Respiration Guides to
Kidney A look
Howdo our BOOKOF
EVERYTHING YOU NEED TO KNOW ABOUT THE HUMAN BODY
How many Inside a Understanding
bones are in human heart
- - Anatomyof
. ... ..fill- • '
• the tongue
The human body is truly an amazing thing. Capable ofawe-Inspiring feats of
speed, agilityand strength, while being mind-blowing In complexity, your
bodyts unmatched bythat ofany otherspedeson Earth. In this updated
edition of HowItWorks Book of the Human Body, we celebrate the human
body's capabilitiesand beauty. as well as analyse bow it can be Impaired
or hampered. From how you bear, to how your digestion works, through
how your bones repair fractures and on to bowwe express emotions and
experience touch, we explore the human body like never before. Packed full
of high-quality anatomical illustrations, detailed pbotographyand easy-to-
understand authoritative explanations. this book is Oiled with Incredible
facts thatwiU make you see yourself ina whole new light.
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Kow tt Works Book of the Human Body Third RewiNd Edition C 2015 lm~ Publlthln& Lld
010 50 amazingbodyfacts 028\ ""'-..
020 ruumJnating cells The power of 010
021 Inside a nucleus your brain Your body
022 Stemcells explained
024 Bow do we smell? 022
025 Taste I Tastebuds
026 The tonsils 1 Whatare
027 Vocal cords stem cells?
OJO Brain power
OJ2 Vision and eyesight I
OJ4 Bow ears work
OJ6 All about teeth o66 The humanribcage
oJ8 Anatomyofthe neck o68 Howthe pancreas works
040 Thehuman skeleton 070 Howyour bladder works
042 Bowmuscleswork 072 Human pregnancy
044 Skin colour I Skingrafts 074 Embryo development
045 Under the skin 076 Insidethehuman stomach
046 Rheumatoidarthritis 078 Bow does angioplasty work?
047 Bone marrow o8o Thehuman hand
048 The human spine o82 Nails I Knee-jerk reactions
050 Heart attacks o8J Insidethe knee
051 Heart bypasses 084 Bowyourfeet work
052 Bloodtransfusions o86 Achil1es' tendon I Smellyfeet
053 Strokes I Blood dotting o87 Blisten I Cramp
054 Human kidneys
056 Kidney transplants
058 VestigJaJ organs
059 Bow the spleen works
o62 Bowthe liver works
064 The small intestine
- - - 165
090 Foodandthe body Curious questions 1 142 /
098 The blood-brain barrier
099 Pituitaryglandup close 142 Ageing The signs
100 Brainelectricity I Synapses of ageing
101 Adrenaline 146 Left or right brained?
102 Humanrespiration 161 Correctingheart rhythms I
104 Dehydration I Sweating 148 Brainfreeze Salt I Adam's apple
105 Circadian rhythm 149 Runny nose I Comas Seasickness I Rumbling
106 The immune system 150 Ears I Freckles I Sore throat stomachs
110 Bone fracture healing
111 Making protein MemoryI Toothpaste I 16) What aremoles?
112 The cell cycle Epidurais 164 Braincontrol/ Laughing
114 White blood cells Blush I Caffeine I Fainting
116 The science of genetics 153 Eyebrows I Earwax I SeH DandruffI Eye adjustment I
12.1 Burns 154 72-hour deodorant I Distance the eye cansee
12.2 Blood vessels Modem fillings 166 Allergies I Eczema
12.4 Howyour blood works 155 What powers cells? 167 Bruises I Water allergy I
u.8 Hormones 156 Canwe see thoughts? Cholesterol
1)0 The urinary system 158 How anaesthesia works 168 Alveoli
1)2 Tracheotomy surgery 159 Stomach ulcers I Mouth ulcers 169 Migraines/Eyedrops
1)) Hayfever 160 Hair growthI Blondhair 170 What are twins?
1)4 Exploringthe sensorysystem I appearance 172 Paper cuts I Pins and
1)8 Chickenpox needles I Funnybones
1)9 Whywecry 17) Aching muscles I Fat hormone
174 Raw meat I Inoculations I
175 Feet size I Gout
How 50 fantastic
we think facts about
010 ~o amazin~ body facts 027 Vocalcords 0""
rom head o toe See how they help us talk Q
018 Bumancells 028 Brainpower 0)8 Anatomyofthe neck
How are they structured? The human brain explored Impressive anatomical design
020 mumina~cells 0)2 The science ofvision 040 Thehuman skeleton
Making cells g ow Inside the eye Abounty of honey facts
021 Inside a nucleus 0)4 Bow earswork 042 Bowmuscles work
Dissecting a cell's control centre Sound and balance explained Muscle power revealed
022 Stem cells 0)6 Allabout teeth 044 Skincolour I Skingrafts
Building block bring new life Dental anatomy and more Skin facts explained
024 Bow do we smell? 045 Under the skin
Alook at your nose Anatomy of our largest organ
025 Taste I Taste buds 046 Rheumatoidarthritis
The science of taste explained How is inflammation caused?
026 The tonsils 047 Bone marrow
What are these fleshy lumps? Why is this jelly vital to us?
