How It Works Book Of The Human Body

•• •• •

wortd : When AndWelcome to the • Amino what now? 5•• F"19htor flight

1 • 2 • 3Ababy'sstress level dumg : 4 Adrenaline can be obtainedfrom
birth ishighand,asa result.
theiractenalinelevel isalso
•\lei)'highatthis time.This
subsides post birthbackdown

to normallevets.
5 TOP- you need to breathe : relaaax
•
FACTS ! Due toitsblooc:I"Vessel· Afterstressful situiJt~ it's : animalsorsynthesised in thetJb. •• Thesayw.g 'fightor15ghr ;,
••• oftena good ideatophysically ••••••••
ADRENLINE • constricting properties.adrenaline wort<.off the adrenaline inyour associated vMhadrenalinebecause
• body soitdoesn'tstay in your
isalso used to treat breathing Thechemical namefa it is ••• whenwe'restressedwe produce the
system, keeping)'OU awakeat
difficulties associated with •••••• n9>~ for example. aminohydroxyp~ic hormoneinorder thatwe caneither
anaphylactic shockcaused by getreadyto ~Efendoorselvesor
alergic reacOOns. acid, v.'hich isrepresentedwith the ••• makea runfor iL
chemical form1JaC9Hl3N03.

li Medulla - - - - - - , . - - - - - - - - -Cortex

Discoverthe science behind your bodys At the core of the At the edge of the adrenal gland, the
amazing chemical coping mechanism adrenal gland, the cortex produces steroid hormones that
adrenal medulla include cortisol (for balancing blood sugar
produces, stores and
releases adrenaline. and carb metabolism) and aldosterone

(for balancing the body's salts and water).

Nestling on a layer offat as adrenaline. Identified in 1900, . - - - - Kidney
locatedjustabove each adrenaline is a fast-acting hormone
ofyour kidneys are the that helps the bodydealwith The organ that
body'sadrenal glands. unexpectedstresses- not to mention
AroundScm long, the adrenal glands high levelsofexcitement - by upping filters waste

produce hormones thataffectyour your heart rate and the flow ofblood from the blood.
body's consumptionofenergyas well to your muscles.
asyour stress responses. r - - - Fat
The effectofthis is that your blood
Adrenal glands consistoftwo main vessels and air passages dilate, Each adrenal
gland is protected
layersofhormone-secretingcells: the meaning that more blood passes to
the muscles and more oxygengets to by a layer of fat.
outer cortexand the inner medulla the lungs quicker, temporarily
While the cortex producesenergy- improving the body's physical
balancing hormones, the medulla performanceand potentiallysaving
producesa chemicalcalled
your life.
epinephrine, which we know better

"Adrenaline is o fast-acting
hormone that helps the
body deal with stresses"

101

=··

ow we breathe

Respiration is crucial to an organism's /
survival. The process of respiration is the
transportation of oxygen from the air that
surrounds us into the tissue cells of our
body so that energy can be broken down

The primaryorgans used exercising, breathing rate increases L Nasal passage/ • .,.
oral cavity
for respiration in humans and consequentlyso does heart rate ..)
are the lungs. Humans to ensure that oxygen reaches tissues These areas are wllere air
have two lungs, with the that need IL Oxygen is then used to • .....
left lung beingdivided Into two lobes breakdownglucose to provide enten into the body so that
energyfor the body. This happens in •
and the right into three. Lungs have axyge<1can be tr.lnsi>Orted into {
between300-500milUon alveoli, the mltochondriaorcells.Carbon andaround the body towllere
which is where gasexchangeoccurs. dioxide Is oneorthe waste products ji •. r
ofthis, which iswhywegeta build up it's needed Carbon cloxide
Respiration oroxygen breaks Into ofthisgasIn our body that needs to also exls tlrough these areas. .... •
four mainstages: ventilation,
be transported back into the lungs to
pulmonarygas exchange, gas be exhaled.
transportation and peripheralgas
exchange. Eachstage ls crucial in The bodycanalso respire
getting oxygen to the body's tissue, anaerobically, but this producesfar

and removing carbondioxide. less energyand Instead orproducing
Ventilationand gas transportallon
need energy to occur,as the cozasa byproduct, lacticacid is
diaphragm and the heart are used to
faciUtate these actions whereasgas produced. The body then takes time
to break thlsdown after exertion has
exchangingis passive. As air Is drawn finished as the body has a so-called
Into the lungs at a rate ofbetween10-
oxygen debt.
zo breaths per minute wh lie restl ng,
5. Alveoli - -
through either your mouth or nose by
The alveoli are lily fittle sacswhich are situated
diaphragm contracllon.•and travels at theend of !OOes inside the lungs and are in
through the pharynx, men the directcontact with blood. Oxygen and carbon
larynx, down the trachea, and Into dioxidetransfer to and from the blood stream
oneofllle two main bronchial tubes.
Mucus and cilia keep the lungs clean through the alveoli. - -

bycatchingdirt particlesand .••• • • y ••
sweeping them up the trachea. •••
•
When air reaches the lungs, oxygen
is diffused into the bloodstream How our
work
through thealveoU and carbon
dioxide is diflused from the blood Capllary beds Lungs ore the major
into the lungs to beexhaled. Diffusion
ofgasesoccursbecauseofdifferlng respiratory organ in humans
pressures in the lungsand blood.This

isalsothesamewhenoxygen
difluses into tissue around the body.
When blood has beenoxygenated by
the lungs, it is transferred around the

body to where ills most needed In the
bloodstream. If the body Is

102

• 2••••••••- ••- •• ••

STOP ~ c;qJaCi:ty The rightlung We have excess Alveoli have massive • We breathe 11,090
is bigger : 3•• lamg capacity •• litres of air per day
FACTS 1vanes hUgely On average. t.Jmansonly use 4: surface area •• s
Dependantonsex a1d body lntere:stiogly, the lefU .1ng is tfoneperson's entire Onaverage, one individual will
LUNGS size. alongside external
factors such as altitude, lung • slightlysmaUer than theri!;#lt in • about one-ei~ of the ! alveoliwere &aidouttheywould breathe in 11.000 itres ofairin
•••••• ••••
capacityrangesbetween the human body because the left capacityofour lungsfOt'each • havethe surfaceareaofabout70crnl ••••• any given day.lftheyexercise
4 ,0 0 0 a n d 6 , 0 0 0 a n '. breath sowehave a large
lung has tomake room for the • reserve volume. ! ... that'sroughly thesize ofhatf a he<Miyduring 111at day, thiswill
increase fLI'ther.
heart to fll in. • tenniscourt!

!•U•I\1•1!/Itj~I•IW Trained free-divers con hold their breath underwater for up to nine minutes

This is part ofboth How do we breathe? Chest cavity
the respiratory and
This isthespace that
digestive system. A flap The intake ofoxygen into the body is complex is protected by the

ofcoonectilie tissue rils, w here the lungs
and heart are
called the epiglottis Breathingis notsomething that we have to the alveoli at the ends, which are the final
closesover the trachea branching.The chest will beseen to rise situated. The space
to stop choking when think about, and indeed is controlled by muscle changesas the
an incfrvidual takes food contractionsinour body. Breathing is because of this lung expansion. Alveoli are
into their body. controlled by the diaphragm, which contracts surrounded by blood vessels, and oxygenand diaphragm 111011es.

3.Trachea and expands ona regular, constant basis. carbondioxide are then interchangedat this Ribcage
When itcontracts, the diaphragm pullsair into point between the lungs and the blood. Carbon
Air is pulled into the dioxide removed from the bloodstream This is the bone
the lungs byavacuum-likeeffect. The lungs
body through the nasal structurewhich
protects the organs.
.""';sespassages and then expand to fill the enIarged chestcavity andair that was breathed in but not
into the trachea. and air is pulled right through used is then expelled from the lungs The rib cage can
move slightly to
the maze oftubes that bydiaphragm expansion. Lungs
makeup the deflate back to a reduced size alow for lung
when breathing out. expansion.
--....:.:.lungs to
____.....:---._...._
Lungs

Deoxygenated blood

arrives backat the

lungs, where another

gas exchange occlS"S at

the alveoli. Carbon

4. Bronchial tubes dioxide isremOIIed and
oxygen is placed back
These llbes lead to either the
•• left or the right lung. Air passes into the blood

•t:, through these tubes intothe Diaphragm - - - - - - '
lungs, where they pass
through progressiwly smaller This is a sheet of muscle situated
at the bottom oftherib cage
and smaler tubesuntil they
which contracts and expands to
reach the alveoiL
•'·•' draw air into the lungs.

<{

•• Heart

The heartpumps oxygenated

blood away from the lungs,

around the body to tissue,

where oxygen is needed to

break down glucose

- 6.Ribs into a usable form
of energy.

These provide protection Tissue
for the lungs and other
internal organs situated Oxygen arrives
where energy is
.•• in thechest cavity.
needed, and a gas

exchange of

oxygen and carboo

dioxKie occurs so

that aerobic
respiration can

occur within cells.

I' do we oxygen?

'• . We need oxygen to live as it is crucial for the release
of energywithin the body
'I •
'• Although we can releaseenergy through more thana few minutes, anindividualwill die.
anaerobic respiration temporarily, this method Oxygen is pumped around the body tobe used
._______.. Is Inefficient and createsan oxygendebt that in cells that need to breakdown glucoseso that
the body must repay after excessexerdseor energyis providedfor the tissue. The equation
exertion has ceased. Ifoxygensupplyis cutofffor
that illustrates this Is:

103

=·· I
drotion

Pore Skin

Sweat is Once the sweat ison the skin's
...-face.its absorbed moisture
releaseddirectly
evaporates,
intothedemlis
heat into·theafro'fi:'lre
Ilia the seaetaoy

c1JC1. wl1ich then

filters IIYough
the skin's pores

tothe surfaoe.

do we

As your doctor may tell you, it's glandular...

Sweat Is produced by dedicated sweat internal temperatureofthe bodyrises, secretea "c'
glands, and Is a mechanism used
primarilyby the bodyto reduceits salty, water-based substance to the skin's surface. Q
Internal temperature.Thereare two This liquid then cools the skinand the body
types ofsweat gland In the human body, the through evaporation, storing and then transferrl ng Secretary Secretary part Nerve fibres
eccrineglandand theapocrinegland.The former excess heatInto theatmosphere.
regulates body temperature, and Is the primary duct This is where the DeiNermessages to
source ofexcreted swea1.. with the Iauer only Boththeeccrlneandapocrinesweatglands only majorityof the glald's
secretingunderemotional stresses, ratherthan Secreted sweat glands to produce
those Involved with body dehydration. appear in mammals and, ifactive over the majority tnM!Is up to the secretary eelscan
Eccrine sweatglandsarecontrolled by the oftheanimal's body,aetas the primary sweat when the
sympathetlcnervoussystemand,when the skin Ilia thiscb:t. be located. body's temp rises.
thermore.gulatory device. Certain rna mma Is such

as dogs, catsand sheep only have eccrine glands In
specificareas-suchaspawsand lips-warranting
the need to panttocontrol their temperature.

a concentrationof
particles in the
blood, indicating a

Other symptoms at
this level include
fatigue, a dry mouth

nowsose~~ere include sunken
eyes. low blood
that IV fluid
Too much H 0? replacement
2
Here symptoms
Hydration is all about finding the perfect balance.
Too much hydration can be harmful as well as become much
too little; this is known as water intoxication. If
too much liquid is in your body, nutrients such cognitive abilities

as electrolytes and sodium are diluted and the

body suffers. Your cells bloat and expand and
can even burst. and it can be fatal if untreated.
The best treatment is to take on IV fluids
containing electrolytes.

••• •• ••

STOP Jet lag • 2Mental state••••••••••••Heatthoonditions such as 3:••• Latinname •• The 6ving dock • nme to take your pills
depression, bipolardisorder
FACTS l rmezone changes canoften With these rhythms known to •4 In the 18th Cenh.ry, a botanist s• DoctorsteUyoutotakemedicine
disrupt circacian rhythms. and seasonalaffective •• OCCIX approximatelyf?t~e~Y 24 •••••••
CIRCADIAN Y011body clock may beoul disorder (SAO) are all • calledCarolusUmaeusissaid ata prescribed time because the
of sync with yourwristwatch, associated with abnormalities l"l.lmanbodydock can affect
RHYTHMS but it will reset itselfaftera •••• hours. the phrase 'circadian' ••• to have invented a iving d ock.
few days. i'l circadian rhythms.. stemsfrom Latin for •circa", Hisgarden coukfhelp himtell their effecti\'eness. Aspirins
thetime based onthe flowers
which means'about', and 'diem'. • function betterwhentakenearty

•• which means 'day'. •• he planted. •• in the morring.

t•U•I'\JII!IItj~l•l!l!LP The pineal gland, located near the centre of the brain, is about Bmm long and shaped like opine cone

How does our internal body clock tell uswhen to sleep? !::~~

10.00 NOON The variationsin the amount of
melatoninsecreted by the body create
High alertness 12.00
a dailyrhythm of risingand falling
09.00 14.30 hormone levels.These hormones,
along with the SNC,affect appetite,
Highest testosterone Best co-ordination
body temperature and a lotelse.
secretion here
15.30
08.30
Fastestreaction time
Bowel movement likely
17.00
07.30
Highest cardio-
Melatonin secretion ends vasculareffkiency
and muscle strength
06AS
18.00
Steep rise in blood
pressure. Heart attacks 18.30
are more likely to ace..- in
the morning than any Highest blood
other time due to this rise pressure time
in blood presst.re

06.00

04.30 19.00

To conserve energy during Body temperature is
highest during the
sleep, body temperature
drops. It is at its lowestjust late afternoon
before waking

02.00 22.30 21.00

Deepest sleep Bowelm~ With the fading of sW~Iight into
the evening, melatonin secretion
suppressed here
begins - and increasestenfold-
mak ing us sleepy

00.00

MIDNIGHT

Circadian rhythms are biological changes that occurat roughly 24-hour
intervals, wbetherwe'reaware ofthe time onourwatch or not. These
changes, which are controlled by Internal biological time-keeping
systems,affect us physically, mentally and behaviourally.

Located behind the eyes in the hypothalamus is a region of the brain called the
suprachlasmaticnucleus. No larger than a grain of rice, the SCNis a kind of master
bodyclock that controlsall ourotherinternalclocks, which in turn control our
circadian rhythms, or daily wake-sleep cycles.Circadian rhythms respond mainly

to lightand dark cues buteven ifthe body was monitored under conditionsdevoid
ofday or night signals, ourcircadian rhythms still cycleina period ofaround24
hours. The retina In the eyesenses light levelinformation, which is relayed to the
SCN, whichsendsasignal to the pinealglancl Thispea-si2edgland, located
beneath the thalamus, is responsible for the secretion ofmelatonin - a hormone

that tells the bodytosleep- andsoat nigbtwhen lightlevelsfall, the productionof
melatonin increases, telling us to head to bed...

105

umon immune system

Your body is locked in a constant Human anatomysubscribes to the notion
war against aviscous army that good fences rna ke good neighbours.
Yourskin, made up oftightly packedcells
It's true: whileyou'resittingaround that take over host cellsand replicate inside them; and an antibacterialoil coating, keeps
watching TV, trillions offoreign invaders and fungi, a type of plantlife. most pathogens from eversetting foot in
are launching a full scaleassault on the body. Your body'sopeningsare well-
Bacteria and viruses are byfar the veryworst fortified too. Pathogens that you inhale
trillions ofcells thatconstitute'you'. face a wall of mucus-covered membranes
Collectively known as pathogens, these attackers offenders. Dangerous bacteria release toxins in the in your respiratory tract, optimised to
include bacteria, single-celledcreatures that live to trap germs. Pathogens that you digest end
eatand reproduce; protists, largersingle-cell body that cause diseasessuchas E. coli, anthrax, and upsoakingina bathof potentstomach
add. Tears Hush pathogensout of your
organisms; viruses, packetsofgenetic Information the black plague. Thecell damage fromviruses causes eyes, dousing bacteria with a harsh
measles, the Ouand the common cold, among enzyme forgood measure.

numerous otherdiseases. justabout everything l.n ourenvironment is
teeming with these microscopicintruders... including
you. The bacteriainyourstomachalone outnumber
all the cells inyour body, ten-to-one. Yet, your scrappy
microscopicsoldiers usuallywin the dayagainst
pathogens, through a combination ofsturdy barriers,
brute force, and superior battlefield intelligence,
collectivelydubbed the immunesystem.

