and chickenpox always be corrected by glasses or con-
(caused by the varicella–zoster virus). tact lenses. Other disorders include
AIDS is caused by the human immuno- amblyopia; double vision; and disorders
deficiency virus (HIV). of the eye or optic nerve, of the nerve
viscera A collective term used to pathways connecting the optic nerves
describe the internal organs. to the brain, and of the brain itself.
viscosity The resistance to flow of a fluid;
its “stickiness”. The viscosity of blood The eye may lose its transparency
affects its ability to flow through small through corneal opacities, cataract, or
vessels. An increase in the viscosity of vitreous haemorrhage. Defects near the
blood increases the risk of thrombosis. centre of the retina cause loss of the
vision The faculty of sight. When light- corresponding parts of the visual field
rays reach the eye, most of the focusing (see macular degeneration). Floaters,
is done by the cornea, but the eye also which are usually insignificant, may in-
has an automatic fine-focusing facility, dicate a retinal tear or haemorrhage, or
accommodation, that operates by altering they may herald a retinal detachment.
the curvature of the lens. Together, these Optic neuritis can cause a blind spot in
systems form an image on the retina. the centre of the visual field.
The light-sensitive rod and cone cells in
the retina convert the elements of this Damage to the brain (for example, from
image into nerve impulses that pass a stroke) may cause visual impairment
into the visual cortex of the brain via such as hemianopia, agnosia, visual pers-
the optic nerves. The rods, which are everation (in which a scene continues
more concentrated at the periphery of to be perceived after the direction of gaze
the retina, are highly sensitive to light has shifted), and visual hallucinations.
but not to colour. The colour-sensitive vision, loss of Inability to see. This may
develop slowly or suddenly and may be
temporary or permanent, depending on
the cause. Vision loss may affect 1 or
both eyes. It can cause complete blind-
ness or may affect only peripheral, or
only central, vision.
Progressive loss of visual clarity is
common with advancing age and may
be due to a number of disorders (see
vision, disorders of).
Sudden loss of vision may be caused
by disorders such as hyphaema, severe
uveitis, vitreous haemorrhage, or retinal
haemorrhage. Optic neuritis can reduce
vision in 1 eye. Damage to the nerve
585
VISION TESTS VITAMIN
connections between the eyes and brain, normally extend outwards over an angle
or to the visual area of the brain, can of about 90 degrees on either side of
cause loss of peripheral vision and may the midline of the face, but are more re-
be a result of embolism, ischaemia, stricted above and below, especially if
tumour, inflammation, or injury. the eyes are deep-set or the eyebrows
vision tests The part of an eye examina- are prominent. The visual fields of the 2
tion that determines whether there is eyes overlap to a large extent, giving
any reduction in the ability to see. Most binocular vision. Partial loss of the visual
vision tests (for example the Snellen field may occur in glaucoma or stroke.
chart) are tests of visual acuity. vital sign An indication that a person is
VISION TESTS still alive. Vital signs include chest
movements caused by breathing, the
Adjustable arm Phoropter presence of a pulse, and the constric-
tion of the pupil of the eye when it is
Test lens exposed to a bright light.
vitamin Any of a group of complex org-
anic substances that are essential in
small amounts for the normal function-
ing of the body. There are 13 vitamins:
A, C, D, E, K, B12, and 7 grouped under
the vitamin B complex. Apart from the
B vitamin niacin and vitamin D, which
the body can synthesize itself, vitamins
must be obtained from the diet. A var-
ied diet is likely to contain adequate
amounts of all the vitamins, but vitamin
supplements may be helpful for some
people, such as young children, women
who are pregnant or breast-feeding, or
those taking drugs that interfere with
vitamin function.
In this type of test, a device called a Vitamins can be categorized as fat-
phoropter is used to hold different lenses soluble or water-soluble.
in front of each eye. The lenses in the The fat-soluble vitamins (A, D, E, and K)
phoropter are changed until the letters are absorbed with fats from the intestine
near the bottom of the Snellen chart can into the bloodstream and then stored
be read. Tests of visual field may also be in fatty tissue (mainly in the liver). Body
performed to assess disorders of the reserves of some of these vitamins last
eye and the nervous system. Refraction for several years, so a daily intake is not
tests can detect hypermetropia, myopia, usually necessary. Deficiency of a fat-
or astigmatism; the effect of lenses on soluble vitamin is usually due to a
movements of light reflected from the disorder in which intestinal absorption
eye is observed to calculate the correc- of fats is impaired (see malabsorption)
tive glasses or contact lenses needed. If or to a prolonged poor diet.
V presbyopia is suspected, close-reading Vitamin C, B12, and those of the B
tests are used to assess accommodation. complex are water-soluble. Vitamin C
visual acuity Sharpness of central vision. and B complex vitamins can be stored
Refractive errors, such as myopia, hyper- in the body in only limited amounts and
metropia and astigmatism, are the most are excreted in the urine if taken in great-
common causes of poor visual acuity. er amounts than needed. A regular intake
Poor visual acuity for near objects occurs is therefore essential to prevent defi-
in presbyopia. ciency. However, vitamin B12 is stored in
visual field The total area in which visual the liver; these stores may last for years.