008 048 The human spine
33 vertebrae explained
Howyour feet wctrk
050 Heart attacks o6o Humandiraestion 076 Inside the human stomach
Why do they happen? How does ood get processed? How does this organ digest food?
051 Heart b~asses 062 Howthe liver works 078 How does ancftoflasty work?
How are ockages bypassed? The ultimate multitasl<er Inside the me ica procedure
052 Bloodtransfusions 064 The small intestine o8o The human hand
This vital procedure explained How does this organ work? Our most versatile body part
05) Strokes I Blood dotting o66 Thehuman ribcage 082 Nalls I Knee-jerk reactions
Why do these occur? Offering essential protection A look at fingernails and more
054 Human kidne~s o68 How the~ancreas works 08) Inside the knee
How do your ki neys function? The body s digestive workhorse See how itallows us to walk
056 Kidney transplants 070 Howyour bladder works 084 Howyourfeet work
The booy's nafural filters Waste removal facts Feet facts and stats
058 Vestigial orf,ans 072 Human prepancy o86 Achilles' tendon I Smellyfeet
Are ttiey real y useless? Nine months of growth explained Are they our weak spot?
059 How the spleen works 074 Embryo development 087 Blisters 1cramfo
Learn how tt staves off infections The core processes revealed Why do blisters orm?
op so body facts
- - - - - -I•U•JW•1!113N•l!i'i> Useless body parts include the appendix the coccyx and w1sdom teeth -
l Howdo Frontal lobe . - - - - - - - - - Primary motor cortex
The frontal lobe iswhere)'<lUI' Theprimarymotorcortexand the primary
persmality is, andwhere )'<lUI'
lhcughts and emolians fonn. somatosensorycortexare the a-easwljch
receiYesensory imervations and then
What are thoughts? This question wUI Rem<Mng this ordamaging itcan CXHlrdinate)'<lUI'whole r.l:1geat~
keep scientists, doctors and persona.
philosophers busy for decades to Parietal lobe
come.llall depends bow you want to Theparietal lobe is responsi>le for
define the term 'thoughts'.Scientists )'<lUI'complex sensorysystem
activation in response to a stimulus Bloca's - - + -;;.;..;;; - Primary auditory
(such as seeingan apple and
recognising it as such). Philosophers, area complex
andalsomanysdentists, will argue
that a network of neurons cannot Btoca'sareais The primaryauditory
possiblyexplain the many thousands
ofthoughtsand emotions thatwe when! lJOU form complex is ri~ next to
must deal with. Asports doctor might
complex words the ear and is where you
and speech interpret sound waves
patterns. into meaningful
state thatwhen you choose to run, you Temporal lobe Occipital lobe
pathways that lead from your brain to The temporal lobe decides what to The occipital lobe is all
yourmusclesin lessthan a second. do with SOl.l1d informationand also
Therearesomespecificswe do know combines it with visual d~at~a. ::;:=----- the way atthe back, but
brainare responsible forvarious types Wernicke's area is where lJOU interpret it inletpo ets the light
L...- the language )IOU hear, and then )IOU .___ signals in )'<lUI' eyes into
W11 fonn a response via Broca's area. sllapes and pattems.
' S Whycan
: some people
i: others can't?
3Do eyeballs ! Although we're often taught In school that
grow like the tongue rolling Is due to genes, the truth Is
likely to be more complex.There Is ll.kely
rest of the body? to be an overlap ofgenetic factors and
~ Only a smallamount families and twins haveshownthalli
2 1nthe appear so beautiful, as I cannotbea case ofsimplegenetic
do we wakeup their eyes are slightly . inheritance. As!< around- the facttbat
[email protected] our some people can learn to do It suggests
eyes first? Iout of proportion and that in at leastsome people It's
environmental (ie a learned behaviour)
Sleep is a gift from nature, which Is Iso appear bigger. rather than genetic (Inborn).
more complex than you think. There
Why do we fiddle
are five stages ofsleep whlch represent
the increasing depths of sleep - when subconsciously?
eyes spring open, it's often a natural I'm con ntly I
awakening andyou're coming out of playing with my hair
rapid eye movement (REM)sleep; you
maywellrememberyourdrearns.lf This is a behavioural response-
you're coming out of a different phase,
egwhen youralarm clock goes off, It some people playwith their hair (
when they're nervous or bored. for
will take longerand you might not the vast majorityofpeople such I
want to open your eyes straight awayI traits are perfectly normal; if they
: begin to interfere with your life, I
behavioural psychologists can help
i -but it'sextremelyrare that you'll
! end up there. :
op so body facts
2Dfield - - - - - - - . 7 What's my 1 Why do
field of vision · we burp?
