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Published by Elkhan Julian, 2016-09-12 08:46:40

How It Works Book Of The Human Body

How It Works Book Of The Human Body.

Keywords: how it works,human body

STOP Risk scores •••• How much does it cost? :•••• How much blood? Beating heart bypass :•••• New techniques
: 3Theop is free on theNHS butin •
FACTS 1Usingcomplex mathematical 2 theprivate sector it wouldoost • Onaverage, the heartbeats 70 4 A bvpasscanbeperformed s•: New techniques indudeusing
models, each individual patient is without stopping the heart.
BYPASSES times perminute (about • minj.inc:isionsinto thechest
givena riskofdying from the
operation, alowingthem tomake £16,000-£20.000 ! 100,000 times perday}which usinga special retractor. tn a few ! and also the useofrobots.
a decision about how risky the
($23,300·$29.000). Thepric<! ! pumpsfivelitresof blood per places. surgeryhasbeen ! Smalcamerasarealsousedto
operation is.
varieswith the risks and if it'sthe ! minute.F"tve per cent flows : performed this 'NaY on patients : harvest the new vessels for the

first surgeryora re-do. ! through the coronaryarteries.. : who are awake. ! bypassgrafts.

ltU•JU•11J!3N•IW The heart has four separate chambers, four valves to control blood flaw and twa main coronary arteries

3. Bypassing Heart bypass

the heart - - - - --. What happens in surgery?

Blood is removed by pumping , - - - - 1. The problem
it outof the body, oxygen is
added to it in a bypass machine Fatty plaques narrowand
eventually block the
and the blood pumped back in. coronary arteries,

Thisa llows oxygenated blood preventing oxygen-rich
blood flowing to the
tocontinually flow while the heart m uscle.

heart is stopped.

-4.Stopping - - --+- -

the heart
The aorta, the main

vessel out of the

heart, is damped.

The heart is then

cooled and stopped

using a potassit.m·

rich solution.

6. Restarting - - - - -2. Getting to ~
the heart the heart
The chest is opened grafts
Once the new vessels through a cutdown the
m iddle of the breastbone The body has certain
have been secured, the (sternum). A special bone
-:J"O saw isused to cut through vessels which itcan do
the sternum, whichdoesn't without, and these act as
aorta is undamped damage the heart below. conduits for bypass

which washes the 7.0osing surgery. Commonly
+-- - - the chest used,thelongsaphenous
potassium-rich solution
After making sure there is vein runs from the ankle
from the heart. The - - - to the groin.Ashallow
patient is warmed and no bleeding, thin metal
wires are used to hold the incisionallows the vein to
the heart restarts. two halves of the sternum bedissected away from
Itssurrounding tissue.
5. Attaching the - - back together.
new vessels Othervessels often used
include small arteries
The new 1/<!Ssels are tested and from behind the rib cage
then sewn into place. The opening {Internal mammary
artery) or the arms
is sewn to one ofthe large arteries (radial artery).
carrying oxygen-rich blood. The

end of the bypassgraft is sewn
beyond the fatty plaque, aDowing
blood to freelyflow to the

affected heart muscles.

When too little blood is getting to the muscles ofthe heart, a StoP.Ping
surgeoncan bypass the blockagesusing the bodys ownvessels
theliean
Although the heart pumps ofoxygen- angina. Ifavessel becomes Thesurgeon uses healthyvessels from
other partsofthe patient's body to Cardiopulmonary bypass
oxygenated bloodaround the completely blocked, no bloodgets (where a machine takes
body, the heart's muscular through, causinga heart attack where bypass the blockage, allowing a new over the heart's pumping
route for blood to flow. This delivers action and the gas
walls need their own blood the heart muscle dies. higher volumes ofthe oxygen-rich blood exchangefunction ofthe
supply. Oxygen-rich bloodis delivered to The firstway to treat this type of to the heart muscles beyond the lungs) is established to
provide oxygenated
these tissues viasmalIvessels on its coronaryartery disease is with blockage, preventing the pain. blood to the rest ofthe
surface- the coronaryarteries. These Most bypassesare performed by body. Next, the heart is
arteries canget narrowed or blocked up medicines. Secondly,angioplasty can be stopped.This is achieved
with cholesterolcausing fatty plaques used, where narrowings within the stopping the heart and usinga heart- usinga potassium-rich
arteries are stretched usinga balloon, lung bypass machine to deliver solution, pumpeddown
whichslow bloodflow. At times of with or without placinga stent to keep the coronaryarteries.
exercise, not enough bloodgets to the oxygenated blood to the body. The new Thisstops the heart
heart muscles, leading to pain due to lack the vessel open. Finally, a heart bypass vessels are then sewninto place. contracting. The surgeon
operationis an option for some patients. can now carefullyattach
the fresh vessels to
bypass the blockages.

051

sct•ence blood transfusions
------------------------------~------ r-~~
Noone can get
a transfusiOn What's in
unlessblood
donors keep

ondona!lng

Red blood cells

- blood eels are the most
abundantcellsin blood and
gM! it a red colour. They carTY
oxygen from the lungs iii"<J<W1d
the body, boo.nl to a prcn;,

caled haentoglobi!L

Plasma

Plasma is a straw-<:dowed
walefy fluid thatcarries..

of the cellsandproteinsin
blood, incbling the vital
clotting factors.

Platelets

Plateletsare tiny frayooOBots of
blood that are aucial in
st01>1>ing bleeding, along with
clotting factors, by fomoioog a

plat-plug.

Whether it's a patient ~ Safety first Receiving White blood cells
haemorrhaging to a blood
death or a 'top up' for Twonurses rn.ost doublecheck the These are yow irilecticwr-
life-long diseases, de!ails on thebag of blood with the The pallentIs atta.ched to a f"o9otioog eels; theyc:irculab!
blood transfusions patient's ide llify label befol" drip and the donorblood Is in the blood so they can
are vital procedures administe i ~ it. qooiddy nWJitiplyand be
transfused through this. b30~ to an area where
Blood screening "fYplcallyanarmveln Is there's an ioftdiooo flaring.

All blood transfusions are rv:tN normally used. Lymphocytes
saeened fu< HIV, hepatitis iWld otller
infections carried .. blood. lyrT111oocytes are a type of
- blood cell that dioects
the body'simmunesystem.
They have a memory fu<
invading bacteria and viruses.

-• •• Ablood transfusion takes
~
place when a pallentIs given
componentsofblood from a
'levelsare too low. Having enough blood
' donor when their own blood

is essenUal becauseIt carries oxygen

around the bodyand returns carbon The ABO

dioxide to the lungs to beex haled as a blood groups

waste product. We all belong to one of fOUl' blood

When a doctor deddes a pallent needs types (below). Different antigens

blood, they are 'cross-matched' with ~- Blood pcesent on the surface of red blood
The blood is in a sterie, clear
donor blood. Afew mlllllitresofthelr bag containing the details of cells identify to which group you
the blood groupiWld type,iWld
bloodis collectedInto a sma II bottle the patient's detais it is belong_ A patient mtl'St receive
intended fu<.
which must be hand-labelled to prevent blood with the correct antiqensor
~~=--:--::---:--::~e. ~~:-.;;==.,::~:J
else their · e system wil
which is placed directly
confusion between pallents.l nthe lab into the patient'swin so recognise that the red blood ceUs
the transfused blood joins
the bloodIsmatched with donor bloodof thecirrulatilg blood. are foreign cellsand wil attack.

the samegroup (either A, Bor0).The • Aantigens on red blood
cells and anti-8 antibodies in
unit ofdonor blood Isthen transfused plasma

via a drip into the patient's veln over two • Bantig<>m on red blood

to three hours. cells and anti-A anhbodies in
plasma
During this time the nurse keeps
• A andB antigens on red
closeobservation ofthe patient to look
blood eels and no antibcxlies
for transfusion reactions. Thesecan be in plasma

mild (such asa fever, chills ora rash), • No antigens on red blood
cells and anti-A and anti-B
which are solved byslowlngdown the antibodiesin plasma

rate offlow, tosevere, life-threatening

allergic reactions.

052

STOP 1Anaemia •••••• Haematology 3•••••••••••••••••Orthopaedics • 4•••••••Gastrointestinal bleeding • sChildbirth••••••••••••••••Thefifth mostcorrvnon
One ~arterofblood
FACTS transfusions are ~nto : 2 Some patients have blood Inorthopaedic surgery .. such Blood loss (rom the causeofblood transfusion
asspinal fusion and hip •• gasb'ointestinal tract. such
BlOOD patientswith anaemia. whose : disorders where their ownred • as stomach ulcersand is t\Jring or following
-•••••• artiToplasty - bloodislost trai..IITB'ticchildbirth. Normally
blood levels have been '*-;ng bloodoeAs are deficient. such duringthe operation. This is •• oolorectalcancer. accounts
as in sickleceH disease orred common with large joint •••• blood tossduringchadbirth is
slowtyover tinedue to cells destroyedat a high rate for 11peroent ofallhuman
replacement surgery. less than 600ml.
diseases likecancer. called haemolysis. bbod transfusions.

ltU•JU•11J!3N•I'AW The first ever successful blood transfusion was performed on o dog in 1665 by Richard Lower

The loss ofblood supplyto the brain How the body reacts to bloodvessel
can cause long-term damage or death damage to aia the healing process

Strokesare caused when the flow of blood to the brain is Through the action ofthe thrombin system, coagulation of
interrupted.Thereare two main reasons why this might the blood occursinstantlyat the location where there is a cut
occur,and ischaemicstrokesare the most common.They orotherinjury to the skin.The blood clot, which consistsofa
occur becauseofa bloodclot that forms in an artery combination ofcellular plateletsand stickystrings offibrin,
forms a plugin the damaged blood vessels.
(thrombosis) ora bloodclot that forms and travels to a brain artery{arterial The clotstops blood from freely flowing out ofthe bodyand at the
embolism) that reduces orblocl<s the blood flow{ischemia). same time allows theblood to continuecirculating. As the skin heals,
plasminenzymes break down the webs offibrin and the clotis
Thesecond reason is bleeding(haemorrhaging)ofa blood vessel in the eventuallydissolved into the body.
Clotscanalso form in blood vessels due to inactivity, oldage, obesity,
brain.This can becaused when a thin partofa vessel{ananeurysm) smoking, poordiet orduring pregnancy. This condition is known as
thrombosis and can lead to an embolism.
bursts. Betweenoneandsix percentof the population have an
intracranialaneurysm and everyyear in the United Kingdom1,400 people L Skin layer ------::~~
die of ruptured intracranialaneurysms.
Composed of a water·
Astrokeis defined when iteithercauses death or hasa long-termeffect resistant and protective layer
called the epidermis; beneath
after24 hours. You can experiencesignsofa ministroke thatare called itis the dermis layer that
consists of blood vesselsand
transient ischemicattacks (T!As) thatlast onlya few minutes or hours.The
onset ofa ful lstroke is characterised by numbness in the face and limbs. connective tissue.
Vision can beimpairedand you can have trouble wall<ing or talking.
2. Cut -----~
Theeffects ofa strokedepend on which partofthe brainwas most
If skin iscut, platelets in
starvedofoxygen from the bloodsupply. In many cases,stroke victims the blood wssels of the
damaged a-ea become
will find itdifficulttowalkoreatdue to musclewealmessandinextreme 'sticky' and clump
cases, they might experience paralysis.
together at the damaged
Areas of impact site to funn a white clot

Carotid arteries ~-- Vertebral arteries Otherchemical reactions
create sticky web~il<e
Carotid bloodvessels, served by Vertebral arteries supply blood strands offibrin that
the internal and external carotid adhere to the damaged
arteries, supply blood tothe front to the rest of the brain and blood vessel wal~ to fonn
partof the cerebrum. enterthe skuR through the a red clot.

foramen magnum. Strands of fibrin - - - - - - '
Platelets _ _ _ _ _ _ _ __,
lsdlaemic strokes are caused by blood clots, When part ofa thin
which can eitherfunn directly in an artery, or blood vessel bursts 3. Healing -------~
funn and then travel to a brain artery that it
then blocks, reducing blood flow. haemorrhaging The blood clot stops
blood escaping from the
canoccur. wound, and allows the
normal circulation of the
red blood cells which
transportoxygen around
the bodyand thewhite
blood cells that protect it
against infection.

053

ow your kidneys work

Inside

How do your kidneys filter As blood enters the kidneys, It Is passed -... .
waste from the blood to through a nephron, a llny unit made up of
keep you alive? blood capillariesand a waste-transporting RenaJ ---l
tube.These work together to filter the blood,
returning clean blood to the heart and lungs capsule
for re-oxygenation and recirculation and
removingwaste to the bladderfor excretion. The kidney's filrous outer
edge,wnch provides
Kidneys are bean-shaped organs Renal cortex - - - - - - - - - - protection for the
situated hallway down the back kidney's 0rtema1 fibres.
just under the ribcage, one on This is ooe of two broad intemal sections of the
eachside of the body, and weigh kidney, theother being the renal medulla. The
renal tubules are situated here in the protrusions
between u5and170grams each, dependent that sit betweenthe pyramidsand sean the
on the individual'ssex and size.The left cortex and medulla together.
kidney iscommonlya llttle larger than the
right and due to the effectivenessof these Renal artery - -

organs, individuals born with only one This arterySl.Wfies the
kidneycan survive with llttleor no adve.rse
health problems.lndeed, the body can kidney with blood that
is to be fitered.
operate normallywith a 3o-40 per cent
decline in kidney function. This decline In Renal vein

function would rarefy even be noticeable After waste has
and showsjusthow effective the kidneysare been removed. the
at filtering out waste productsas well as clean blood is
maintaining mineral levels and blood passed out ofthe
kidney via the
pressure throughout the body. The kidneys renal vein.
manage to controlall of this byworkingwith
otherorgansand glandsacross the body Ureter Thisfmnel-likr s1rucbJre i; Renal medulla
suchas the hypothalamus, which helps the
kidneys determine and controlwater levels Thettbe that howo.rile travels outof the Thekidney'siMersection, where blood i;
trarosports the waste kidneyand forms the top part
in the body. products (o.rile) to of thetnter, wNch takes filtered after passng through rumerous
Each day the kidneys will filter between the bladder folowing o.ri1e down tothe bladder.
blood 61traoo.. a-tet ioles. It'sspit intosections called
150and18o lltres of blood, but only pass
around two lltres ofwaste down the ureters py!1111lids and each tunan kidney wil
normaly have seven of these.
to the bladderfor excretlon.This was te
product is primarily urea- a by-productof
protein being broken down for energy-and
water, and It's more commonly known as
'urine'. The kidneys filter the blood by

passing it through a small filtering unit
called a nephron. Each kidney has around
a million of these, which are made up of a
number ofsmall blood capillaries, called

glomerulus, and a urlne-<:ollectlng tube
called the renal tubule. The glomerulussl.ft
the nornlal cellsand protelns from the blood
and then move the waste products Into the
renal tubule, which transports urine down

into the bladder through the ureters.
Alongside this filtering process, the

kidneys also release three crudal hormones
(known as erythropoietin, renin and

calcitriol) which encourage red blood cell
production,aid regulation of blood pressure
and aid bone developmentand mineral
balance respectively.

054

Two for the price of one

Weare thoughtto havetwo kidneys because theyaresocrucial to oursurvival,
thesecondis purelya 'backup'. Having two organsobviouslyincreases our
chancesofsurvival and reproductivefitness.

ltU•JU•11J!3N•IW Useless body ports include the appendix, the coccyx and wisdom teeth

r---------------------------------------·I 1be glomerulus
I Nephrons - the filtration Collecting
duct system This group ofcapillariesis the first step of
I filtration and a crucialaspect ofa nephron.
I units of the kidney Proximal tubule Although not As bloodenters the kidneysvia the renal
technically part of the
artery, it is passeddown through a seriesof
I Nephrons are the units which filter all blood that passes Unks Bowman's cap5Uie nephron, this collectsall arterioles which eventuallylead to the
glomerulus. This is unusual, as instead of
I through the kidneys. Thereare around a million in each and the loop of Henle, waste product filtered draining intoa venule (which would lead
back to aveln)itdrains back intoan
I kidney, situatedin the renal medulla's pyramidstructures. As and w ill selectively by the nephronsand
I well as filtering waste, nephrons regulate waterand mineral facilitates its removal arteriole, which creates much higher
I salt by redrculatingwhat is needed and excreting the rest. reabsotb m inerals from pressure than normallyseenin capillaries,
the filtrate produced by from the kidneys.
.I Bowman's capsule. which in turn forces soluble materials
... .~ and fluids outofthe capillaries.This process

-.. , Glomerulus is knownas ultrafiltration and is the first
step infiltration of the blood.These then
Hi~ pressure in the pass through the Bowman'scapsule
glomerulus, caused by it (also know as the glomerularcapsule) for
c%aining into an ateriole
further filtration.
insteadofa venule,
""":-- +-- foroes fluidsand soluble Afferent arteriole Proximal tubule

materials out of the Thisarteriole suppliesthe Where reabsorptionof
capillary and into blood to theglomerulus
mineralsfrom the
- Bowman's cap5Uie. for filtration.
filtrate from Bowman's
--+- '=-"""+-- Bowman's
capso..M ,;11 oocur.
capsule
Thismassof
Also known as the capilaries is the
glomerular capsule, this
filters the fluid that has glomerulus.
been expelled from the

glomerulus. Resulting
filtrate is passed along

the neptvon and
will......rtually make

up urine.