106

••• • ••••••••

STOP. The are can • Immunity soldiers • You can 'bonow' • Itdeals with internal It has trouble with
•
FACTS 1sometimes hart : 3•• immunity troubles, too change
Sneezing, coughing, a sore :2: are everYwhere Antibodies inbreastm ikgive 4•• :s Unfortunatelyyou cannot
IMMUNE SYSTEM throat, and fe\'er areall common A single dropof blood contains In addition to fighting
• pathogens, T-<:eAs fightthe
meansol expelting pathogens. so • arol..nd 375,000white blood babies temporary immLW'lity : developinv"nulitytothe

asamoying astheyare, each •• cells, and blood constituteslor •••• from diseases their mother is body'sown cancerouscells and ••••• ftu andoommoncold
one is necessary. because thevirusesare
•• sewnper cent ofyourtotal invnuneto, preventing •• some cancer ther apies boost alwaysmutating.
the rumberofT-cells.
bodywei~l infancy infection.

!•U•Jtl•l!l!tj~!•mG> or Karl Londsteiner first identified the major human blood groups -A, 8, AS and 0 - in 1901

• system

Fighting theg ood fight, and white blood cells are 2. Bacterium antigen

right on the front line... These distinctive m olecules allow your

When a pathogenis tough, wily; The B-cells flood your body 4 .Engulfed im mune system to recognise that the
or numerous enough to survive with antibodies, molecules that
non-specificdefences, it's up to eitherdisarm a specific pathogen bacterium bacterium is something otherthan a body cell
or bind to it, marking itas a target
the adaptive immune system to During the initial 3. Macrophage 1. Bacterium
clean up the mess.The key forces for other white bloodcells. When
inthe adaptive immunesystem T-cellsfind their target, they Joel< inflammation react:iof\ These white blood Any bacteria that enter
cells engulf and digest
a maaophage engu~s your body haw

are white blood cellscalled on and release toxic chemicals the bacterium. any pathogens they characteristic antigens

lymphocytes. Unlike their thatwill destroy it. T-cellsare come across,

macrophage cousins, especiallyadeptat destroying

lymphocytes are engineered to your body's cells that are infected

attack only onespecifictype of with a virus.

pathogen.There are two types of This entire process takes

lymphocytes: B-cellsand T-cells. several days to get going and may

These cellsjoin the action take even longerto conclude.AU

when macrophages passalong the while, the raging battlecan

informationabout the invading makeyou feel terrible.

pathogen, through chemical Fortunately, the immune

messages calledinterleukins. systemisengineered to

After engulfinga pathogen, a learnfrom the past While

macrophage communicates your body is producing new 7.Non-
details about the pathogen's B-cellsandT-cells to fight the matching 8-cells
pathogens, italso produces
antigens - telltale molecules that Other B-<:ells, engineered to
characterisea particular memory cells- copiesofthe
pathogen. Basedon this B-cellsandT-cells, whichstayin attack other pathogens,
information, the immunesystem the systemafter the pathogenis
don't recognise

the antigen.

identifiesspecific B-cellsand defeated. The next time that 5. Presented -

T-cellsequipped to recognise and pathogenshows up in your body, bacterium antigen

battle the pathogen.Once they these memory cells help launch a After engulfing the bacterium, the

aresuccessfullyidentified, these counter-attack much more macrophage 'presents' the
cells rapidly reproduce, quick ly. Your bodycan wipeout bacterium's distinctive antigens,
the invaders beforeany infection
assembling anarmy ofcells that comrrunicating the presence of
are ready and equipped to take takes hold. In otherwords, you
the specific pathogen to B-cells.

down theattacker. develop immunity. 6. Matching 8-cell 9. Memory cell
Vaccinesaccomplish the same
Non-specific The specific lk:el that The matching B-<:ell also
defences thing bygivingyoujustenough
pathogenexposure foryou to recognises the antigen. and replicates toproduce
As goodasyour physicaldefence system is, pathogens develop memory cells, but not can help defeat the pathogen,
do creep pastit regularly. Your bodyinitially responds enough to mal<e you sick. memory cells, w hich wil
with counterattacks known as non-specificdefences, rapidly produce copies of
so named because they don't target a specific type How
itse~ if the specific
ofpathogen.
Aftera breech - bacteriarushing in through a cut, for 1 - - - - - - - bacteria ever returns.

example- cells releasechemicalscalledinflammatory .)....~ y
-r ~
mediators. This triggers the chief non-specificdefence, a -cells target and
known as inflammation. Within minutes ofa breach,
destroy specific bacteria
and other invaders

your blood vessels dilate, allowingbloodand other fluid ~~~~;r.te ~-~-~ ~ -

to flow into the tissue around the cut called phagocytes J10. Antibodies 8. Plasma cell
The rush offluid in inflammationcarriesvarious types recognise the antibody
The plasma cells release The matching B-cel
ofwhite bloodcells, which get to work destroying marker, engutf the
intruders. The biggestand toughest of the bunch are antibodies, which replicates itself,
macrophages, white bloodcells with an insatiable bacteria, and disablethe bacteria by
appetite for foreign particles. When a macrophage detects digest them.

a bacterium's telltale chemical trail, it grabs the intruder,
engulfs It, takes itapart with chemicalenzymes, and

spitsout the indigestible parts. Asingle macrophage can latching oo to their creating marry

swallow up about100 bacteria beforeits own digestive antigens. The antibodies plasma cells to fight
chemicals destroy itfrom within. aR the bacteria of this
alsomark the bacteria
for destruction. type in the body.

107

=·· I

umon t• mmune s

LLTo~nsil~s ~~~:-~=- --------:;~~~1r~- ~

lymphocytes,wl1ich attad<
bacteria thatgetintothe body
through yar noseormouth.

Disorders of 2. left subclavian vein G. l ymph

the· Oneal two large veins that serve node d uster
as the re-entry point for lymph
Who watches the r1!h.ming to the bloodstream. Located along lymphvessels
watchmen?
3. Right lymphatic duct throughout the body, lymph nodes
The immunesystem !sa powerful set of fi~er lymph as it makes its wey back
defences, so when It malfunctions, It Passageway leading from lymph vessels
candoasmuch harm asa disease. to the right subclavian vein. -----------...:..0:~ into the bloodstream.
Allergiesare the result ofan overzealous
immunesystem. Inresponseto S. Spleen - - - 7.Left
somethingrelatively benign, like lymphatic duct
pollen, tbe immunesystem triggers An organ that houses white
excessivemeasures to expel the blood cells that attad< Passageway leading from
pathogen. On the extreme end, a llergles pathogens in the lymph vessels to the left
maycauseanaphylacticshock,a body's bloodstream - - - stbclavian vein.
potentiallydeadly drop In blood
pressure, sometimes accompanied by 10. Lymph vessels - ...__ _ _ 8. Thymus gland
breathingdifficulty and loss of
consdousness.lnautolmmune Lymph collects in tiny capilaries, Organ that prollides area for
disorderssuchas rheumatoidarthritis, which expand into larger vessels. lymphocytesprodJced by bone
the immune system falls to recognise Skeletal mliSCies move lymph
the body's own cells and attacks them. through these vessels, back into rnarn:M' to mature into
the bloodstream. specialised T-<:ells.

!nan allergicreaction, thebody may reson to The lymphaticsystem is a network of ·~1 r - - - - 9. Thoracic duct
sneezing toexpel a fairly harmless pathogen organsandvessels that collects lymph The largestlymphvessel
- Ould that has drained from the in the body.
108 bloodstream intobodilytissues- and
returns It to yourbloodstream. Italso 11. Peyer's patch
plays a key role inyour immune
system, filtering pathogens from Nodules at lymphoid tissueSl.pporting
lymph and providing a home-base for
disease-fighting lymphocytes. while bloodeels that battle pathogens
inthe i 1lesti01 tract.

~~t--- 12. Bone matTOW

The siteat allwhite blood

cell production.

ex1Jiained
Lymph nodes
filter out
pathogens moving

through your

lymph ves sels

Your immune system depends
on these .04-t-inchsweUingsto
fight all manner ofpathogens.

As lymph makes ilsway
through a network offibres in

the node, white bloodcells
filter it, destroyingany
pathogens they find.

1. Influenza 2. Measles 3. Tuberculosis

The nu kills hundreds of One person infected with Excavated Ancient Egyptian
thousands of people In a measles will sptead the virus mumfries show signs of
tuberculosis, and the disease
good year. And evory to just about every Is still thriving today. Around
once in a while, a virulent unvaccinated petson they 2 billion peoplearound the

form CaJl take out tensof e.ocounte(.luckily, the w<rid are infected.
miJIJons of people. vaccine is ve:ry effective.

!•U•I\1•1!1!tj~l•lmP In 2008, approximately 33 million people worldwide were living with HIV or AIDS

innercontents Know

enemy:

Bacteriaare the smallestand, by far, the most populousform oflife
on Earth. Right now, there are trillions of the single-celled creatures
crawlingonand in you.ln fact, they constituteabout fourpoundsof

your total body weight. To the left is a lookat bacteriaanatomy...

Major points of the lymph node

- - l4 1. Outgoing lymph 7. Sinus

vessel Achannellhatslows the

Thevessel thatcarries !lowoflymph,glvlng
lllieredlymphouto1the macrophages the
lymph node opportunltyto destroyany
2. Valve detectedpathogens

Astructure thatprevents 8. Incoming lymph

lymph !rom!lowingback vessel
Into the lymph node Avessel thatcarrieslymph
3. Vein Intothe lymphnode

Passageway lorblood 9. Lymphocyte
leaving thelymphnode TheT-cells, 8-cells and
4. Artery naturalkillercells that

Supplyollncomlng blood fight lnlection

lor thelymphnode 10. Genninal centre

5. Reticular fibres This Isthe siteor

Divides the lymph node lymphocytemultiplication
Into Individualcells and maturation

6. Capsule ll. Macrophage

Theprotective_shielding Large whlle blood cells that
fibres thatsurroundthe enguUand destroyany
lymph node detectedpathogens

109

=··

ending bones

1• n rocess

Learn howyour bodymends broken bones

Ifa bone has too much pressure put gradually fuse together, lil<e a bridge being All-star cast
on it, there is a chance it will break. constructed from eitherside ofa river until both
Your body has ways of repairing ends meet in the middle. Most breaks on an arm or a leg will have a plaster
these breaks, butittakes time and cast put on them to prevent the bone from
care.There are different kinds of break, ranging Once both sectionsof bone are connected setting at a wonky angle or not setting at all.
from a hairline fracture to a fully shattered again, spedalised cells calledosteoblasts enter to
bone, but they all mend in a similar way. produce bone cells.These new cells replace the It will generally be made from plaster of Paris.
As a bone breaks, the blood vessels are also callus, returning the bone to its originalshape. This is a mixture of water and gypsum that sets
severed. Blood leaks out and forms a clot called really hard once it has dried. The broken bone is
a fracture haematoma. This stops blood flow to Much like repairing a broken toywith glue, bandaged and the wet mixture is applied to the
thearea and also helps keep both pieces of bone the bone needs to be kept straight and steady gauze. Once it has dried then it should provide
aligned, ready for healing. for the fusion to happen correctly. This is why safety and st ability for the bone.
The body then makes fibrous cells and doctors will put a cast on the broken bone. The
cartilage, which reinforce the bondand cast provides essential support, protection and Fibreglass is an increasingly common cast
strengthen it. This creates a callus, which is stability, ensuring the broken bone doesn't material. As with the plaster cast , the broken
essentiallya weakened bone. Over time, the move. Acast will generally stayon for a few bone is bandaged up. Next, another bandage,
callus builds up and the two parts of the bone weeks until the bond has become strong made of f ibreglass and layered with resin, is
enough, but it could take months for a properly soaked in water. This makes it f lexible enough to
set bone to fully recover. be wrapped around the bone before it hardens as
it dries. This is much lighter than a plaster cast
and the outer layer is waterproof.

The stages of bone repair

Blood -..,Jttri'l:-i~ 1-+ollt-'-IF+- New Healed
clot blood fracture
forms vessels
Internal callus --1
(fibrous tissue
and cartilage)

Rupt ured Hard --4+.
blood bone
vessels callus

External Blood flow
callus improves

Blood clot Tissue growth Remodelling
When a bone breaks, the blood vessels Afew days later, the blood clot- called the fracture Bone-forming cells called osteoblastswork in
that run through the bone are severed. haematoma - is gradually replaced by tougher teams to build a new bone, creatlnga more solid
The blood forms a clot to align the bones. tissue, which becomesa soft callus. Fibrous tissue
This createsa solid yet weak structureto and cartilage are produced that begin to bridge the structure called a hard bone callus. It takes several
prepare for mending. The clotalso cuts off gap between the fractured ends. New blood vessels months to fill the cavitywith harder bone,
blood Dow to the edges of the broken bone, begin to form and the callus usually lasts around strengthened by nutrients like calciumand
phosphorus. However, it may take longer for the
so these cells die. three weeks. bone to be completely healed.

no

•••• •• ••

STOP 1Polu!mon • PloteW. from food •••• PI'OteWI we need : Biuret test • Genome studies
Speedy Pd<emon character ; 2 We get protein from meat, 4; 3 Yourbodymakesdlousands • TheBiurettestlsachemical . 5 Fromstudies into the hutnan•
FACTS Pikachu had a protein named
: fiSh, eggs, l'<ltSand dairy • of proteins every day. For each : form ofanalysis that is used to • genornes sequenced sofar,it
PROTEIN after itin 2008. The protein, •••••••
pikachurin, isused in kinetic ••••••• products. Wedigest the !kg you weigh, you typicaDy •• measure the amount of ••••• has been discovered that the
vision, which, aptly, is the proteinthat Is present in food. bodycontains over' 2 million
proteins Into aminoacids, require lg of protein. So daity a : It wori<s out protein levels by • proteins, coded byjust
detectionof fastobjects.
which ......e later useto J"eplace 70kg man mustmanufacture ••• analysing the peptide bonds. 20,000·25,000genes.

these proteins inour bodies. 70g of protein for hisneeds.

!•U•Jtl•l!l!tj~l•mG' Around half of your body's 'non-water' moss is mode up of proteins

nusisthe 'pn)leiJHTlaking
machfle' nthecel! It uses

This IS the control centreof Why are
the ced whereall important amino acids
genetic data JS stored important?

How do we make protein? Aminoacidsare vital to
our bodies beingable to
Proteins are the building blocks ofthe human body, operateas theyare the
but how do we go about manufacturing them? bulldlng blocks of

Proteins are large complex molecules made up ofa and T}andthese shortsequences, which are knownas triplets proteins. Each type of
chain ofamino acids. Every cell in our body needs orcodons, then code mRNA templates; these templates are amino acid performs a
protein to stayalive as it is necessary for tissue 'translated' bycell ribosomes intoamino acids. differentjob,which aids
repair and replacingdead cells. proteinactivity in the
They have many otherfunctions as well as aidlng cell repair Each protein is made up of hundreds of thousands ofamino
acids, which are in longchains.There are 20 different types of bodyand determines the
and production includingformingantibodies to help fight off protein's primary
disease, forming enzymes whichspeed up or trigger chemical amino acid that can becombined to builda proteinand it is the function(s). Without these,
reactions and co-ordinatingprocesses within the body (via sequence ofamino acids that determines each protein's unique proteins would not be
hormone regulation, for instance}. Proteinsalso provide able to help the bodywith
three-dimensionalstructureand itsfunction.
supportfor cellsand form structural elements of the body, such However, notal! amino acids can be made by the body.The movement, defence
as nails and teeth, as well as facilitating the transportation of against disease,
ones that need to be consumed via ourdiet are calledessential processingfood or
somesmall molecules around varioussystems. amino acids. Ifpossible, the bodywill also conserve energy by co-ordinating general
We build proteins using informationencodedin ourgenetic using amino acids from food rather than producing them itself.
Protein deficiency cancause diseases suchas kwashiorkor, a growth and development.
code. DNAcode utilises groups of three letters (a mix ofA, G, C form ofmalnutrition commonin poverty-strickenareas.
Thereare nine
essentialamino acids for
humansthatmustbe
absorbed from external
proteinsources(eg meat/
fish) as they cannotbe
synthesised by the body.
Without the required

amount ofamino acids,
the bodycan really suffer.