lThe a-eas from 1201D 180
dog! eesare seen as 20as
r.: .. in degrees? Aburp is a natural
odi one eye <Uibibutes,but (
30field- - - - -- '~ Thehumanfieldofvlslonlsjustaboutt8o ; release Of gas from
the stomach. This gas
The central 120-degree • degrees.Thecentral portionofthis
portion is the 30 part of I has either been
(approximatelyuodegrees)is binocularor swallowed oris the
oorvisionas both eyes
0 stereoscopic- ie both eyes contribute. I1 result ofsomething
contribute - this is tt.e part you've ingested-such
: :!':::;~:~!~~~i~t:d~~O:~~wecan as a fizzy drink. The
we use the most
~ monocular. meaning that there Is no
__.....,.......--······---········--·-·--·····-----··--·--,..-..-...-...-.·----·····..·-·--- ~···- ....... - .... ····· ·• sound comes from the
! n How fast does
8 Whatis I vibration of the
the P.Oint I! bl00d trave1round
of tonsils? I.1· sopehsoinpchtaegreaatlthe
the human body?! oesophago-gastric
The tonsils are collections of • junction, whichis the
I Your total 'circulating volume' Is about five lltres. Each ! narrowest part of the
lymphatic tissueswhich are
I red blood cell Within this has to go from your heart. gastrointestinal tract.
thought to help fight off
I: downthe motorway-Uke arteries, through the
pathogensfrom the upper back-roadcapillarysystem. and then back through the
respiratory tract. However,
they themselves can ji rush-hour veins to get back to your heart. The process
sometimes becomeInfected- typically takes about a minute. Whenyou're ln a rush
leadingto tonsillitis.Theones ! andyourheartrateshootsup, the timereducesas the
you can see at the back ofyour · blood diverts from the less-Importantstructures (eg
throatarejustpart of the ring i large bowel) to the more essential(eg muscles).
of tonsils. You won't miss them !' L The most ---...
2. Under pressure i
ifthey're taken out for , important organ Blood is moving fastest
recurrent Infections as the : The bra01 has itsown and underthe highest 1
rest ofyour immune system
will compensate. i special blood supply pressureas it tea...s the
i ara)Qedinaade. heart and enters the
11QWhy does it feel so weird when I 13Howmany
~ you hit your funny bone?
I inches of
You're actually hitting the ulnar ne.rve as Itwraps around the bony hair does the
prominenceofthe 'humerus'bone, leadingtoa 'funny' sensation. I!
Although notso funnyasthebrain Interprets thissudden trauma 4. The inferior averay~rson
as pain toyour forearm and fingers! vena cava ; grow their
i Thismas.sNe vein sits
.i betWldtheaorta but is S. lhe head each year?
: furthest point
! nopoor relation-
i These arteries and
without it, blood It's different for everybody-your
veins are thefurthest age, nutrition, health status. genes
l woUdn'tget bad< and genderall playa role. In terms
!! to )'Ot.l' heart. -from)'Ot.l' of length, anywhere between
heart. and blood flow
'!. 3. The kidneys 0.5-tlnch (1.2-2-5Cm)a month
hereI s -·As you might be consideredaverage,
l Thesedemanda mas.sNe ; butdon'tbesurprisedifyou're
growolder, these outside this range.
! 25 per cent ofthe blood
vessels are often the
t from each heart beat!
first toget blodo!d by
STOP 1Emotions blood cells••••• ••••••••••••••••• Red • 4Hard liVOI'ker•••••••••••••••• • s••••••••••••••••Liquid
FACTS chimpsand orang·utansuse facial •: 2 3••••••••• Red bloodoells • also known Humans aremadeupof70 per
expressions to show their Sneeze fast! aserythrocytes • live on Theheartbeatsonaverage
BODY feelings, h...-nan beings are the <J\Ief'agefor 120days. There centwater, which is essential
ROUNDUP A sneeze is typically expelledat areapproximately 25 trilion 100,000 timE5 per day. Of lorbodygrowth and I'EpiW. The
onlyanimalsknown tocryasa a"""d J6lkmlh ()OOmpl1). red bloodcells inyour bodyat co...se thiswil greatly vary NHSsuggestsdrinking L2
Sneezing helpsprotect the body any givenmoment. dependingonyourlevel of ~tresofwatera daytoavoid
result of theiremotions. by ...,p;ng the nose freeof ~ngdecyd...-
bacteriaand viruses.There's a environnental conditions.
ltU•JU•11J!3N•IW The overage person breaks wind between 8-16 times per day
Idifferent?Yourfingerprints are fine ridgesof .
skin in the tips ofyour fingers and
toes. They are useful for improving
the detection ofsmall vibrations
and to add friction for bettergrip.
No two fingerprints are the same l7Why do we all
-eitheron your hands or between have different
two people-and that's down to coloured hair?
your unique setofgenes.
Why do Most ofit Is down to the genes that result
we only fromwhenyourparentscome together to
remember makeyou.Somehair colours win out
(typically the dark ones) whereassome (eg
blonde) are lessstrong in the genetic race.
18some dreams? 1s it possible to
keep your eyes
Dreams have fascinated humans open wtlen you sneeze?
for thousands ofyears.Some
1~6Why, as we people think theyare harmless Your eyes remain shutas a
~ get older, defence mechanism to prevent
while others think they arevital to
ouremotional wellbeing. Most the sprayand nasal bacteria
people have four to eightdreams enteringand infectingyour
per night which are influenced by eyes. The urban myth that
your eyes will popoutUyou
stress,anxietyand desires, but keep them openis unlikely
they remembervery few of them.
There is research to prove thatU to happen- but keeping
you awake from the rapid eye them shut will provide
movement (REM) partofyour sleep some protectionagainst
nasty bugs and viruses.
cycle, you're likely to remember
your dreams more dearly.
does hair growth
become so erratic?