perception is possible while a person is The role of all the vitamins in the body
looking straight ahead. The visual fields is not fully understood. Most vitamins
586
VITAMIN A VITAMIN B COMPLEX
have several important actions on 1 or Deficiency is almost always due to V
more body systems, and many are the inability of the intestine to absorb
involved in the activities of enzymes. the vitamin, usually as a result of
vitamin A A fat-soluble vitamin essen- pernicious anaemia (see anaemia, meg-
tial for normal growth, for the formation aloblastic). Less commonly, deficiency
of bones and teeth, for cell structure, may result from gastrectomy, malab-
for night vision, and for protecting the sorption, or veganism. The effects of
linings of the respiratory, digestive, and vitamin B12 deficiency are megaloblas-
urinary tracts against infection. tic anaemia, a sore mouth and tongue,
and symptoms caused by damage to
Vitamin A is absorbed by the body in the spinal cord, such as numbness and
the form of retinol. This is found in liver, tingling in the limbs. There may also be
fish-liver oils, egg yolk, dairy produce, and depression and memory loss. A high
is added to margarines. Carotene, which intake of vitamin B12 has no known
the body converts into retinol, is found harmful effects.
in various vegetables and fruits. vitamin B complex A group of water-
soluble vitamins comprising thiamine
Vitamin A deficiency is rare in deve- (vitamin B1), riboflavin (vitamin B2),
loped countries. In most cases, it is due niacin, pantothenic acid, pyridoxine (vit-
to malabsorption. Vitamin A deficiency amin B6), biotin (vitamin H), and folic
may also result from long-term treat- acid. Vitamin B12 is discussed above.
ment with certain lipid-lowering drugs.
Deficiency is common in some develop- Thiamine plays a role in the activities
ing countries due to poor diet. The first of various enzymes involved in the uti-
symptom of deficiency is night blindness, lization of carbohydrates and thus in the
followed by dryness and inflammation functioning of nerves, muscles, and the
of the eyes (see xerophthalmia), kera- heart. Sources include whole-grain cere-
tomalacia, and eventually blindness. als, wholemeal breads, brown rice, pasta,
Deficiency also causes reduced resis- liver, kidney, pork, fish, beans, nuts, and
tance to infection, dry skin, and, in eggs. Those susceptible to deficiency
children, stunted growth. include elderly people on a poor diet,
and people who have hyperthyroidism,
Prolonged excessive intake of vitamin malabsorption, or severe alcohol depen-
A can cause headache, nausea, loss of dence. Deficiency may also occur as a
appetite, skin peeling, hair loss, and result of severe illness, surgery, or
irregular menstruation. In severe cases, injury. Mild deficiency may cause tired-
the liver and spleen become enlarged. ness, irritability, and loss of appetite.
Excessive intake during pregnancy may Severe deficiency may cause abdominal
cause birth defects. In infants, excessive pain, constipation, depression, memory
intake may cause skull deformities, impairment, and beriberi; in alcoholics,
which disappear if the diet is corrected. it may cause Wernicke–Korsakoff syn-
drome. Excessive intake is not known to
The drug tretinoin (a derivative of vita- cause harmful effects.
min A) is used to treat severe acne.
vitamin B See vitamin B12; vitamin B Riboflavin is necessary for the activi-
complex. ties of various enzymes involved in the
vitamin B12 A water-soluble vitamin breakdown and utilization of carbohy-
that plays a vital role in the activities of drates, fats, and proteins; the production
several enzymes in the body. Vitamin of energy in cells; the utilization of
B12 is important in the production of other B vitamins; and hormone produc-
the genetic material of cells (and thus tion by the adrenal glands. Liver, whole
in growth and development), in the pro- grains, milk, eggs, and brewer’s yeast
duction of red blood cells in bone are good sources. People who are sus-
marrow, in the utilization of folic acid ceptible to riboflavin deficiency include
and carbohydrates in the diet, and in those taking phenothiazine antipsychotic
the functioning of the nervous system. drugs, tricyclic antidepressant drugs, or
Foods rich in vitamin B12 include liver, oestrogen-containing oral contraceptives,
kidney, chicken, beef, pork, fish, eggs,
and dairy products.
587
VITAMIN C VITAMIN C
and those with malabsorption or severe beans. Pyridoxine is also manufactured
alcohol dependence. Riboflavin defi- by intestinal bacteria. People who are
ciency may also occur as a result of susceptible to pyridoxine deficiency
serious illness, surgery, or injury. Pro- include elderly people who have a poor
longed deficiency may cause soreness diet, those with malabsorption or severe
of the tongue and the corners of the alcohol dependence, or those who are
mouth, and eye disorders such as taking certain drugs (including penicil-
amblyopia and photophobia. Excessive lamine and isoniazid). Deficiency may
intake of riboflavin is not known to have cause weakness, irritability, depression,
any harmful effects. skin disorders, inflammation of the
Niacin plays an essential role in the mouth and tongue, anaemia, and, in
activities of various enzymes involved in infants, seizures. In very large amounts,
the metabolism of carbohydrates and pyridoxine may cause neuritis.
fats, the functioning of the nervous and Biotin is essential for the activities of
digestive systems, the manufacture of various enzymes involved in the break-
sex hormones, and the maintenance of down of fatty acids and carbohydrates
healthy skin. The main dietary sources and for the excretion of the waste prod-
are liver, lean meat, fish, nuts, and dried ucts of protein breakdown. It is present
beans. Niacin can be made in the body in many foods, especially liver, peanuts,
from tryptophan (an amino acid). Most dried beans, egg yolk, mushrooms,
cases of deficiency are due to malab- bananas, grapefruit, and watermelon.