111

=··

Cell division explained

What is a optosis? Answer:

APPETITE FOR SElF.· A Another cty-Ap e of cell division B Prog r ammed Essentially a cell committing suicide. apoptosis is a
DESTRUCTION conltOied biological system that kills off ooneeded
eel death new type of soft drink Otexcess celts. One example is theretn011al of

webbing in between )'OU" fonge<s and toes before

)'OU are botn.

I•U•Jtl•IYt3~1•1@ A common theory 1s that every living cell is descended from a single ancestral cell from 3-4bn years ago

An expert's view

Paul NU"se, Nobel PIize Willolel' and diredor of the Francis Crick Institute, chats
about cell cycle

What is the cell cycle? Why do skin cells divide so quickly and nerve
The cell is the basic unit of life for all living things.
One of its many properties is the ability to reproduce. cells so slowly?
Cells change at varying rates and some nerve cells
The cell cycle is a series of processes that occur barely divide at all. This is one reason why it is
between the birth of the cell and its division into two. difficult toregenerate the nervous system when it
becomes damaged. Because the body has to deal
What is mitosis? with cuts and abrasions, it is much easier to get skin
Mitosis describes what happens near the end of the cells to divide.
cycle. The replicated chromosomes are separated
from each other into opposite ends of the cell just What is tissue culture and why is it important?
before t he cell divides.
It Is simply a way of growing cells from animals and
What are the different parts of the cycle? plants in t est tubes. They will divide under these
c ircumstances so you can study the cell cycle away
The other major part occurs before m itosis and is the from the complexities of an animal or plant

process in which the DNA that makes up the What are the differences between plant and
chromosomes replicates itself. This is called the animal cell cycles?
S·phase or DNA synthetic phase [which is part of Fundamentally, not very much. They both undergo
interphase]. The S·phase replicates and mitosis the same processes but are subject to different
separates and divides. overall controls.

What is the difference between mitosi.s and What is proteolysis and how doesthat
meiosis and does cell division occur in both? mechanism help the cell cycle?
It is a biochemical mechanism that breaks down
Meiosis is usuallyconsidered to be the mitotic futl
cycle and also leads towards cell reproduction. protein. It takes away certain proteinsas part ofa
regulatory system for a variety of biological process
However, in meiosis there are two M·phases or
such as the ceU cycle. It is used at the end of the
divisions so thenumberof DNAand chromosomes
are halved. Meiosis uses gametes for fertilisation in cycle to destroyexcess protein and prepare for the
diploid cells in animal and plants.
next cycle.
Does it occur in eukaryotic or prokaryotic cells?
Only in euk.aryotic cells. In prokaryotic cells there is a You discovered CDK (Cyclin-dependent kinase).
cell cycle but it is not mitosis. This [procesS] is
simply the copying of DNA and then a much less How do they contribute to the cell cycle?

obvious separation of the copied DNA into the two CDK is a type of enzyme and my research group was
divided cells. involved in discovering that they were the major
regulators in the cycle. CDK brings about the S·phase
Why did you use yeast in your experiments? and mitosis and controls them.
Yeast is a very simple eukaryote, which reproduces
in much the same way as more complex cells in us. It How can the cycle help understand potential
only has 5,000 genes compared to our 25,000. It cures for cancer?
simplifies cell div ision so is extremely convenient to To understand cancer, you have to be able to
study. It 's got fantast ic genet ics and genomics, understand the cell cycle. Crudely blocking t he cell
which allow you to invest igate complicated cycle is a problem as a therapy as ourbody is full of
processes like t he cell cycle. other cells that have to divide.

••
•

••• •

Paul Nurse is also the

former director of Cancer
Research UK and president
of the Royal Society

=··

load cells explained

ite Monocyte

ce wo • Monocyteshelp prepare us
for another infectionby
One ofthe body's main defences against infectionand presenting pathogens to the
pathogens, how do these cells protect our bodies?
body, so that antibodies can
be created. later in their life,
rnonocytes rno~~e from the

bloodstream into tissue,
and then ~Ill<! into
macrophages which can
conduct phagocytosi.s.

White blood cells, or leukocytes, are Types of leukocyte
the body's primary form of defence
against disease. When the body Is Different kinds of WBC have different roles, which
invaded by a pathogen of any kind, the complement one another to defend the body
white blood cells attack in a variety ofways; some
produce antibodies, whi le others surround and •
ultimately devour the pathogens whole.
In total, there are live types ofwhite blood cell I
tWBC), and each cell works In a dHrerent way to
light a variety of threats. These live cellss it In two Lymphocyte
groupings: thegranulocytesand the
agranulocytes.Thegroups are determined based These release antibodies
on whether a cell has ·granules' In the cytoplasm. as well as attack virus and
Thesegranulesare digestive enzymes that help tumour cells through three
break down pathogens. Neutrophlls, eosl nophlls differing types of cell. As a
and basophilsare all granulocytes, the enzymes group, they are some of
in which also give them a distinct colouratlon the longest li~~ed of the
whichtheagranulocytesdo not have. white blood cells with the
As the most common WBC, neutrophlls make up memory cells surviving for
between55and 70 per cent of the white blood cells years to allow the body to
in a normal healthy Individual, with the other four defend itself if repeat
types teosinophils, basophils, monocytes and attacks occur.
lymphocytes) making up the rest. Neutrophlls are
the primary responders to Infectlon, actively
moVing to the site of infection following a call from
mast cells after a pathogen Is Initially discovered.
They consume bacteria and fungus that has
broken through the body's barriers In a process
called phagocytosis.
Lymphocytes- the second-most common kind
of leukocyte- possess three types of defence cells:
Bcells, T cells and natura ll<l ller cells. Bce lls
release antibodies and activate Tcells, while T
cells attack diseases such as virusesand tumours
when directed, and regulatoryT cells ensure the
immune system returns to normal after a n attack.
Natural killer cells, mea nwhlle, a ld Tcell response
by also attacking virus-infected a nd tumour cells,
which lack a marker known as MHC.
The remaining types ofleukocyte release
chemicals suchas histamine, preparingthe body
for future infection, as well as attacking other
causes of illness like parasites.

"Natural k1ller cells Eosinophil
aid T cell response
by also attacking Eosinophils are the white
VIrus-infected and blood cells that primarily
tumour cells" deal with parasitic
infections. They also hall<!
a role in allergic reactions.
They make up a fairly small
percentage of the total
white blood cells in our
body - about 2.3 per cent.

114

t•U•Jtl•I!J001•1t;l0 W8Cs have colour but appear white when blood is put through a centrrfuge, hence their group name

•

Basophil

Basophils are involved in
allergic response via

releasing histamine and
heparin into the

bloodstream. Their
functions are not fully
known and they only
account for 0.4 per cent of
the body's white blood

cells. Their granules
appear blue when viewed

under a microscope.

A faulty immune system

Neutrophil Ifthe immune system stops working We can often treat these conditions with
property, we are at risk of becoming ill. immunosuppressants, which deactivate
Neuttophils are the most However, another problem is if the immune elements of the immune system to stop the
system actually goes into overdrive and body attacking itself. However, there are
common of the leukocytes. drawbacks with this treatment as, if the
They have a short life span starts attacking the individual's cells, person exposes themselves to another
pathogen, they would not have the normal
so need to be constantly mistaking them for pathogens. There are a white blood cell response. Consequently,
produced by the bone large number of autoimmune ailments seen the individual is less likely to be able to fight
across the world, such as Crohn's disease, normally low-risk infections and, depending
marrow. Their granules psoriasis, lupus and some cases of arthritis,
appear pink and the cell as well as a large number of diseases that on the pathogen, they can even be fatal.
are suspected to have autoimmune roots.
has multi-lobed nuclei
which make them easily

differentiated from other
types of white blood cell.

115

science of genetics

116

THE LONGEST GENOME

An ordinary-looking white flower, Paris japonica, has the
longest known genome with150 billion base pairs. II
stretched out it would measure over 91 metres (300 feet)!

!•Jf•J\t!I!ll;W•1~W If oll46 human chromosomes were stitched together and stretched they would measure nearly 2m [6.6ft]

Genes define who weare. Theyare How is our genetic code stored?
the basic unit of heredity, each
containinga codedset of Genetic information is coded into DNA using just four nucleobases: A, C, G and T
instructions to makea protein.
Humans have an estimated 20,500 genes, Chromosome
varying in length from a few hundred to more
than 2 million base pairs. Theyaffect all Humans have 46
aspects ofour physiology, providing the code chromosomes - 23 pairs
that determines ourphysical appearance, the containing around
20,500 genes.
biochemical reactions that occur inside our
cells and even, manyargue, our personalities. 7'--- Nucleus

Everyindividual has two copies ofeverygene Surrounded by a double-
-one inherited from each parent. Within the
population there are several alleles ofeach Double stranded - - - - - - . thid<ness membrane, the
gene - that is, different forms of the same code,
nucleus contains the genetic
with a number ofminoralterations in the
sequence. These alleles perform the same informationof the cen.

underlying function, but it is the subtle DNA has two ccmplementary strands
differences that make each ofus unique.
- one forms a template to make the
Inside each of ourcells (except red blood
cells) is a nucleus, the core which contains our other, aJiowing aca.B'ate replication.
genetic information: deoxyribonucleic acid
(DNA). DNA is a four-letter code made up of Base pairs
bases: adenine (A), guanine (G), cytosine (C) and
thymine (T). As molecular biologist Francis The bases of DNA
Crick once put it, "DNA makes RNA, RNA makes are always found
protein and proteins make us." Our genes are
stored in groups ofseveral thousand on 23 pairs in pairs: adenine
ofchromosomes in the nucleus, so when a cell pairs with thymine,
needs to use one particular gene, itmakesa
temporarycopy of the sequence in the form of and guanine pairs
with cytosine.

Double helix _ ___J

DNA is arranged in a double heix
shape, with the bases fomning the
ladder·like rungs in the centre.

DNA's chemical structure Nucleotide

We put deoxyribonucleic acid under the microscope DNA is a polymer made up of

r - - Phosphate building blocks called nucleotides.

Phosphate groups I
link the sugars of
adjacent nudeotides ++
together, forming a
phosphate backbone.

- - - - +- Hydrogen bond

Two bases interact with

eaclh otherby hydrogen

boods (weak electrostatic

interactions that hold the
strands of DNA together).

Sugar ' - - - - - Nucleobase

Each base isattached Each nucleotide containsa
to a fwe-carbon sugar base, which can be one offour.
adenine (A), thymine (T),
caDed deoxyribose. guanine (G) or cytosine (C).

117

=··

The science of genetics

ribonucleic acid (RNA). This copy containsall of fully understood, but having the genome Geneticmutations are the source ofvariation
the information required to make a protein- available to study is making the task of inall organisms. Most genetic mutation occurs
the building blocks of the human body. identifying genetic risl< factors much easier. as the DNA is being copied, when cells prepare
to divide. The molecular machinery responsible
The Human Genome Projectaimed to map Interestingly, the Human Genome Project for duplicating DNA is prone to errors, and often
the entire human genome; this map is discovered we have far fewer genes than first
effectivelya blueprint for making a human. predicted; in fact, only two per cent of our makes mistakes, resulting in changes to the
genome codes for proteins.The remainder of DNAsequence. These can be as simple as
Using the information hidden within our the DNA is known as 'non-coding' and serves accidentallysubstitutingone base for another
genetic code, scientists have been able to (egA for G), or can be much larger errors, like
identify genes that contribute to various other functions. In many human genes are adding or deleting bases. Cells have repair
diseases. By logging common genetic variation non-coding regions called introns, and machinery to correct errors as they occur, and
inthe human population, researchers have between genes there is intergenic DNA. One even to kill the cell ifit makes a big mistake, but
been able to identify overt,Boo disease- proposed function is that these sequences act despite thissome errors still slip through.
as a buffer to protect the important genetic
associated genes, affecting illnesses ranging information from mutation. Other non-coding Throughout your life you will acquire many
from breast cancer to Alzheimer's. The DNA acts as switches, helping the cell to turn mutations in yourcells. Manyoftheseare
underlying genetic influences that affect genes on and offat the right times. completely harmless, eitheroccurring in
complex diseases like heart disease are not yet

The Human Mapping the human genome
Genome
Project How does our genetic makeup compare to that of other creatures?

The Human Genome Project, an Zebrafish - - - - - - - - - - - - - - - - . . . . ,
initiative to map the sequence of
the entire human genetic code, Divergence between fish and
began in 1990 and was completed mammals occurred very early
in evolution, so similarities in
in 2003. The 3.3·billion base pair our genesare very
sequence was broken into
fragmented.
sections of around 150,000 base
pairs in length and the sequence Human that we are not
.,.,~~~:;::;_~ closely related to
for each identified. These were This ring represents
then joined and used to map the birds, the chicken
information on to chromosomes the genes on a still has regions of
to determine which genes were DNA that are quite
human ctvomosome. simjlar to ours.
found on each - and in what order.
The genome map (right) shows a with the m.rnbe<s • " ' - - - - Dog
human chromosome compared
providing a Some regions of the
with other animals; the colours
are a 'heat map' demonstrating representation caninegenome are
areas where genetic information
has been conserved through of scale. very different to ours,
evolution (the more fragmented but the pink bands
the pattern, the more differences '"
there are in the genetic code). showan area that has

. been conserved.

Chimpanzee -...r ".~+=;""------ Rat

One of our closest living The mouse and rat genomes

relatives - the sotid bands have sinilarpatterns,

demonstrate we share a demonstrating these rodents'
greatdeal of genetic close 0110lutionaryrelationship.
infonnation (ie 98 per oent).

Mouse

There is iess incommon between
human and mouse (90 percent),
butwe are sufficiently similar that
mice make a good scientific model
for studying human disease.

118

1865 1905 1953 1983 2003

GENETICS HISTORY Grego<Mendel, the fatherof William Bateson Is the first Francis Click (light) and Polymerase chain reaction Completion of the
person touse the term James Watson ~I the (PCR)is inll<!nted, enabUng
I"'''Idem genetics, observes double helix structure of smal DNA samples to be HumanGenome Project
patternsof genetic inheritance 'genetics' tode<cribe the stlJdy
DNA using X·rays. amplified for testing. providesaccess to the
in peasgrown inhis garden. of biological inheritance. humanDNA blueprint.

!•Jf•J\t!I!ll;W•1~W Humans shore 98 per cent genetic similarity with chimpanzees but just seven per cent with E coli

non-coding regions of DNA, orchanging the mutant gene, which gave them black wings; Asingle nucleotide mutation causes
gene so nominally thatthe protein is virtually this made them an easy target for predators and haemoglobin, the protein involved in binding
unaffected. However, some mutations do lead kept their numbers low. When factories began oxygen in red blood cells, to misfold. Instead of
to disease (see 'Whengenes go wrong' box). to cover the trees in soot, however, the light- forming its proper shape, the haemoglobin
coloured moths struggled to hide themselves clumps together, causing red blood cells to
If mutations are introduced into the sperm against the newly blackened environment, so
a nd egg cells they can be passed on to the next black moths flourished. Theysurvived much deform. They then have trouble fitting through
generation. However, not all mutations are bad, longer, enablingthem to pass on their mutation narrow capillariesand often become damaged
a nd this process of randomly introduced or destroyed. However, this genetic mutation
changes in the DNAsequence provides the to their offspring and altering the gene pool. persists in the population because it has a
biological underpinning that supports Darwin's It is easy to see how a genetic change like the protective effect against malaria. The malaria
theory ofevolution. This is most easily observed parasite spends part ofits life cycle inside red
in anima ls. Take, for example, the peppered one that occurred in the peppered moth could blood cells a nd, when sicl<le cells rupture, it
giveanadvantage to a species, butwhat about prevents the parasite from reproducing.
moth. Before the Industrial Revolution the geneticdiseases? Even these can work to our Individuals with one copyof the sickle cell gene
majority of these moths had white wings, advantage. Agood example is sickle cell and one copy of the healthy haemoglobin gene
enabling them to hide against light-coloured anaemia - a genetic disorder that's quite have few symptoms ofsickle cell anaemia,
trees and lichens. However, a minority had a common in the African population.