Hairfollicles in different parts ofyour
body are programmed by your genes to
do different things, eg the follicles on
yourarm produce hair much slower
than those on your head. Men cango
bald due to a combinationofgenes and
hormonal changes, which may not
happen in otherareas (eg nasal hair).
- - _ _ - -_It's different
for everybody! _............ ..............,_....................,...... ..,.... ................................................. ......................................... .....................
l 9What gives me
Researchers have spent their whole lives trying to
answer this one. Your personality forms in the front
lobes ofyour brain, and there are clear personality
types. Most ofit is your environment- that is, your
upbringing, education, surroundings. Howeversome
ofitIs genetic,although it's unclear how much. The
strongest research in this comesfrom studying twins
- what influencesonesetoftwins to grow up and be
bestfriends, yet in another pair, one might becomea
professorand the othera murderer.
op so body facts----------------------------------------------------
What makes some blood What is a pulled
others are universa ? muscle?
Your blood type isdetermined by protein markers known asantigens on thesurface ofyour The hamstrings Strain
red blood cells. You can have Aantigens, Bantigens, or none - in which case you're blood type
0. However, ifyou don't have the antigen, yourantlbodleswlll attack foreign blood. ifyou're These are a !1'0UP of Apuled rruscle. or
type Aandyou're given B, your anllbodles attack the Bantigens. However, ifyou're blood type ttree main fT'lJSdes
AB, you can safely receive any type.Thosewho are blood group 0 have no antigens so can give strain, is a tear i1 a 47tJUP
which flex the knee.
blood to anyone, but they have antibodies to Aand Bso canonly receive 0 back! at rn.osc:le filres as a
• , ~ ., .,.._ an!lbodles. Youcanreceiveblood
• ,- • groupsAandO,butcan'trecelveB. I
._• .-...• 8
, • • • YouhaveBantlgensandA
~ • • ~.,.._ antibodies.You canreceive blood
• • • groups Band O, butcan't receive
• . .. .••• • AB
• . ''~ • • You haveAand Bantigens and no
, • • .- antibodies.Youcan receiveblood
, •f groupsA,B, ABandO(Uiliversal
recipient), andcan dooa!etoAB.
0 Thoughwarmingup can belp prevent
You havenoantigensbuthaveAandB sprains, tlleycan happen toanyone.
O, butcan' treceiveA.BorABandcan
donate toall: A. B,ABand0. PulledmusdesaretreatedwilbRICE:
... ,_. ·-·----:-;;::::=:_::_;;;j:., rest,. lee.compresslonandelEwtlon
28What is the
heard it has no use
but can kill you••.
The appendix Is useful in cows for
dlgesllng grassand koala bearsfor
digesting eucalyptus- koalas can have
a 4ffi(tJft)-longappendlxlln humans,
however, theappendix has no useful
function and Isa remnant of our
development. It typically measures
27Which 5-tocm (1.9-).9ln), but ifit gets blocked it
organ cangetlnflamed.lflt Isn't quickly
uses up the removed, the appendix can burst and
lead to widespread Infectionwhich can
most oxygen? What
The heart is the most gag reflex? 3. Vagus nerve
efficient- it extracts
8o per cent of the L F<lr'e91 bodies The V"!J..S """"' is stim.Jiated,
oxygen from blood. leading toforcefula> olla:tion
But the liver gets the TNs isa PiotectM! mechanism to ~X'£"~'!01
atthestomach and cfli!llhra!1n
most blood-40 per food or lan!;gn bodiese otei og the back at
cent of the cardiac to expel the object forwards.
output compared to the throat at times-than swabNing.
the kidneys, which
TNs forceftJ expoolsK>n
get 25 per cent, and 2. Soft palate leads to 'gagging', which
heart, which only
The scft palate (thefleshy part at the candevelop into retd:ling
Ireceives 5per cent. and vomiting.
mouth roof) is strn.Jiated, sending signals
l.Human .,....... 2. Human i:lta:r 3. Human
HEAD2 ~~~~: vscheetah vsgiraffe vsflea
While the mrld rE!C<ll'd
The average man In England The men's outdoor high
HEAD .'~'1$~! ~ hoide( Usain BoltcanrunIt Is L7m (55ft) tall. The jump wortd (eoo(d is 2.4Sm
HUMANS VS .Jf \ '1~ io 9.58 seconds, a cheetah tallest 1'1'\an ever was 2.7m (less than twice the height
'- . ~ can run lOOm (328ft) in (8.8ft).A giraffecangrow ofa man).A fleacan jump
up to 6m 0 9.7ft). up to 100 timesIts heighL
• just ovet six seconds.
ltU•Wi•IIJ!3N•IW Your broin interprets poin from the rest of the body, but doesn't hove ony poin receptors itself
l 3 2Why don't eyelashes
! keep growing?
I, Your eyelashesare formed from hair follicles,justlike those on your
head, arms and body. Eachfollicle is genetically programmed to
j function differently. Your eyelashesare programmed to grow to a
i certainlength and even re-grow ifthey fall out, but they won't grow
; beyonda certainlength, which Ishandy for seeing!