sorption disorders or to severe alcohol Biotin is also manufactured by bacteria
dependence. Prolonged niacin deficiency in the intestines. Deficiency may occur
causes pellagra. Excessive intake is not during prolonged treatment with antibi-
known to cause harmful effects. otics or sulphonamide drugs. Symptoms
Pantothenic acid is essential for the are weakness, tiredness, poor appetite,
activities of various enzymes involved in hair loss, depression, inflammation of
the metabolism of carbohydrates and the tongue, and eczema. Excessive
fats, the manufacture of corticosteroids intake has no known harmful effects.
and sex hormones, the utilization of Folic acid is vital for various enzymes
other vitamins, the functioning of the involved in the manufacture of nucleic
nervous system and adrenal glands, and acids and consequently for growth and
growth and development. It is present reproduction, the production of red
in almost all vegetables, cereals, and blood cells, and the functioning of the
animal foods. Deficiency of pantothenic nervous system. Sources include green
acid usually occurs as a result of mal- vegetables, mushrooms, liver, nuts, dried
absorption or alcoholism, but may also beans, peas, egg yolk, and wholemeal
occur after severe illness, surgery, or bread. Mild deficiency is common, but
injury. The effects include fatigue, can usually be corrected by increasing
headache, nausea, abdominal pain, dietary intake. More severe deficiency
numbness and tingling, muscle cramps, may occur during pregnancy or breast-
and susceptibility to respiratory in- feeding, in premature or low-birthweight
fections. In severe cases, a peptic ulcer infants, in people undergoing dialysis,
may develop. Excessive intake has no in people with certain blood disorders,
V known harmful effects. psoriasis, malabsorption, or alcohol de-
Pyridoxine aids the activities of vari- pendence, and in people taking certain
ous enzymes and hormones involved in drugs. The main effects include anae-
the utilization of carbohydrates, fats, mia, sores around the mouth, and, in
and proteins, in the manufacture of red children, poor growth. Folic acid sup-
blood cells and antibodies, in the func- plements taken just before conception,
tioning of the digestive and nervous and for the first 12 weeks of pregnancy,
systems, and in the maintenance of have been shown to reduce the risk of
healthy skin. Dietary sources are liver, a neural tube defect.
chicken, pork, fish, whole grains, wheat- vitamin C A water-soluble vitamin that
germ, bananas, potatoes, and dried plays an essential role in the activities
588
VITAMIN D VITAMIN SUPPLEMENTS
of various enzymes. Vitamin C is impor- activities of certain enzymes, and for the V
tant for the growth and maintenance of formation of red blood cells. Vitamin E
healthy bones, teeth, gums, ligaments, also protects the lungs and other tissues
and blood vessels; in the production of from damage by pollutants and is
certain neurotransmitters and adrenal believed to slow aging of cells. Sources
gland hormones; in the response of the include vegetable oils, nuts, meat, green
immune system to infection; in wound vegetables, cereals, and egg yolk.
healing; and in the absorption of iron.
Dietary deficiency is rare; deficiency is
The main dietary sources are fruits most common in people with malab-
and vegetables. Considerable amounts sorption, certain liver disorders, and in
of vitamin C are lost when foods are premature infants. It leads to the de-
processed, cooked, or kept warm. struction of red blood cells, which
eventually leads to anaemia. In infants,
Mild deficiency of vitamin C may re- deficiency causes irritability and oedema.
sult from a serious injury or burn, major
surgery, the use of oral contraceptives, Prolonged excessive intake of vitamin
fever, or continual inhalation of carbon E may cause abdominal pain, nausea,
monoxide (from traffic fumes or tobacco and diarrhoea. It may also reduce intes-
smoke). It may cause weakness, general tinal absorption of vitamins A, D, and K.
aches, swollen gums, and nosebleeds. vitamin K A fat-soluble vitamin that is
More serious deficiency is usually essential for the formation in the liver
caused by a very restricted diet. Severe of substances that promote blood clot-
deficiency leads to scurvy and anaemia. ting. Good sources are green vegetables,
vegetable oils, egg yolk, cheese, pork,
If the daily dose of vitamin C exceeds and liver. Vitamin K is also manufac-
about 1g, it may cause nausea, stomach tured by bacteria in the intestine.
cramps, diarrhoea, or kidney stones
(see calculi, urinary tract). Dietary deficiency rarely occurs. De-
vitamin D The collective term for a ficiency may develop in people with
group of substances that help to regu- malabsorption, certain liver disorders, or
late the balance of phosphate and chronic diarrhoea. It may also result
calcium in the body, aid calcium absorp- from prolonged treatment with antibi-
tion in the intestine, and promote strong otics. Newborns lack the intestinal
bones and teeth. bacteria that produce vitamin K and are
routinely given supplements to prevent
Good sources include oily fish, liver, deficiency. Vitamin K deficiency may
and egg yolk; vitamin D is also added to cause nosebleeds and bleeding from
margarines. In the body, vitamin D is the gums, intestine, and urinary tract. In
synthesized by the action of ultraviolet rare, severe cases, brain haemorrhage
light on a particular chemical in the skin. may result. Excessive intake of vitamin
K is not known to cause harmful effects.