Why do we look
like our parents?

Jt's a common misconception that we inherit

entire features from our parents - eg "You have

your father's eyes." Actually inheritance is much
more complicated - several genes work together
to create traits in physical appearance; even eye
colour isn't just down to one gene that codes for
•blue', 'brown' or 'green', etc. The combinations of
genes from both of our parents create a mixture of

their traits. However, there are some examples of
single genes that do dictate an obvious physical

characteristic all on their own. These are known as
Mendelian traits, after the scientist Gregor Mendel
who studied genetic inheritance in peas in the

1800s. One such trait is albinism - the absence of
pigment in the skin, hair and eyes due to a defect
in the protein that makes melanin.

Carrier children - , . - - Carrier parents

Two outof four wiR be Each parent carries the
carriers, like theirparents, albinism gene (dark pink), but
with ooenormal and one
faulty gene. they have one normal gene
(li!# pink), so they are able
Healthy child
to make melanin.
One in four children will
reoeive ooe healthy gene - - Gametes
from the father and one
Each child inherits one
from the mother.
gene from the motherand

one from the father.

Affected child

One in four children wil

receive two copiesof the

faulty gene and as a

result will be unable to

produoe melanin.

119

=··

science of genetics

butare protected from malaria too, allowing ( Repairing faulty genes X
them to pass the gene on to their children.
We reveal how donated cells can be used to mend Fertilised egg
Genetics isa complex and rapidly evolving any damaged genes within the human body
field and more Information about the function A furtiised human egg is a
of DNA is being discovered all the time. It is now Target gene
known thatenvironmental influencescan alter source at l.l1cifferenliated
the way that DNA is packaged in the cell, The healtt1y gene is
restricting access tosome genes and altering Isolated from the DNA stem celts, which can
protein expression patterns. Known as of the donor in<ividlal
epigenetics, these modifications do notactually becomeant type atcell
alter the underlying DNA sequence, but Packaging
regulate how it isaccessed and used by the cell.
Epigenetic changes can be passed on from one The gene is
cell to its offspring, and thus provide an packaged into a
additional mechanism bywhich genetic delivery vector,
information can be modified across generations like a virus. to
of humans. h.-, itget inside
the targetceiL

Embryonic ' - - Transduction
stem cells
The new gene is irllrodx:ed
The furtiiised egg into the stem eels pn:rlx:ed

be<:a ooes a blastocyst. by the lertiised-
wl1ich axotaios
When our genes Ll1<iflerenliat

go wrong... embryonicstemeels.

Cancer is not just the result of one or two genetic Differentiation -----1 Transplant t
mutations - in fact, it takes a whole series of
mistakes for a tumour to form. Cells contain Chemical signals are The new cells are transplanted
oncogenes and tumour supp!'essor genes, whose added to the stem cells to into the recipient, caoTylng with
healthy function is to tell the cell when it should them the healthy gene.
force them to diffe<entiate
and should not divide. If these become damaged, into the desired cell type,

the cell cannot switch off its cell division eg Iiiiercells.
programme and it will keep making copies of
itself indefinitely. Each time a cell divides there is
a risk that it will make a mistake when copying its
DNA, and gradually the cell makes more and more
errors, accumulating mutations that allow the
tumour to progress into malignant cancer.

•How tumours develop

Tumour-associated Mutagens l ocalised Invasion Metastasis ..~
genes
EnWonrnental ~actors. or Cancerusualyslats withjust As the tumour grows in Ft.1her mutatiionsalloweels !!
Genes normally irwoM!d in mutagens- such as raciation slz.e ~ starts to Invade of the tJ..mour to break free and
and dlemicals- can cause oneor a few mutated cells; erterthe bloodstream. From 'l!
regulating cell behaviol.r can damage to the DNA, leading to these begin to civide the suroundingarea. herethey can be distributed
LI1<Xll'llrollably in !her local .L...
go on to cause cancer ff they mutations in keygmes. il'ea aeating a tumour. taking <MY thO'OU!I>oot the body.
become mutated. "."E".'
neighbouring tissues.
120 a:..t

I>

!•U•I\1•1!1!tj~l•lmP Approximately 3ao,aoo people die from burns eoch year worldwide

urn ourse •

Burns range from irritating to life-threatening
-learnabout the different types now

Most peopleassociate burns with red skin, but without large blisters. Only the no sensation. The basalgrowth layer is
flames, but they have many other epidermis is damaged, so regrowth is fast. destroyed so no new skin can grow.
causes. Aburn is medically defined Second-degree burns (partial thickness! can be
as 'coagulative destruction' of skin, either superficial or deep. The skin usually Even minor burns can cause problems ifnot
meaning any energysource can cause one.This blisters and can be very painful. The dermis treated properly. The first priority is to stop the
energydamages underlying skin proteins and layer is also damaged so regrowth isslow, burning process; cold running water is ohen
fat cells, causing breaks in the skin. the best first treatment. Infection, dehydration
Burns are generallyclassified by their depth. taking several weeks oreven months. In and protein loss are all problems that occur
third-degree burns (full thickness! the skin is next, which ourresilientskin can solve itself if
First-degree (superficialI burns leave painful, left white or pale, with no blistering and little to the injury isn't too severe.

How bums are measured

Classified by their depth, each bum case requires unique treatment

i ( f l ;- .......... /II

'

0The skin ~ First-degree burn 0Btisters

Your skin is vital to your wellbeing. It has multiple Only the uppermost skin layers (known as the epidermis) Blisters appear when the epidermis separates from the
dermis, and are especially common in first and
important functions, including temperature control, are affected, but the burn is painful, leaving the area red, second-degree burns.
sensation and appearance. raw and tender to the touch.
@Third-degree burn
f) Basal layer 0 Second-degree burn
Deep burns destroy the basal layer and nerve ending.s, so
This layer is the key to regeneration, as new skin cells These partial-thickness burns affect the upper or deep they are painless. Regrowth will not occur alone, so skin
grow from hae. If undamaged, regrowth occurs w ithout dermal layers, and like first-degree burns hurt a lot grafts are needed.
any need for medical assistance. because the nerve endings remain active.

..

(lmownas wet burns can be coverthe deep bums that lieal
burns) orcontact
Sunburnlsaconunon
typeofradlatlon burn,

caused l!Y exposure to

UV.tn suiillghtJ

121

=··

Blood vessels

Mostoftheamyloid
consisted ofacellularpink

globules that effacedand
expandedthe node, but

this imageshows the
characteristicinvolvement

ofbloodvesselwalls

Arteries and veins form the plumbing system ofthe human
body, carrying blood through a complex system of different

sized and shaped pipes. We find out howtheywork..

The network ofblood vessels in the two varieties; oxygen-rich (oxygenated} blood is likesmall back-roads connecting motorways to
human body must cope with different what the body uses for energy, and is bright red. dual carriageways.

volumes of blood travellingat different After it has been used, this oxygen-depleted Arteries and veins are constructed differently to
pressures.These blood vessels come (deoxygenated} blood is returned for recycling and is copewith the varying pressures, but work in perfect
ina multitude ofdifferentsizesand shapes, from dark red (not blue,as is often thought).
the large, elastic aorta down to very tiny, one-cell- tandem to ensure that the blood reaches its final
thick capillaries. Blood is carried in vessels, ofwhich there are destination correctly. However, sometimes things go
two main different types - arteriesand veins. wrong which can lead to certain medical problems:
Bloodis the ultimate multitasker. Itcarries oxygen
for various tissues to use, nutrients to provide Arteries carry bloodaway from the heart and deal varicose veins from failing valves; deep vein
energy, removes waste productsand even helps you with high pressures, and so have strongelastic thrombosis from blood clots blocking the deep
warm up orcool down. ltalso carriesvital clotting walls. Veins carry blood back towards the heartand venous system; heartattacksfrom blockedarteries;
deal with lower pressures,so have thinnerwalls. and lastly life-threatening aneurysms from weak
factors whichstop us bleeding. Blood comes in just
Tiny capillariesconnectarteries andveins together, arterywalls.

ConnectiVe Elastic layer ----:~"/ Cell nucleUs Capillary wall

tissue Inner fining L _j

L Muscle Outer
protective
Valve Connecting it
layer
How do veins all together
' - - Muscle layer
work? Capillaries are the tinyvesselswhich
-under connectsmallarteries and veins together.
Veins carrylow pressure blood.They Theirwalls are onlyone cell thick, so this Is
contain numerous one-way valves which pressure! the perfect place to trade substances with
stop backwards flow ofblood, which can surrounding tissues. Red bloodcells
occur when pressurefalls in-between Arteriescopewithall of the pressure within these capillaries trade water,
heartbeats. Bloodflows through these generated by the heart and deliver oxygen, carbondioxide, nutrients, waste
valves towards the heart butcannotpass oxygen-rich blood to where it needs to be 24
back through them in the otherdirection. hours a day. The walls ofarteriescontain and even heat Because these vessels are
Valves can fail over time, especially in the elastic muscles, allowing them to stretch onlyone cell wide, the cells have to line up
legs. This leads to saggy, unsightly veins, and contract to cope with the wide changes to pass through.
known as varicose veins. in pressuregenerated from the heart. Since
the pressureis high, valves are
122 unnecessary, unlike the low-pressure
venous system.

I•U•Jtl•l!l!:W•l!l.U vascular surgeons con bypass blocked arteries using either the patient's own veins or synthetic grafts

Arteries - - - - , A of two

AD arteries carry blood away In human beings, the heart is a double body tissuesIthesystemicdrculation}.
from theheart They carry pump, meaning that there are two sides The rightside of the heart pumps
oxygenated blood, except
to the drculatory system.The leftside of deoxygenated blood towards the lungs, so
for the pulmonary arte<y, the heart pumps oxygenand nutrient-rich it can pick up new oxygen molecules to be
whictl carries deoxygenated blood to the brain, vital organsand other used again (the pulmonary circulation).

blood to the lungs. Aorta "Plasma carries all

Lungs The aorta isan artery whictl o the dif erent

In the lungs, carbon dioxide carries oxygenated blood to the ypes o cells"
is expelled fran the body
body; it is the largest blood
and is swapped for fresh
oxygenfrom the air. This ~~<!Sse! in the body and copes
oxygen-rich blood takes on with thehighest pressure blood.

a bright red colour.

Veins - - - ' - - - The left side What's in

AU veins carry blood The leftside of the heart blood?
to the heart. They p<.mps oxygenated blood
It's only the iron in red bloodcells which
carry deoxygenated forthe body to use. ~ make blood red- take these cellsawayand
blood, except for pumps directly into what you're left with is a wateryyellowish
solution called plasma. Plasmacarriesall
the pulmonaryvein, arteries towards the brain of the different types ofcellsand also
which canies containssugars, fats, proteinsand salts.
and other body tissues. Themain cell types are red blood cells
oxygenated blood (formed from iron and haemoglobin, which
carriesoxygenaround the body), white
back to the heart bloodcells(which fight infectionfrom
bacteria, viruses and fungi) and platelets
The n-ght (tinycell fragments which stop bleeding by
forming dots at thesitesofany damage}.
side - - -
Blood vessels
The right side of the
Different shapes and sizes
heart pumps
deoxygenated Capillary sphincter muscles Capillary bed

blood tothe lungs, Thesetiny musdes can open and close, This is the capillary network that
whichcan decrease orincrease blood flow
w here blood through a capillary bed. When musdes connects the two systems. Here,
exchanges carbon exchange ofvarious substances
dioxide for exercise, these muscles relax and blood
freshoxygen. flovv into the musde increases. ~- occurs with surrounding tis~

Capillaries _ _, through the one-cell thickwalls.

Tiny capiDariesconnect Venule

arteries and vejns Arteriole
together. They aDow
exchange of oxygen, Vein Artery
nutrients and waste in the
body's organs and tissues. 123

A look inside your blood

The science behind the miraculous fluid
that feeds, heals and fights for your life

••••••••••• .

••

HEAD~ l.Dis~of 2. First blood ••• 3. Discovery of "1818- first human-to-
transfusion blood types human transfusion"
HEADt = veins and arteries
After' a centwy of animal· • In 1901, Austtlan physician
LANDMARK ln 300 BC,Gr'eekanatomist humanblood transfusions. Kafllandsteiner wasthe fitst
BlOOD EVI:'MTc:
Her'ophilus ot Chakedon figured • James Blundel perfom>ed the • to Identify three basic blood
• first r'ecOf'ded t.JmarHo--humao
out that anerles and veins transfusion in 1818. • gr'oups. tevolutionising the
not only cany blood. but ate
• success of blood transfusions.
distinct pathways.

!•U•I\1•1!1!tj~l•lmP If you took oil of the blood vessels out of your body and laid them end to end, they would stretch for 16o,oookm

Monocyte

The largest type ofwhite blood cell, monocytes are born in bone
marrow, thentirculate through the blood stream before maturing
into macrophages. predatory immllle system cells that live in
organ tissue and bone.

Bloodis a mix ofsolidsand liquids, a blendof highlyspecialised
cellsand particlessuspendedin a protein-rich fluid called
plasma. Red blood cellsdominate the mix, carryingoxygen to
Jiving tissue and returning carbon dioxide to the lungs.for
every6oo red bloodcells, there is asingle white blood cell, of
which there are five different kinds. Cell fragments called
platelets use their irregularsurface to cling tovessel walls and
initiate the clotting process.

54%
Plasma

Bone marrowcontributes
four per centofaperson's

total weight

•

j

J.

~

"Red blood cells ore so numerous
because they perform the most

essential runction of blood"

Blood is the river oflife. It watery currentofplasma- a straw- deliveroxygen to everycellin the blood cells onlylive120 days, the
feeds oxygenand coloured, protein-rich fluid - carrying bodyand carryaway carbondioxide.
billions ofmicroscopic solids As an adult, all ofyour red blood cells supplymust be continuously
essential nutrients to consistingof red blood cells, white are producedin red bone marrow, the replenished; roughly 2 million red
livingcellsand carries bloodcellsand cell fragments called spongy tissue in the bulbous endsof blood cellsare borneverysecond.
1wa1yVllaste.lt transports the foot
platelets. The distribution isfar from long bonesand at the centre offlat Amature red bloodcell has no
soldiersofthe immunesystem, white equal. Over halfof blood is plasma, boneslike hips and ribs.ln the nucleus. The nucleus isspitoutduring
blood cells, whichseekoutand marrow, red blood cellsstartoutas the final stagesof the cell's two-day
destroy invading bacteriaand 45 percentis red blood cells and a development before taldng on the
parasites. And itspeeds platelets to tiny fragment, Jess than one percent, undifferentiatedstemcells called shape ofa concave, doughnut-like
hemocytoblasts.Jfthe body detects a disc. Likeall cells, red bloodcellsare
the site ofinjuryor tissue damage, is composedofwhite blood cells minuscule drop in ox:ygencarrying
triggering the body's miraculous and platelets. capacity,a hormone is released from mostly water, but97 percentoftheir
process ofself-repair. the kidneys that triggers the stem cells sol!d matter is haemoglobin, a
Red bloodcellsare so numerous complex protein that carriesfour
Bloodlooks l!ke a thick, because they perform the most to become red bloodcells. Becausered
essentialfunction ofblood, which is to atoms ofiron.Those Ironatoms have
homogenous fluid, but it's more likea

125

=··

A look inside your blood

Waste product 6. Reuse and recycle . . - - - - L Born in the bones 2. One life to live
of blood cell
As forthe globin and othercellular When the body detects a low oxygen Mature red blood oells,
membranes, everything is carrying capacity, honnones released from
atso known as
converted back into basic amino the kidneytrigger the production of new
acids, sane of which wil be used red blood cells inside red bone marrow. erythrocytes, are
stripped of their nucleus
to create more red blood oells.
in the final stages of

dev<>lopment, meaning
they can\ cfl\lide

to replicate.

Waste Life cycle of
excreted cells
from body
Everysecond, roughly2 million red blood cellsdecay and die.The
bodyis keenlysensitive to blood hypoxia - reduced oxygen

carryingcapacity-and triggers the kidney to releasea hormone
callederythropoietin.The hormonestimulates the productionof

more red bloodcellsin bone marrow. Red bloodcells enter the
bloodstreamand drculate for 120days before they begin to

degenerate and are swallowed up by roving macrophages in the
liver, spleenand lymph nodes. The macrophages extractIron from
the haemoglobin in the red blood cellsand release it backinto the

bloodstream, where It binds to a protein that carriesit back to the
bone marrow, ready to be recycled in fresh red blood cells.