- - i' - - - - - - Distal Efferent arteriole Bowman's
'--- capsule
convoluted This arteriole is how
blood lealles the This is the surrounding
tubule glomerulus followng
capso..M that wil filter
Partly responsible ulbafibation. thefiltrate produced by
for the regulation of
the glomerulus.
minerals in the
bdood, linking to the

collecting duct

system. Unwanted
minerals are

excreted from
the nephron.

Renal artery What is urine and what
is it made of?
This artery supplies the
kidneyw ith blood The Urine is made up ofa range oforganic 94o/o water
blood travels through compoundssuchas proteinsand
this, into arterioles asyou hormones, inorganicsalts and
travel into the kidney,
ootil the blood reaches numerous metabolites.These
the glomerulus.

by-productsare often rich in nitrogen

Renal vein and need to be removed from the blood
stream through urination. The pH-level
This removes blood that has
of urine is typically around neutral
been filtered from the kidney.
(pH7) but varies depending ondiet,
hydration levelsand physical fitness.

Loop of Henle Renal tubule Thecolourofurine lsalso determined
by these factors, with dark-yellow urine
Made up ofthree parts, the proximal indicatingdehydration and greenish

The loop of Henle controls the mineral and tubule, the loop of Henle and the distal urine beingindicative ofexcessive
asparagus consumption.
water concentration leliels within the kidney convoluted tubule. They remove waste 6% other organic
compounds
to aid filtration offluids as necessary. It also and reabsorb minerals from the filtrate

controls urine concentration. passed on from BcMrman's capsule.

~~--~--~-------~------~----------·

055

Kidney transplants

The kidneys are the body's natural filters. You can survive
onjust one, butwhen that fails you may need a transplant

Transplantingorgansis a year receive their transplant. The someoneelse's fortune. for those who register to a suitable recipient A
complex process,although number ofpatients registered for a are declared brain-dead, the beating ·retrieval' team froma central
itcangive a new leaseoflife kidney transplant Increaseseachyear, heart will keep the kidneys perfused
to recipients. The lddney is and has risen by 50 per centsince 2000. until they are ready to be removed. In transplant unit (of which there are20
based around the UK)will go to
the most frequently transplanted Kidney transplants comefrom two some patients, the ventilator wUl be
organ, both in the UK and around the switched offand It'sa race agal nst lime whichever hospital the donor isln.
world. However, there Is a discrepancy mainsources: the livingand the to harvest organs. Either way, consent They will remove the organs, while the
between the numberof patients recently deceased. Ifa healthy, from the family Is needed, even at such recipient is being prepared in the base
compatible family member is willing to hospital. During the tricky operation,
waiting for a transplant and the an emotionaland pressurlsed Ume.
number ofavailable organs; only donate a lddney, they cansurvive with When a suitableorgan becomes the new kidney is 'plumbed' Into the
around one third of those waiting per justone remaining lddney.ln other pelvis, leaving the old, non-functioning
cases, someoneelse's tragedy is avallable, it is matched via a nat.lonal
ones In-situ.

( to per f01111 a kidney transplant

Transplantinga lddneyIs 1. Thedonor ,....- 2. Out with the old? 3. Into the pelvis

a caseofcarefuland The donorkidnoy .. harwstl!d, indu!ing en<llJ!jllength at As long as !here's no <JJOSticn An incision ..madein the
clever plumbing.Thefirst
step is to harvest the artery. ....... and ..-eter (which carries lAine tothebladde<) atcancer. the original kmeys lowerpart at the abdomen to
donorkidney, and then
t o - tl!n5iorHn!eirniJiantation i1ID the re<:ipielll. are left in place. nogain a<X>'S5 the pelvis.
it'sa dash to transplant
the new lddney Into the 7. What's that
recipient When the lump?
brain-dead donoris
transferred to the The new kidney can
befelt underneath
operating theatre for the sea< in the
organ harvest, theyare recipient. These
patients are often
treated with the same
careand respect as If they reauited to medical

werestlll alive. When student exams.
consent has beengiven
for multiple organ B. Catheter
harvest, a cutis made
from the top of the chest A catheter i!>left
in-situ fa< a short
to the bottomof the
pelvis.The heart and while. so that the

lungs are retrieved first. lrine outputof the
followed by the new kmeycan be
meastnd exactly.
abdominal organs.

5. PIU'l'Dng it in I

The renal arteryand....... " - - - - - - - - - - - - - - 6. The f inal link

are cmnected tothe The treler, which drains lAine from the kidney, ..

~~dng~artery --------~------~ cmnectedto the bladder. This alows the kidneyto
function in the same~ as one ofthe original kmeys.
and ....... in the redpie ~··
body. Holes (a leliutoories)

arecreated in the main 4. Makespace!
arteries, and thekmey's

YeSSels are anasiDmo5ed The...-geon wil aeate space in the pelvis. and identify the large
(,a SU'gical join between YeSSels which run from the heart to the leg (the iiac arteriesand

two IUJes using sutures}. - ~. The new kidney's YeSSels llwil beconnected to these.

056

1Pioneers 2••••••••••••••••• The 'organ gap' • 3••••••••••••••••Which other organs? 4 the•••••••••••••••••Through keyhole Do something about it
Thewryf;r.;tkidneytransplant
totakeplaceintheUK was Aro111d 7,000 people i'l the Organs thatcan be When removing a kidneyfroma s You can register to
performed in Edinburgh. 1960. United Kilgdom lastyear transplantedincble kidneys, liWlg donor, themost modem becomean organ donor
Herea surgeon transplanted a centres use keyholesurgery at http://www.
werewaiting for organ livers. hearts, lungs. the ()aparoscoP1f}lodol • this organdonation.nhs.uk/
kidneyfrom a 49")'eaf''idinto transplants. butonly around pancreasand intesOOes; tissues
2,.300 kidney transplants include bones. heart vatves,. leads to smaler scars.lesspain - don't forget to talk to
his twinbrother. skin and ccwneas. and faster recovery. )'OUr kwed ones about i t.
actually took place.

1•U•Nl!l!J13.,-C•1WP Of the millions of people in the UK suffering from kidney disease, sa.ooo will suffer end-stage renal failure

Dom·

Patient1 needs a newkidney but their faFmroimly ipnaetmiebnet 1r From patient 2
flllolily member
family member isn't compatible.
Patientzalso needsa kidneyand has
an lncompatiblefamily memberas
well. However, patient2's relation is
compatiblewith patient1and vice

versa.Thesurgeonarranges aswap-
a'paired' transplant. Alongerline of
patientsand familymembers
swappingcompatible kidneys can be

arranged-a 'daisy-chaln'transplant.
A'goodSamaritan'donor, who isn't
related toany ofthe redpients, can
start theprocess.This first redplent's
family memberwillsubsequently

donate to someoneelse- a'domino'
transplant effectwhichcango onfor

several cycles.

Who is Antibody

Of the several miUion people in If the antigensare too dissimilar, the host's existing
the UK with kidney disease, only
around 50,000will develop immune system thinks the new ki~ey isa foreign invader
end-stage renal failure (ESRF). For and attacks it with antibodies, leading torejection
these people, dialysis or kidney
transplantation are the only Antigens
options. Kidney damage from
diabetes is the most common Antigens from the recipient kidney's ABO
cause of transplantation. Other blood IJ'OUP and HLA system should be as
causesinclude damage from high close a match tothedonor's as possible.
blood pressure, chronic kidney
scarring(chronic pyelonephritis) When things go wrong...
and polycystic kidney disease
(the normal kidney tissue is Kidneys need to becarefully matched to suitable donors, or rejection ofthe new organ
replaced with multiple cysts~ will setin fast. Rejection occurs when the host body's natural antibodies think the
many otherless common causes new tissue Is a foreign Invaderand attacks; careful pre-operative matching helps limit
existalso. the degree ofthis attack. The mostimportant match is via the ABObloodgroup type -
the bloodgroup must match orrejectionisfast and aggressive. Next, the body's HLA
Patients must beselected (human leukocyteantigen) systemshould bea closea match as possible, although it
carefullydue to the scarcity of doesn't need to be perfect. incorrect matches here canlead to rejection over longer
organs.Those with widespread periods of time. After the operation, patientsare started onanti-rejection medicines
cancer, severelycalcifiedarteries, which suppress the host's immunesystem(immunosuppressantssuchas Tacrolimus,
persistentsubstanceabuse and A2athioprine or Prednisolone). Patients are monitored for the rest of theirlivesfor
unstable mental problems mean signsofrejection.These immunosuppressantsaren't without their risks - since they
that transplants are likely to fail suppress the body's natural defences, the risks ofinfectionsand cancersare higher.
and so these patientsare
unsuitable to receive a precious
kidney transplant.

"Patients ore

monitored for
the rest or,
their lives '

0 57

stigiol organs

Why have humans and otheranimals stopped using certain
organs and functions whichwere once crudal for survival?

Charles Darwin Is one of history's much as other creatures; some of our physical
most famous naturalists. Living in attributesand behavioural responsesare
the 19th Century, he became functional in otheranimals, but theydo not
celebrated for his theories on seem to be ofany benefit to us. These
evolution. In his seminal work On The Origin Of evolutionary remnants that no longerserve any
Species he described how sim ilar animals were purpose are calledvestigial organs, though this
likely to be related by common ancestors, can apply as much to behaviourand other body
rather than be completely unre lated. As structures as it does to actua Iorgans.
subsequentgenerations are born, traits and
features that did not bring a survival benefit to Evolution has also adapted some existing
thatspecies were eliminated. That, in a features to help us in new ways, ina process
nutshell, is the theoryofevolution. known as exaptation. For example, birds' wings
As a consequence, some organsand traits left not only help them to fly but keep them warm
in the body lose their function and are no longer too. These changes may take thousands of years
used. Thisapplies to modem human beings as to develop, and insome cases the original role
is eventuallyeliminated altogether.

Appendicitis In focus

What happens when yourappendixgets Infla med?

Surgery Progression

OurlngsurgerytoremO\Ie TheInflammation can
theappendbc, the surgeon lead to perloratlonof the
Ues offthebase to prevent appendix and
bowel contents leaking, lnflammatlon of
and removes the whole surrounding llssues.
appendixorgan
Thepain worsensand
Blockage then localises to lhe
lowerright-hand side of
Ablocl<age. caused byeither theabdomen.
atinypleceofwasteor
swoUen lymphatic tissue In
the bowelwall.causes

appendixswelling.

Inflammation

Beyond theblockage.
Inflammationsetsln.wblch
causeslntenseabdomlnalpaln.

058

THE sizE 7.6 x 12.7 x 2.5cm 200gwEIGHT
STATS
~~6~1JLP 75°/o WJt% PULP 25% ~~~~~~~GT -5o/a
THE SPLEEN

I•U•JW•1!113N•IW Around 15 per cent of us hove an extm spleen - a small sphere close to but separate from the principal organ

Perhapsnotaswelllmownasfamous organslike the heart, ..-------- Location
the spleenservesvitalfunctions that help keep us healthy
The spleensitsmdemeath the
Thespleen's main functions are to remove old Inside the spleen 9th, 10th and llth rils (below
blood cellsand fight oHinfectlon. Red blood cells the diaphragm} on the
have an average IUespan of120 days. Most are We take you on o tour ofthe left-hand side of the body,
created from the marrowoflong bones, such as major fecjtures in this ofiPn- which provides it with some
the femur.When they're old, It's the spleen's job to ldentHy overlooked organ protection against knocks.

them, filter them out and then break them down. The smaller Hilum ------.. Splenic vein
particlesare then sent bacl< Into the bloodstream, and either
The entrance to the spleen, Thewaste products
recycled or excreted rrom other parts of the body.This takes this is where the splenic artery from filtration and
divides into smaller branches pathogen digestion
place in the 'red pu lp', which are blood vessel-rich areas of the and the splenic vein is formed
from its tributaries. are returned to the main
spleen that make up about three-quarters oflts structure. circulation via this vein
The remainder Is called 'white pulp', which are areas filled Spleric artery fur disposal

with different types of immune cell (such as lymphocytes). The spleen receives a bbxl
Theyfilteroutand destroy foreign pathogens. which have stJpplyvia ll>s artery,
invaded the body and are circu lating in the blood. The white which arises froma branch
of theaorta called the
pulp breaks them down intos maller, harmless particles. coeiactnd.
Thespleen Is surrounded by a thin, fragile capsuleand sols

prone to injury. Itsits beneath the lower ribs on the left-hand
side of your body, which affords It some protection, but car

crashes, majorsportsimpactsand knife wounds canall
rupture the organ. In the most serious cases. blood loss can
endangerthe person's life, and In these situations It needs to
be removed by a surgeon. Since this reduces the body'sabUity
to fight infections, some people will need to take antibiotics to

boost their immunityfor the rest ofthelr lives.

The immune system

Although theredblood thai nowslhrough ourbodiesgetsall the
glory. the transparentlymphaticnuldtsequallytmportant. Ithas Its
ownbody-widenetworic whJcll followsbloodvessel flowcloselyand
allows for thetransportofdlgested lat.$. Immune cellsand more...

Spk!en Adenoids ~
Oneofthemasterco-ordlnators
thatstavesofflnlecttonsand Thesearepart of!hetonsillar !!
flltersold red blood cells. II system thatare onlypresen!ln
contains anumberof children up until theageofnve; ~--~~------------_.~------------------_j ~
lymphocytesthat recogniseand Inadults!hey have disappeared.
destroy Invading pathogens Theyaddanextra layerof Whitepulp ~ .---- Splenic capsule
presentIn the blood as It flows
_ _.d..e.f..e..n..c..e..I.n.._o.u...r..e..a...r.l.y...y...e.ar..s........ ..... MaiOOg up roughlya The capsule provides some
through thespleen. ~ofthe spleen.
Bone marrow protection. but it's tiWl
....,...·-··-·····0<--000.000..........._._..... the-""" is and relatillely weak. Strong
Thtsformsthecentral, Oexlble \/\/here w n t e b b x l
Thymus partofourlongbones (egfemwj. blowsorlcrife womds can
A small organ thaisitsjustabove eels identify and
BonemarrowIS essentfal as It easiy .....,rure it and lead to
theheartand behindthe destroy- type of
producesourkeyctrculatfng irorading pathogens. if~HhreatEI oi19bleeOOg.
sternum.IIteaches cells, Includingred blood cells,
Redptjp - --- ......_____ SintiSOid
T4ympbocytestoldentifyand whlre blood cellsandplalelets.
Fonning app~axi ooately Simiar tothose fomd .,the
destroyspedfic foreign bodies. Thewhiteblood cells mature three-quarters ofthe IM!r,thesecapilaries alow
spleen, the red pulp is
ltsdeYelopmentlsdtrectly Into<llfferent rypesteg fur the easypassagP.of
\/\/here red blood cells are large eelsintothe splerjc
n!lated tohormones In thebody lymphocytes a n d neutropbfls~ fitered and bro4<en down.
tissue fur processing.
so It'sonlypresentuntU puberty whlthserveas thebasisofthe
059
- - - - - - - - - - · -end.$;adtdtsdon'tneedone. human lntmunesystem.

Tonsis -L-ym--p-h-o-o-d-e-s--------

Tbesearemassesollymphold Thesearesmalljaboutv:mJ

tissueat thebackolthe throat o#nlsphericalnodesthatare

and can beseenwbenthe mouth paclcedwllh~and

Iswideopen.Tbeyform the first lymphocytes todefendagainst
foreign agents. T b e s e a r e o l t e n
line oldefenceagalnsllnhaled llnl<ed Inchainsand are
prevalentaround thebead,
foreignpatbogens. although neck. a x i l l a e j a r m p l t s l a n d groin.

theycanbecomeInfected

themselves, causing tonsUUtls.

umon digestive system

How does food get large intestine
turned into energy?
Thecolon, as the large
... Thedigestive systemIs agroupoforg;ms that
intestine is also known, is
• • process food into energy that the human body wllere waste material will
be stored until expeled
' can use to operate. It Isan Immenselycomplex fn:m the digestille system
~ system that stretchesall the way between the
mouth and theanus. tlwough the recwm.