Deficiency may occur in people with a vitamin supplements A group of diet-
poor diet, in premature infants, and in ary preparations containing 1 or more
those deprived of sunlight. It can also vitamins. Most healthy people who have
result from malabsorption. Other causes a balanced diet do not need them. Sup-
include liver or kidney disorders and plements are used to treat diagnosed
some genetic defects. Prolonged use of vitamin deficiency. They are also given
certain drugs, such as phenytoin, may to prevent vitamin deficiency in suscep-
also lead to deficiency. Deficiency in tible people, such as those who have
young children causes rickets; long-term increased requirements (for example,
deficiency in adults leads to osteomalacia. women who are pregnant or breast-
feeding); those who follow a restricted
Excessive intake of vitamin D may diet (in veganism, for example); those
lead to hypercalcaemia and abnormal with severe alcohol dependence; and
calcium deposits in the soft tissues, people who have malabsorption, liver
kidneys, and blood vessel walls. In chil- disorders, kidney disorders, or another
dren, it may cause growth retardation. serious illness or injury. In addition,
vitamin E The collective term for a group
of substances that are essential for nor-
mal cell structure, for maintaining the
589
VITILIGO V O LV U L U S
vitamins are used to treat certain disor- are attached at the front to the thyroid
ders. For example, vitamin D is used to cartilage and at the rear to the aryten-
treat osteomalacia, and vitamin A deri- oid cartilages. To produce sound, the
vatives are given for severe acne. vocal cords, which normally form a V-
vitiligo A common disorder of skin pig- shaped opening, close and vibrate as
mentation in which patches of skin, air expelled from the lungs passes
most commonly on the face, hands, between them. Alterations in cord ten-
armpits, and groin, lose their colour. sion produce sounds of different pitch,
Vitiligo is thought to be an autoimmune which are modified by the tongue,
disorder. It may occur at any age but mouth, and lips to form speech.
usually develops in early adulthood. voice-box See larynx.
Spontaneous repigmentation occurs voice, loss of Inability to speak norm-
in some cases. A course of phototherapy ally. Temporary partial loss of voice
using PUVA can also induce repigmen- commonly results from straining of the
tation of the skin, and creams containing muscles of the larynx through overuse
corticosteroid drugs may help. of the voice or from inflammation of the
vitreous haemorrhage Bleeding into vocal cords in laryngitis. Persistent or
the vitreous humour. A common cause recurrent voice loss may be due to
is diabetic retinopathy. Vitreous haem- polyps on the vocal cords, thickening of
orrhage often affects vision; a major the cords in hypothyroidism, or inter-
haemorrhage causes poor vision until ference with the nerve supply to the
the blood is reabsorbed, which may not larynx muscles due to cancer of the lar-
be for several months, if at all. ynx, thyroid gland, or oesophagus. Total
vitreous humour The transparent, gel- loss of voice is rare and is usually of
like body that fills the rear compartment psychological origin. (See also hoarse-
of the eye between the crystalline lens ness; larynx, disorders of.)
and the retina. The vitreous humour Volkmann’s contracture A disorder
consists almost entirely of water. in which the wrist and fingers become
vivisection The performance of a sur- permanently fixed in a bent position. It
gical operation on a live animal, occurs because of an inadequate blood
particularly for research purposes. (See supply to the forearm muscles that con-
also animal experimentation.) trol the wrist and fingers as a result of
vocal cords Two fibrous sheets of tis- an injury. Initially, the fingers become
sue in the larynx that are responsible cold, numb, and white or blue. Finger
for voice production. The vocal cords movements are weak and painful, and
VOCAL CORDS there is no pulse at the wrist. Unless
treatment is started within a few hours,
Arytenoid cartilages wrist and finger deformity develops.
Treatment is by manipulation back
into position of any displaced bones,
Vocal cords followed, if necessary, by surgical res-
toration of blood flow in the forearm. If
Cut edge of there is permanent deformity, physio-
thyroid cartilage therapy may help to restore function.
V Larynx volvulus Twisting of a loop of intestine
or, in rare cases, of the stomach. Volvu-
lus is a serious condition that causes
Ligament obstruction of the passage of intestinal
contents (see intestine, obstruction of)
Trachea and a risk of strangulation. If strangula-
tion occurs, blockage of blood flow to
the affected area leads to potentially
fatal gangrene. The symptoms of volvu-
lus are severe episodes of abdominal
LOCATION SIDE VIEW OF LARYNX pain followed by vomiting. Volvulus may
590
VOMITING VON WILLEBRAND’S DISEASE
be present from birth or may be a result peptic ulcer, or, rarely, stomach cancer. V
of adhesions. It requires emergency Blood can also be vomited if it is swal-
treatment, usually by surgery. lowed during a nosebleed. Vomited
vomiting Involuntary forcible expulsion blood may be dark red, brown, black, or
of stomach contents through the mouth. may resemble coffee grounds. Vomiting
Vomiting may be preceded by nausea, of blood is often accompanied by the
pallor, sweating, excessive salivation, passing of black, tarry faeces.
and slowed heart-rate. It occurs when
the vomiting centre in the brainstem is The cause of vomiting blood is investi-
activated by signals from 1 of 3 places gated by endoscopy of the oesophagus
in the body: the digestive tract; the bal- and stomach, or by barium X-ray exami-
ancing mechanism of the inner ear; or nations. If blood loss is severe, blood
the brain, either due to thoughts and transfusion, and possibly surgery to
emotions or via the part of the brain stop the bleeding, may be required.
that responds to poisons in the body. vomiting in pregnancy Nausea and
The vomiting centre sends messages to vomiting in early pregnancy are com-
both the diaphragm, which presses mon and are most likely to be caused
down on the stomach, and the abdomi- by changes in the hormone levels. Vom-
nal wall, which presses inwards, thereby iting occurs most frequently in the
expelling the stomach contents upwards morning, but it may occur at any time. It
through the oesophagus. is sometimes precipitated by stress,
travelling, or food.