5. Iron ions ------J 3. In circulation

In the bellyof Kupffer cells, Red blood cells pass from
haemoglobin molecules are split into
heme and globin. Heme is broken the bone marrow into the
down further into bi~ and iron ions, bloodstream, where they
some ofwhich are carried back and circulate foraround 120 days.

stored in bone marrow.

4.1ngestion - - - - - - - - - -

Specialised white blood cells in the iver and
spleen called Kupffer eels prey on dying red blood
eels, ingesting them w hole and breaking them
down into reusable components.

the ability to form loose, reversible red bloodcells release their oxygen, another type ofwhite bloodcell, proteinsand clottingfactors found in
bonds with bothoxygenand carbon they pick up carbon dioxide produceanti-bodies that build up our
molecules, then course through the immunity to repeat intruders. And plasma, platelets weave a mesh of
dioxide - think ofthem asweak veins back toward the heart, where monocytes, the largest of the white
magnets - making red bloodcellssuch they are pumped back into the lungs blood cells, enterorgan tissue and fibrin that stems bloodlossand
an effective transportsystem for triggers the formation ofnew collagen
to 'exhale' the excessco,and collect become macrophages, microbes that
respiratorygasses. Haemoglobin, ingest bad bacteriaand help break and skin cells.
which turns bright red when some more precious0,.
oxygenated, Is what gives bloodits White blood cellsare greatly down dead red bloodcellsInto Buteven these three functions of
reusable parts. blood- oxygensupplier, immune
characteristic colour. outnumbered by red bloodcells, but system defender and wound healer -
To provideoxygen to everyliving Plateletsaren't cellsat all, but only begin to scratch the surfaceof the
they are critical to the function of the fragments of much largerstem cells critical role ofblood In eachand every
cell, red blood cells must be pumped found in bone marrow. in theirresting
through the body'scirculatorysystem. immunesystem. Most white blood state, they looklikesmoothoval bodily process. When blood circulates
The rightside of the heart pumps cellsare also producedin red bone plates, but when activated to form a through the small intestine, itabsorbs
marrow, but white bloodcells- unlike sugarsfrom digested food, which are
CO,-heavy blood into the lungs, where clot they take onan irregularform transported to the liverto bestoredas
it releases its waste gasses and picks red blood cells- come in five different with many protrudingarms called
up oxygen.The leftsideofthe heart varieties, each with its own pseudopods.Thisshape helps them energy. When blood passes through
then pumps the freshly oxygenated specialisedimmunefunction. The the kidneys, it isscrubbedofexcess
blood out into the bodythrougha first threevarieties, collectivelycalled stick to blood vessel walls and to each urea and salts, waste that will leave
granulocytes, engulfand digest other, forminga physical barrier the bodyas urine. The proteins
system ofarteries and capillaries, transport vitamins, hormones,
someas narrowasa singlecell. As the bacteriaand parasites, and play a role around wound sites. With the help of
in allergic reactions. Lymphocytes, enzymes, sugarand electrolytes.

126

Sr~~~v~~f~fGE 7°/o ~~<A~9 p~~~ sv 7,000 litres
~\:R~£>~~oov 5 litreS ~£>o~~$~~5oND 2 million

l•lf•Jtl•I!JOOI•lt;lQ until the 23rd week of foetal development, red blood cells ore produced in the liver, not red bone morrow

"lia lbalassentJa

lblsraregenetic blood dlsordersewrely lnhlblls the Another rare blooddisorderalfectlngtoo,ooo
newbornsworldwide eachyear,lbalassemla
cloU1ng mecbanlsmofblood. causlngexteS11lw
Inhibits theprodliCfioo of haemoglobin. leading
bleeding. Internalbruls1Jl8andjoint problems. Platelels tose~~ereanaemla Peoplewhoarebomwtth the
most senousform of thedisease.alsocaUed
are essential to theclott1Jl8and heallngprocess. Cooley'sanaemla,suHetlromenlalgedbeans,
Uwrsandspleens,and brlnJe bones.Tbemost
producingthreads offibrin with help from proteinsIn effectllletreatmentIs frequentblood
transfuslons_allhougha fewJuckypatlents baw
thebloodstreamcalledclotUnglactors.~plewho been cured throughbone marrowtransplants
from perfectly matchingdonors.
suHet from baemophllla -almostexclusivelymales-are

mlsslngoneoftboseclolt1Jl8 facoors. maldng udlfflrultto

seal oU bloodvesselsaltereven minorinJuries.

Sickle cell anaemia Oneofthe mostcommon geneUc

Anaemia Isthe name foranyblood dlsorderthat results blood disorders, hemochromatosis Is
In a dangerously lowred blood eel Icount. in sickle cell themedicalterm for"lron overload;
anaemia, whlchaffllctsoneout ofevery6z5 children of Inwhich your bodyabsorbsand
Africandescent, red blood cells elongate Intoa sickle stores too muchIron from food
shapealterreleasingthelr oxygen.Theslclde-shaped Severityvarieswildly,
cells dieprematurely, leadingtoanaemia, orsome<lmes and many peopleexperience few
lodge In bloodvessels, causingterrible palnand ellen symptoms, butotherssuffer
organdarnage.lntetestlngly, peoplewho carryonlyone
geneforsicklecell anaemiaareImmune tomalaria. serious liverdamageor

scarrlngjclrrhosls~ Irregular

heanbea~ diabetesand even heart
failure. Symptomscan beaggravated
bytaldngtoomuchv!tamlnC.

Deep vein

ThrombosisIs themedical term foranybloodclotthat Is
large enough toblocl<a blood vessel.When a blood dol
formsin the large. deepveinsoftheupperthlgb.lt's

calleddeepvein thrombosis. IIsuch a dotbreaks free. it

cancirculate through the bloodstream, pass through
the beanand becomelodged lnanetlesInthe lung.

causlngapulmonaryembollsm.Suchablockagecan
severely damage ponlonsofthe lungs,and multiple
embolisms caneven be fataL

hea More than a one-trick pony, your blood
is a vital cog in the hea1ing process
Think of blood as the body's
emergency response team to an STAGE! STAGE4

injury. Platelets emltsignals that . "-'

encourage blood vessels to

contract.stemmlngbloodloss.

The platelets then collectaround

thewound, reactingwitha

protein in plasma to form fibrin, a

tissuethatweaveslnioa mesh.

Blood Dow returnsand white

blood cellsbegin their hunt for

bacteria fibroblasts create beds INJURY HAEMOSTASIS INFLAMMATORY STAGE PROLIFERA11VE STAGE

offresh collagen and caplllarles Whenthe sidn surfaceisCUI, tom Activatedplateletsaggresate Once thewound Is cappedwitha Fibroblastslaylresb layersof
drytngcloc. blood vessels open up collagenlnsldelbewoundand
to fuel skin cell growth. The scab orsoaped deeplyenough.blood around thesurfaceollbewound, caplllaries begin to supplyblood
seeps from broken bloodvesselsto again, releasingplasma andwhite for lbe formingofnewsldncells.
begins to contract, pullingthe 1111thewound.To stemthe flowof stim1•Jat1ngvasoconst:rictln. blood cellsInto thedamaged Fibrinstrands and collagenpull
Ussue.Macrophagesdlgest thesidesofthewound together.
growing skin cells closer together bleeding. the bloodvesselsaround Plateletsreactwtthaprotein In harmful bacteria and deadcells.
until damaged tissue Is replaced. thewound const:rl~ plasma toform fibrin, aweb-like

meshofstrtngyllssue.

127

Controlling the human body

How the human endocrine system Hypothalamus
develops and controls the human body
Releases honnones to the
The glands in the endocrinesystem women. The majority of hormones are peptides pituitary gland to promote
use chemlcaiscalled hormones to
that consistofshortchainsofamino acids. as production and
communicatewith and control the Theyare secreted bythe pituitary and
cellsand organs In our bodies. pa rathyrold glands. Amine hormones are seoetiorl d honnones to
Theyare ductless glands that secrete different secreted by the thyroidand adrenal medulla the rest al the body.
types of hormone directly Into the bloodstream and are related to the fightorflight response.
and target specific organs. Pituitary gland
Thechanges thatare caused by the
The target organscontain hormone Releases honnonesto
receptors that respond to the chemical endocrinesystemact more slowly than the the male and female
tnstructlons supplied by the hormone.There nervous systemas they regulate growth, repro<Nctlve organs
are 50different types of hormone In the body moods, metabolism, reproductive processes and to the adrenal
and a relatively constantstable internal
and they consistof three basic types: peptides, glands. Stimolates
ami nes and steroids. environmentfor the body(homeostasis).The growth In childhood and
pituitary, thyroid and adrenal glands combine maintains adult bone
Steroidsinclude the testosterone hormone. to form the major elementsof the body's
This issecreted by the cortexof the adrenal endocrinesystemalong withvarious other and muscle mass.
gland, the male and female reproductive elementssuchas the male testes, the female
Pineal gland
organsand by the placenta in pregnant ovariesand the pancreas.
Secretes melatonin. wt-ich
00<1bolss!Hppatterns and
00<1bols the production of

honnones related to the

~organs.

"Amine hormones ore secreted by the
thyroid and adrenal medulla"

gla endocrine

We have two adrenal glands that are positionedon top ofboth system
kidneys. The triangular-shaped glands each consistofa two-
Thymus J
centimetre thick outercortex that producessteroid hormones,
which include testosterone, cortisoland aldosterone. Is part of the invnune j

Theellipsoid shaped, Inner partof the gland Is known as the system. It produces
medulla, which produces noradrenaline and adrenaline. These
hormones increase the heart rate, and the body's levels ofoxygen thymosins that control
the behaviour of white
and glucose while reducing non-essential bodyfunctions. blood T·cells.
Theadrenal gland Is known as the 'fight orOight'gland as It
Adrenal glands
controls bow we respond to stressful situations,and prepares the
bodyfor the demands ofeitherfighting or running awayas fast as Cattro!s the burning of

you can. Prolongedstressover-loads this gland and causesillness. rpergoutelainteasnbdlofaot,da.,n..d.,......,.

MecUia The medulla secretes
adrenaline to strnulate the
Cortex
fight or fl91tresponse.

Kidney

Male testes

Tbesel'INOglandsproduce
testosterone that Is
responsible lorsperm
production, muscleand

bone massand sexdrive.

128

l•U•l\1•lfll!W•Itf.t? When you ore exdted the hypothalamus and pituitary gland release opiate-like endorphins

Hypothalamus itaryg

Hypothalamus ----...: The pea-sized pituitarygland is a major productionofsperm cells. The posterior
endocrinegland that works under the lobestores vasopressin and oxytocin that
' -- 'neurons
control of the hypothalamus. The two issupplied bythe hypothalamus.
These synthesise and organsinside the brain work in concertand Vasopressin allows the retention ofwater in
send honnooes to the mediate feedback loops inthe endocrine the kidneysandsuppresses the need to
posterior lobe. system to maintain control and stability excrete urine.It also raises blood pressure

Portal veins within the body. bycontracting the blood vessels in the heart
The pituitaryglandfeatures an anterior and lungs.
Honnones from the
hypothalamus are (front) lobe and a posterior(rear) lobe. The Oxytodn influences the dilation ofthe
anterior lobesecretesgrowth hormones cervix beforegivingbirthand the
carried to the thatstimulatethe development ofthe
contraction of the uterusafter birth. The
anterior lobe muscles and bones; it also stimulates the lactation ofthe mammaryglandsare
through theseveins. development ofovarian follicles in the stimulated byoxytocin when mothers begin
female ovary. Inmales, itstimulatesthe
Anterior lobe to breastfeed.

Posterior lobe

Parathyroid Thyroid and

Wcxl<s in combination Thyroid cartilage The two lobesof the thyroid sit oneachside of the
with the thyroid to r - - - (Adam's apple) windpipeand are linked together bythe isthmus that
control lewis ofcalcium. runs in front of thewindpipe. Itstimulatestheamount
. .. ofbodyoxygenand energy consumption, thereby
Thyroid Right
Trachea _ .,. keeping the metabolic rate ofthe bodyat the current
Important fur maintaining lobe (windpipe) levels to keep you healthyand active.
Parathyroids -lO..,~- ""'
the metabolism of the Left The hypotha lamus and theanteriorpituitarygland
body. It releases n and are in overall controlofthe thyroid and they respond to
lobe -
T4 honmones to control changesin the body byeithersuppressing or Increasing
thyroid stimulatinghormones. Overactive thyroids
the breakdown offood cause excessivesweating, weight loss and sensitiVityto
and store it, or release it heat, whereas underactive thyroids causesensitivity to
asenergy. hot and cold, baldness and weightgain. The thyroid can

Isthmus swellduring pubertyand pregnancyor due to Viral
infectionsor lackofiodine in a person'sdiet.

The four small parathyroids regulate the calcium
levels in the body; itreleases hormones when calcium

levelsare low. Ifthe levelofcalcium is too high the
thyroid releases calcitonin to reduce it. Therefore, the
thyroid and parathyroids work in tandem.

Pancreas Islets of Red blood Acinar cells
Langerhans Thesesecrete
Maintains healthy cells
blood s ugar lewis in digestiveenzymes
the blood stream.
The pancreasis positionedin the abdominal caVityabove the small ~-- tothelntestlne.
Female ovaries
Intestine. It consists oftwo types ofcell, the exocrinecells that do not •• • • •
Are stimulated by
hormones from the secrete their outputinto the bloodstream butthe endocrinecells do. •
pituitary gland and
control the The endocrine cellsare containedin clusterscalled the islets of
menstrual cycle.
Langerhans.They numberapproximatelyt million cellsand •

are only oneor two percent ofthe total numberofcellsin

the pancreas.Thereare four types ofendocrinecellsin

the pancreas.The betacellssecreteinsulinand the ......()

alpha cellssecreteglucagon, both ofwhich ~

stimulate the productionofbloodsugar (glucose} N-..//11

in the body. If the Beta cellsdie orare destroyed

itcauses type t diabetes, which isfatal unless

treated with Insulin Injections.

The other two cellsare thegammaand

delta cells.The former reduces appetite

and the latter reduces the absorption offood

in the intestine.

129

=··

Kidneys

This is where liquids are

• fi~ered and nutrients are
absorbed before urine
exits into the ureters.

Every day the body J?roduces waste
products that enter the bloodstream-
but how do we get rid ofthem?

The human urinary system's water levels in the body, sodium and Ureter
primaryfunction Isto remove potassium levelsamongotherelectrolytes,
by-products which remain In These tubes link the
the bloodafter the body has blood pressure, pH of the bloodandare kmeys and the bladde<".
metabolised food. The process Is made up
ofseveraldifferent key features. Generally, also involved in red bloodcell production Inferior vena cava
thissystem consists of two k1dneys, two throughthecreationand releaseofthe
ureters, the bladder, twosphincter hormone erythropoietin. Consequently, TNs carriesdeoocygenated
muscles (one internal, oneexternal)and a they are absolutely crucial to optimum blood back from the 1<meys
urethraand theseworkalongside the body operation. 1D the rig>~ aorta ol the heart.
intestines, lungs and skin, all of which
excrete waste products from the body. After bloodhas beenfiltered bythe Abdominal aorta
Theabdominalaorta !san Important k1dneys, the waste products then travel
artery to the system a s this feeds the renal This artery5l4llllies blood
arteryand vein, whichsupplythe kidneys down the ureters to the bladder.The
with blood. This blood is filtered by the bladder'swallsexpandout tohold the 1D the kic*leys, w therenal
kidneys to remove waste products,suchas urineuntil the bodycanexcretethewaste
urea which isformed through amino acid artery and veinThis blood
metabolism. Through communication outthroughthe urethra The internaland is thencleansed 1)11
with other areas of the body, such as the external sphincters then control the the kic*leys,
hypothalamus, the kidneys also control
release ofurine. Bladder
Generally, a human will produce
This is where urine
approx1matelyz.s<J litres ofurine a day,
a !though this can vary dramatically gathers after being

dependantonexternalfactorssuch as pass«! down the
waterconsumption. ureters from
the kidneys.