Primary organs that make up the systemare the mouth, Small intestine
oesophagus,stomach. small lntest.lne, large Intestineand the
anus. Each organ has adifferent function so that the maximum Nu1rlents that have been
amount ofenergyIsgained from the food, and the waste can
released from food are
besafelyexpelledfrom the body. Secondaryorgans,suchas
the liver, pancreasand gall bladder,aid the digestive process absoobecl into the blood
alongside mucosa cells, which line all hollow organsand stream so they can be
produceasecretion which helps the food passsmoothly transported to w11ere they ate
through them. Muscle contractionscalied peristalsisalso help needed in the body through
the small intestine waM.
to push the food throughout the system.
The whole digestive processstarts when food is taken Into Further breaking down occurs
here with enzymes from the
the body through the mouth. Mastication (chewing) breaks liverand pancreas.
down the food intosmaller piecesand saliva starts to break
How
starch in these pieces offood lntoslmplersugarsas they are
swallowedand move Into the oesophagus.Once the food has
passed through the oesophagus, It passes Into the stomach. It
can bestored in the stomach lor up to four hours.The stomach
will eventually mix the food with digestivejuicesthat It

produces, and this breaks down the food further into simpler
molecules. These molecules then move Into the small intestine
slowly, where the final stage ofchemical breakdown occurs
through exposure to juicesand enzymes released from the

pancreas, liverand glands In the small intestine. Nutrients are
then absorbed through the Intestinal walls and transported
around the body through the bloodstream.

After all nutrients have beenabsorbed from food through the
small intestine, resulting waste material, lncludlngHbreand

old mucosa cells, Is then pushed Into the large lntestlnewhereit
will remain untll expelled bya bowel movement

"Nutrients ore then Many different organs Rectum
absorbed through the ore Involved in the
intestinal walls ond digestion process This is wllere waste
material ('-:es) exits
transported around the digestiwsystem.

the body"

060

STOP Complete digestion •••••••• Some food •••••••• Thestomach can 4•••••••••••••••••Weuse P.ints ol s!••••••••~':.rtordouucgthioange
for thought... hold two litres saliva a Clay!
FACTS 1takes time! : 2 Anaverage humanmale will : 3 The stomachwil normally Enzymesarecrucial for
Generally, itcan takebetween Up to four pintsofsalivacan be
DIGESTION 24and 12 hoLrS for thefood : constJmeapproximately 50 ••••••• feel fulwhen it reachesa produced byan.,dividual each : ~.but as we age,
capacityofonelitre, but
you eat to be fuUy digested, ••• tonsoffood Wring hislifetime. dayandithelps todigest food ••••• enzyme productionred.K:es ... at
That's the eqlivalentoften ultimately it canstretchup and protect teethand tissue 70a person may produce half
meaningyou're constantly •• Afri::an elephants. inside themouth. what theydidat20.
totwolitres.
digestng food!

ltU•JU•11J!3N•IW The human digestive system is between 20 to 30 feet long!

- - Mouth How : ~ our
work?
This is where food enters the bodya nd first gets broken into
more manageable pieces. Saliva is produced in the glands
and starts to break down starch in the food.

Oesophagus Oesophageal - d

The oesophagus passesthe food sphincter

/ into the stomach. At this stage, it This is the control The stomach is one ofthe most crucial
organs within the digestive system
has been broken down through valve for letting food

mastication and saliva will be into the stomach.
breaking down starch.

Corpus body - ....J Thestomach'sfunction is to break down food

This is where stomach into simple molecules before it moves into
the smallintestine where nutrients are
acid iss ituated.
consequently it is absorbed. The organactuallysplitsinto four
where food is broken distinct parts,all ofwhich have different

down into molecules functions. The uppermost sectionis the
that the small intestine cardia, where food isfirst stored, the fundus
can then process.
is the area above the corpus body, which
Mucosa makes up the main area of thestomach

These cells lineal of the where food is mixed withstomachadd. The
final section is the antrum, containing the
stomach toaid rr>Clii<!Oleflt of pyloricsphincter, which is in control of
emptying the stomach contents into the
food throughout the organ.
small intestine. Food is passed down into the

stomach by mucosa and peristalsis through
the oesophagealsphincter, and then mixed

in the stomach withacidsandjuices by

muscle contractions.

Stomach - - - - - ' Duodenum ----, How the
I• ne
This is where food is broken The area at the top ofthe
down tosmaller molecules small intestine, this is
which can then be passed into
where mostchemical
the small intestine. Stomach breakdown occurs.
acid and enzymes produced
by the stomach aid this.

The intestine is a crucial
part ofthe digestive
that is heavilyL .............
involved in breaking
down and absorbing

nutrients released from
ingested food

Rectum The intestinesplitsinto two distinct parts,
the smallintestineand the large intestine.
This is where Thesmall intestine is where the food goes
waste is stored
through final stagesofdigestion and
briefly ll1til it
is expelled by nutrients are absorbed into the bloodstream,
the large intestine is where waste isstored
the body. until expelled through the anus. Both the
smalland large intestinescan be further
Villi
divided into sections, the duodenum,
These cells are shaped like fingers jejunumand ileumare the three distinct

and fine the smaJI intestine to increase sectionsof the smaII intestineand the
cecum, colonand rectum are the sectionsof
Sll'faoe area for nutrient absorption. the large intestine. As wellasstoringwaste,

the large intestine removes water and salt
from the waste beforeit is expelled. Muscle

contractionsand mucosa are essential for the
intestine to work properly,and we seea

variation of mucosa, called villi, presentin

the lower intestine.

061

liver explained

The human liver is the '~ Theliveris the largestinternal organ in The liver Is the body's main powerhouse, producing
ultimate multitasker - •• the h11 rnan bodyandamazingly has over500
different functions. In fact, it is the second andstorlngglucoseasa keyenergysource.ltisalso
it performs many responsible for breakingdown complex fat molecules and
different functions J most complexorganafter the brainand is building them up Into cholesterol and triglycerides. which
the body needs but In excessare bad.The livermakes
allat the same time lnUinslcally involved in almost everyaspect of the body's
withoutyou many complex proteins, Includingclottingfactors which
metabolic processes.The liver's main functions are are vita lin arresting bleeding. Bile, which helps digest fat
even asking in the intestines. is produced In the liverandstored in the
energy production, removal ofharmful substancesand adjacent gallbladder.

the production ofcrucial proteins.These tasksare carried The liveralso playsa l<ey role In detoxifying the blood.

out within livercells, called hepatocytes, which sitIn Waste products, toxins and drugs are processed here into

complexarrangements to maximise their overall

efflclency.

The ::.....__ _ _ _ Eight segments

~"~~reCI•Iignlon :;...- Ftnctionally, ltlere are
eicj1tsegiiiE'IIts cl the
Two halves ------..
a-,IMlichare based
The live- is anatomicaly spit
into two halves: left and right. upon lt1e <istriJution
There are foor lobes, and lhe
right lobe is lt1e largest. aof veins ailling

The gallbladder - - these segllM3Its.

The gatiodder and._
are intrnately related. Bie.
wiOch ~<igest ful, is
pnxb:ed., lt1e IM!r and
stored ., lt1e g;albladde<.

The common bile duct

This duct is smalt but vital in
lt1e tunan body. Itcarries bile
from lt1e iver and gallbladder
into tile duoder<Jm where ~
helps digest fat

Feel your liver

Take a drepbreath in and feel
just under lhe right lower
edge of your ribs- in some
people lhe lower edge of the
liver can be felt. - - - - - -

The portal triad

The common bile duct.
hepatic artery and

hepatic portal vein form
lt1e portal triad, which

are lt1e vital inflows and
outflows fc< this iver.

+--+-....._-+-- The biggest organ - -1, . . - - - - - - - - - - Digestion

The._ istile largestot Once nutrieols from food have
been absorbed.,tilesmal
~-------­lt1e internal organs, sitting in lt1e
intestine, they are transported
right -quadrantoiltleabdomen,
just under lt1e rib cage andattached to to tile ivervia tile hepatic
portal"""'(not shown here)
tile undersideot lt1e <iaplyagm
fc< energy production.

062

STOP 1Ice cold liver 2•••••••••••••••••Uver transplants :••• Maximising numbers :••• Largest organ in the body :••• Greek mythology
Polarbear liver is an incredibly :4 • 5Theliver is the largest internal
FACTS rich sourceol vitarrin A .. In theUK600·700 liver • •• Wtse Trtan Prometheus
somuch sothat Arctic transplants are performed
LIVER explorers haveactually died eachyear.The donorli\ler •3 W<JYSaround theshortageof • organ in the human bodyand in ! waschained foretemity to a
can bepreservedina solution : donor-li'-Ersinclude splitting an
fromeating it, asitcan cause
extreme vitaminA poisoning. for upto24 hours before it : adult liverin hatfand givi'lg itto ! most arWnals' bodiestoo. It ! rock in the Caucasus, where
is transplanted. •••••• • •••••• •••••
two chilli-en, and live.cfonor typ«:ally has the same shapeas an eaglewouldeatat his liver
transplantation (a portion ofa ahuman's, exceptin snakes
relative·s iYeristransplanted}. where i t i s elongated. and eachday the liver would

bereoewed!

ltU•JU•11J!3N•IW The liver con regenerate itself. If up to 75 per cent of the liver is removed. it con grow bock to restore itself

formswhich are easierfor the rest of the body to use or A high demand n
The liver deals witha massive amountofblood. branches from carryingoxygen which
excrete.The liveralso breaksdown old blood cells,
producesantibodies to fight infection and recycles It is unique becauseit has two bloodsupplies. 75 the liver needs to produce this energy.The blood
percentofthis comesdirectly from the
hormones suchasadrenaline. Numerous essential intestines(via the hepatic portal vein) which flows in tiny passages inbetween the livercells
vitamins and minerals are storedin the liver: vitamins A, carries nutrients from digestion, which the liver
where the many metabolicfunctionsoccur.The
D, Eand K, iron and copper. processesand turns into energy.The rest comes
Sucha complexorganis also unfortunately prone to from the heart, via the hepaticarteryIwhich blood then leaves the liver via the hepatic veins

diseases. Cancers (most often metastaticfrom other to flow into the biggestvein in the body- the
sources), infections(hepatitis) and cirrhosis (a form of
fibrosis often caused by excessalcohol consumption)are inferiorvena cava

justsomeofthose which canaffectthe liver.

"The liver also breaks Liver
down old blood cells The functional unitwhich
ond recycles hormones performs the liver's tasks
such os adrenaline"

3. Sinusoids - - - . , The liver is considereda 'chemical factory; asIt

These blood filled forms large complex molecules from smaller
chamels are lined by
1. The lobule ones brought to itfrom the gut via the blood
hepatocytes and provide
This arrangement ofblood stream.The functional unit of the llver Is the
the site oftransferof lobule- these are hexagonal-shaped
vesseis, bile ducts and
molecules between blood hepatocytes form the structurescomprising of blood vessels
and fivercells.

functional unit of the fiver. and sinusoids.Sinusoidsare the

speciallsedareas where blood

2. The hepatocyte comesintocontactwith the
hepatocytes, where the liver's

These highly activecells biological processes take place.

perform all ofthe liver's

key metabolic tasks.

9. Central vein --. 4. Kupffer cells

Blood from sinusoids, now These specialised eel s sit
containing all of its neo.v
within the sinusoids and
molecules, flows into destroy any bacteria which
central veinswhich then
flow into largerhepatic are contaminating blood.

veins. These drain into r - - - 5. Hepatic
the heart via the artery branch
inferior vena cava.
Blood from here supplies

oxygen tohepatocytes and
carries metabolic waste
which the liver extracts.

gal 8. The portal triad - - - 6. Bile duct

Bile,a dark greenslimy liquid, is produced in the The hepatic artery, portal vein and bile duct are known as Bile,wnch helps digest fat, is
hepatocytes and helps to digest fat. It isstored in a the portal triad. These sitat the edges ofthe liver lobule
reservoir whichsits on the under-surfaceof the liver, and are the main entry and exit routes for the liver. made in hepatocytes and
to be used when needed. This reservoir is called the secreted into bile ducts. It then
gallbladder. Stonescan form in the gallbladder
(gallstones)and are very common,a!though most flows into the galllladder for
don't cause problems. In2009,just under 6o,ooo
gallbladders were removed from patients within the ...._,... storage before being
NHS makingitone ofthe most commonoperations secreted into
performed; overgo percentof these are removed via the duodenum.
keyholesurgery. Most patients do very well without
theirgallbladderand don't notice any changesatall. '------ 7. Portal vein

This vein carries nutrient·rich blood
directly from the intestines, which
flows into sinusoids for conversion

into energy within hepatocytes.

063

Structure of the
small intestine

Examine the anatomy of this vital
organ in the human digestive tract

Lumen - --------..

This is the space inside the
small intestine in which the
food travels to be digested ~~-.::=:::;,j
and absorbed.

or1• Mucosal folds- _J Mucosa - - - - - - - -

sma intestine These line the small The internal lining of the
intestine to Increase small intestine where the
Crucial for getting the nutrients we need from the surface area and help plicae circulares (mucosal
food we eat, how does this digestive organ work? push the food on Its way folds) and villi are situated.
by creating a valve-like
structure, stopping food Submucosa - - - - - -
travelling backwards.
This supports the mucosa
and connects it to the layers
of muscle (muscularis) that
make up the exterior of the
small intestine.

The small intestine is one of the turning food intoan amino add state. While - and mucosal folds line the passage and
mostImportant elements ofour the duodenum isvery important in breaJdng increase thesurface area dramatically to aid
digestive system, which enables us food down, using bile and enzymes from the this process. The ileum is the final section of
to process food and absorb gallbladder, liver and pancreas, it is the thesmall bowel and serves to catch nutrients
nutrients. On average, itsits at a little over six shortest element of the small bowel, only that may have been missed, aswell as
metres (19.7 feetllong with a diameter of 2.5-3 averaging about 30 centimetres (tLB inchesl. absorbingvitamin Buand bilesalts.
centimetres (1-1.2inches1, and it's made up of
three distinctive parts: the duodenum. The jejunum follows the duodenum and Its PeristaIsis is the movement used by the small
jejunum and the ileum. primary function is to encourage absorption of intestine to push the food through to the large
The duodenum connects thesmall intestine carbohydratesand proteins bypassingthe bowel. where waste matter is stored for a short
to the stomach and is the key place for further broken-down food molecules through an area period then disposed of via the colon.This
enzyme breakdown, follow! ng the stomach with a large surfacearea so they can enter the process isgenerated bya seriesofmuscles
bloodstream. Villi - small finger-like structures which make up the organ'souter wall.

064

THE 6mLENGTH DIAMETER 2.5•3cm tg.wA1JsT~~682° 1-4 hours
STATS
suRX~f~ 250m2 ~~Yfi.JT0As~<6~ttloN 90°/o ~~~~A~~~1 10-40
SMALL BOWEL

I•U•JW•1!113N•l!i'i> The small intestine is actually Ianger th:Jn the large intestine, but is sa called because af its mrrawer diameter

Serosa What exactly are nutrients?

This protective outer layer stops There are three main typesof nutrient that we process in the
the small intestine from being body: lipids (fats), carbohydrates and proteins. These three
damaged by other organs. groups ofmolecules are broken down into sugars, starches,
fats and smaller, simpler molecule elements, which we can
absorb through the small intestine walls and that then travel in

the bloodstream to our muscles and other areas of the body

that require energy or to be repaired. We also need to consume
and absorb vitamins and minerals that we can't synthesise
within the body, eg vitamin 812 (prevalent in meat and fish).

Fat Carbohydrate

I

Protein

Nutrients Blood vessels

Nutrients move through These sit close to the
small intestine to
the tube-like organ to be allow easy diffusion
diffused into the body,
of nutrients into the
mainly via the bloodstream. bloodstream.

Villi A closer look at villi

Villi are tiny finger·like What role do these little f inger-like
structures that sit all over prot rusions play in the bowel ?
the mucosa They help
_j t..________ Longit udinal Ep i t h eli um Lacteal
increase the surface area (epithelial cells)
muscle layer Mucosa The lacteal i.s a
massively, alongside the These individual cells that lymphatic capillary
This contracts and extends mucosal folds. The lining of the small
sit in the mucosa layer intestine on which that absorbs nutrients
Ci r cu lar to help transport food with villi are located.
muscle layer the circular muscle layer. are where individual that can' t pass directly
into the bloodstream.
microvilli extend from.

This works in partnership

with the longitudinal

muscle layer to push the

food down via a process

called peristalsis.

M icrovilli - - - - - ,

These are a mini version
of villi and sit on villi's
individual epithelial cells.

Capillary bed

These absorb simple
sugars and amino acids as
they pass through the
epithelial tissue of the villi.

065

Inside the thoracic cavity

It may not look like it at first glance,
but there are more than two dozen
bones that make up the ribcage...

,.. ..

Clavicle - - - - J

Also known as the
collarbone, this pair of
long bones Is a support
between the sternum
and the shoulder blades.

True ribs ----~
Rib pairs one through

seven attach to the
sternum directly via

a piece of cartilage.

uman False ribs ----.~

r1• Rib pairs eight through
ten connect to the
Ribs are not merelyarmour for the organs sternum via a structure
inside our torsos, as we reveal here... made of cartilage linked
to the seventh true rib.