Whyarewe 1 33=resus 34~~uld
.! surv1• ve on
3 1ticl<lish? No, you need a diet
i Onesideof the brain is
! typically dominant over the balanced in
Light touches, byfeathers, spiders, insects orother 1 carbohydrate,
humans, canstimulatefine nerve-endings in the skin protein, fat,
other. Sinceeach hemisphere
Iwhichsend impulses to the somatosensorycortexin the vitamins and
: of the braincontrols the minerals to survive.
oppositeside (ie the left You can't cut one of
brairL Certainareas are more ticklish - suchas the feet - I controls the right sideofyour these and expect to
which may indicate that it is a defence mechanism ! body), right-handed people
against unexpectedpredators. Itis the unexpected I havestronger leftbrain However, it's the
nature ofthis stimulus that meansyou can be tickled. hemispheres. Occasionally proportions of these
which keep us
Although you cangive yourself goosebumps through i you'll find an ambidextrous healthy and fit. You
light tickling, you can't makeyourself laugh.
I person, where hemispheres can get these from
..........-·--···..........................- ...- ........- ..- .........................- •••- ....1 areco-dominant, and these the five major food
! peopleare equally capable
.! with both right and left hands!
I groups. Food charts
can help with this
l balancing act.""~•-••o'9••..............•••..,.........•••..,...-...'9....,.....,,..,,,,0 0Ooooo_..,.....,.,...,"",-..._o-H-••>•••-••t>H_..no•oo_o_..•..._..,..
when we're ill.
The immune response leads toinflammationand the release of
inflammatoryfactors into your blood stream. These lead to an
increased heart rate and bloodflow, which increases your core body
temperature - as ifyour body is doing exerdse. This can lead to
increased heat productionand thus dehydration; for this reason, it's
important to drink plentyofclear fluids whenyou're feeling unwell.
op so body facts
L Atrial systole 2 Ventricular systole 3. Ventricular diastole 39What triggers
the heart and
The atria are the The lll!ntrides contract next, The heart is rcw relaxed a:>d can keeps it beating?
a:>d theysend hql-pre5Slft refill, ready for the next beat.
low-pre5Slft- The heart keeps Itself beating. The
blood out into the aorta to sinoatrial node (SAN) is in the wall of the
chambers, a:>dare the supply the body. right atrium of the heart, and is where the
heartbeatstarts.These beatsoccurdue to
mt to contract, emptying changes In electrical currentsas calcium,
sodium and potassium move across
membranes. The heartcan beatat a rate of
6o beats per minute constantly ifleftalone.
However- we often need it to go faster. The
sympathetic nervous systemsends rapid
signals from the brain to stlmulate the
heart to beat faster when we need it to- in
'fight or Olght'scenarios. Ifthe SANfails, a
pacemakercan sendartificial electrical
signaIs to keep the heart going.
Why do bn.lises go
4 0 41=purple or yellow?
Abruise forms when capillaries under the skin leak and allow .' cutting
blood to settlein the surrounding tissues. The haemoglobin in onions make
red blood cellsis broken down, and these by-products give a J
dark yellow, brown or purple discolouratlon dependingon the
' us cry?
volume of bloodand colour of the overlyingskin. Despite Onions make your eyes waterdue to their expulsion of
popular belief, you cannot age a bruise -different people's an irritant gas once cut. This occurs aswhen an onion
bruises change colourat different rates. is cutwitha knife, many of its internal cellsare broken
down, allowing enzymes to break down amino acid Why do
1. Damageto the 3. Discololration sulphoxidesand generatesulphenicacids. These men go bald
blood vessels than women?
Haemoglobin is then sulphenicacids are then rearranged byanother
After trauma such as a faR, 'Simple' male pattern baldness is due
the small capillaries are broken down into its j enzymeand, as a direct consequence, syn-
to a combination ofgenetic factors
tom and burst smal~ components,which propanethial-5-oxide gas is produced, which is volatile. and hormones. The mostimplicated
are what giw the dark I This volatile gas then diffuses in the air surrounding hormone ls testosterone, which men
have high levels of but women have
discololo'ation of a bruise. .i the onion, eventually reaching the eyes of the cutter, low levels of, so theywin (or lose?) in
I where it proceeds to activate sensory neurons and
this particular hormone contest!
2. Blood leaks createa stingingsensation. As such, the eyes then
'. follow protocolandgenerate tears from their tear
into the skin !• glands in order to dilute and remove the lrrltant.
Interestingly, thevolatile gas generated by cutting
Bk>od settles into the
tissues SUTOU'lding the
vessel. The pressure , onions can be largely mitigated bysubmerging the
from the bruise then onion inwater prior to or midway through cutting.
~stem the bleedio~g.
-• with the liqtlidabsorbing much of the Irritant
tria~le sha~ 43When we're
I!I tired, why do
on the side Of
the ear? we get bags under
ThisIsthe tragus. Itserves : our eyes?
no major function that we
Blooddoesn'tcirculatearound yourbody as
knowot butltmayhelpto efficientlywhen you're asleep so excesswater can
reOect sounds Into the ear pool under the eyes, making them pulfy. Fatigue,
to Improve hearing. nutrition, age and genes also cause bags.