Vomiting may be due to overindulgence
in food or alcohol, is a common side In rare cases, the vomiting becomes
effect of many drugs, and may follow severe and prolonged. This can cause
general anaesthesia. Vomiting is also dehydration, nutritional deficiency, altera-
common in gastrointestinal disorders tions in blood acidity, and weight loss.
such as peptic ulcer, acute appendicitis, Immediate hospital admission is then
gastroenteritis, and food poisoning. Less required to replace lost fluids and
commonly, it is due to obstruction (see chemicals by intravenous infusion, to
pyloric stenosis; intussusception) or a tu- rule out any serious underlying disor-
mour of the digestive tract. It may also der, and to control the vomiting.
be due to inflammation (see hepatitis; von Recklinghausen’s disease An-
pancreatitis; cholecystitis). other name for neurofibromatosis.
von Willebrand’s disease An inheri-
Other possible causes are pressure on ted lifelong bleeding disorder similar to
the skull (see encephalitis; hydrocepha- haemophilia. People with the condition
lus; brain tumour; head injury; migraine), have a reduced concentration in their
conditions affecting the ear’s balancing blood of a substance called von Wille-
mechanism (see Ménière’s disease; laby- brand factor, which helps platelets in
rinthitis; motion sickness), and hormonal the blood to plug injured blood vessel
disorders (see Addison’s disease). walls and forms part of factor VIII (a
substance vital to blood coagulation).
Vomiting may be a symptom of keto- Symptoms of deficiency of this factor
acidosis in poorly controlled diabetes include excessive bleeding from the
mellitus. It may also be a symptom of an gums and from cuts and nosebleeds.
emotional problem or be part of the Women may have heavy menstrual bleed-
disorders anorexia nervosa or bulimia. ing. In severe cases, bleeding into joints
and muscles may occur.
Persistent vomiting requires medical
investigation. Treatment depends on the The disease is diagnosed by blood-
cause. Antiemetics may be given. (See also clotting tests and measurement of blood
vomiting blood; vomiting in pregnancy.) levels of von Willebrand factor. Bleeding
vomiting blood A symptom of bleed- episodes can be prevented or controlled
ing from within the digestive tract. by desmopressin (a substance resem-
Vomiting blood may be caused by a bling ADH). Factor VIII or concentrated
tear in the lower oesophagus (see Mal- von Willebrand factor may also be used
lory–Weiss syndrome), bleeding from to treat bleeding.
oesophageal varices, erosive gastritis,
591
VOYEURISM V U LV O VA G I N I T I S
voyeurism The observation, on a regu- Treatment depends on the cause. A
lar basis, of unsuspecting people who combination of drugs applied to the vulva
may be naked, getting undressed, or and good hygiene is usually recom-
engaged in sexual activity, in order to mended. A biopsy may be taken, if there
achieve sexual arousal. are skin changes, to exclude the slight
VSD The abbreviation for ventricular possibility of vulval cancer. (See also
septal defect. vulvovaginitis; vaginitis.)
vulva The external part of the female vulvovaginitis Inflammation of the vulva
genitalia, comprising the clitoris and 2 and vagina. Vulvovaginitis is often pro-
pairs of skin folds called labia. voked as a result of the infections
The most common symptom affecting candidiasis or trichomoniasis. (See also
the vulva is vulval itching. Various skin vaginitis; vulvitis.)
disorders, such as dermatitis, may affect
the vulva. Specific vulval conditions
include genital warts, vulvitis, vulvo-
vaginitis, and cancer (vulva, cancer of).
vulva, cancer of A rare disorder that
most commonly affects postmenopausal
women. Cancer of the vulva may be pre-
ceded by vulval itching, but in many
cases the first symptom is a lump or
painful ulcer on the vulva.
A diagnosis of vulval cancer is made
by biopsy. Treatment is by surgical
removal of the affected area. The out-
look depends on how soon the cancer is
diagnosed and treated.
vulval itching Irritation of the vulva.
Most commonly, vulval itching is due to
an allergic reaction to chemicals in
spermicidal or hygiene products. Itching
is also common after the menopause,
when it is due to low levels of oestrogen.
In addition, vulval itching may be
caused by a vaginal discharge due to
infection (see vaginitis) or by vulval skin
changes (see vulvitis).
Treatment may be with antibiotics or
hormones, depending on the cause.
vulvitis Inflammation of the vulva.
Infections that may cause vulvitis are
candidiasis, genital herpes (see herpes,
genital), and warts (see warts, genital).
Infestations with pubic lice or scabies
V are other possible causes. Vulvitis may
also occur as a result of changes in the
vulval skin. These changes tend to affect
women after the menopause, although
there is no apparent trigger. They may
take the form of red or white patches
and/or thickened or thinned areas that
may be inflamed. Other possible causes
of vulvitis include allergic reactions to
hygiene products, excessive vaginal dis-
charge, or urinary incontinence.
592
WALKING WART
W risk of an embolism. It is also prescribed
to prevent emboli from developing on
walking Movement of the body by lifting replacement valves (see heart-valve sur-
the feet alternately and bringing 1 foot gery). A faster-acting anticoagulant, such
into contact with the ground before the as heparin, may also be prescribed for
other starts to leave it. A person’s gait is the first few days following a deep-vein
determined by body shape, size, and thrombosis or pulmonary embolism.
posture. The age at which children first
walk varies enormously. Warfarin may cause abnormal bleeding
Walking is controlled by nerve signals in different parts of the body, so regular
from the brain’s motor cortex (see cere- tests are carried out to allow careful
brum), basal ganglia, and cerebellum that regulation of dosage. Warfarin may also
travel via the spinal cord to the muscles. cause nausea, diarrhoea and a rash.