.=a-' The ribcage-also known as the rather, most of them do. Rib pairs one through
• • thoracic cage or thoracic bas.ket- is seven are called ' true ribs' because they attach
directly to the sternum. Rib pairs eight tnrough
... easily thought ofas justa ten attach indirectly through other carti!age
framework protecting your lungs, structures, so they're referred to as 'false ribs'.
The final two pairs - the 'floatingribs'- hang
heart and other majororgans. Although that is unattached to the sternum.

one key function, the ribcage doesso much Rib fractures area common and very painful What are hiccups?
injury, with the middle ribs the most likely
more. It provides vital supportas part of the ones toget broken.A fractured rib can be very Hoccupping - known medically as singultus, or
dangerous, because a sharp piece could pierce
skeleton and, simply put, breathing wouldn't the heart or lungs.There'salso a condition synchronous doaphragmatic flutter (SOF) - is an
called flail chest. in which several ribs break
be possible without it. and detach from the cage, which can even be involuntary spasm of the diaphragm that can
fatal. Butotherwise there's not much you ca n
All this means that the ribcage has to be do to mend a fractured rib other than keep It happen for a number of reasons. Short·term
stabilised, resting and giving it time to heal.
flexible. The conical structure isn't just a rigid causes include eating or drinking too quickly, a

sudden change in body temperature or shock.

system ofbone- it's both bone and cartilage. However, some resear have suggested

The cage comprises 24 ribs, joining In the bac.k that hiccupping in premature babies -who tend

to the 12vertebrae making up the middle ofthe to hiccup much more than fuft·term babies - is

due to their underdeve lungs. It could be an

spinal column. The cartilage portionsofthe evolutionary leftover, since hiccupping in humans

ribs meet In the front at the long, flat three- is simolar to the way that amphibians gulp water

bone plate called the sternum (breastbone). Or and aor into their golls to breathe.

066

2 :3 : 4 5••••••••••••••••• •• •• •••••••••
Sunken chest Tasty ribs
STOP l inF1exible cage Endless ribs :• Fractures :• :
normalad<Jits, the ribcage Pectusexcavaturntsa lar-ge carniVores, suchaslions,.
FACTS expandsby three to five Snakes can have up to 400 Thesewnthand the tenth ribs : •••••• often head towards the
vertebrae, withal but the tail ! are theones most likelytoget congenital deforrrity caused by ribcages oftheir kills first to
RIBCAGE TRIVIA centimetres (L2 to two inches) Vl!rtebrae havW1g apar ofribs. •••••••• •••••••• aboormalgrowth of the ri>cage,
Each rib is attached to a belly broken in humans, while the resufting ina caved-in dwoor both the rib meat and
when you lnhale. ln anaverage scale which Isa keypart of fii'St pair israrely fractl.l'ed rich organs, like the heart,
haYti snakes slither. becatJse of Its location behind appearance thatcan also affect which ar'E! encased within.
breath at rest.~take Inabout thedavide. the heartand lungs.
500 mil61itros (0.9 p;nts) of air.

ltU•JU•11J!3N•IW The condition known os flail chest is fotol in almost so per cent of cases

, - - - - - - - - - - - - - - - - - - - Manubrium Breathe in,
breathe out...
This broadest and thickest part
of the sternum connects with Consciously take in a breath, and think about the
the clavicles and the cartilage fact that there are t en different muscle groups
for the first pair of ribs. working together to make it happen. The
muscles that move the ribcage itself are the
... intercostal muscles. They are each attached to
the ribs and run between them. As you inhale,
'------"'-'-"...:..,..:;_----:__;,~-'---- Sternal angle the external intercostals raise the ribs and
sternum so your lungs can expand, while your
This is the angle formed by diaphragm lowers and flattens. The internal
the joint between the intercostals lower the ribcage when you exhale.
This forces the lungs t o compress and release air
manubrium and the body, (working in tandem with seven other muscles). If
often used as a sort of you breathe out gently, it's a passive process
that doesn't require much ribcage movement.
'landmark' by physicians.
Inhalation Contraction

As you inhale, the The diaphragm contracts by
intercostal muscles
contract to expand moving downward, allowing
and lift the ribcage.
the lungs to fill with air.

Body

The main body of the
sternum (breastbone) is

almost flat, with three
ridges running across its
surface and cavities for the
cartilage attaching to rib
pairs three through seven.

Xiphoid process .,__ _ _ Floating ribs
(not shown)
This exten.sion from the
sternum starts as cartilage, Pairs 11-12 are only attached
to the vertebrae, not the
but hardens to bone and
fuses to the rest of the sternum, so are often called
breastbone in adulthood. the floating, or free, ribs.

Ribs in other animals

Most vertebrates (ie animals with ribs overlap one another with hook·like Exhalation Relaxation
structures called uncinate processes,
backbones) have a ribcage of sorts - which add strength. Frogs don't The intercostal muscles The diaphragm relaxes,
have any ribs, while turtles' eight rib relax as we exhale,
however, ribcages can be very compressing and moving upward to force
pairs are fused to the shell. A snake's lowering the ribcage.
different depending on the creature. air out of the lungs.
For example, dogs and cats have 13 'ribcage', meanwhile, runs the length
pairs of ribs as opposed to our 12. of its body and can comprise hundreds
Marsupials have fewer ribs than of pairs of ribs. Despite the variations
in appearance, ribcages all serve the
humans, and some ofthose are so tiny
they aren't much more than knobs of same basic functions for the
bone sticking outfrom the vertebrae. most part: to provide support and
protection to the rest of the body.
Once you get into other vertebrat es,
the differences are even greater. Birds'

067

e pancreas up-close

KEY 336 BCE 1st century CE 1642

DATES The GrC!<'k Matornist The name 'pancnas' is giwn, The pancreaticduet Is Gemlan scientists l't'l'l"'IYe TheflfSt l'r'lOdem hl.l'nan
wl1ow~l fH'SI diSCCM!I' rnerilg 'all fle-sh',as it's panaeatic transplant Is
PANCREATIC PAST found In Padua, Italy. It Is thepancreas In a dog and perfonned in theUSAon a
thepancroas - believed to......., solely as a
nam<!d aile< ~• discolle<er: induce diabetes, proving 28-year-old female patlert.
Ho<ophllus -Is bam. cushioning, protective fatpad.
the clJct ofWOsun!l. an iiTOiutilblclink.

l•U.1\1•li i :'W•mJP In the UK. Bo per cent of acute pancreatitis cases ore caused by gallstones or excessive alcohol ingestion

What brings on diabetes?

Diabetes is a condition where a other disorders of the pancreas.
person has higher blood sugar than Inflammation of the organ (ie acute
normal. It is either caused by a pancreatitis) causes severe pain in
failure of the pancreas to produce the upper abdomen, forcing most
people to attend the emergency
insulin (ie type 1, or insulin· department as it can be life
threatening. In contrast. cancer of
dependent diabetes mellitus), or the pancreas causes gradually
worsening pain which can often be
resistance ofthe body's cells to mistaken for otherailments.
insulin present in the circulation (ie

type 2, or non-insulin-dependent

diabetes mellitus). There are also

Beta cells Insulin released

It is the beta cells The vesicle releases its
within the islets of stored insulin into the
langerhans which blood capillaries
control glucose tlvough exocytosis.
levels and amount
of insulin secretion.

High glucos e Calcium

When the levels of effects
glucose within the
bloodstream are high. The calcium
the glucose wants to
move down i ts diffusion causes the
gradient Into the cells. vesicles that

store insulin to
move towards

the cell wall.

Does the vary in

humans and animals?

Every vertebrate animal has a pancreas of some form, GLUT2 De polarisation '--- Calcium channels

meaning they are all susceptible to diabetes too. The This is a glucose· The metabolism of glucose Changes in potassium
arrangement, however, varies from a-eature to creature. In transporting channel,
humans, the pancreas is most often a single structure that sits which facilitates the leads to changes in the levels cause voltage-gated
at the back of the abdomen. In other animals, the arrangement uptake of glucose
into the cells. polarity of the cell wall calcium channels to open in
varies from two or three masses of tissue scattered around
and an increase in the the cell wall, and calcium
the abdomen, to tissue interspersed within the connective
tissue between the bowels, to small collections of tissue within number of potassium ions. ions to flow into the cell.
the bowel mucosal wall itself. One of the other key differences
is the number of ducts that connect the pancreas to the bowel.

In most humans there's only one duct. but occasionally there

may be two or three - and sometimes even more. In other
animals, the number Is much more variable. However, the

function is largely similar, where the pancreas secretes

digestive enzymes and hormones to control blood sugar levels.

human bladder THE COMPLETE

Wbenyou'vegot to URINARY SYSTEM
go, you'vegot togo...
but reaUy ourbodies Kidneys
are reactln& toour
Thekicftys
bladders' direction un...........-ded
substances in the
blood into urine.

Ureters

Uretencany
urlnefrcm
the kicftys to

the bladder.

Urethra

Thelfttlnruns
frcm the bottom
olthebladderto
theoutsidewor1d.

I

As a key part ofthe urinary system, the bladder Bladder

is crucial to removingwaste from your body This muscular
bag generaly
The bladderlsoneofthe keyorgansln the urinary the bladder becomesfull, or nearly lull, the nerves in the
holds around a
systemand Itstores urine following productlon by bladdercommunicatewith the brain, which In turn Inducesan pintof urine.
the lddneysuntll the bodycan release lt. urge to urinate. Thissensation will getstronger Ifyou do not go
- creating the 'burstinglor a wee' feeling thatyou can
Urine Is awastesubstance produced by the occasionallyexperience. When ready to urinate, both the
kidneys as they filter our bloodof toxins and other unneeded
internaland externalsphincters relax and the detrusor muscles
elements. Up to150 lltres (40 gallons} of bloodare filtered perday in the bladder wall contractin order to generate pressure,
byyour kidneys, butonlyaround two litres (0.5 gallons} ofwaste forcing urine to pass down the urethra and exit the body.
actually passdown the ureters to the bladder.
Aswell as telling you when you need to pass fluid, the urinary
Urine travels down the ureters and through the ureter valves, systemalso helps to maintain the mJnera land salt balance In
which attach each tube to theorganand preventany llquid
your body. For instance, when saltsand minerals are too highly
passing back.The bladder walls, controlled by the detrusor concentrated, you feel thirst to regain the balance.
muscles, relax as urineentersandallow the organ to Hll. When

For the bladderto work correctly, urlnewithoutcontrol Itis oftencaused pressure(eg while coughing.laughing
by involuntaryspasmsby the detrusor
severalareas withinIt must all functlon orsneeztng). Thlsklndoflncontlnence
properly. It is most commonly the muscles which can bea result ofeither is most commonin the elderly.
failure ofoneofthese features that nervous system problemsorinfections.
leads to incontinence. One modem remedy Isa preventative
Another type isstress incontinence, implant that has beendeveloped to
Acommon type ofurinary replace post-eventIncontinence pads.
incontinence Is urge incontinence.ThIs caused when the externalsphincteror
is when an indlvidual feels asudden This comesin the form ofa collagen-
compulsion to urinate and will release pelvicfloor musclesare damaged. Tbis basedsubstanceInjectedaround the
means urine canaccidentally escape, urethra in order to support it.
especiallyifthe pelvic Dooris under

070

STOP Urethras- all the same? •••••• Getting the urge •••••• Duration •••••• Can you drink urine? •••••• How to keep healthy
1 2Women's urethrasare much : 3 4Urine can stay in the bladder- : Of course,thiswould not
FACTS ! The urge. tourinate normally ; 5 It's advised to drink around1-1.5

B DERS shorter than men's due to ; comes whenthe bladder ; for anywhere betweenone to ; generaDy berecommended in ; litres (2.1-3.1 pints)o f water a
differing genitalia. Women ate: •••••••• •••••••
consequently far more likely to ••••••• reachesbetween 25-50% of eTvaiMgryhttdmheo:epuoirtostdbeiemnfgoaroi-nensethtxhceeraermetiowonuil.lnt:•••• oonnal circumstances, but day. Thiswill keep the urinary
yes, urine is completely sterile system working mosteffectively.
get bladder/urine Infections full volume toavoid reaching of liquid consumed.
becaLJSe of this. - itcontains no bacteria, We k>se more water than this
100%when lni/Oiuntary virusesor fungi.
but obtain some from food.
urination will occur.

I•U•JU•111!3N•IW Everyone's bladder differs slightly in size. The overage maximum copodty is between 6oo-Booml [1-3-l.lPt]

Inside the bladder Bla~~ •IS

How this argon acts as the middleman muscles) • 1nade
between your kidneys and excretion
The detrusor muscles up of?
FULL 1+ - - - - - - Ureters - - - - - -- .: make up a layer ofthe
Ahuman bladder usually holds around
BLADDER These tubes link thekidneys bladder wall. These 350millilitres(0.7 pints) ofurine, though
male bladders can typically holdslightly
Ureter valves and the bladder, transporting musclescause the wall more than those offemales. Urine is
the urine for disposaL to relax and extend as made up of urea, the waste by-product
These sit at the end of the bodyformswhile breakingdown
the ureters and let urine enters, while proteinacross the body. The kidneys will
urine pass into the filter this outand pass it with extra water
nerves situated in the to the bladderforexpulsion. Other waste
b ladderw ithout letting wall m easure how full products producedorconsumed by the
the bladder is and will body that pass through the kidneys will
it flow back. alsoexltthe bodyvia thisroute.
signal to the brain 1}'plcally, urine is made up of95 percent
water and 5percent dissolved or
when to urinate. suspendedsolids Including urea, plus
chloride, sodiumand potassiumions.
Pelvic floor muscles ----. --~"'---- Internal
URINE
These hold the b ladder in place, Lrethral sphincter
CONTENTS
and sit arOlBld the urethra The internal sphincter is
stopping unintended urination. controlled by the body. It Uric acid
0.6g ---.
stays dosed to stopurine
passing out of the body. Bicarbonate

External urethral
sphincter

(distal sPhincter)

This sphincter is controlled
by the individual, and they
control w hether to open or

close the valve.

EMPTYING Pd •sim ions

BLADDER 3.2g

Internal urethral ---~~;;.::5~~:;:]~ &~~+--- Bladder wall Sodium ions
sphincter
(~~ 4.lg
This relaxes when the
muscles) 01loride ions
body isready to expel 6.6g
These musclescontract
Urea
toforce the urineout
25.5g
of the bladder.

the waste liquid.

~~!~thrai ------J ,·;~t'+"-.----------- Urethra

~stal sphincter) Urine travels down this
passagewayto leave the body.
Thisalso relaxes for the urine

to ex~ the body.

071

uman pregnancy explained

Nin.e months of change and growthPregnancyIsa unique pe.rlod Ina woman'slife thatbringsaboutphysicaland

- . emotional changes. When Itoccurs, there!sanIntricatechange inthe balanceof

a the oestrogenand progesterone hormones, which causesthe cessationof
~ menstruallon and allows the conditions In the uterus (womb) to becomesuitable
for the growth of the fetus. The lining ofthe uterus, rather than beingdischarged, thickens
and enables the development of the baby.
At first, it!sa collecllon ofembryoniccells no bigger than a pinhead. Byweek four the
embryo formsthe brain, spinal cord and heartlnsldethe newlyOuid-filledamnloticsac.
Protected by this cushion offluid, It becomes recognlsably human and enters the fetal stage
by week eight.
Many demands are puton the mother's bodyand she Is IU<ely to experiencesickness,
tiredness, lower-back pain, heartbu rn,lncreased appetite and muscle cramps, as well as the
enlargementof her breastsa nd stretch marks.Her bloodsugar levels, heart rate and
breathingalso increase to cope with the growing demands of the fetus.
As the date of labourapproaches, the mother feels suddencontractions known as
Braxton-Hicks, and the neck ofher uterus begins to softenand thin out. Meanwhile, the lungs
of the fetus fill withsurfactant.Thissubstanceenables the lungs to soften, making them able
to inflate when it takes itsfirst breathofair. Finally, chemicalsignalsfrom the fetus trigger the
uterus to go into labour.

"Many demands ore put on the

mother's body and she is likely to

experience sickness and cramps"

ARST TRIMESTER (0-12 weeks)

This beginsafter the last menstrual period, when an egg is Thefetusgrows rapidly and Its organs Hair and teeth
released and fertilised. It takesabout nine weeks for the
resulting embryo to develop Into a fetus. During this period, mature. By week zo its movements can At16weeks,fine hair
the motherwill be prone to sick ness and mood swings due to (lanugo) grows """"the
hormonal changes. befelt. Atweek 2.4 it cansuck Its thumb fetal body. By 20 weeks,
and hiccup, and can llve Independently
oflhe mother with medical support. teeth startforming inthe

Head Heart jawand hairgrows.

Face begins to AI the internal Movement

look t.Jman and organs are By week 16 the eyes
the br.lin is can move and the
developing 131>idly. fonned and the whole fetusmakes

heart is able to vigorous movements.
pump blood
Sol.l1d and light
around its body.
The fetus will respond
Weight Length I Weight to light and is able to
I
~ lOg 5.San I Week 16: l40g hear sounds such as
I Week 20:340g the mother's voice.
072 I
I Length Vernix
I
I Week 16: l8cm 8y20weeks,
I Week 20: 25em
I this white. waxy

I substa""'
I covers the siOO,
I
I protec:mg it
I from the
I
I a •~•lioticfluid.
I
Sweating
:
An increase in
I blood ciraJiation
causes mJtltetto

sweat more.