The heart is amazing
It stimulates its own heartbeat, beats around 1oo,ooo times a day and pumps
about 2,ooo gallons ofblood per day. It's also the most efficient of organs and
extracts the highest ratio ofoxygen per unit of blood that it receives. The heart
has its own blood supply too that supplies its muscular wall.
ltU•JU•11J!3N•IW The hyoid is the only bone that isn't connected to another bone - it sits ot the top of your neck
II 4 7 Whydowe Why do some
get itchy? hereditary
conditions skip a
! Itching Is caused by the release ofa generation?
I transmitter called histamine from
Genes work in pairs. Some genes are
j mast cells which circulatein your body. 'recessive' and ifpairedwitha
'dominant' half, theywon't shine
:· These cellsare often released In through. However, iftwo recessive
1, response to a stimulus,suchas a bee
genes combine (one from your mother
l! stingoran allergic reaction. They lead and one from your father), the
to inflammationand swelling, and recessive trait will show through.
! send impulses to the brain vla nerves
which causes the deslre to itch.
Blinkinghelps keepyour eyescleanand moist Blinking
spreadssecretions from the tear glands (lacrinlal fluids)
over the surfaceof the eyeball, keeping it moistand also
sweepingaway small particlessuch as dust.
____ ____...., ...._.............-~--··-··--······-··-·..................... ~-·-·-·······-~
ISQWhich muscle produce~ the
1 most_powerful contraction
i relative to its size?
j Thegluteus maxinlus is the largest muscle and forms the bulkofyour buttocl<. Theheart (cardiac muscle) is
!! the hardest-working muscle, as itisconstantly beatingand clearlycan never take a break! However the
strongest muscle basedon weight is the masseter. This is the muscle that clenches thejawshut- puta
! fingerover the lowest, outer partofyourjawand clench your teethand you'll feel it
Myosin head t Actin filament Actin filament
I. c._----=======... is pulled
!j 1. Taking the first step 2. Preparation
• Musclecontract!onslartswithanlmpulserecel\ledfromthe Thecalcium bindsto troponinwhich Is a receptoron
j nerves supplyingthe muscle - anactionpotential.Tbis
theactin protein.Thisbindingchanges theshape of
j action potential causescalciumIons to flood across the
tropomyosin.anotherprotelnwbich Isbound toactin.
! protein muscle fibres. The musdefibresare formedfromtwo Thesesbape changes lead to theopeningofaseriesof
keyproteins: actinandmyosin. bindlngsltes on theactinprotein.
How come most ! ~- Energised myosin
people have one foot !•' head
larger than the other? 3. Binding
Most people'sfeet are different sizes-in fact the two Nowthe binding sitesare free onactin. the myosin beads
halves of most people's bodiesare different! We all start ! forgestrongbonds in these points.Tbis leads tothe Wben theenergyrunsou~ the proteins losetheirstrong
from onecell, butas the cells multiply, genes give them ,• contractionof the newly formedproteincomplex; wben all bondsanddlseng;~ge,and from theretheyreturnto
varying characteristics. 1 oftheprotelnscontrac~ themuscle bulk contracts. theiroriginal restingstate.
Cells under the microscope
St.mxning and "'ippOI ti '!I
eacheel isa plasma meaba-.e
that ""' lbulsewrything that
There are around 75 trillion cells Nucleus --------~
in the human body, butwhat are
The nucleus is the cell's 'brain'
they and how do theywork?
ex control centre. Inside the
nucleus is DNA infonnation,
which explains how to make
the essential proteins needed
.:.*-~ Cellsare lifeand cellsare Ribosomes - - - - - - - - - - - . . .
, alive. You are here because
everycell insideyour body These tiny structures make proteins and
... has a speclllcfunctlonand a can be fol.lld eitherfloating in the
cytoplasm orattached ike studs to the
very specialised jobto do. Thereare
many different types of cell., each one endoplasmic rt'ticulllll, which is a CO"""Y''"
working to keep the body's various belt-like membrane that transports proteils
systemsoperating. Asinglecell Is the around the eel.
smallest unitofliving material In the
bodycapableof life.When grouped
cells with similarjobsto do form tissue,
suchas skin or muscle.To keep these Endoplasmic reticulun - - - -
chemical reactions going onall the time. The - o f folded memblanes (ca>als)
oonnecting the nucleus tothecytoplasm are
All animal cellscontaina nucleus. called theendoplasmic relicuk.m (Ell). If
which acts likea control hub telling the studded witll ribosomes the ER isrefeoed to
cell what to do and contains the cell's as "rou!to' ER; if oot it isknown as '5mooth'
material within a cell is awatery, E:R. Both~ transport materials around the
jelly-like substance called cytoplasm
cell but alsohaw diffe 0"19 functioos.
(cyto means cell}, which circulates
around the cell and is held In bya thin
external membrane, which consists of
two layers. Within the cytoplasm Is a
variety ofstructurescalied organelles. Smooth - --...J
which aU have different tasks, suchas
manufacturl ng proteins- the cell's key endoplasmic
chemicals. One vital example ofan reticulum
organelle Is a ribosome; these numerous
structurescan be found either floaU ng R~h~ic ------------
around in the cytoplasm orattached to
Internal membranes. Ribosomes are reticulum (studded
crucial in the production of proteins with ribosomes)
from amino adds.