Abnormal gait may be caused by joint wart A common, contagious, harmless
stiffness, muscle weakness (sometimes growth that occurs on the skin or mucous
due to conditions such as poliomyelitis membranes. Only the topmost layer of
or muscular dystrophy), or skeletal abnor- skin is affected. An overgrowth of cells
malities (see, for example, talipes; hip, in this layer causes a visible lump to
congenital dislocation of; scoliosis; bone develop. Warts are caused by the human
tumour; arthritis). Children may develop papillomavirus, of which at least 30 dif-
knock-knee or bowleg; synovitis of the hip ferent types are known. These cause
and Perthes’ disease are also common. different types of warts at various sites,
Adolescents may develop a painful limp such as on the hands or genitals.
due to a slipped epiphysis (see femoral
epiphysis, slipped) or to fracture or dis- WART Excess cells
ease of the tibia, fibula or femur. produced
Abnormal gait may also be the result Raised surface of wart
of neurological disorders such as stroke Basal cell
(commonly resulting in hemiplegia), par- Epidermis layer
kinsonism, peripheral neuritis, multiple
sclerosis, various forms of myelitis, and Dermis Nerve
chorea. Ménière’s disease may cause sev- fibre
ere loss of balance and instability.
Blood vessels
walking aids Equipment for increasing
the mobility of people who have a dis- Flat warts are flesh-coloured, sometimes W
order that affects their ability to walk. itchy lumps with flat tops that occur
Aids include walking sticks, crutches, mainly on the wrists, backs of hands, and
and walking frames. face. About 50 per cent of warts disap-
pear in 6–12 months without treatment.
walking, delayed Most children walk However, genital warts should be treated
by around 15 months of age. Delayed promptly. Common, flat, and plantar
walking may be suspected if the child is warts can sometimes be destroyed using
unable to walk unassisted by 18 months a wart-removing liquid or special plaster.
(see developmental delay). Several treatments may be necessary,
and sometimes the wart returns. Warts
warfarin An anticoagulant drug used to are commonly treated by cryosurgery.
treat and prevent abnormal blood clot-
ting. Warfarin is used to treat deep vein
thrombosis, pulmonary embolism, and
people with atrial fibrillation who are at
593
WART, PLANTAR WATERING EYE
wart, plantar A hard, horny, and rough- as exhaled water vapour, and by sweat-
surfaced area on the sole of the foot ing (see dehydration). The amount of
caused by a virus called a papillomavirus. water excreted in urine is regulated by
Plantar warts, also known as verrucas, the kidneys (see also ADH). Extra water
may occur singly or in clusters. The wart is needed to excrete excess amounts of
is flattened and forced into the skin and substances, such as sugar or salt, in the
may cause discomfort or pain when blood, and high water intake is essen-
walking. Infection is usually acquired tial in hot climates where a large amount
from contaminated floors in swimming of water is lost in sweat.
pools and communal showers. In some disorders, such as kidney fail-
Many plantar warts disappear without ure or heart failure, insufficient water is
treatment, but some persist for years or excreted in the urine, resulting in oedema.
recur. They can be removed by cryo- water-borne infection A disease caus-
surgery or by applying plasters or gel ed by infective or parasitic organisms
containing salicylic acid. transmitted via water. Infections can be
warts, genital Fleshy, painless, usually contracted if infected water is drunk, if
soft lumps that grow in and around the it contaminates food, or if individuals
entrance of the vagina, around the anus, swim or wade in it. Worldwide, contami-
and on the penis. Genital warts are nation of drinking water is an important
transmitted by sexual contact and are mode of transmission for various dis-
caused by a papillomavirus. There may eases including hepatitis A, many viral
be an interval of from a few weeks up to and bacterial causes of diarrhoea, typhoid
18 months between time of infection fever, cholera, amoebiasis, and some
and the appearance of the warts. types of worm infestation.
Genital warts have been linked with Swimming in polluted water should
the development of cervical cancer (see be avoided because, if swallowed, there
cervix, cancer of). They may be removed is a risk of contracting disease. In addi-
by cryosurgery or by the application of tion, a form of leptospirosis is caused
the drug podophyllin, but there is a ten- by contact with water contaminated by
dency for them to recur. rat’s urine. In tropical countries, there is
wasp stings See insect stings. also a risk of contracting schistosomiasis
water A simple compound that is essen- (bilharzia), which is a serious disease
tial for all life. Its molecular structure is caused by a fluke that can burrow through
H2O (2 atoms of hydrogen bonded to 1 the swimmer’s skin.
of oxygen). Water is the most common waterbrash The sudden filling of the
substance in the body, accounting for mouth with tasteless saliva. It is not to
about 99 per cent of all molecules, but be confused with acid reflux (the regur-
a smaller percentage of total body gitation of gastric juices), which has an
weight. Approximately 2 thirds of the unpleasant, sour taste. Waterbrash is
body’s water content is contained with- normally accompanied by other symp-
in the body cells, and the remaining toms, and usually indicates a disorder
third is extracellular (found, for example, of the upper gastrointestinal tract.