"Generally, a human will produce

2.5-3/itres of urine a day"

How do the kidneys work?

The kidneys will havearound 15o-t8o lltresofblood to filter per day, butonlypassaround
two lines ofwaste down the ureters to the bladder for excretion, therefore the kidneys
return much of this blood, minus most of the waste products, to the heart for re-
oxygenationand reclrculaUon around the body.

Thewaythekidneysdothlsls to pass the blood through a small filtering unit calleda
nephron. Each kldneyhasarounda million ofthese, which are made up ofa number of
small bloodcapillariesanda tubecaliedtherenal tubule.Thebloodcapillariessiftthe
normal cells and proteins from the blood forrecirculation and then direct thewaste
products into the renaItubule. ThIs waste, whlch will primarily consist ofurea, mixeswith
waterand forms urineasitpasses through the renal tubuleand theninto the ureteron its
way to the bladder.

130

I•UaJW•IIlt:W•WlP On overage, you make the some amount of unne in the day as in the night

(How do store~ until

we're ready to expel it?

The bladderstores waste produCts byallowing the urine to enter
through the uretervalves, which attach the ureter to the bladder.
The walls relax as urine entersand thisallows the bladder to
stretch. When the bladder becomes full, the nerves In the bladder
communicate with the brainand cause the Individual to feel the
urge to urinate.The Internal and externalsphincterswill then
relax, allowing urine to pass down the urethra.

Bladder 1. Ureters

These tubes connect to t he kidneys and urine
flows down to the bladder through them.

Why do we 2. Internal urethral sphincter

get thirsty? This remains dosed to ensure urile does
not escape unexiJ"Ctedly.
Malntalnlng the balance between the
minerals andsalts in our bodyand water is I
very Important. When this is out of balance,
the body tells us to consume more liquids to 3. Extemal G
redress this Imbalance In orderfor the body U'ethral 5. Bladder walls
to continueoperatingeffectively. sphincter (controlled by
detrusor muscles)
This craving. or thirst can be caused by TNs secondary
too high a concentrationofsalts In the body, spiWlcteralso The detrusor rnJSdes in thewaU of
orby the water volume In the body dropping remains dosed
too low for optirna Ioperation. Avoiding the IJjadder relax to allowexpansion
dehydration is Importantas long term to ensure no
dehydration can cause renal failure, among of the bladder as neoessary.
other conditions. o.aine escapes.

Tbe 4. Ureter valves

un• These..,_an! situated
at the end of the ureters
system and let urine in.

Renal artery and vein Bladder L Internal urethral sphincter
empties
This supplies blood to the kidneys This relaxeswhen the body is reacly to expel
in order for them tooperate, and the waste.

then renlOIII!S deoxygenated bjood 2.Extemal
after use bythe kidneys. urethral sphincter

This also relaxes forthe OOne
to exit the body.

~--------------- ~ 3. Bladder Urine travels down tns
walls
The IJjaddersitsin the pelvis, passageway to exit the body/
and the urethra passes t!vough (controled
131
itfor o.aine to exitthebody. by detrusor
muscles)
----~- :1-- - - - - - - Urethra
Thet.n!!lva is the b.i>e These muscles
that..me travels ""'ob act to Ioree
t!vough to exit the body. the o.aine out ol
thebjadder.
!

~

0

Q

=··

rae eoto

Discover the science and tech behind this life-savingprocedure

Lf the upper airway is blocked, by Anatomy of a tracheotomy
trauma, cancer or inflammation, an
The trachea is surrounded by a minefield of major
alternative route must be found for blood vessels, nerves, glands and muscles
air to enter the lungs.
Planned tracheotomies are performed under Larynx Thyroid cartilage

general anaesthesia orsedation. The neck is Thevocal cords sit The surgeon uses the
extended backwards to a llow the surgeon to behind the thyroid
easily identify the structures In the throat and cartilage, al>olre the prom~nt Adam's apple as
pointof the incision.
to make an accurate Incision (see diagram). a ma<1<er to locate the best
First, a vertical cut Is made In the skin, below Cartilage ring
the tracheal cartilage, and the underlying Incision site on the neck.
The trachea is held open
muscle and blood vesseIs are carefully moved Oesophagus
out of the way to expose the trachea. bystiff C-shaped mgs
Theoesophagus lies
The trachea is normally held open by made atcartiage. behind the~so the
C-shaped rings of cartilage, which prevent the st.OgeOnmust tal<e care
airway from collapsing. Ahole is made between A temporary or
permanent tube is not to punciJ.R through
the thirdand fourth rings, allowing the surgeon inserted into the from one to the other.
access to the aj rway without disrupting the
cartilage supports. Atracheotomy tube is then trachea through an Trachea
incisioo between the
inserted into the airway and secured to the The trachea CO I oed.sthe
neck. Lithe tracheal openingis going to be a rings ofcartiage. lungs to themouthand
permanent feature rather than temporary then
Flanges nose: a tracheotomy
a piece of cartilage may be removed to allow the Theouter portion at
tube to sit more comfortably. bypasses them togrant
the tubehas flanged direct access tothe lu:lgs.
The vocal cordssit just behind the tracheal edges,wtich means it
canbesecuely taped Carotid artery
cartilage, above the tracheotomy incision site, to the neck.
but in order to talk, air must be able to pass large arteries supplying blood
through the vocal cords to make them vibrate. to the brainand face run up
either sideofthe trachea
Some tracheotomy tubes contain unidirectional
valves, e nabling the patient to breathe in Thyroid
through the tube and out through their mouth,
The thyroid gland,
which provides good air supply to the lungs,
without hampering speech. responsible for making

If the patient is unable to breathe unaided, a numerous hormones,

ventilator may be attached to mechanically sitsjust beneath the
move ah in and outof the lungs. tracheotomy site.

Have you got a pen?

A tracheotomy is a complex procedure, so in
life-threatening, em~gency situations a faster
procedure- known as a cricothyrotomy (also
called cricothyroidotomy) - may be performed.
A higher incision is made just below the thymid
cartilage (Adam's apple) and then through the
cricothyroid ~brane, directly into the trachea.

It is possible to perform this pmcedure with a
sharp instrument and any hollow tube, such as a
straw or a ballpoint pen case. However, finding
the correct location to make the incision is
challenging, and without medical training there
is great risk of damaging major blood vessels,
the oesophagus or the vocal cords.

132

STRANGE Where did hay fever get Answer:
BUT TRUE
its name? The term hay f...,.rhas nothing to do with hay, and
MISLEADING NAME
A Hay allergy B Harvesting C Doctor's name e""'Y!hing todo with trees. grasses and ragweed.
The namecame about because symptons W'OlAd

strike during hay·har"Vesting season. when these
pollens woold be rife.

!•Jf•J\t!I!ll;W•i~W Allergic diseases, including asthma. ore the fifth most common chronic disease in all ages

When summer strikes, why do some ofus suffer?

We trample on lawns and mow headaches from blocked sinuses or coughing Too much histamine
them down. but eventuallygrass caused bymucus drippingdown the back ofthe
gets revenge. Its pollen causes throat from the nose. Histamine irritates the upper
many of us to suffer from hay fever, respiratory passages, making
and so do trees, weedsand even some fruit. People genetically predisposed to hay fever them swell and produce the
Despite being smaller than the tip ofa pin, are called atopies. Hay fever usually develops typical hay feve< symptoms.
pollen is carried by the wind and lodges in the during childhood orteenageyears, butadults Histamine makes your mucus
nasal lining tissues and throat, where it can can get it too. This is likely to follow repeated membranes work over time,
causean allergic reaction. This is when the contactwitha substance thatyour immune producing enough mucus to
body mistakenly thinks it has been invaded by system perceivesas a threat. No one knows for flush the pollen out.
a threat, such as a virus. sure why hay fever starts affecting someone at
To fight back, the body produces a type of the point in time it does.
antibody known as immunoglobulin E (IgE) in
response to the allergen, causing nasal Hay-feversufferers are in trouble when the
passages to become inflamed, producing more pollen count reaches 50 pollen grains percubic
mucus. This is designed to help flush out the metre ofair. You'll experience it worse in the
allergens but can lead to other symptoms like morningwhen plants release their pollen.
Allergens collect in the air on humid days and
Why do we get a during storms, but rain clears the pollen.

An inside look at how pollen nynose?
can affect us
Airborne pollen
Allergy in numbers
Rne dusty pollen is carried
15%: Of UK poptjation get by the wind and inhaled
hay fever through the nasal passage.
People with a genetic
40%: Risk if one parent suffers disposit ion to hay fever,
80%: Risk if both parents suffer known as atopies, will have
95%: Of hay·fever sufferers are an alle<gic reaction.

allergic to grass pollen Antibodies ----......iir
1 in S: Affected by hay fever
The pollen protein trigge<s
21 milion: UK adults suffer your immune system,

from one or more which creates thousands
of antibodies. The
type ofallergy antibodies attach
themselves to mast cells,
which release h istamine

- a substance the body
produces to fight infection.

Protein problem

Proteins on the surface of the
pollen grain irritate and
inflame the cells that lineyour

mouth, nose, eyes and throat.
The body's immune system
t reats the pollen like a virus
and takes action to expel it.

•• I I

The sensory system is what enables us There are thousands of different stimuli that can can cause excruciating pain; this particular
to experience the world. It can also trigger our senses, including light, heat, chemicals condition is known as phantom limb syndrome.
warn us of danger, trigger memories in food and pressure. These 'stimulus modalities'
and protect us from damaging stimuli, are then detected by specialised receptors, which However the sensory system !sable to adapt to
such as hot surfaces. The sensory system is highly convert them into sensations such as hot and cold, change, with the Joss of one often leading to others
developed, with many components detecting both tastes, images and touch. The incredible receptors being heightened. Our senses normally function to
physical and emotional properties of the - like the eyes, ears, nose, tongue and skin - have gently inhibit each other in order to moderate
environment. for example, it can interpret adapted over time to work seamlessly together individual sensations. The Joss of sight from
chemical molecules in the air into smells, moving and without having to be actively 'switched on'. blindness is thought to lead to strengthening of
signals from the ears, nose and tongue. Having
molecules of sound into noises and pressure However, sometimes the sensory system can go said this, it's certainly not universal among the
p laced on the skin into touch. Indeed, some of our wrong. There are hundreds of diseases of the blind, bel ng more common in people who have
senses are so finely tuned they allow reactions senses, which can have both minor effects, or a been blind since a young age or from birth.
within milliseconds ofdetecting a newsensation. life-changing impact. for example, a blocked ear Similarly, some people who listen to music like to
can affect your balance, or a cold your ability to close their eyes, as they claim the Joss of visual
The five classic senses are sight, hearing, smell, smell - but these things don't last for long. input can enhance the audio experience.
taste and touch. We need senses not only to
interpret the world around us, but also to function In contrast, say, after a car accident severing the Although the human sensory system is well
within it. Our senses enable us to modify our spinal cord, the damage can be permanent. There developed, many animals out-perform us. f or
movements and thoughts, and sometimes they are some very specific problems that the sensory example, dogs can hear much higher-pitched
directly feed signals into muscles. The sensory system can bring as well. After an amputation, the sounds, while sharks have a far better sense of
nervous system that lies behind this is made up of brain can still detect signals from the nerves that smell - in fact, they can sniff out a single drop of
receptors, nervesand dedicated parts of the brain. used to connect to the lost limb. These sensations blood in a million drops of water!

134

STRANGE Which creatures can have Answer:
up to a hundred eyes?
BUT TRUE Scallops are an unde.water mollusc that
A Scallops B Spiders C Peacocks amazingly can have as many as 100 eyes!
SIGHT TO BEHOLD Although they can't create as cleara picture as

our eyes, they can detect enough lig:ht and
movement to warn them of oncoming predators.

f •lft1\1!ID~'Wil!i!li' Toste ond smell ore closely linked. To test this, pinch your nose os you eot something ond it will toste blond

Body's messengers Retinal neuron Olfactory neuron

The sensory system is formed from neurons. These are These retinal bipolar cells are found in The many fine dendritic arms
specialised nerve cells which transmit signals from one the eye, transmitting tight signals from of the olfactory cell line the
end to the other- for example, from your skin to your the rodsand cones (where fight is
brain. Theyare excitable, meaning that when iooersurface of the nasal
stimulated to a certain electrical/chemical threshold 1~~ detected) to the ganglion cells, w hich
they wilJ fire a signal. There are many different types, cavity and detect thousands of
a nd they can interconnect to affect each other'ssignals. ~ send impulses into the brain.
different smells. orodorants.

Motor neuron Purkinje cell Anaxonic neuron

These fire impulses 'These are the largest neurons Found within the retina ofthe
from the brain to the body's in the brajn and theirmany
muscles. causing contraction eye, these oells lack an axon
and thus ll'l<M!Olent. They dendriticarms form multiple (nervefibre) and allow rapid
have lots ofextensions (ie comections. They can both
they are multipolar) to modification of fight signals
spread the message rapidly. excite and inhibit movement. to and from bipolarcells.

Unipolar neuron ----""""-----~ Pyramidal neuron

These sensory oeuroos These nel.D'ons have a
transduce a physical
stimulus (for example, when triangularcell body, and
you are touched) into an
electrical impulse. were thus named after

How do we smell? pyramids. They help
toconnect motor
Find out how our nose Oeli"'OS together.
and brain work together
to distinguish scents Olfactory nerve

Olfactory bulb New signals are rapidly

Containing many types of transmitted via the
eel . oMactoryneurons
branch out ofherethrough olfactory nerve to the brain,
the cribriform plate bellow.
which collates the data
Olfactory neuron with sight and taste.

These neurons are highly =---• Cribriform plate Total recall

adapted todetect a wide Abony layerof the skull Have you ever smelt something that
with many tiny holes, transported you back in time? This is
range ofdifferent odours. known as the Madeleine effect because
whichallow the fibresof the writer Marcel Proust once described
Olfactory t he olfactory nerws to how the scent of a madeleine cake
epithelium suddenly evoked strong memories and
pass fromnose to brail. emotions from his childhood.
lining the nasal cavity, this
layercontains the long The opposite t ype of recall is
extensions ofthe olfactory voluntary memory, where you actively
neurons and is where try and remember a certain event.
chemical mlltecldes in air Involuntary memories are intertwined
trigger an electric impulse. with emotion and so are often the more
intense of the two. Younger children
under the age of ten have stronger
involuntary memory capabilities than
older people, which is why these
memories thrust you back to childhood.
Older children use voluntary memory
more often, eg when revising for exams.

135

=··

sensa

Key nerves Olfactory nerve

These transmit vital sensory information Starting in the nose, this nerw
to our brain while also sending motor COI1I.1!rts chemical molerules
function signals all around the body irto electrical signals that are

Optic nerve interpreted asdistinct odours
Ilia chernoreceptors.
The optic nerves eorwert tight signals
into electrical impulses. w hich are
interpreted in the occipitall<lbc at the
back of the brain. The resuHing Image
is seen up5ide down and back to front,
but the brain reorients the image.

'' Eye movements Trigeminal nerve

.' ' The trochlea', abd!ICEI'It nos nerve is an example of a
'
' andoculomotornerves mechanoreceptor, as k fres when
cu otrol the!!)" muscles yo<r face is touched. It is spit into
L Touch receptor and so the cirection in tiYee parts,~ the top. middle
wNdl we look. and bottom thirds ofyour face.
When a IDuch receptor is
activated, information about the
strnulus is sent to the spinal cord.
Reflex actions. wNdl don~
imlolve the brain. produce rapid
reactions to dangerous stimu~.

Facial and
trigeminal motors

The motor parts of these
nervescontrol the muscles of

facial express<on (for
example, when you smile),

and the muscles ofthe
jawto help youchew.