In turn, proteinsareessenUal to
biochemical reactions the body needs In
order to grow and develop and also to
repair itselfand heaL
Mroxboodria ------~ Golgi body - - - - - - - '
Theseorganeles ~eels witlltheenergy
necessary for them to canyout their functioos. Another organele. the Golgi body isone
The atn01.1>t of energy used l>ya cell is mea5l.l1!d
in molecules of adenosine IJ1>hosphate (ATP'). thatprocessesand packages protOOs.
Mitoc:hondria use the products of~ including ton oones and enzymes. for
metabolism as fuel to llfoduoe the ATP. transportation either in and around the
cell a out towards the membrao oe for
seaetion outside the eel where itcan
enter the bloodstream.
Stem cells are self-renewing cells with the potential to become any other
type ofcell in the body. Unlike regular cells, they do not have a spedalisation,
such as nerve cells. Experts have discovered that adult stem cells can be
manipulated into other types with the potential to grow replacement organs.
ltU•JU•11J!3N•IW Bacteria ore the simplest living cells and the most widespread life form on Earth
anatomy Types of human cell
,..--- Cytoplasm So far around 200 differentvarieties ofcell have been
identified, and they all have a veryspecificfunction to
This is the jelly·like perform. Discoverthe maintypes and what theydo...
substance - made of
water, amino acidsand NERVE CEliS move.Wecancontrolskeletalmusclesbecausethey
enzymes - found inside arevoluntary. cardiac muscles, meanwhile, are
the cell membrane. system andthe brain are nerve ceUs Involuntary,whichIs fortunate becausethey
Wrthin the cytoplasm are orneurons. Electrlcalmessages areusedto keepyourheartbeating. FoundIn
pass betweennerveceUsalong thewails oftheheart, these muscles create
organelles such as the longffiarnents caJJedaxons.To theirownstimuli to contractwithout Input
nucl~ mitochondria cross thegaps between nerve from the brain.Smooth muscles,whichare
and ribosomes, each of ceUs(the synapse)thatelectrical prettyslowandalso Involuntary, make up
which perfcxmsa specific
role, causing chemical signal Isconvertedintoa cbernical thellnlngsofhoUowstructuressuchas blood
signal.These ceUs enable us to feel vesselsandyourdigestivetracLTheir
reactions in the sensations,suchaspain, andtheyalso wave-likecontractionaidsthe transportofblood
cytoplasm. enable us tomove.
around thebodyandthe digestion offood.
- - • - • • • o oooo,..ooo ouooooo-uooooo. .._ , _ , , , ,, , _• .,,,..,,,,, • • - • • • ' ' ' ' ' ' ' " " '
This digestive enzyme breaks down
unwanted substances and worn-out BONE CEliS FAT CEliS
organeHes that could hann the cell by These ceUs- also known as
digesting the product and then structurethatmakes bonesstrong- consistofthree adipocytesor lipocytes-
ejecting it outside thecell. makeupyouradipose
main types.Yourbone massis constantlychanging tissue, or body fa~ which
andreformingandeach ofthe three bone ceUsplaysIts cancushion, Insulate
partIn thisprocess. First theosteoblasts,whichcome
from bonemarrow, build up bone massand This tissueIs found
s t r u c t u r e . These ceUs then become beneathyourskinand
burledinthe matrixatwhich otherorgans.Theslzeofa fat
point theybecome known as ceUcan Increase ordecrease
osteocytes. Osteocytes make dependingontheamountof
cetlsInyourskeletonandare energyItstores. Uwegalnweight theceUsli!Jwith
the bonematerial Finally, morewateryfat. and eventually the numberoffatceUs
while theosteoblastsadd to wtll begin to Increase. Therearetwo typesofadipose
bonemass, osteoclasiS arethe tissue:whiteand brown. Thewhiteadipose tissue
ceUscapableofdissoMng bone storesenergyand Insulates the bodybymaintaining
and changingits mass. bodyheatThe brownadiposetissue, on theother
PHOTORECEPTORm IS band. canactuallycreateheatandIsn'tburned for
Theconesandrodson theredna at ·-"···---· · - - - - -- ...energy- thisIswhyanimalsareabletohibernatefor
the backof the eyeare known monthsonendwithoutfood. ..... .......-..._.._
asphotoreceptorceUs.These --··~......... ....