HEAD2 MENONLY 1. Seahorses ED:mt----=-., 2. Komocto 3. Spotted hyenas
HEAD dragons
·.~,~ - ~ ' · . '.~~~ The female seahorse female komodo dragons Female spotted hyenas have
ANIMAL can gfve birth to male
deposits her eggs In the babies without fertilisation • genitalia like a penis. It
PREGNANCIES stretches toaIbN the Insertion
pouch of the male sealhors:e. from a male partner. This Is ofthe male penis during
known as parthe~is.
He fertilises the egQS and copulation. and sttetches again
when giving birth through it.
·1 carr'ies them f()( the full
tetm of threeweeks.

ltU•JU•11J!3N•IW 200 extra calories o doy ore needed in mid-pregnancy, which is 10 per cent more than the usual

place11la Wharton's jelly

The placentais an essential interface between The umbilical blood wssels arecoated with

the mother and fetus. When mature itisa 22cm this jely~ike substance and protected by a

diameter, flatovalshape with a2.5cm bulge in .tough yet flexibleouter membrane.
the centre.The three intertwined blood ~
vessels from the cord radiate from the centre
to the edges ofthe placenta. Like tree roots,
thesevillousstructures penetrate the

placenta and link to15to 20 lobes on
the maternalsurface.

The five major functions ofthe

placenta deal with respiration, •
nutrition, excretionofwaste
products, bacterial protection
and the productionof hormones.

Placenta body- - - --+

Is firmly attached to the inside

of the mother's uterus.

Maternal su-face ---~r

Blood from the mother is absorbed and

transferred to the fetal surfaoe.

Fetal surface ----------

Blood vessels radiate out from the umbilical

oord and penetrate the placenta. The surface

is covened with thethin amnion membrane.

Umbilical cord - - - - - - - - - - -

Consists of three blood wssels. Twocarry carbon

dioxide and waste from the fetus, the other supplies -

mcygen and nutrients from the mother. CSctencePhotoLibrary

Breathlessness Movement THIRD TRIMESTER (28-40 weeks) "The three
intertwined
The increased size of the By the 28th week, Now almostat full term, the fetus can recognise and blood vessels
respond to soundsand changes in light. Fat begins
fetus by 24weeks due to less room in to be stored under the skinand the lungs are the radiate from
causes compression of uterus, the fetus wiJ very lastorgans to mature.
rib cage and diSC<lfllfort the centre to
for mother. wriggle if it feels the edges of
the plancenta"
Week24 uncomfortable.
Under pressure
W eig h t Hands 1
Pressure on the diaphragm and
Week 24:650g The fetus can move other organs causes indigestion
and heartblrn in the mother. She
Week 28: 1,250g itshandsto touch
its 001bilical cord at will find it diffiCUlt to eata lot.
Length
24weeks. Position
Week 24 : 34cm
Position Head positions itselfdownwards,
Week 28: 38cm in preparation for labour.
By 28 weeks, the
Sleep patterns
uterus has risen to a
position between Fetus wiDsleep and wake in

the nawland the 20-minute cycles.

breastbone. 073
'''''''''''''Head
'Thehead I'
Weight
can move I

at 28weeks t l ,SOOg
and the eyes I
t
can open t Length

and see. t 41cm



Discover how a fertilised egg transforms into
an embryo and eventually a new human being

After fertilisation, the single-celled zygote splits cells, orouter coat, will become, among other thl ngs, the

into two, then the two cells double to four, fourto placenta that nourishes the baby; the Inner cells, known as
eightand so on.Thejourneyalong the Fallopian the inner cell mass, wUJ become the foetus Itself. On contact,
tube is quite slow, while growth continues. On its the blastocyst burrowsinto the uterine wall for nourishment;
way, the zygote divides to mal<e a clump ofJzcells, known as this process is known as implantation. Blastocyst formation
the morulastage. lfthe early embryo splits Into two clumps usually occurs on the fifth day after fertilisation.

before this, it may develop into Identicaltwins. Every cell In The embryonicstage begins in the fifth week. From weeks
the morula could still become part of the growing embryo. live to eight, development is rapid. Major bodyorgans and
systems, including the brain, lungs, liverand stomach, will
By the time the womb cavity Is reached, the cell cluster begin to emerge. At this time, the first bone cells will also
becomes hollow and Hlled with fluid; It Is now referred to as
appear. By the endof the eighth week, the embryo Is known
the blastocyst. Ablastocyst is an embryo that has developed to as a foetus and increasingly looks likea mini human.
the stage where it has two different cell types: the surface

Fertilisation and IVF explained

Natural fertlllsatlon takes place via sexual wbere It Implants into tbe uterine lining. Invitro Ovulated egg
lntercourse.Anegg,orovum, isreleased byan fertilisation (JVFIIsa form of assisted reproductive
ovaryand Is fertilised bya sperm. Fertilisation technology, wbere tbe sperm nucleus Is combined ,....,spenn eels...,

occurswben tbe sperm and esg unite In one of the wlthanesgcelllna lab. Tbe resultanternbfYOis c:herricalyatb3c:ted tothe
manuallyIntroduced to tbe uterus, wbereIt egg and attach thernseM!s
female's Fallopian tubes. Tbe fertilised egg, known develops In tbe samewayasa naturalconception.
in an attorrc>t tobreak
asa single-relied zygote, then travels to the uterus,
~theouter mat.
Uterus (womb)
Ovary - - - - ,
,...., whole process from ejaculation to
A "'""""" LISualiy has twotubes and
fertiisation can -less than an hour. ~a two ovaries, one eitherside of her

woman has an iM!r'age 28-daymenstrual uterus. Every month one of the
ovaries releases an egg. which
cycle, fertiisation is ocx.nted ashaving - n passes slowly along its Falopian

place around day 14, not on day one. tube towards the womb.

Fertilised egg _ __, Fallopian tube

Only one spenn wil be If a woman has sexual
successftt,...., egg wit
then lose its atlJitdi<Y, intercourse during the
harden its outersl-d and
the- 5j)el'tTIwillet days of her moo ol!llycycle,
go. If eggs..., not
fertiised witm 12 hours just ~ore"' afteran egg
ol release, they die.
has been relNsed from
the CNatY. a spenn cell
from herpartner cooJd

lriO\Iel to the Fa~c!>ian tube
and fertilise the ovum.

In vitro ('k1 glass') Spenn

IVf is the pooa55 by-..hcheggs are o..ing sexual~ millions ol spenn are
ejarulated into thevagina. with O<lly ~
remo....d from the ovaries and milced suviving to make thejourney to meet the egg.
with sperm in a labooaiOIy culble dish.
fe tiisa6uoI talces place .. INsdish.

074

f.U•JtJ•l!lltW•lfi!ii> In zoog, almost two per cent of oil oobies born in the UK were conceived as o result of IVF

075

human stomach

Discover how this amazing digestive organ stretches, churns and holds
corrosive acid to break down our food, all without getting damaged

Thestomach's major role is as a the rugae flatten, allowing the stomach to cells (G-cells} to make the hormone gastrin,
reservoir lor food; it allows large expand, and the outer muscles relax.The which encourages even more acid production.
meals to be consumed In one sitting stomach can accommodate about a litre (1.8
before being gradually emptied into pints} offood without discomfort. The stomach empties its contents into the
the small intestine. Acombi nation ofacid, sma ll intestine through the pyloricsphincter.
protein-digesting enzymes and vigorous The expansion ofthe stomach activates Liqu ids pass through the sphincter easily, but
churning action breaks the s tomach conte nts stretch receptors, which trigger nerve solids must be s maller than one to two
down into an easier-to-process liquid form, signalling that results in increased acid mi ll!metres (0.04·0.o8 inches} in diameter
preparing food lor absorption in the bowels. production and powerful muscle contractions before they wi ll fit. Anything larger is 'refluxed'
In its resting s tate, the stomach is contracted to mix and churn the contents. Gastric acid backwards into the rna in chamber for further
and the internal surface of the organ folds into causes proteins in the food to unravel, allowing churningand enzymatic breakdown. lttakes
characteristic ridges, or rugae. When we start access by the enzyme pepsin, which breaks about two hours for halfa meal to pass into the
eating, however, the stomach begins to distend; down protein.The presence of partially small intestine and the process isgenerally
digested proteinsstimulates enteroendocrine complete within lour to five hours.

Lining under the microscope Chief cell (yellow)
Qjefeels mal<epepsmgen; at the low pH
The stomach is much more than just a storage bag.
Take a look at its complex microanatomy now... "'the stomach it becooleS the digestille
enzyme~ wnchdea:>nsiJUc:ts .,..._...... ..
Gastric pits - - - - - - - - ---.
. - - - - - - - - - - - - - Mucous cell
The entre ...-faceofthe
Thesecellsseaete-.e
stomach is~"' my rrucus to protectthe

holes,wiW::h lead to the stomach fining from damage

glands that prodJoe nu:us. by stolooach acid.

acid and enzymes.

Mucosa - - - - - - - - G-cell (pink)
Submucosa - {
Also known as
enteroendocrine cells,

these produce hormones
li<e gastrin, which regulate

acid production and

stomach contraction.

These cells prodJoe hldoc:hloric Muscle layers

acid. .....nich kils off onicro- The stomachhasthree layers

organisms.I-IY<M!Is protei'os and ol rn..oscle llnling "' o:ifferent
activates digestive enzymes. orientalioos.These produce

the C<Hlrdmted contraction

requi'ed to mix food.

076

I•U•JW•1!113N•IW Stomach rumbling, also known as borborygmus, is actually the noise of air movement 1n the intestines

Gastric anatomy ~-------- Fundus
The topportico I of the
This major organ in the digestive system has several distinct
stomach Q.I'Ve5upa:ld
regions with different functions, as we highlight here alowsgases created
dfilg tigestiol I to

be collected.

Pyloric sphincter Cardia - - - - - - -

The pyloric sphinot..- is a strong The oesophagusempties into
nng ofmuscle that regulates the the stomach at the cardia. This
passage of food from the region makeslots ofmucus,
stomach to the bowels. but ittle acid orenzymes.

Ant rum - - - ----.,

The antnm cootains cells that
can stim uJate or shutoff acid
prodJction, regulating the pH
level of the stomach.

'------- Body

Alsocalled the corpus, this
is the largest part of the

stomach and is respoosi:>le
for stomg food as gastric
juicesare i1trodJced.

Small intest ine -...J Panc reas ~- Large intestine

The stomach empties into The bottom of the stomach The large intestine curts
the fi'S! section of the smaU Is located In front of the around and rests just below
intestine: the duodenum. pancreas, although the two the stomach in the abdomen.
aren't directly connected.
Vomit reflex
Why doesn't it Produced by parietal step-by-step

digest itself? cells in the stomach Vomiting is the forceful expulsion
lining, gastric acid has a
Your stomach i.s full of corrosive acid and pH level of L5 to of the stomach contents up the
enzymes capable of breaking down protein - if oesophagus and out of the mouth.
left unprotected the stomach lining would
quickly be destroyed. To prevent this from It's the result of three co-ordinated
stages. First, a deep breath is
occurring, the cells linlng the stomach wall
drawn and the body closes the
produce carbohydrate-rich mucus, which form.s glottis, covering the entrance to
the lung.s. The diaphragm then
a slippery, gel-like barrier. The mucus contains contracts, lowering pressure in the
thorax toopen up the oesophagus.
bicarbonate, which is alkaline and buffers the pH At the same time, the muscles of
at the surface of the stomach lining, preventing the abdominal wall contract,
damage by acid. For added protection, the which squeezes the stomach. The

protein-digesting enzyme pepsin is created from combined shifts in pressure both

a zymogen (the enzyme in its inactive form)- inside and outside the stomach

pepsinogen; it only becomes active when it forces any contents upwards.
comes into contact with acid, a safe distance
away from the cells that manufacture it. 077

ur heart

1. The blocked artery _.....,;._ _,

Angioplasty is a cutting-edge Fatty plaques can block any of

the four main arteries that fe«<

meaical procedure that helps the heart. leading to pain.

your heart last longer 2 Access _ _ _ _ _ _ _ _~...-.-;.._______,

Your heart pumps blood-rich oxygen Guidewires are fed irto these arteries via the small )
to your body's tissues- but the heart arteriesin thegroinorwrist. Even ~ the patient is
muscle needs oxygen Itself. The ;make. they don't feel itasa local anaestlletic is 9ven,
coronaryarteries are small vessels
lining your heart'ssurface that do this job S. Up dose

perfectly,in exactsynchronlsallonwith the beats Hi!jl blood pres.sue leads to~ spots of damageonartery
wals. These w* fill with cells, inc:luOOg fatty lipid eels. It is

ofthe heart. However, they can become blocked. A the COO'tlinationsof al of these cells that lead to a fbosis.
lack ofexercise,smoking. poordletand unlucky
stiff plaqooe that narrows and thenblocks the artery.

genes canall lead to plaquesoffatty tissue. called

atheroma, blockingthesevitalanertes.Then,If

your heart needs to pump harder. suchas during

exercise, the reduced blood Row cannotsupply

enough oxygen.This leads to pain -angina -

which is an early warningsign that the heart

muscle is dying. Previously, the onlyway to cure

advanced cases was to go under the surgeon's

knife. However, cardiacsurgery Isa risky

procedure.Thenalong cameangloplasty.

Viaa small artery in the patient'sgroin or wrist,

doctors Insertaguide wire directly Into the

coronaryarteries ofthe heart. This Is tricky,and

so they use rea l-time X-ray images to guide them

to exactly the right place.They feed a tiny. thin,

flexible hollow tube over this wire (a catheter).

Injecting dye into these arteries (via the hollow

catheters)and looking carefullyat the resu It

shows them exactlywhere the blockagesare.

Next, they inflate tiny balloonsattached to the end

ofthese long cathetersat the exactspotofthe The
blockage.lnsomecases, this Is enough.ln others,
to prevent thearterydoslngagaln,a stentcan be

placed through the affected area. Theseare clever Angioplasty is one ofthe most commonly
performed medical procedures around
stentsand cancontain drugs that prevent them the world - there's a good chance that you
blocking. A6nal check X-ray completes the know someone who's had one. However,
angioplasty process. the procedurestill requires a lot of
technical skill and a steady hand. Even in
Angioplasties like this canalso be performed
the best hands there are risks and
on blockedarteriesIn the legs, where the complications, but most people get good
principle is exactly the same. But no matter results from it
where the blockageis, this procedure requires a
steady hand and a doctor who can think fastand
think in real-timeJOwhlle looklngat2D

black-and-white Images.

078

1Drug eluting 2!•••••• No napping ••• • 4All the•••••••••••••••• way up? •••••• Lasers
The mostmodem stents that
are used in angioplasty lnthemodem era, High tech all the way Althoughan angbplastyis : 5 Recentangioplasty·
proceduresaren'tjust bare mainly usedonooronary
: angioplasty patients stay 3 Once the ballooring and arteries, therearesome : related te<::Mological
metalsomealsosecretedrugs stentingisdone. the tech doctors trialingangioplasty for
overtime, which work to ••••••• awakeduring the entire doesn't stop.Thereare devices •••••••developmentsinclJde using
prevent a blockage. procedure, as itis now to closeholes madein thegroin narrowed arteries thatfeed lasersat the eod ofthe
performedwith thepatient or wrist arteriestostop them blood to thebrain
under localanaesthetic. catheters to bum awaythe
getting bigger. offending plaques.

ltU•JU•11J!3N•IW Emergency ongiop/osty is the best treatment for acute heart attacks

3. X-rays

Under real·time X·ray
image guidance, the

guidewires and catheters
are fed through the maja-

arteries and then into the
tiny coronary arteries.

lr~'-'-;;---=--;;;;;~~---~ 4. The blockage

Using dyes, the X·raysshow
the doctors where the exact
blockages are, and then the

catheters are introduced
t hrough thesenarrowings.

6. Widening the gap From a

The stent is placed through the horsetotM

blockage, and then expanded whole

within it. This is all done under The firsta ngioplasty ofthe heart was carriedout
X·ray guidance so it's in exactly in the18thCentury ona horse. It took a while to

the right positio n. perfect!tforhumans, and in1929 the first
angioplasty ona person's heart was performed
7. The stent
in Germany. Over the next3oyearsasmall
Onoe the stent isfully number ofdoctors pioneered the angioplasty
expanded, the catheterholding
it is removed, leaving it in place intoa diagnosticand therapeutic technique.
While in theSixtiesandSeventiesopen heart
to prevent reblockage. surgerybecameestablished, intheSeventies
and Eightiesangioplastystarted to take overas a
r-- - - 8. Increased flow lowerrisk butequally effective treatment.

Naw the artery is wider, more Astonishingly, In the late-Nineties, over1million
angioplasties were performed worldwide,
blood flows. delivering vital making it oneofthe most common medical
oxygen to the heart muscle and procedureson the planet.

preventing the pain ofangina.

catheter

The ballooncatheteris oneofthe key piecesofthe angioplasty
doctor's equipment. Once the guidewire is inserted, the catheteris
fed overitand floated into exactlythe right place.Through this
catheter,special dyes thatcan be seen onX-rayimages(radio-opaque
contrastdye) can be injected through the hollow catheter to confirm
its position and then confirm the locationofthe blockages.