2. Si~nal sent 3. Motor neurons
to sp1ne feed back

When sensory....,.., The signals b iggol motor
...,....,. that iritiate their
endi 1§15 fire.
information passes own irnpoJses that feed back

tlrough """"' fbres to the muscle. telling ft to
to the spO>al cord move the body part

136

• •Amatter of taste ••••••••••••••••• • ••••
••••• ••••
1 2 3 4 5Thereareabout9,000taste • •••••••
budson thetongue and tf1roaL •
••
These OOill<!rtchemicals found
in saliva Into electrical.signals, •

split intofille tastes: swee~ salt. •••

sour,bitter and umarni.
Smell vs sight Sensitive skin Upsidedown Staying steady

Odoursofferbettermi!I110<Y Human skin contains a.ter half The imagesformed in the Ears do more thandetect
recallthan ~I cues. as smell amillion sensory receptors. occipitalcortex are upside sound.The fluid and file hairs
Is tied toemotion.Looking at down, before the brain flips in t~inner-ear maintain
••• These are of the highest balance. If you sp;n roundand
anold photograph can trigger concentration W1: the fingerti~ them. H~ babies start stop, this fluidisstillmoving
memory,but a smellcan ev<lke
howyou lett at the time. ••• the ends of the toes and lips, byseeing upside down, until which Is why we get dizzy.
where tl1ey're most needed. thebrainlearns to adapt

!•JfiJt<!l!Ila~I•I~'Q The three smallest bones in the human body - the hammer. anvil and stirrup - ore located in the middle ear

Intermediate nerve Vesti bulococh l e a r
nerve
This isa small part of the larger
This nerve provides
facial netw. It provides the key
sensation to the innerpart
sensation to the forward part of
of theear.
the tongue to help during eating.

J 5 5 5 5 5
5 5
Glossopharyngeal motor 5 'i

The motor part of this nerve controls 5 25 ~5 5 25

the pharynx, helping us 5 25 2 5 5 5 25 2
to speak and breathe normally.

5 52 2 2 5 52 2 2
5 5

555 5 5 555 5 5

A patient's sen.se of proprioception
is being put to the test here

~::::::::::~ Vagus motor Is there really a
'sixth sense'?
Vagus nerve This portion of the vagus
nerve can slow" the Our sense of balance and the position of our
'The vagus nerve is spread aU bodies in space are sensations we rarely think
around thebody. It is a m ixed heartbeatand breathing about and so are sometimes thought of as a
rate, or increase the 'sixth sense'. There is a whole science behind
sensory and motor nerve, and them though, and they are collectively called
is responsible foroontrolting all speed of digestion proprioception. There are nerves located
of the functioos we don~ think throughout the musculoskelet al syst em (for
about - like Oll' heartbeat. Accessory nerve example, within your muscles, tendons,
ligament s and joints) whose job it is t o send
The hypoglossal nerve Connecting them uscles ofthe neck information on balance and posture back to the
to the brail, this nerve lets ustum brain. The brain then interprets this information
This nerve controls the our heads from side to side. rapidly and sends instructions back to the
movementsofthe tongue. muscles to allow for fine adjustments in balance.
Since you don't have to think about it and you
can't switch it off, you don't know how vital
these systems are until they're damaged. Sadly
some medical conditions, including strokes, can
affect our sense of proprioception, making it
difficult t o stand, walk, talk and move our limbs.

137

=·· -

ickenpox •••

erstan I•

I•

Discover the biologybehind the infamous childhood
ailment and whyit never really goes away...

Chickenpox isa strain ofthe face, arms, legs, stomach and back. These weak immunesystem or be particularly
Varicella zoster virus, which many develop into fluid-filled blisters and are ohen vulnerable to the disease.
of us have experienced during our accompanied bya fever. The blisters burst, scab
youth. Most prominentin children, overand fall off within a few days, but new After the outbreak, chickenpox doesn't
waves ofspots can emerge to replace them; it disappear entirely. The disease lies in a
the virus is contracted through coughing and usually takes one to two weeks for the body to dormantstate within the body asyour immune
sneezing or transferred on shared objects, regain control. Chickenpox is rarelyserious but system keeps it under wraps.The infection can
which makes schools a prime location. it is important notto interfere with the scabsas
infection can make it more severe. breakoutagain laterand reappear as shingles.
The most famous symptom is the appearance Arash builds up on a certain point of the body
ofsmall itchy red spots, which vary in size from Avaccine is only offered in extreme and the symptoms return, most commonly in
circumstances when an individual may have a
10-20 millimetres (o-4-0.8 inches) across. The people over 50. On average, three in everyt,ooo
extent can vary but in most cases they cover the people contract shingles in the UK each year.

When chickenpox strikes back... Grown-up
chickenpox
Get under the skin to see how shingles can catch the body unawares
90 per cent of adults are immune
Start of the illness - - - ,.I -- ._- ....--+- - -1----11-- Blisters emerge if they've had the disease as a
child but it still affects adults and
The virus infiltrates the Blisters become visible and teenagers. Ifyou develop
skin and causes Inflamed rashes appear on chickenpox at a later age, all the
all affected areas. symptoms are more severe, with
Inflammation and a more chronic pain, headaches and
burning sensation. sorethroats; therefore, there is
greater need for treatment, such
The Varicella virus .. Don't scratch! as pain relief and soothing creams.
becomes active
when the immune The blisters then The disease tends to affect
system is weak, harden into scabs and
overcoming the fall off. Scratching at adults more dramatically as it can
body's natural the spots makes the
defences. healing process slower. now mutate into a variety of other
strains, such as shingles or, in
Dormancy - Future effects extreme cases, lead to
encephalitis, postherpetic
Once the immune system regains In around 10·20 per neuralgia or pneumonia. However,
control, the virus retreats and lies cent of people who the chances ofthis happening are
dormant in the body's nervous have shingles, the only around ten per cent.
system, but it can return later. nerve fibres become
damaged which can
lead to postherpetic
neuralgia (nerve pain).

138

5 TOP. Runny noses • • Crocodile tears Darwin's discovery
. Hush, litUe baby
FACTS l li )'OU f1ndthat )'OUr nostrunS a Onion weeping 4 While! aocodllos.,..known far 5 Thereisa condifun called the
lotwhonyouay.• ; , - . . . 2 Babiestypically ayforabout PseudoBulbarAffect (PBA) in
CRYING l!ltCtu lNrS artI'U"'nhg fr·om . 3 Syn·propanethla>S...IdeIs • lookingt<ory.. they...food
)'OUr I)<IS. down )'OUr . . . . . duets • oneto threeholrsperday. This createdbyanen:zyme Ina cut ~. . . . . .~~they . . . . .\ -.llichpeople aryar ~
a n d I n t o -. . . .. .....,;ng Ad. Thtt•.,.sm<'<'elyU>ricato ~y. FirStdescribed by
! ean befora variety rAreasons. • onion.When it evaporates. this thtiroyoswhon they..,...Stime OartesOarwYlit isoften the result
. _ '""""' orifflos. compot.ndiTitates cu bcrlmiM o u t o l t h t -.
because th?y'n!lulgry, thirsty, glands andtaats arell1ggnd In rAbrain ifluries.
tnd. sca<ed art- just beento
ader tocikJteit.
• thetalet.
-

I•U•Jtl•IYUW•I@ The overage person will produce 140-28og [5-10oz] of bosol tears per day to keep the eyes moist

The lacrimal Battle of
system the sexes

0 lacrimal gland W hile there is a stereotype that
women are tearier than men,
This gland receives the there is some science to explain
message from the cerebrum the reasons behind this. Studies
to produce tears. have shown that women cry
about four times as often as
@ Cornea men and, while there are
cultural factors to betaken into
Tears help protect the surface consideration, there are
of the eye. biological factors too.

E) Tear ducts Until their adolescent years,
boys and girts cry fairly equally.
This is where the water flows As testosterone levels rise in
to. If there's too much, it flows boys, they are more likely to get
downthe face. angry than upset. Meanwhile,
girls gain increased oestrogen
3 Runnynose levels, which modifies
endorphin production, often
Tears that flow tlvough the leading to more emotional
responses to stimuli.
tear ducts go down a nasal

passage, which is what
causes a runny nose.

168 / 148

What do Brainfreeze
alveoli do? explained

155

Powering
cells

173

How do we
knowhow
much to
eat?

142 ~eing 153 Eyebrows I Earwax I Sell
y do we grow old?
Do we need eyebrows?
ut6 Left or rlret brained? 161 Correcting heart rhythms I
I:-154 hour deodorant I Salt I Adam's apple
The truth ehind thinking odem flllin~
How do we com at body odour? Is salt bad for your heart?
ut8 Brain freeze
155 What Jthwers your cells? 162 Seasickness I
Why do we feel this cold pain? Rumbling stomachs
Inside e mitoChondria
149 Runny nose /Coma Explaining seasickness
What makes your nose run? 156 Can we see thoughts?
16J What are moles?
150 Ears I Freckles I Is this sdence or a myth?
Sore throat Alook a mole formation
158 How anaesthesia works
Why do your ears pop? 164 Brain control/ Laughing
The drug that stops pain signals
151 Memory I Toothpaste I Do our brains control us?
159 Stomach ulcers I
~durlils Mouth ulcers 165 Dandruff I Eye adjustment I
at is a memory? Distance the e!e cansee
How do ulcers form?
152 Blus~ I Caffeine I Fainting Revealing how andruff forms
160 Hair growth I Blondhair
Tbetellt esignsofblushing
Ourhair explained

140



VVhathappenstothe
human body as we age?

The whys ofageing. at its most basic ourcellscan no longer function. Free radicals- Infirmitiesassociated with ageing that have to do
level,seem simple: over the courseofour unstable oxygen molecules that are a natural with stiffeningor hardeningof tissues, suchas
atherosclerosis.
lives, our bodiessimply wearout Or by-productofcell function- can build up and bond
that's whatwe've been led to believe, to othercells. As a result, DNA can bedamaged. They Cellscanalso mutate ona geneliclevel due to
anyway.Scientistswho studygerontology, or the mayalso result in protein cross-linking. or environmentalorother factors. Problemswith
processofageing. don't yet have a deflnltlve answer glycosylalion,a phenomenon by which protein mitochondria,structures that proVide energyinside
as towhyweage. Thereare two schoolsof thought molecules in our bodiesinappropriately bond cells, cancause cells to dieaswell as diseases

Thewear-and-tearconcept- meaningourcells are together. Theyaren'taselaslicanddon'tmoveor associated with old age suchas Alzheimer'sdisease.
used up over time- that many peoplesubscribe to Is breakdown like they're supposed to. Another group oftheories putsforth the idea that
justone exampleofan error theory.
There'ssomeeVidence for this theory- wrinkles, ourlifespansare predeterminedor programmed.
Proponentsofthe error theory believe that for example, are caused bya breakdown ofcollagen, Onescenariosuggests that the biologicalclock is
'set' by bothourneuroendocrinesystem, which
random external eventscause damage that builds a type ofprotein found in the skin. Protein cross-
up inourbodiesoverthe courseofourllfetlmeumll linking may also be responsible for a lotof produces hormones, and our immune system.The

142

STOP Grey hair ••••• Wrinkles •••:•• Missing teeth :••••• Loss of eyesight :••••• Loss of hearing

FACTS 1WhenyourhairtLITlS grey has 2 The loss of siOnelasticityalso • 3• Enamelonourteeth wears • 4• Withageingcan come a number •
a tot to do with yourgenetics. agesustiTough thecreation of
SIGNS OF AGEING but thelossofmelanin wrinkles, although in some : down OYer time and : of vision problems that can • 5 Age-related hearing loss can
associated with geyhair is casesitcan be prevented orat : causea lossof sight. including
due to olderage. teast slowed down. : maintaining dental hygiene : cataracts,gl:auccmaand : becaused byeveryttjng from
: environmentalfactors toa
! becomes more difficult, : maci.Aardegeneration.. : degeneration ofthefine hair
: cells in theoochlea.
: resuftingin tooth loss.

I•U•~•I!l!3N•1MP The process of ageing by o living system, or organism. is known os orgonismol senescence

Ageing skin Age spot Shaft

Whatlooks likespots and Slll damage, as well as Each hair follicle in our heads The hairshaft itself is
wrinkles is actuallya number of the ageing process in contains melanin - a pigment that
changes going on under theskin gives ourhairits colour. Overtime the composed ofkeratin, a
general, cancause melaninproductiondecreases and fibrous protein.
Younger
Epidermis dumps of melanin to unpigmented hair begins to grow

The skin is kept smoolh by concentrate into spots.
the proteins collagen and
Hair bulb
e&ast:in,which break down
The bulb is at the base of
and lose theirstretch """'" the root Itcootains the
bne, causing V111'i'*les.. follide, which forms a

socket for the hair. Hair root

The root comprises three layers

- the outerroot the inne< root
and the bub - which gilleS hair

its structure and rigidity.

- Papilla - - Cortex

This specialised cell isfed by Haircolour is
detennined through
the bloodstream and is
responsible forthe growth the cortex,which is
part ofthe shaftof
of new hairs, and their
rn.mber ofpigment cells- visible hair.

Subcutaneous fat layer - - ---" Older Greying

As we age, the fat pads underthe skin A reduction in
melanin production
diminish and cause siOn and muscle to sag. causes hairto grey.

hypothalamus in the brainsends insteadof8o (theaverage lifespanin Hair loss Hearing loss
messages via hormones to the pituitary developedcountries}. Most researchers
believe that ageing is a complex process A full head of hair The sensory hair eels in the
gland, which in tum stimulatesor will thin as the cochlea deteriorate,
restricts hormonesecretions by the that no single theorycanexplain - it'sa autoimiTM.lnesystem causing age-related hearing
thyroid, adrenal glands, ovariesand combination ofourgenes, our biological attacks the follicles. loss, known as presbycusis.

even the testicles. functions and environmental factors. Wrinkles 143
Over time this complexsystem does We tend to focus more on the visible
Thesed"""'op
not function as effidenlly, leading to signs ofageing at first, likeWTinldes and as collagen and
everythingfrom problemssleeping to grey hairs, and these changesare prime skin cells begin
menopause (which isa normal partof examples of how complicatedthe to deteriorate.
ageingforwomen,butcanleadto processcan be. We've already talked a
Skin tone
additional health problems}. bitabout the cause ofwrinkles: the
Different types ofcells in the connective tissues collagenand elastin, Decreased
that keep skin lookingsmooth, both subcutaneous fat
immunesystemdecline in number as and elastic tissues
we age and do notfunctionas well. Some break down over time. Without the firm cause sagging.
scientists point to the fact that the overall connections underneath, theskinsags.

risk ofcontracting cancersgoes up as we Many people Josefat deposits in their
get older; younger, more efficient faces, and theskin'soil production
immunesystems may have beenable to decreases. Many of these things have a
geneticcomponent, butoutside factors
fend them off. suchas exposure to ultraviolet radiation
Orit could all simplybegenetic.That
and smoking both cause wrinkles and
is, our DNA tells our bodieswhen life is at sags faster. TheSun's rays breakdown
an end. Theredoes seem to bea genetic connective tissues, whilesmoking
component to ageingamong most
animals - they have predictablelife causes blood vessels to contract.
Grey hair is caused bya Joss of
spans. Women also tend to live longer
than men. ifyour parents liveda long melanin, the pigment that is responsible
time, you are more likely to do so for our haircolour.Only recently have
yourself. Onegroup ofgenes, knownas
scientistslearned that melanin
the longevityassurance gene. ha been productiongets interrupted when
determined to influencelifespan. Ifyou
inherit the 'helpful' version then youare hydrogen peroxide levels in the body
more likely to have a longer life. increase over time. Other proteinsfound
ln hair cells that are responsible for
Although ourgenes playa partin our regrowth diminish over time too. Unlike

lifespan, obviously they can be with wrinkles, however, there isn't much
you cando to avoid goinggrey other than
influencedorchanged. Otherwise. we'd dye your hair. Geneticsdoappearto play
still beliving to the ripe old age of30

Old age explained

a part, though.lfyourparentswent correspondingdecrease In growth Bone loss
grey at a youngage, Itis likely thatyou factors (hormones or proteins that
wiJI too. stimulate ceilgrowth). Loss of tone in Acondition that affects ageing bones

The internal signs ofageing are musclessuch as the anal sphincter Osteoporosis Is a degenerative bonedisease that resu Its In lower bonedensity,
more serious, health-wise, than the and the bladdercan cause oneof the which makes the bones weak and fragile. The rlskoffalllngaswellas breaking
externalones. When and how they most embarrassingsigns ofageingfor
occurare also basedona wide many people: Incontinence. bones Increasesas thedlseaseworsens.ltlscausedbya loss of the minerals that
make up bone,suchas ca!dum.There Is ageneticfactor, and the decrease ofsex
variety offactors. Somegerontologists Theageing brain Isstill very hormones1n bothgenders Increase the likelihoodofdeveloping osteoporosis.
like to generalise that some partsof
the bodyget harderas we age, while mysterious compared with what we L Healthy bone 2. Bone with osteoporosis
othersgetsofter, but everythingIs know about the rest ofthe human
interconnected. As we mentioned body. Itwas once thought that s bHo neaglsthtryubconn enss"a"n"d"a' "r'etai gllhlte. t o Benes with osteopclrosis have
age-related Issuessuchas memory gapped. porousstrucl1.-es. They
before, arteries get harderdue to a easiy ._.bodyweight in
buildup of plaque.The heart builds loss bad to do with a decrease in most circ:unstances. are fragile and can frac:nn easiy,
up pressure because It has to work neurons. Now, however, researchers
more to pump blood through the believe that unless you have aspecific as_. as lead totals.
disease that damages neurons,
harder, narrower blood vessels, complex chemica l processes are
which results In high blood pressure.
Other muscles. like the lungs, get more likely to blame. Forexample,
harder due to calcium deposits. the brains ofpeople with Alzheimer's
Thesecan becaused by hormonal disease tend to have deposits of
fibrous proteinscalled amyloids. The
changesorfrom havtng serious
infectionssuchas tuberculosis. exactcause remains unknown,
although onecurrent theory Is that
Meanwhile, hormonal changes the amyloids manage to get into the
causecalcium to leech from the brain because the system that
regulates the exchangeof bloodin
bones, maklngthemsoftandbrtttle
and redud ng their density. Known as the braln, known as the blood-brain
osteoporosis, this loss means that barrier, malfunctions.
we're at a greater risk of breaking
bones.Sarcopenla, or loss ofmuscle What is arguably most fascinating
about the ageing processIs that it's
mass, Is another 'soft'signofageing.
Muscles containspecial cellscalled different for everyoneand it's
satellites, a form ofstemcell.These unpredictable Inso manyways.
cellsare responsible for muscle Thanks to the advances being made
in medicine, we're learning more
growth as well as regeneration when everydayabout not only what causes
there's some form ofdamage. These
cellsgradually becomeless proficient the most unpleasantsigns ofageing.
over time, possiblydue to a butalso what we can possiblydo to
counteract them.