in the blood plasma, lymph, and cere- Waterhouse–Friderichsen syndrome
brospinal and tissue fluid). A serious condition caused by infection
Water provides the medium in which of the bloodstream by bacteria of the
all metabolic reactions take place (see meningococcus group. The main features
metabolism), and transports substances are bleeding into the skin, low blood
W around the body. The blood plasma car- pressure, and shock. Without urgent
ries water to all body tissues, and excess medical treatment, coma and death fol-
water from tissues for elimination via low in a few hours. The syndrome is
the liver, kidneys, lungs, and skin. The often associated with meningitis.
passage of water in the tissue fluid into watering eye An increase in volume of
and out of cells takes place by osmosis. the tear film, usually producing epiph-
Water is taken into the body in food ora (overflow of tears). Watering may
and drink and is lost in urine and faeces, be caused by excess tear production
594
WATER INTOXICATION WEIGHT
due to emotion, conjunctival or corneal weal A raised bump on the skin that W
irritation, or an obstruction to the chan- is paler than the adjacent tissue and
nel that drains tears from the eye. (See which may be surrounded by an area of
also lacrimal apparatus.) red inflammation. Weals are character-
water intoxication A condition that is istic of urticaria.
caused by excessive water retention in
the brain. The principal symptoms are weaning The gradual substitution of
headaches, dizziness, nausea, confu- solid foods for milk or milk formula in
sion, and, in severe cases, seizures and an infant’s diet (see feeding, infant).
unconsciousness.
webbing A flap of skin, such as might
Various disorders can disrupt the occur between adjacent fingers or toes.
water balance in the body, leading to Webbing is a common congenital abnor-
accumulation of water in the tissues. mality that often runs in families and
Examples include kidney failure, liver cir- which may affect 2 or more digits. Mild
rhosis, severe heart failure, diseases of webbing is completely harmless, but sur-
the adrenal glands, and certain lung or gical correction may be performed for
ovarian tumours producing a substance cosmetic reasons. In severe cases, adja-
similar to ADH (antidiuretic hormone). cent digits may be completely fused (see
Water intoxication is also seen in asso- syndactyly). Webbing of the neck is a
ciation with the use of Ecstasy (MDMA), feature of Turner’s syndrome.
during which excessive amounts of
water are drunk. There is also a risk of Wegener’s granulomatosis A rare
water intoxication after surgery, caused disorder in which granulomas (nodular
by increased ADH production. collections of abnormal cells), associated
water on the brain A nonmedical with areas of chronic tissue inflamma-
term for hydrocephalus. tion due to vasculitis, develop in the
water on the knee A popular term for nasal passages, lungs, and kidneys. It is
accumulation of fluid within or around thought that the condition is an auto-
the knee joint. The most common cause immune disorder (in which the body’s
is bursitis. (See also effusion, joint). natural defences attack its own tissues).
water retention Accumulation of fluid Principal symptoms include a bloody
in body tissues (see oedema). nasal discharge, coughing (which some-
water tablets A nonmedical term for times produces bloodstained sputum),
diuretic drugs. breathing difficulty, chest pain, and
wax bath A type of heat treatment in blood in the urine. There may also be
which hot liquid wax is applied to a part loss of appetite, weight loss, weakness,
of the body to relieve pain and stiffness fatigue, and joint pains.
in inflamed or injured joints. Wax baths Treatment is with immunosuppressant
may be used to treat the hands of peo- drugs, such as cyclophosphamide or aza-
ple with rheumatoid arthritis. thioprine, combined with corticosteroids
weakness A term used to describe a lack to alleviate symptoms and attempt to
of vigour or strength. This is a common bring about a remission. With prompt
symptom of a wide range of conditions, treatment, most people recover com-
including anaemia, emotional problems, pletely within about a year, although
and various disorders affecting the heart, kidney failure occasionally develops.
nervous system, bones, joints, and mus- Without treatment, complications may
cles. When associated with emotional occur, including perforation of the nasal
disorders, weakness may represent a lack septum, causing deformity of the nose;
of desire or ambition, rather than loss inflammation of the eyes; a rash, nod-
of muscle strength. ules, or ulcers on the skin; and damage
to the heart muscle, which may be fatal.
More specifically, the term describes
loss of power in particular muscle weight The heaviness of a person or
groups, which may be accompanied by object. In children, weight is routinely
muscle wasting and loss of sensation. used as an index of growth. In healthy
(See also paralysis.) adults, weight remains more or less sta-
ble as dietary energy intake matches
energy expenditure (see metabolism).
595
WEIGHT LOSS WEIGHT REDUCTION
WEIGHT
lb kg
210 95
WEIGHT 200 90 Overweight
(BMI > 25)
190 85
180 80 Healthy weight
170 (BMI 20–25)
75
160
70
150
140 65
130 60
120 55 Underweight
110 50 (BMI < 20)
100 45
90 40
144 146 148 150 152 154 156 158 160 162 164 166 168170 172 174 176 178 180 182 184 186 188 190 192 194 cm
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 in
HEIGHT
WEIGHT ASSESSMENT CHART
Weight loss or weight gain occurs if the cause loss of appetite due to the effect of
net balance is disturbed. uraemia. In anorexia nervosa and bulimia,
Weight can be compared with standar- complex psychological factors affect an
dized charts for height, age, and sex. At individual’s eating pattern.
all ages, divergence from the normal Digestive disorders, such as gastro-
weight for height may have medical enteritis, lead to weight loss through
implications. For example, if weight is vomiting. Cancer of the oesophagus (see
below 80 per cent of the standard oesophagus, cancer of) and stomach
weight for height, the individual’s nutri- cancer cause loss of weight, as does
tion is probably inadequate as a result malabsorption of nutrients in certain
of poor diet or disease, and if 20 per disorders of the intestine or pancreas.
cent above the standard, he or she is Some disorders cause weight loss by
considered to be suffering from obesity. increasing the rate of metabolic activity
An alternative method of assessment is in cells. Examples are any type of cancer,
use of the body mass index (BMI, or chronic infection such as tuberculosis,
Quetelet’s index), obtained by dividing and hyperthyroidism. Untreated diabetes
weight in kilograms by the square of mellitus also causes weight loss due to
height in metres. A healthy weight is a number of factors.