At the tip of the catheterisa balloon. Usingwater, this balloon can
beinflatedfrom outside to precise pressures. When this is done from
the centre of the blockage, the atheromatous plaque is expanded to
allow more bloodflow. There are many different sizesofcatheterand
widths ofballoons,allowing exact tailoring to the patient's needs.
Sometimes the doctorwillstart with a small balloon when the
blockageis very narrow, and then sequentiallyinsertlarger balloons
to allow for the maximum effect. However, care is needed - too large a
balloon or too much pressureand the vessel can rupture, which is a
life-threatening complication. Experience, careand controlofthe
pressures prevent this.

079

ow do our hands work?

The human hand Is an Important n
feature ofthe human body,
which allows Individuals to We take our hands for granted, but theyare
manipulatetheirsurroundlngs actually quite complex and have been
crucial in our evolution
and also to gather large amounts ofdata from
the environment that the lndivldualls • Distal phalanges - - - - t -
situated within. Ahand Isgenerally defined
as thetermillal aspect ofthe human arm, the hand A disU!I phalange (fingertip) is situated

which consistsof prehensile digits, an The human handcontalns27 at the endofeach finger. Deep flexors
opposable thumb, and a wristand palm. bones, and these divide upInto attach to this booe to allow for
Although many otheranimals have similar three dlstlnctgroups: the maximt.m movement
structures, only primatesand a limited carpals, metacarpalsand
number ofother vertebrates can besaid to phalanges.These also then Intermediate --------...
further breakdown into three:
have a 'hand'due to the need for an the proximal phalanges, phalanges
opposable thumb to be presentand the Intermediate phalangesand
degree ofextraarticulation that the human distal phalanges. Eight bones This is where the
hand canachieve. Due to this extra
aresituated In the wrist and superfiCial fte><>rs attach
articulation, humans have developed fine theseare collectivelycalled
motor skillsallowing for much Increased the carpals. The metacarpals, via tendons to alow the
control in this limb. Consequently we see which aresituated in the palm digit to bend.
improved ability to grasp and grip Items and ofthe handaccount fora
development orskillssuch as wrlll ng. further five outof the 27, and Proximal ------i:-11-""~
each finger has three
Anormal human hand Is made up of five phalanges, the thumb has two. phalanges
digits, the palmand wrist. It consistsof27 lntrinslcmusclesandtendons
bones, tendons, muscles and nerves, with Interactto control movementof Each fuger has tine
each fingertip ofeach digit containing thedigltsandhand, andattach phal;vlges, and INs phalange
to extrinsicmuscles that
numerous nerve endlngsmaklng the hand a extend further up into the arm, ;oos the nl!r1llledate to its
crucialarea forgathering iniormatlon from which flex the digits.
the environment usingoneof man's most respediye~
crucial five senses: touch. Muscles Interact
togetherwith tendons to allow fingers to ~~~ ------~~~~~

bend,straighten, pointand, ln the caseofthe These""" bones make~ l!le
thumb, rotate. However, the hand Is an area
thatseesmanyinjurlesdue to the numberof P<*n and each one ai!;J1s
ways we use it. one in ten Injuries In A&E
with one ol the hand's digits.
being hand related, and there are also
severaldisorders that can affect the hand ~~ ----------~--~
development In the womb, suchas
polydactyly, where an lndivldualls born Thecarpals(SC<~Phoid, ~·· ~.
with extradigits, which are often In perfect
trapezoid. k.nrte. hamate. capitateand
working order. pisiform) sit between the !Ana and radius
and the metacarpals.

080

1. Julio Cesar 2. Gianluigi 3. lker Casillas
Buffon Fernandez
Soares de
Espindola Named the 'Se.-le A Voted bestgoalie in the
Goalkeepe,;of the Year' a
Having r'ecovered From a rec:Of'dnine times, this is wor1d by the lnten'lational
few eaflier' blunder'S, the one guy It would be hard Federation of Foo!OOII
Brazilian keel)e(is now
to put one past HistOtY and Statistics for
considered one ofthe best. two yearsrunning.

ltU•JU•11J!3N•IW Skin is attached to tendons and so when you bend you fingers bock, dimples appear on the bock of your hand

Muscles and other structures

The movementsand articulations ofthe hand and complex mix of tendons and intrinsic muscles to
by the digits are controlled by tendonsand two operate(extensors). These muscles will contractin
muscle groupssituated within the hand and wrist.
order to causedigit movement and Oexorsand
These are the extrinsicand intrinsic musclegroups, extensors work in a pair to complementeach to

so named as the extrinsics are attached to muscles straightenand benddigits. The intrinsic muscles
which extend into the forearm, whereas the are responsiblefor aiding extrinsic muscleaction
and other movements in the digits and have three
intrinsicsare situated within the hand and wrist. distinctgroups; the thenar and hypothenar
The flexors and extensors, which make up the
(referring to the thumb and little linger
extrinsic muscles, use either exclusivelytendons to respectively), the interosseiand the lumbrical.
attach todigits they control(flexors) ora more

Thenar space --""""

Thenar refers to the thumb,

and this spaoe is situated

between the first digit and
thumb. One of the deep

flexors(extrinsic ITKJSCie) is

located in here.

Interossei Ulnar nerve
muscle
(intrinsic) - - - - - - This nOM! stretches
down the forearm into
This interossei musde sits the hand and allows for
between metacarpal
bones and will unitew ith sensory information
tendons to allow extension to be passed from
using extrinsic muscles. hand to brain.

Arteries, veins HYPothenar
and nerves --~ musde (intrinsic)

These supply fresh Hypothenar refers to the little

oxygenated blood (and fingerand thismusde group is one
take awaydeoxygenated
blood) tohand muscles. of the intrinsic ITKJSCies.

Extrinsic musclesare so Insertion of flexor tendon ....____ Mid palmar space
called because they are
primarily situated outside This is where the tendon attaches the Tendons and intrinsic muscles
the hand, the bodyofthe flexor muscle to the finger bones to
musclessituatedalong the primarily inhabit this spaoe
allow artirulation.
underside orfront of the within the hand.
forearm. This bodyof
Tinetnridnosnicssand ..:::::::=;~~~~~~
muscles actually breaks
down into two quite distinct These attach the
groups: the Oexorsand the
flexor muscles to the ~----- Extensors
extensors.TheOexors run
alongside the underside of phalanges, and facilitate Thenars Superficial flexors Deep f lexors Exter=rs on the back of
bending. Tendons also
the armandallow for the
bendingof the digits, interact \Yith the intrinsics The intrinsic group of The other flexor that acts on The digits halie two extrinsic flexcxs that the foreann st raighten the

whereas the extensor and extensors in the wrist, m uscles is used to flex the the digits is the superior flexor, allow the.-n tobend, the deep flexor and cfigits. Divided into six
muscles' main purpose Is the
palm and forearm to thumb and control its which attaches to the the superficial The deep flexor attaches sections. their connection
reverse thisaction, to
straighten the digits. There to the distal phalanges.
are both deep and superficial
Oexorsand extensors,and

whichareusedatanyone
time depends on the digit to

be moved.

straighten the digits. sideways rllO'w'em ent. intennediate phalanges. to the digits is complex.

081

ee- jerk reactions 1 Fingernails - 3. Interneuron

The knee-jerk step-by-step The intErneumJ)fOVWies a

L Quadriceps and hamstring muscles comectian betweenthe
The knee jerl< reflex means that the q.Jadriceps....-s sensory a1d motornetrOflS.

IOns mnlractat the sane trne theharnsbWlg musclerela-.
I•

Why does your leg kick out 4. Motor neuron
when the doctor taps just
belowyour knee? The motor, or efferent
neuron, carries the nerve
Doctorsoften test the knee-jerk, or patellar impulse to the muscles.
reflex, to look for potential neurological
problems. Lightly tappingyour patellar tendon • Sensory neuron 2. Sensory neuron _..J ' - - - 5. Spinal cord
justbelow the kneecap stretches the femora l • Motor neuron
nerve located In your thigh, which In turn causes your The sensory, or affetent The spinal cord has both gey
thigh muscle (quadriceps) to contractand the lower leg to Interneuron matter,whid:l conta01s nerve eel
extend. When struck, impulsestravelalonga pathwayIn neu-on. ~an impulse
the dorsal rootganglion,a bundleof nerves In the 41evel bodies, a1d while matter, whid:l
of thespinal cord. ReOexactions are performed from the femcral """"'· contains the """"'fbres.
independentlyof the brain.Thisallows them to happen
almost instantaneously-lnabout50 milliseconds In the "Reflex actions ore performed
caseof the knee-jerk reOex.This reOex helpsyou to
maintain balanceand posture when you walk, without independently of tfie brain"
having to think about everystep you take.

are r
fi ils

maCie

And how are they formed?

fingernails are made ofa tough protein called keratin (from the
Greek word 'Kera', meaning horn).Keratin Is also what animals
hooves and horns are made from. Most animals have a supportive
bonestructure In their horns, although rhinoceros horns are made
completelyof keratl ncompacted together. The onlyother biological material
which hasa similar toughness to kerall nlsed tissue is chitin, the main
componentofexoskeletons belonging toarthropods. The half-moon shape
thatyoucanseeat the bottom ofyournail(apart from maybe your littlelinger)
is called the lanula.Thlsls agroupofcells that produce keratinandother living
cells. As these livlngceUs arepushed forward by newer cells, they die and
merge with the keratin to become kerltlnlsed.They then becomeOauened,
stiffand known as your fingernails.

"The half- moon shape that you
con see at the bottom of your nail
is called the lonulo"

082

the leg at the knee.

...
.. ...





Feet are immensely complexstructures,
y:et we put huge amounts ofpressure on
them every day. How do they cope?
·. &-"The human footandankle Iscrucial for locomotion
• •• and Is one of the most complexstructuresof the T~ ------------------~
human body. Thls Intricatestructure Is made
Te<minal aspectsof the foot
J up of no less than 26 bones. 20 muscles, 33 that aid balance by grasping
onto the ground. They are the
joints-although only 20are articulated- as well as numerous equivalent of fingers in the
foot structure.
tendons and ligaments.Tendonsconnect the muscles to the
Muscles - including the extensor
bonesand facllitate movement of the foot, while ligaments hold digiton..m brevis m.Jscle _ _...../

the tendons in placeand help the foot move up and down to Muscleswithin the foot~ the foot lift and
articulab> as necessary.The extensordgitonm
inltiatewalking.Arches In the foot are formed byligaments, brevis rruscle sits on the top of the foot, and
helpsflex cijts tw<Hot.-on the foot.
musclesand foot bonesand help to distribute weight. as well as
Blood vessels _ _ _....../
makingiteasier for the foot to operateefficientlywhen walking

andnmning.ltIs due to the unlquestructureof the foot and the

wayitdistributes pressure throughout all aspects that itcan

withstand constant pressure throughout the day.

Oneof the othercrudal functions of the foot Is to aid balance, Thesesupply blood to the foot,
and toesareacruclalaspectof this. The big toe In particular
helps in this area. as we can grip the ground with ItIfwe feel we f<ditati19 rruscle upeatitwoby
~energyandoxygen and
are losing balance. rer"llOIIWlg deoxygenated blood.
Theskin, nervesand blood vessels make up the restof the
~~ ------~~Ligaments support the ....__
foot. helping to hold the shapeand also supplyingItwith all the
necessary minerals, oxygenand energy to help keepItmoving tendons and help to form
the
easilyand constantly.
arclles of the foot, spreadO>g

weight aaoss it.

What happens when Tendons (extensor digitorum

you spra1n your ankle? longus, among others) ----------~~+

Fibrous bands of tissue which corvJeCt

A sprainedankle Is the most common type ofsoft tissue muscles to bones. They can w ithstand a lot
Injury. Theseverltyof the spraIn can depend on how you
sprained theankle, and a minor sprain will generally of tension and IJnkvarious aspects of the
consistofa stretched oronly partially torn ligament foot, facilitating """""""nt

However, more severesprainscan cause the ligament Tibia - - - - - - - " " '
to tear completely, oreven force a pieceof bone to
breakoff. The larger and strongerof the lower
leg bones, this ~M5 the knee and the
Generallya sprain happens ankle bones of the foot

when you lose balanceorslip, Fibula
and the foot bendsInwards
towards the otherleg. ThIs then Thisbone sits alongside the Iilia,also
overstretchesthe ligaments
~thekneeandthe~. --------~

and causes the damage.Over The...._

a quarter ofallsporting ofthefoot
injuriesare sprains
of the ankle.

andhowthe

work

084

STOP 1Bunions • 2••••••••••••••••Athlete's foot 3•••••••••••••••••Warts 4••••••••••••••••Ingrown toenails 5••••••••••••••••Achilles tendonitis
Thisisan enlargementofthe skin
FACTS ortissue around thebig toe. A fmgal infection that'soften Warts aresmaH, benign Ingrown toenaisarea form ol This i s t h e inRammation
Formation is often attributedto tra'lsmitted in areas where nail diseasewhere thenail of the Achillestendon.
FOOT AILMENTS ill.fitting shoes. thou~ it's peoplewalk around barefoot, lumpsofskin. whichappear grows intoeither sideofthe wl'jch occurs prior to the
following exposuretoa nail bed.Infectioncanoften ruptl.re o f t h e tendon.
suspected that genetics is the thisdevelops when t heskin is occurifil is notcaught and and iscommoriy seen
-problem. virus ... mostcommonly
not properly driedand aired.It • treated early. • inathletes.
displaysasflaky. itchy skin. the humanpapillomavirus
2and7.

ltU•JU•11J!3N•IW In a lifetime, a person will walk the equivalent of four times around the globe - more than 1oo,ooo miles!

'Humangait' is the term to describe how we 4. Leg swing _ !
walk. This gait will vary between each
person, but the basicsare the same The lower leg wiD
then swing at the
2. Weight transfer ---... knee, l.Wlder the body,
tobe placed in front
The weight wiD transfer fuRy ofthe stationary,
to the foot still in contact weight· bearing foot.
with the ground, normally
with a slight leaning
movement of the body.

6. Repeat

3. Foot lift - --/ S.Heel - - ' 1. Heel lift - - - - - J process

After weight has placement The process is

transferred and the The heel will normally be The first step ofwalking is for then repeated with
individual feels
balanoed, the ball of the part of the foot that's the foot to be lifted offthe the other foot. During

the first foot will then placed f.-st. and weight ground The knee wil raise and nonnal walking or

lift off the gound, wiB start to transfer back the calf muscle and Achilles running. one foot will
raising the thigh. onto this foot as ~ hits
the ground. tendon, situated oo the back of start to lift as the other

the leg, wiD contractto allow starts to CClflle into

the heel to lift off the ground. contact with the ground.

Distal Proximal M etatarsals Cuneifonns Navicular Ababylsbomwlth22.
phalanges phalanges outofa tota!2.6 bones in each foot
The five, long bones that are bones (three) This booe, which is
The booes which These booes link the the metatarsals are located
Three booes that fuse so named due
sa at the farend metatarsals and the between the tarsal booes together during booe to its resemblance
distal phalanges and and the phalanges. These development and sit to a boat, articulates
of the foot and arethe eqlivalentofthe
make up the tips stretch from the between the metatarsals with the t hree
baseof the toes. metacarpals in the hand and the talus. cuneiform booes.
of the toes.

6

0

3"

i

- ,•

.~

·•-

' - - - Cuboid The talus is the Calcaneus
secood largest
One of five irregular bones This bone
(cuboid, navicular and three booe of the foot, constitutes the
and it makes up heel and is crucial
cooeiform booes) which make the lower part of for walking. It is
up the arches ofthefoot the largest bone
These help with shock the ankle joint.
in the foot.
absorption in locomotion.
085

Achilles' tendon 1 Smelly feet

Tt'"ndmu o.f ~I? Facts: Well known for tl>eirability

Pf:701HU. Um!JI.U Producing up to a to secr~te a liQuid with a strong.
Qintofsweateach foul smelhng oclcu which they
rl brn:~ aay, no wonderxour CM use as adefensiveweapon.
feet get a bit whtffy They can shoot it up to 5 metres.

Sweatactually keeps the 2. Rotorua, New
sldn ofour feet moist and Zealand
flexible to cope with the
constantly changing Facts: located in the most
pressure when we walk.Without geclogio:alyactiveareaof New
this moisture the skin would dry and Zealand,Racruaissuroun:led
crack,and walking would become bymud pools. geysers ard
extremely painful. $teamvents.
Despite the huge number ofglands
(Z5o,ooo perfoot) and amount of 3. Titan arum
sweat that comes from our feet,
remember It'sstilljust saltand water. facts: This monsttOus. ttwe-
Theodourcomesfrom the bacteria
that liveon human skin which, while metre tal plant smells li~ a
unsettling. are perfectly naturaI. Our combination of rotten eggs and
socksare a dark, moist-Infested feast
for them, as they eatsweatand dead ronlng meat to attract insects.
skin. ItIsthe waste products they
excretefrom thls consumption that
are what smells bad.The more the
bacteria eat the worse ourfeet smell.
To keep the smell down, makesure
you changeyoursocksand let your
shoesalr for24 hoursIfyou can. Also,
wash your feet and spray them with
antiperspirant!