The seven 3. Puberty 5. Adulthood 6. Late adulthood
stages of man
r This growth spurt Muscles are After middleage tissues
What are the principal indicates the start
stages ofthe visible of sexual matlrity. de~~eloped and begin to deteriorate and
human ageingprocess Girls tend to reach strong. Organs are
throughout our lives? puberty two years fully functional. weaken, while hair loses
earlier than boys.
its pigmen tation.

L Infancy

The oompletely
dependent irian\
experiences rapid
physical growth.

2 . Childhood 4. YOlll9 adulthood

TISSUe. muscle and A period ofincreasing
bonethengrow
gr.Waily IIIIi puberty. physical rnattmyand body

~

144

1. Nutritional MORE DRASTIC 2.Honnone 3. Plastic
therapy
changes surgery
1aTshehuumseaonfghl'ootwrtnhohno~rmsuocnhe
Antioxidants such as vitaminE The visible signs of <)9eiog
tocombat signs of ageing, canbecombated -
and calorie·restrictivedets
have both been shown to such asdecreased muscle temporarily - through

exteOO life span. but not mass. Is verycontrover"Sial SIXgery and other
without potential health rlsl<s. cosmetic pr-ooedur~

I•U•~•I!l!3N•1MP Ageing changes con be universal [happen to most people] or probabilistic [only occur in some people]

Life
aroun the world
! 5. Asia
LEurope

Mucho!Europeenjoysa ; Aslahasnearlyeveryrangeofllfe

healthylifeexpectancyofmore : expectancywithin its borders.

75-77.5 than?Zyears. G. Japan

72.5-75 2. North America japan Is theAsiancount:rywilh
10-72.5
..,o canadianshaveasUghtlyhlgher i the highestaverage Ute
67.5-70 llfeexpectancythanAmericans. i expectancyonthe continent
65-67.5 t 7. Indonesia
60-65 3. South America
55-60
The largestcountryhasone of : lndonesla Is roughlyon a par
50-55
45-50 the lowest life expectandes. : withmucho!Asia

40-45 4.Africa 8. Australia and
0 -4 0
Most ofAfrica, being New Zealand

undeveloped, has much lower ! Theseindustrialised countries
lifeexpectancy. have an 8o+lifeexpectancy.
:r

7. Old age - - - , Slowing down the
age1• ng process
A more elder1y
appearance results Although ageing itselfis inevitable (at leastcurrently),
there's alot thatwe can do to slowdown the ageing
from wrinkles, hair process. Vlsiblesignsofageing like wrinklescan be
loss and decreased diminished byavoidingSun exposureand other risk
muscle tone. factors likesmoking. Internalsignsofageing canall be
combated to someextent bylifestyle changes. Weight-
beaTingexerdsessuchas weight-lifting, for example, Thereareanumberofways to
have beenshown to help maintain bone density and slowdowntheagelngprocess
staveoffosteoporosis.Aerobicexerciselike walking or
cyclingcan prevent weight gain- which leads to 145
numerous diseasesand conditions that age us - aswell
as improve cardiovascular health. Dietalso playsa part
inageing - a balanced onecan not onlyreduce the risk of
diseases like type two diabetes but also keep our
immunesystemsoperatingat their peakfor longer.
Some researchers treat ageing likea disease. To that
end, stem-cell treatments and even cryogenics are
looked to as a potential cure. But at what cost?Others
feel thatwe weren't meant to liveforeverand should
focus onways toage comfortably.

I

ow we think

or r1• ra1• ne

Actually, you're neither. Discoverthe truth behind the way we think

It's true that the different sides of of over t,ooo people, in order to determine local hubs, each responsible for a different

the brain perform different tasks, whether the networks on one side of the brain set of functions.

butdo theseanatomical werestrongerthan the networks on the other. Hubswith related functions cluster

asymmetries really define our Despite the popularity of the left versus right together, preferentially developing on the

personalities?Some psychologists argue that brain myth, the team found no difference in the same side of the brain, and a llowing the nerves

creative, artistic individuals have a more strength of the networks in each hemisphere, to communicate rapidly ona local scale. One

developed right hemisphere, while analytical, or in the amount we use either side of our example is language processing - in most

logical people rely more heavily on the left side brains. Instead, they showed that the brain is people, the regions of the brain involved in

of the brain, but so far, the evidence for this more like a network of computers. Local nerves speech, communication and verbal reasoning

two-sided split has been lacking. can communicate more efficiently than distant are a ll located on the left-band side.

In a study published In the journal PLOS ONE, ones, so instead ofsending every signal across Some areas ofthe brain are lesssymetrical

a team at the University of Utah attempted to from one hemisphere of the brain to the other, than others, but both hemispheres are used

answer the question. They divided the brain up neurones that need to be in constant relativelyequally.There is nothing to sayyou

into 7,ooo regions and analysed the fMRI scans communication tend to develop into organised can't be a brilliantscientist and a great artist.

Examining the human brain [ lParietal lobe Occipital lobe - - .
(vision)
What do the different parts of the brain actually do? (pressure, taste)
Incoming information
Broca's ar•~a·------------, The parietal lobes handle
(speech) from the eyes is
sensory information and processed at the
are involved in spatial
awareness and navigation. backof the brain in

the visual rortex.

Broca's area is responsible

for the ability to speak and

is almost always found on

the left side of the brain.

Frontal lobe - - - - - - - - .
(planning,
problem solving)

At the front of each

hemisphere is a frontal

lobe, the left side is more

heavily involved in speech

and verbal reasoning,

while the right side

handles attention.

Auditory cortex - - - -
( heari ng)

The auditorycortex is

responsible for processing

information from the ears
and can be found on both

sides of the brain, in the

temporal lobes. Temporal lobe
r(heceoagrinnigti1ofnac, imalemory)
Wernicke's area
The temporal lobes are (speech
processing)
involved in language
The region of the brain
processing and visual memory.
responsible for speech

processing is found on

the left-hand side.

146

I•U•Jtl!I!JI3~1•l!.'i> It is a myth that we only use ten per cent of our brains. even at rest. almost o/1 brain regions are active

. . .•,,

Give your brain a
fun workout

l Boost your memory
Look at this list of items for one minute,
then cover the page and see howmanyyou
can remember:

Coin Telephone Grape

It took 82,944 Duck Potato Pillowcase
computer processors Key Teacup Bicycle
40 minutes to simulate Pencil Match Table
just one second of
human brain activity,
it's that powerful

'Myth-taken identity Difficult?Tryagain, but this time, make up a
story in yourhead, linking the objects
The left vs right brain personality myth is actually left, they couldn't describe it. Speech and language together in a narrative.

based on Nobel Prize-winning science. In the are processed on the left side of the brain, but the

1940s, a radical treatment tor epilepsy was trialled; information from the left eye is processed on the

doctors severed the corpus callosum of a smaH right. The patients were unable to say what they
number of patients, effectively splitting their brains
saw, but they could draw it. Psychologists
in two. If a patient was shown an object in their
right field of view, they had no ditloculty naming it, wondered whether the differences between the
but if they were shown the same object from the
two hemispheres could create two distinctive

personality types, left-brained and right-brained.

1tlll0: •. . . BAit ~

Left •~ Right

...You get the idea. Make itas sillyas you like;
strange thingsare much more memorable
than the mundane.

Rational Emotional 2 Slow brain ageing
Learning a new language is one ofthe

bestways to keep your brainactive. Here are

four new ways to say hello:

Problem solving Creative • Polish: Czesc! -~

lche-sh-ch) sJ

• Russian: ZdravstvuJ· ~~•
lzdrah-stvooy)
. .•Arabic: Marhaba /[7"-':::::::=:...::,_~"~
Precise Intuitive
lmar-ba-ba) ..,

· Swahili: Hujambo

fhud-yambo)

logical Spiritual

Dog lovers Cat lovers

147

I I•S '

rain freeze •

The Oplrthalmic brardl - - - - That intense painyou sometimes getwhen
carries sensory messages
from the eyeball, tear gland. you eat ice cream too fast is technically
._.:~per nose, upper eyelid, called sphenopalatine ganglioneuralgia,
forehead, ard scalp. andit's related to migraine headaches

The Mardibular branch The pain ofa brain freeze, also know asan Ice cream headache, comes from
carries sensory signaJs your body's natural reaction to cold. When your bodysensescold, itwants
from the skin, teeth and to conserve heat. Oneofthe steps It takes toaccomplish this is constricting
gums of the lowe- jaw, as the blood vessels nearyourskln. With less blood flowing nearyourskin,
~I as tongue, chin, lower less heat is carried away from yourcore, l<eeplngyou niceand warm.
lip and skin of the
temporal region. Thesame thing happens when somethl ng really cold hits the backofyour mouth.

The bigenio...facial- The blood vessels In your palateconstrict rapidly. When the coldgoes away{because
is positjoo IOd ._yclose IX> you swallowed the ice creamorcold beverage), they rapidly dilate back to their
standard, normalstate.
the palate. nos,.,.,.,
This is harmless, buta major facial nerve called the trigeminal liesclose to your
merprets palateblood palateand this nerve interprets the constriction/dilation processas pain. The location
vessel 001tSbi:OOn cn:t ofthe trigeminal nerve can cause the pain toseemlike Its coming from your forehead.
Doctors believe this same misinterpretation of blood vessel constriction/dilationis the
cilation as pah - - causeofthe intense painofa migraine headache.

148 "A major

___., facio/ neNe
coiled the
trigeminal
lies close to
your palate"

~-+------- TheMaxitaryboadlcarries
sensory messages fromthe
skin, gums and teeth of the

._.:>perjaw, cheek, ._.:>perlip,
lowernoseand lowereyeid.

at makes your nose run?

Discoverwhat is going on inside a blocked nose andwhyit gets runny when we're ill

Itsurprises many people but the main Cilia Mucus Goblet cell Epithelial cells
culprit responsible for a blocked and The liningof!henose
runny nose Is typtca Uy not excess Tinybalr.fike Theglycoprotelnsthat TbenoseIsllned
mucus butswelltngand Inflammation. makeupmucusdissolveIn has many mucus-
lithe nose becomes infected, oran allergic stn.ICtuJeS move water, forminga gel-like byepithelial cells,
reaction is triggered, the lm mune system produces substance !hat trapsdebris. producinggoblet cells.
large quantities ofchemicaI messengers that cause mucustowards lhe Themorewater, !herunnier ~redlncllla
the local blood vessels in the lining ofthe nose to
dilate. This enables more white blood cells to enter backollhe lhroatso !hemucus.
the area, helping to combat the infection, but It a lso tbatltcan be
causes the blood vessels to become lea l<y, al low! ng '\
fluid to bulld upIn the tissues. swallowed.
Decongestant medicine contains a chemicaI that's
simllar to adrenaline, which causes the blood
vessels to constrict. stopping them from leaking.

Con nective
tissue

Beneath Lhecells

liningLhenoseIsa

layerofrollJlettlve

tissuethat Isrlcb

Inbloodvessels.

Macrophage Blood vessels •-.

Cells oflhe Immune lnflammatorychemlcalslgnals

system produce chemical cause bloodvessels to dilate,

mediators like histamine, allowingwatertoseepInto the
tissues, dilutingthe mucusand
whichcause local blood maklnglt runny.

vessels to becomeleaky.

How do we bring a

person out of a coma?

When we talk about 'bringing Doctors induce the coma
someone out ofa coma', weare usinga controlled dose of

referencing medically Induced drugs. To bring the person out
comas. A patient with a of the coma, they simplystop
trnumatlc btaln Injury Is the treatment Bringingthe
deliberately put Intoa deep patient out of the comadoesn't
state ofunconsciousness In wake them immediately.They

order to reduce swelllngand grndually regain consciousness
allow the btalnto rest When over days, weeks or longer.
the btaln Is injured, Some people make a full
itbecomesinflamed. The recovery, others need

swellingdamagesthe brain rehabilltatlon or lifetimecare
because It Is squashed Inside and othersmayr.:>main
the skull. unaware oftheirsurroundings.

149

I

Ears popping 1 Sore throats 1 Freckles

Why do our
'pop' on planes?

Theeardrum Is a thin membrane that helps to transmit sound. Air
pressure Is exertedon both sidesofthe eardrum; with the
surroundlngatmospherlcpressurepushingitinwardswbileair
beingdelivered via a rube between the back ofyournose and the
eardrum pushes it outwards.Tills tube Is called the Eustachian tube, when

youswallowotopensandasmall bubbleofair Is able to move causinga 'pop'.

Rapid altitude changes In planes make the 'pop' much more noticeable
due to biggerdifferences In pressure. Air pressuredecreases as a plane
ascends; hence air must exit the Eustachian tubes to equalise these pressures,
again causinga ·pop'. Conversely, as a plane descends, theairpressurestarts
to increase; therefore the Eustachian tubes must open to allow through more
air in order to equalise the pressureagatn, causlnganother'pop·.

What are freckles?

Frecklesare clustersof the pigment melanin. Itis
produced by melanocytesdeep In the skin, with greater
concentrationsgiving rise to darkerskin tones, and
hence, ethnIdly. MeIanlnprotects the skinagainst
harmful ultravloletsunlight, but Is also found In otherlocations
around the body,. Frecklesare mosllygenelicallyinherited, but not
always. They become more prominent during sunlightexposure,
as the melanocytesare triggered to Increase productionofmelanin,
leading to a darker complexion. People with frecklesgenerally have
paleskin tones, and lftheystayln theSun for too longthey can
damage theirskin cells, leadlngtosklncancers llke melanoma

Why does hot honey

and lemon

throat when it's sore?

Honey and lemoncan be areas. This meansitwill be less
painful when these areas comeinto
t 9 drankwarmasacomfort
remedy when suffering contact with othersurfaces whenyou
• from a sore throat orcold, eat orswallow.

and isa populardrlnkwlth many Lemon also helps to settle the
who are feellngunwell. The Idea Is
thathoneycoatsthetbroatand stomach too, as itcontainsacid,
thereforeany inJlamedareaswlll be which can beparticularly helpful
'protected' bya layer of honey, while whenexperiencinganupsetstomacb

at the same time soothing painful from the effectsofa coldorother

digestion-related illness.

150