20–25 BMI; a BMI of greater than 25 indi- weight reduction The process of los-
cates that a person is overweight. ing excess body fat. A person who is
weight loss This occurs any time there severely overweight (see obesity) is more
is a decrease in energy intake compared at risk of various illnesses, such as dia-
with energy expenditure. The decrease betes mellitus, hypertension (high blood
may be due to deliberate weight reduc- pressure), and heart disease.
tion or a change in diet or activity level. The most efficient way to lose weight
W It may also be a symptom of a disorder. is to eat 500–1,000 kcal (2,100–4,200 kJ)
Unexplained weight loss should always a day less than the body’s total energy
be investigated by a doctor. requirements. Exercise also forms an
Many diseases disrupt the appetite, extremely important part of a reducing
which may lead to weight loss. Depres- regime, burning excess energy and
sion reduces the motivation to eat, peptic improving muscle tone.
ulcer causes pain and possible food In most circumstances, drugs play lit-
avoidance, and some kidney disorders tle part in a weight loss programme.
596
WEIL’S DISEASE WHIPLASH INJURY
However, sibutramine and orlistat may reverses most of the symptoms, some- W
be useful adjuncts to a reducing diet times within a few hours.
and may be appropriate for some peo-
ple with a high BMI (see body mass Korsakoff’s psychosis may follow Wer-
index). Appetite suppressants related to nicke’s encephalopathy if treatment is
amfetamines are not recommended. not begun promptly enough. Symptoms
Weil’s disease Another name for lepto- consist of severe amnesia, apathy, and
spirosis. disorientation. Korsakoff’s psychosis is
welder’s eye Acute conjunctivitis and usually irreversible.
keratopathy (corneal damage) caused by Wernicke’s area An area of the cere-
the intense ultraviolet light emitted by bral cortex in the brain that is involved
an electric welding arc. Welder’s eye, in the interpretation of spoken and writ-
which is also known as arc eye, results ten language.
from the failure to wear adequate eye Wernicke’s encephalopathy See Wer-
protection while welding. nicke–Korsakoff syndrome.
wen A name for a sebaceous cyst. West Nile virus A virus transmitted
Werdnig–Hoffmann disease A very from infected animals or birds to hum-
rare inherited disorder of the nervous nans by a mosquito bite. In most cases,
system that affects infants. Also known there are either no symptoms or a flu-like
as infantile spinal muscular atrophy, illness. Rarely, a serious and potentially
Werdnig–Hoffmann disease is a type of fatal illness, in which the virus infects
motor neuron disease, affecting the nerve the brain, can develop. The virus is
cells in the spinal cord that control found in Africa, Eastern Europe, West
muscle movement. Asia, the Middle East, and, since 1999,
the East coast of the US.
Marked floppiness and paralysis occur wet dream Ejaculation that occurs dur-
during the first few months, and affected ing sleep. See also nocturnal emission.
children rarely survive beyond age 3. wheelchair A chair mounted on wheels
used to provide mobility for a person
There is no cure for the disease. Treat- unable to walk. Manual wheelchairs are
ment aims to keep the affected infant as designed so that the hand-rims can be
comfortable as possible. easily gripped by a disabled person.
Wernicke–Korsakoff syndrome An They can also be pushed by a helper.
uncommon brain disorder almost always Powered wheelchairs use batteries and
related to malnutrition occurring in are controlled electronically by finger or
chronic alcohol dependence, but occa- chin pressure, or breath control.
sionally due to that which occurs in wheeze A high-pitched, whistling sound
other conditions, such as cancer. Wer- produced in the chest during breathing,
nicke–Korsakoff syndrome is caused by caused by narrowing of the airways. It is
deficiency of thiamine (see vitamin B a feature of asthma, bronchitis, bronchi-
complex), which affects the brain and olitis, and pulmonary oedema. Inhalation
nervous system. of a foreign body may also be a cause.
(See also breathing difficulty.)
The disease consists of 2 stages: Wer- whiplash injury An injury to the soft
nicke’s encephalopathy and Korsakoff’s tissues, ligaments, and spinal joints of the
psychosis. Wernicke’s encephalopathy neck caused by a forcible and violent
usually develops suddenly and pro- bending of the neck backwards (hyper-
duces nystagmus (abnormal, jerky eye extension) and then forwards (flexion), or
movements), ataxia (difficulty in coordi- vice versa. Such injury most commonly
nating body movements), slowness, and results from sudden acceleration or de-
confusion. Sufferers usually have signs celeration, as occurs in a car collision.
of neuropathy, such as loss of sensation,
pins-and-needles, or impaired reflexes. Damage to the spine usually involves
The level of consciousness falls progres- minor sprain of a neck ligament, or sub-
sively and may lead to coma and death luxation (partial dislocation) of a cervical
unless treated. The condition is a medi- joint. Occasionally, a ligament may rup-
cal emergency. Treatment with high ture or a cervical vertebra may fracture
doses of intravenous thiamine often
597
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