Thewonderful smell of
freshlycut grass, daisies

and feet...

Is it really a weal< spot and how
important is it?

Tbis tendon, the strongest In your body, connects the calfmuscles to
the heel. When everythingIs Hne, It pulls the backof the foot up
when the call muscles contract.This way, your heel raisesand your
weight goes to your toes. Itenables us to do such things as sprinting.
boppingorjumping. Italso storeselasticenergy to do these tasks more
efficiently. Biologicalanthropologists believeall thiswas very importantfor the
way we evolved to run around on two legs and survive.
The Achilles' tendon Isseemingly named thus after the mythological Greek
characterofAchilles, who during th.eTrojan War- made famous by Homers epic
poem The Jlliad-Isshot by a poisoned arrow In his unprotected heel -hence the
common phrase describing a person's weak point.

086

I•U•Itm!Jt:W•l!illi> writers' cramp occurs in the hands and lower arms but is actually a form of dystonia. a neurological condition

are Why do our muscles tense up?

Why do burns cause bubbles to develop CrampIs an Involuntarycontractionofa muscle, oftenin
below the surface of the skin? a limbsuchas the leg, that can cause pain and discomfort
for seconds, minutes or, in extremecases, forseveral
~~ Though ourskin Isan and Hils the spaces between the layers hours. Theyare most commonafter orduring exerctse,
amazing protectoragainst ofskin in order to cushion the coinciding with low bloodsugar levels, dehydrationand a high lossof
underlying skin that is being rubbed sa It from sweating. Although the full range ofcausesissomethingofa
Jil the elements, it can become and protect it from further damage. As mystery due to limited research in the area, cramp Is believed to be
' damaged bysuch factors as moreandmoreserumpoursintothe the result of muscle fatigue. Ifa muscle has been shortened through
space, the skin begins to inflate under prolonged use but Is repeatedlystimulated, It isn'table to properly
beat, cold, friction, chemicals, light. the pressure, forming a small balloon relax. Areflexarc from the centralnervous system to the muscle
full of the serous liquid. Given time to informs It to continue contractingwhen It Is not necessary, leading to
heal, the skin will reabsorb the plasma a painfulspasm knownascrampas the muscle continuallyattempts
after about 24 hours. to contract.This Is why athletes pushed beyond their limits,suchas
football players who have to play extra lime In a soccer match, and
Similarly, a blood blisterisa variation long-distance runners. will oftenexperience this condition..
of the sameinjury where the skin bas
electridtyand radiation, all of which been forcefully pinched orcrushed but
not pierced, causingsmall blood vessels
'burn' the skin.A blisterIs the resulting ro rupture, leaking blood into the skin.
All blisterscan be tender butshould
injury that develops in the upper layers never be popped in order to drain the Rest
fluid as this leaves the underlying skin
oftheskinasa result ofsuch burns. unprotected and also invites infection N. rest the calf
Into the open wound. trU5de is in its
The most commonexample ofa relailltd poWon.
r------- Plasma
blister, which we've no doubt all I
Serum is released by the damaged
experienced at some time, Is due to the Stretch
tissues into the upper skin '-rs to
repeated friction caused by the material prc~~ent furtherdamage below in the When the leg is
binorstretdied
ofa pairofshoes rubbingagalnst. and epidermal'-<· It also aids the
healing process, which is why you thecalf rTUicle
irritating. the skin.The resulting water
should avoid pojll)ing your blisters. wi1 ""' illa;t, and
blisteris a kind ofplasma·filled bubble
then relax......,
thatappears justbelow the top layers or
itis not.
your skin. The plasma, orserum- which

is a component ofyour blood-Is

released by the damaged tissue cells

Blister caused by

second-degree bums

Skin - . / Dlration ,.----- Cramp
Ant generated
When arry type of tun is Prolonged
Cfilll1lusualy lasts dstJ~.e..t..d.....~l!l of the
experienced. the C>llertying slcin leg jll'ell'l!l1ts the
expands as it receivesthe protec:tille fur a few seconds. call rTUicle from
plasma/serwn I.--some ...taxing. which can

Damage -------~ lasthours. - - - - lead t o 00111 rp.

Tlis pa-tjcUar exa '"*ofa blister tun Ruid reabsorbed 087
has caused damage to the loeratii iC)Cytes
in the sl<in. Second-degree bums are I'Jtera day <X so the senm wil be
most oftencaused ..t.en theslcin comes absabed back intothe body and the
into""' •tact with a hot surface, S<.dl as raised skin '-rs wil dry out and ftal<e
an iron <Xboil01g water,<Xevenafter
OXposlR toe>o:essive ..night offin their own time.



104 •I

Whydo we uac:z1e3r3
sweat?
exp ed

110
How ow
bones heal

I

0"

g

090 Foodand!our body 106 The immune system 124 How yow bloodworks
Inside the igestive system Combating viruses The miraculous fluid analysed

098 The blood-brain barrier 110 Healin~bone fractwes us Hormones
What important role does it play? How bro en bones are mended
The human endocrine system
099 Pituit:f;gland up dose 111 Makinglf:otein 110 The u,rinarysystem
The 'mas ergalnd' explored Howare ey manufactured?
How do we pass waste?
100 Brain electrid~ SY.Dasses 1U Thecell~cle
Revealing the tru behin both 1)2 Tracheotomysur~ery
Insidea vi al process
101 Adrenaline 114 White blood cells A life-saving proce ure
How does it effect the body? 1)1 Hayfevel'
How infection is fought
102 Human respiration Why do people suffer?
The lungs explained u6 The science ofgenetics 1)4 Exploring the sensorysystem

10ft Dehydration I Sweat::tf How genes defirie who we are How we experience the world
Why we sweatand using uids 121 Burns 11..1 Chickenpox

105 Cinadian rh~ The causes and effects of burns How harfuful can it really be?
Our body doc explored 12.2 Bloodvessels 1)9 Why do we cry?

Our drculations system The different types of tears

088

n6

DNA

explored

128

The role of
hormones

I

I

112
The cell cycle

I



"The cell damage
from viruses
causes diseases"

089

Join us as we unravel all nine
metres ofyour digestive system

The digestive tract is a long, muscular tube that
runs the entire length ofyour body. It is separated
into five distinct sections, each with its own
particularand specialised function.
Digestion begins in the mouth. As you chew your food,
saliva is released, providing a slippery lubricant and
kick-starting the break down ofcarbohydrates with an
enzyme known as amylase. Touch receptors in you r
mouth tell you when it is time to swallow, and as your
tongue comes upward, the food is pushed to the back
ofyour throat.
As you swallow, you pass control of digestion
over to your automatic motor functions. Aflap of
skin called the epiglottis folds down to cover the
voice box, a nd the entrance to the lungs, and
thena wave pushes the mouthful all theway
down the oesophagus. When the food reaches
your stomach, it passes through a ring of muscle
!mown as the cardiac sphincter, which prevents
it from coming back out the wayit came in.

The inside ofthe stomach isa hostile
environment, where the cells lining thewalls
pump out hydrochloric acid and protein-digesting
enzymes. The presence of food triggers stretch
receptors in the stomach lining, which in turn triggera series
ofrhytbmiccontractions.These churn the stomach contents,
mixingin the acid and enzymes, grinding down the food.
At the bottom of the stomach th ere is a second ring of muscle
called the pyloricsphincter, which acts as a gatekeeper to the
small intestine. The sphincter prevents anything larger than
about two centimetres (o.8 in ches) in diameter passing
through, returning it to the body of the stomach until it has

090

Shellfish Milk Peanuts

Shellfish allergies tend to Children '-"der the ago or By far the most
dellelop during three are the most likely cOO'Imoo food

adulthood. Foods to ai/Oid to develop an allergy to allergy is peanuts. l.n
Include bamack>s. crabs,
milk, but they usually the UK, as many as
shrimps. lobsters,
outgrow It by the time one in SOchildren
crawfish and krill
they reaeh adulthood. ate sensitive.

I.U•Ill!I!It:W•I@ Bio/ogica/ wash1ng powder uses digestive enzymes to break down the stains on dirty laundry

beengrounddown further. This ensures thatby Journey of - - Swallow
the time it reaches the small intestine, yourfood your fOod
is a runny, slightlylumpy paste, and is ready for Saliva makes each mouthful
the next stageof digestion. It can t ake up to 48 slippe.y, allowing it to slide
hours for a meal to travel easily down the oesophagus
The small intestine is the site of chemical through your body to the stomach.
digestion. He.re, the pancreasadds digestive
enzymes, and the liver adds a generous squirt of Chew Add acid and enzymes
alkaline bile, delivered via the gall bladder.This
bile not onlyneutralises the burningstomach Digestion begins in the The stomach produces
acid, italso acts a little like washing-up liquid on mouth, where our teeth start hydrochloric acid, and
dirtydinner dishes, helpingto separate the work on grinding food Into protein-digesting enzymes.
food particles and forcing fats to disperse into manageable chunks.
tiny bubbles. .-- Add more enzymes
Add bile
Muscles in the sma II intestine continue to The pancreas produces
squeeze and mix the contents together, allowing As the liquid passes into the digestive enzymes, which
the enzymes to get to work inslde the paste. As intestines, stomach acid
the nutrientsare released, theyare then is neutrali.sed by are added to the mixture as
absorbed over the wa lls of the Intestine and into alkaline bile from
the bloodstream. the liver. it enters the small intestine.

To ensure that everything keeps moving Ferment waste naba
through the system, every five to ten minutes a
wave of muscle contractions beginsat the Bacte<ia filling in the LEII&IHCF'IIIE
stomach and travelsall the way down the large intestine help
intestines. Knownas them!grating motor with the breakdown of SIF" III&IZE
complex(MMC), this wave squeezes the digestive
system likea tube oftoothpaste, urging its waste, releasing even Chum
contents further toward the colon.
more nutrients. The muscles of the
As the food progresses through the small stomach rhythmically
intestine, more and more of the nutrients are Absorb nutrients chum itscontents,
released byenzyme activity,and by the time it mechanically
gets to the large intestine, most of the useful As the enzymes begin to breaking food down
material has beenabsorbed into the release nutrients, they are into a lumpy paste.
bloodstream. However, the digestive process is
not over, and here, bacteria help to break down absorbed across the lining Remove water
even more of the undigested food. of the small intestine into
the bloodstream. The large Intestine
The large intestinealso absorbs most of the absorbs excess water
remaining water, leaving behind a combination Get rid of waste
of und igested materia l, dead cellsand bacteria. from the food as it
When the waste has completed its journey All that is left at the
through the large intestine it goes to the rectum end of the digestive passes through.
for storage until there is a convenient time to get process is a
rid of it. combination of
indigestible mate.ial,
dead cells and bacteria.

>I I :..

•0

.' •

..• •• -•- . 091

••

=··

Toste and digestion

Sense Anatomy of a Circumvallate papillae
of taste human tongue
These large bumps are found at the
Taste tells us whether our food is Co ntrary to popular belief, all five bad< of the tongue, each surrounded
safe to eat, but smell gives it flavour
tastes can be detected almost by a dip that collects saliva.
The human tongue is able to detect five different anywhere on the tongue
tastes: sweet, sour, salty, bitter and umami Blood supply
(savoury), providing us with a quick way to Muscle
distinguish between different types of food. The tongue receives
Sweet foods contain sugarand are a good sou rce There are eight blood from the lingual
ofenergy. Salty foods providesod ium, which is muscles in the artery and it drains out
vital for nerve function, but deadly in high tongue that alter through the lingual veins.
quantities. Bitter foods might contain poison. its shape and
change its position. Nerves
Babiesare born with a natural preference for
sweet food and a dislike of bitter, providinga Posterior The front and back
biological safeguard that encourages them to eat tongue of the tongue send
safe, high-calorie food. However, nutrition is not taste information to
that simple. Many vegetables are bitter but not About a third of the
poisonousand so learning to like them comes tongue is hidden the brain.
with experience. right at the back of
the mouth. Foliate
The degree to which we can detect different papillae
tastes varies, and appears to be dictated by our Papillae
individualanatomy. The population can be These contain
broadly divided Into threecategories based on The tongue is taste receptors
the number of taste buds on their tongue. Those covered in tiny and are located on
with the fewest are known as 'non-tasters', those bumps, but not all the back edges of
with anaverage numberare known as 'tasters', of them contain the tongue, where
and thosewith many more taste buds than the taste buds. saliva drips down
rest ifthe population are 'supertasters.'
Supertastersare espedally sensitive to taste and Filiform papillae the cheeks.
will react much more strongly than the rest of
the population. As a resu It, they tend to really Mostof the tongue is Anterior tongue
dislike bitter foods llke green vegetables and covered in thin, rough
coffee, and often shy away from rich desserts bumps that contain no The visible part of the
and s ugary sweets. taste receptors. tongue is responsible for

Though these anatomicaIdifferences can 1UII!C'B I SAlE the majorityoftaste
explain some of our food preferences, most our .uaDE.VERY detection.
individual likesand dislikesare not down to
taste, but to flavour; the combination of taste and TDIIM'IIS Gustatory hair
smell. The act of chewing food releases
chemicals known as volatiles, which evaporate What is a Each taste cell ends with a
rapidly. As we swallow, some of the air inside the tiny hair, covered in
mouth is forced up toward the nose, carrying taste bud?
these volatiles with it Here, they bind to receptors that allow it to
receptors on olfactory cells, triggering sensory Pore detect chemicals dissolved
messagesto the brain.
A tiny gapat the top of the in the saliva.
Recently, sdentists have found that these taste bud allows saliva to
olfactory receptors ca n detect as manyas 1 touch the taste cells. Basal cell
trillion different odours.Taste and smell are
stronglylinked to emotion and memory,and asa Support cell Ageing or damaged
result, experience Is a powerful decider in the taste cells are replaced
development ofour II kes and dislikes. The taste cells are
by the basal cells
surrounded by an waiting underneath.

envelope of non-tasting Sensory cell
support cells.
Each cell is sensitive
Synapse to one of the frve

Taste cells do not transmit the tastes, but au types
signals to the brain themselves,
instead passing the message are found together in
a single taste bud.
over to a nerve ceiL
Nerve

Messages are relayed
to the brain via a nerve

that exits at the bottom
of the taste bud.

092

I•U•T'OOI!/I!W•lr.'i? Stomach ulcers were long thought to be caused by stress. but it's now known the culprit is o bacterial infection

Inside the Oesophagus Fundus Rugae
stomach
Food travels from the Excess gas is collected at The lining of the stomach
This muscular bag turns your dinner the top of thestomach, is stretchy and expandable,
into an acidic soup mouth to the stomach where it can be pushed out and when relaxed, it curls
and up by the diaphragm. up into characteristic folds.
via a muscular tube
that runs behind Body
the windpipe.
The central portion of the
Thestomach actsasa holding chamber, Cardiac stomach helps to create
receiving food from the mouth and preparing it sphincter downward pressure,
to be processed in the s mall intestine.At rest, the
stomach is around the size of a fist, and its lini ng A ring of muscle at keeping food moving in the
is curled into a convoluted network of folds the top of the right direction.
known as rugae. As you eat, these folds stretch stomach stops the
out, allowinganadult to eataround a litre (0.26 acidic contents Muscle layers
gallons) of food In onesitting. Stretching of the moving back into
stomach walls triggers rhythmiccontractions, the oesophagus. There are three
mixing the food with acid and protein-digesting layers of muscle in
enzymes, grinding it to a paste in preparation for Antrum the stomach wall,
the next stage ofdigestion. each running in a
The bottom part of different direction.
the stomach
generates powerful
grinding

contractions.

Duodenum Stomach lining

The stomach The lining is covered in
empties its microscopic pits that
contents into the
first section of the produce mucus, acid and
small intestine. protein·digesting enzymes.

Pyloric
sphincter

A ring of muscle at
the base of the
stomach prevents
the contents from
leaking out before
they are ready.

Chewing
the fat

Fat has a bad reputation, but
the truth is, your body needs it

Every single cell in your body is
surrounded by a membrane made of
fats; it insulates your nerves and it
provides a valuable energy reserve.
Eating fat also provides a number of
vitamins and essential fatty acids

the body can't make on its own.
Saturated fats (the sofid fats found in
meat and dairy) and trans fats

(found in hydrogenated vegetable oil
and many processed foods) have
shown to raise cholesterol, which
can lead to circulatory problems, but
unsaturated fats (the liquid fats
found in plants and fish) can have
the opposite effect. and are
considered good for yourhealth.

093

=··

Toste and digestion

4,soorrr large intestine Brush border Villi

'IIE'IUIIIIJPDL IU The second part of lhe The cells that make up lhe The cells that line lhe walls
intestinal wall are covered of lhe small intestineare
5I f 2"AIEACIF'IIE inlPstineabsorbs water in microscopic fingers arranged into folds
and prepares waste.
known as microvilli. known as villi.

Small intestine

The first part of the

intestine is responsible for

breaking food down and

Appendix Rectum absorbing lhe nutrients.

Near the start of the large Before exiting the body,
intestine is a blind-ending tube
waste products are stored Small vein
known as the appendix - its
In a small pouch known as Nutrients travel across
fLOICtion is largely unknown. the rectum. the wall of the intestine

into the blood stream.

The intestines Lymph vessel Small :_______ Intestinal crypt

Fatty acids are transported artery Between the villi are
away from the intestines via crypts containing
the lymphatic system. Each of the
villi has a rich mucus·producing cells.
blood supply.

After leaving the stomach, food must pass through over 7m (23ft) of intestines

Thestomach contents enterthe intestine areadded bythepancreas.The enzymesactlike small intestine. The remaining undigested
gradually, allowing tlme for the liquid food to be molecularsdssors, breaking proteins, materia l passes into the large intestine, which
processed. Flrsttheadd Is neutra lised by bile, carbohyd.rates and fats down into building blocl<s absorbs water, leaving behindsolid waste that
provided by the liver, and then digestive enzymes small enough to be carried over the wall of the can then be passed out ofthe body.

094

STOP Eight glasses ofwater •• 3Canvt nightvision •• Celery's minus-calories Chocolate causes acne
·• Vitamin Cstops colds
FACTS 1Drinking plenty ofwater is • Calt'otscontainvitamin A, 4 1t isa popular fact among Actually, tl"is one rright be
benellclal for01.1' health, but : 2 Intrials involving over11,000 dietersthateating celery
FOOD MYTHS there is nothing special about v~al for eye health, but the 5••• •• true. Ne'INresearch is
DEBUNKED drinking eight glasses. Drinking
people, it has been shown that
when you feel thirsty is usually
more thaneoough. •• vitamin Cdoes not prevent or idea thatthey help you see in bums moc-e calories than it increasingly suggesting that
curecolds. However,washing thedark Is alie from WWII to
•• handsregularlyis effectiveat •• provides. Although possiblein • diet does have an impact on
keepradartechnologysecret acneand that saturated fats
• preventing transmission. fromthe Germans. theory, no foodshave been •• and sugarsmightbe to blame. -
found to have this effect.

!•lf•M!I!llW1•1~W The human mouth produces 1-2/itres of solivo every doy

The first part of the digestive system prepares washing-up liquid, separating the fats out into can sometimes convert one into anotherif
the food for the next stage, ensuring it is broken smaller blobs. supplies are running low. However, there are a
into a fine paste, mixed to form a homogenous number of nutrients that cannot be synthesised
fluid, and shocked with add to limit the Now that the food is nicely mixed and by the bodyatall or in high enough quantities,
potential for dangerous infection. However, it separated, the enzymes can really get to work. and these must be obtained directly from the
The pancreas produces a cocktail of three diet. These essential nutrients include some
is not until food reaches the small intestine kinds of enzyme, each used to break down a types ofamino adds, fatty adds like omega-3
that the microscopic breakdownand different type of molecule. Proteases clip and omega-6, and all of the vitamins and
absorption of nutrients really begins. amino acids from proteins, lipases break fats minerals needed.
down into fatty adds and glycerol, and
At the start of the small intestine, the liver carbohydrases turn long chains of Vitamins and mineralsare organic and
injects alkaline bile into the acidic liquid food, carbohydrate into sugars. These small blocks inorganic compounds required by the body in
neutralising its pH and preparing it for the can be absorbed into the bloodstream, where small amounts for various different functions.
introduction ofdigestive enzymes. they are distributed around the body, used to Some of these, like calcium, make up vital
structural components ofour bodies, while
Bile also helps to emulsify fats. Fats are not build our own biological molecules, or broken others, like vitamin C, are involved in
watersoluble, so they tend to clump together in down and burnt for energy. The body requires biochemical reactions.
different quantities ofeach of the nutrients, and
large globules to hide from and avoid the
surrounding water, but bile acts a little like

I

IRON-RICH FOOD Iron is a key component of
haemoglobin, the red pigment that
z carries oxygen in our blood.
0 Without it, oxygen cannot be
-0:: transported effectively, result ing in
Egg yolks Red meat iron-deficiency anaemia. This is
most often caused by blood loss,
GREEN LEAFY VEGETABLES so as a result, women are much
more likely to be deficient of iron
Broccoli than men.

OILY FISH Folic acid is essential for the
synthesis of DNA and w ithout it
0 the production of red blood cells
-z~ starts to slow down. It is also
>-~ extremely important in the
Salmon Tuna formation of the central nervous
system, and during the first 12
FRUITS weeks of pregnancy, folic acid
supplementation is recommended
~ to pregnant women.
-;::)
Vitamin D is involved in bone
~ formation in t he body, so
~ deficiency of vitamin Din
a0.. children can result in bone
Dried apricots Avocados deformity. Luckily, this vitamin is
easy to obtain. Not only can
vitamin D be found in oily f ish,
eggs and dairy product s, but our
bodies can also make it
t hemselves using sunlight.

Cells use a combination of
potassium and sodium to maintain
their internal electrical balance.
Potassium is vital to ensure
muscles are able to contract
properly and nerves are able to
transmit their messages. It is
easily obtained in the diet and
deficiency is incredibly rare unless
there is damage to the kidneys.

095

=··

Hunger is one of the body's Food addiction
most basicand
fundamen tal sensations, Research into food same reward pathway that lights up when
addiction is relatively addictive drugs are ingested. In alcoholics,
and it originates in the newand the results cocaineaddicts and heroin addicts, the
stomach. When the are hotly debated, but number ofdopamine receptorsin the reward
stomach isempty, it begins there is increasing pathway is lower than in the rest of the
to producea hormone evidence that food can populationandthe same thingis found in
known asghrelin.This then elicit some of the same obesity. It is thought that people with fewer
travels to a region of the brain brain responses as addictive dopamine receptors might need to over-
known as the hypothalamus. substances ill<e cocaine.ln stimulate their brains to experience the
overweight people, overeatingcan same rewards asnormal people, and
Th e hypothalamus is responsible become a compulsion thatis difficult to therefore turn to alcohol, drugs, or perhaps
for maintaining a constant, optimum state; control, andhasbeenshownto activate the
keeping the bodyata settemperature, regulating even food.
hormonesand monitoring hydration. The arrival

ofghrelin is a signal that energy levels might be
about to dip, so it triggers the production ofa
second hormone, neuropeptide Y. This hormone

promotes eating.
The cue to stop eatingis much more subtle. The

stomach has stretch receptors,and will signal to
the brain that it is full. But what happens if it is
empty, but there is already enough energystored
in the system? fat stores produce a hormone
known asleptin, which tells the brain exactly

Food and the brain how much energy the body has in reserve. When
leptin levels a re high, the hypothalamus makes
Why do we crave these foods? hormones that suppress appetite.

The trouble is that with high levels of fat, we
can become resistantto the leptin message,
similar to insulin resistance in type-II diabetes. If
the brain does not know there is enough fat, we
just keep eating.

Cravingsare slightly different. These are
generated not in th e stomach, but in the brain.

Therearethree main areas ofthe brain
implicated in food cravings, the hippocampus,
the insula and the caudate.

Humans have beenprogrammed through
evolution to enjoy fatty a nd sugary foods; eating
them ensu res we have enough energy to su rvive.
The hippocampus is involved in gathering
sensory information, and processing it for
long-term memory storage, and with food
cravings, these memories becomeassociated
with activation of the brain's reward circuitry.
The more we enjoy eating a food, the more likely

we are to crave it.
Mentalimages are thought to play an

important role in food cravingsand picturing

food makes it much harder to resist. But thinking
about othervisual images can help to curb the
cravings and distractyour brain.

Digestion happens subconsciously, butyou do
have a manual override, and what your brain
thinks it wants isn't always what it needs.

096

STRANGE How long does chewing Answer:
BUT TRUE gum stay in your system?
It is ttue that chewlllQ: gum cannot be digested.
A STICKY MYTH A Seven years 8 A day C Forever but as &ong as Itis a small piece - less than 2cm
(0.81n) in diameter - there is no reason it should
get stuck, and It should pass out oonnally within

adayottwo.

[•!(17\X!IDt:W•~W The digestive system hos its own dedicated neNous system, known os the enteric neNous system

Tea Chocolate

In England, drinking tea is a national pastime. The main chemicals in tea are Chocolate is one of the foods most commonly
known as polyphenols, and each cup contains around 200 milligrams (0.007 associated with happiness, particularly the
ounces). The polyphenols are large molecules made up of smaller building hormone serotonin. The chocolate itself does
contain the precursor to serotonin, an amino acid
blocks, which are known as catechins. When these catechins react with known as tryptophan, but this is also found in
many other foods, including meat. Chocolate also
oxygen, they make two types of chemical; theaflavins, which make the contains phenylethylamine, a molecule
chemically similar to amphetamine, but it is
orange-brown colour of tea, and thearubigins, which are thought to
contribute to the taste. The different amounts of the broken down in the digestive system, and
chemicals present inthe tea are does not reach the brain intact. The
very dependent feel·good factor ofchocolate is
more likely to be down to its fat
on the life of the and sugar content, and a
plants and the property known as mouthfeel.
processing of Chocolate is among the only foods
the leaves. that melts at close to

body temperature.

I

TIE IBIGTH OFAN
I AVEIWlES1UMIICH

l AFTERANEAL

I

Coffee Bacon J

Coffee contains over The distinctive smell of bacon is, as most of us have probably

1,000 different aroma experienced, hard to resist. That fact is all down to the chemistry of ~!
compounds, responsible cooking meat. As the bacon is heated, the amino acids that make up
for its unmistakable smell.
Around 12 per cent of the green the muscle protein react with reducing sugars present in the bacon "
coffee bean is made up of a set of fat. This process, known as the Maillard reaction, occurs only at high ~
chemicals known as chlorogenic acids, and when the beans are
roasted, most of these acids begin to break down. Some produce !temperatures and produces over 150 different volatile molecules, "~!!'
the brown-coloured compounds that give coffee its characteristic
each able to interact with different smell receptors in the nose. Most
dark colour, while others produce the bitter-tasting chemicals of the delicious smell of bacon is attributed to a group of nitrogen·

responsible for its taste. Coffee also contains high quantities of containing compounds known as pyridines and pyrazines. G
caffeine, around 100 milligrams (0.0035 ounces) in every cup. It
works on receptors in the heart and brain, blocking the action of a
natural neurotransmitter and acting as a stimulant.

097

=··

blood-brain barrier

ra1• n -

How does this gateway control the molecules
that pass from the blood into the brain

The blood-brain barrier (BBBI is an Breaking down the barrier Upophilic
essential group of cells that line the
blood vessels In the central ne rvous This built-in gateway is the main line of Substances rich in
system (brain and spina l cordi. defence for the central nervous system
Theyallow passage ofmaterials between the lipids can diffuse
clear Ouidsurroundlng the brain (cerebrospinal Just passing through
Ouid) and the red blood cells in arteries. veins across the barrier
and capillaries. The key advantage of having Some ions are transported with relative ease.
such a barrieris that It prevents large micro- out of the blood cells and
organisms passing into the brain and causing into the astrocytes, and then A tight squee.ze ~
infections. While infections in otherareasare out of the astrocytes and
common (such as after a cut finger. or mild chest into neurons in the brain. The tiny gaps between ~
inJections), those affect! ng the brain are much
rarer. However when they do occu r (eg Astrocyte ----·:>~~~:,e;T~~~ jcells regulate the size
meningitis), they are potentially life
threateningas they are very difficult to treat. These numerous ...and type of particle that ~
The tight junctions between cells regulate star-shaped cells provide are able to fit through. Q
the size and type of particle that pass between biochemical support to the
them, including oxygen molecules, carbon endothelial cells, and also
dioxide molecules, nutrients and hormones. play an Important role in
Since it'sso effective, It also stops medications transportation and repair.
from entering the brain (such as certain
antibiotics), so while they are effective in the
rest of the body, they are Ineffective in this vital
organ. Overcoming this is a major aim of
doctors in the nextdecade, and the battle has
already s tarted. Ma nipulati ng the blood-brain
barrier's natural transport mecha nisms and
delivering drugs within nanoparticles to
squeeze throug h the tightjunctionsa rejust
two examples of the modern techniques that
are under development.

Crossing the BBB Special transport

The endothelial lining of the blood·brain barrier Active and passive
loves lipids (fatty molecules), but it hates transporters across this

particles with high electrical charges (ions) and membrane can overcome
large substances. Thus the ideal substance is
small, rich in lipids and has a low electrical some or these problems,

charge. Barbiturates are such an example, as they and be manipulated to
deliver medications to
freely flow across the blood·brain barrier to the correct place.

suppress brain function; they act as sedatives and Highly charged

antidepressants. However this free movement Highly charged ions are
repelled, meaning that
comes with risks - too much of it will accumulate some medications are
and slow the brain to a point where you can lose ineffective in the brain.

consciousness and even stop breathing.

098

RECORD m TAll EST MAN IN HISTORY
BREAKERS
At 2.72 metres (eight foot, 11.1 inches) Robert Wadlow is the tallest man
TALL TALE
on record. Asufferer of gigantism, he was 0.9 metres (three feet) taller
than his father. Sadly, he was only 22 when he died in 1940.

!•Jf•J\t!I!ll;W•1~W In fish, the intermediate lobe controls skin co/our change, while birds hove no intermediate lobe at all

ituita ose

What does this hormone factory do and why couldn't we live without it?

The pea-sized pituitary gland is The master gland in context
found at the base of the brain, close
to the hypothalamus. Itlooks a Where does this vitally important hormone
relativelyinsignificant part of the manufacturer sit within the human brain?
brain, but it plays a role in many vital systems.
Often referred to as the 'master gland', it not Hypothalamus
only releases hormones that control various
functions, but it also prompts the activity of The seaetion ofhormones
from the pituitary gland is
other gla nds like the ovaries and testes. directly controlled by this
The pituitary gland comprises three sections part ofthe brain, which
links the nervous and
called Jobes: the anterior, the posteriorand the
endocrine systems.
intermediate - the latter of which is considered
part of the anterior lobe in humans.These work Pituitary stalk
together with the hypothalamus, which
monitors hormones in the blood a nd stimulates This is what connects
the pituitary gland to produce/release the the pituitary lobes to
appropriate hormone(s) if levels fall too low.
the hypothalamus.
The anterior lobe producesseven important
hormones, which include those that regulate Posterior lobe
growth and reproduction. Adrenocorticotropic
hormone (ACTH) targets the adrenal glands to Thisdoesn't produce any
produce cortisol and controls metabolism, hormones itself, but
stores and releases some,
while luteinising hormone triggers ovulation in like ADH, made elsewhere
women and stimulates testosterone production inthe hypothaJamus.
in men. The posterior lobe, meanwhile, doesn't

generate any hormones itself, but stores two:

antidiuretic hormone (ADH), which decreases
urine production bymaking the kidneys return
more water to the blood, and oxytocin, which
tells the uterus to contract during childbirth
a nd also prompts milk production.

Gigantism in focus Capillaries

The pituitary gland also produces growth Hormones are exchanged

hormone, which in adults controls the amount between the anteriorlobe

of muscle and fat in the body and plays a key and the hypothalamus via
role in the immune system. In children, of
course, growth hormone has a very noticeable a networi<of capillaries.
ef fect in increasing height and bulk until
adulthood. However, sometimes the pituitary Anterior lobe Thyroid

gland becomes hyperactive - often as a result of Subdivided intothree One of the largest
a benign tumour - and produces excess growth parts, including the thin endocrine glands that
r e gul a t e s metabo~sm
hormone. In these cases, a person can grow to a intermediate lobe, this
far-beyond·average height, with hands, feet and produces s"""" kinds is in turn regulated by
facial features growing proportionally. While this
might not seem so bad, gigantism is nearly ofhormone which each the pituitary gland.
always accompanied by other health issues, target specific organs.
such as skeletal problems, severe headaches
and more life·threatening conditions like heart
disorders. If diagnosed early, treatment such as
drugs that inhibit growth hormone production
and surgical removal of the tumour can help
avert the more serious conditions of gigantism.

099

=··

I ,._,... the brain uce

enough c

power a light

The brain is a complex and extremelypowerful organ, but
would it be strong enough to power any everydayfightbulb?

The brain itself requires a relativelylow neurons are signallingandina highlysynchronised
manner, the generated electricfields are large enough
power to operate on a day-to-day basis, to be detected outside of the skull through
around 20 watts which would be enough to electroencephalography ~EEG) or
powera very weak light bulb. zawatts magnetoencephalography ~MEG).

corresponds to zojoulesolenergy persecond.The "The generation of.

generation olelectricity In the brain results from the electncity results from
movement of ions ~charged atoms) throughout the the movement of ions"
brain, as opposed to electrons moving through a wire.

Interestingly, a uniqueside effectof the brain's
electrochemical processesIs that Is generateselectric

fieldswhen it is active.! ndeed, when large numbers of

Ongoing message

Oncetheneuroaansmltlers
crossthegapbetween thetwo
neurons, ionchannelsinthe

receMngneuronopenallowlng

theposlllveloosInflowintothe

receivingneuron.

100


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