Et11 HELlAI. CR I 5
contain light-sensitive Epithelial cells make uptheepithelial tissue that
pigments thatconvertthe linesandprotectsyourorgans
Image thatenters theeye and constitute theprimary ,
Into nervesignals, which material ofyourskin. • ,••
the brain Interpretsas Thesetissues forma
pictures.Therodsenableyou barrier betweenthe
to perceive light, darkand preclousorgansand .~
movement,while the cones unwanted pathogensor
.b.-r..l..n...g....c...o...l..o...u....r..t..o...y....o...u....r.w.-o...r.l..d........................................_~....................... other fluids. Aswell as
lind epithelial CeliS Inside ,
- - - ..,. TbecellsInyourliverare responsible - -yournose,aroundyour lungs
for regulating thecompositionof
a_.n..d...I.n...y...o..u..r..m....o...u..t.h....... .....~.. ............................................
yootrbl•ood.Tbese ceUsffiter out
toxlnsasweUascontrollingfat, RED BLOOD CEil S
sugarandaminoacidlevels. UnlikeaUthe othercells Inyour
Around Soper centoftheliver's body.your redbloodceUs(also
mass consists ofhepatocytes, knownas erythrocytes)do
whichare the liver'sspeciaUsed notcontain a nucleus.You
__ -- - -- ..ceUsthatareInvolvedwiththe
........_..._p..r.o. du.c..t..i.o...n.. ofp..ro..t.e...i.n...s...and..b..i.l..e......_ around25 trillionred
MUSCLE CEll S
-;;tJ:~~~J- ofaUyourceUs, making
Thereare three types ofmusdeceU- 1 " them themost
skeletal,cardiacandsmooth- and common ceU In
eachdlfiersdependlngonthe yourbody. Formed
function Itperforms and Itslocation In the bone marrow,
Inthe body. Skeletalmusdes these ceUsare important
containlong fibres thatattach to because they carryoxygen toau the
bone.When triggered bya nerve tissues Inyourbody.OxygenIs carried In
signal, the musdecontracts and haemoglobin, a pigmentedprotein that
pullsthe bonewith it, makingyou gives bloodcells their red colour.
·ng cells glow
Find out how GFP and quantum dots are shedding
Hundreds of living organisms produce
light on medical research...
light, although most do not fluoresce,
For millions ofyears, the Aequorea track their movementand interaction. Taggingthe instead getting their glow from
victoriajellyfish held thesecretto HIV virus with GFP, for instance,shows how the chemical reactions. Most of these are
green fluorescent protein (GFP) - a infectionspreads. marinecreatures and bacteria,
protein that absorbs the energy from although terrestrial invertebrates (eg
the blue and ultraviolet (UV) range andre-emits it as a Asimilareffectcan beachleved with quanturn
green light Biologistsgot their hands on the glowing dots - nanoscale semi-conductor crystals which fireflies, inset) and fungi can also
jeUyfish in the Sixties, extracting the protein and also fluoresce under UV light. The dots can be glow. Bioluminescence serves a
then uncovering the gene that codes for it. madein manydifferentcoloursand bound to variety of functions. In many marine
Byinserting this sequence into living organlsrns, proteins, allowingsdentiststo observe complex animals, it provides camouflage by
scientistsequip themwith theinstructionsthatare
required to manufacture GFP, highlighting how biological interactions. aBowing its bearer to blend in with
genesare expressed in everything from bacteria Recently, surgeons wearingspecial goggles the surrounding light when viewed
to human cells.Spedficproteinsand cell types from below. In othet- species it is used
can be tagged with GFP, allowing researchers to identified and removedcancerouscells highlighted
with quantum dots. These gogglescouldalso be as a form of convnunication or, like
used to develop diagnostictests and therapies for
other conditions. the anglerfish, to draw in prey.
Researchers aren't certain what the
Aequorea victoria jellyfish uses its
eerie GFP glow for, but some believe
it may be to evade predators.
I•U•JW•1!113N•l!i'i> Ribosomes are responsible for making proteins out of omrno ocrds
ns1• eanu eus Central command
Dissectingthe control centre ofa cell Take a peek at what's happening inside
Surrounded by cytoplasm, the responsible for making proteins out ofamino the 'brain' of a euk aryot ic cell
nucleus containsa cell's DNA acidswhich take care ofgrowthand repair.
and controlsall of its functions 0 Nuclear pore
and processes such as movement Being so important, the nucleus is the
and reproduction. most-protected part of the cell. inanimal cells orThese channels control the movement molecules
Thereare two main types ofcell: eukaryotic it is a lways located near its centre and away
and prokaryotic. Eukaryotlc cells contain a from the membrane to ensure it has the between the nucleus and cytoplasm.
nucleus while prokaryotic do not. Some maximum cushioning. As well as the jelly-like
eul<aryoticcells have more than one nucleus- cytoplasm around it, the nucleus itself is filled @ Nuclear envelope
called multinucleate cells- occurring when w ith nucleoplasm, a viscous liquid whjch
fusion or division creates two or more nuclei. maintains its structural integrity. Act s as a wall to protect the DNA within the nucleus
At the heart ofa nucleus you'll find the
nucleolus; this particular area is essential in Conversely, in plant cells, the nucleus is more and regulates cytoplasm access.
the formation of ribosomes. Ribosomes are sporadically placed. This is due to the larger
vacuole in a plant cell and the added protection ~Nucleolus
that isgranted bya cell wall.
Made up of protein and RNA, this is the heart of the
nucleus which manufactures ribosomes.
This semi-liquid, semi-jelly material surrounds the
nucleolus and keepS the organelle's structure.
Produces chromosomes and aids cell division by
condensing DNA molecules.
Nucleus in context /
Explore the larger body t hat a nucleus 0
rules over and meet its 'cellmates•
Made up of two separat e Double membraned. How do cells
entities, ribosomes make this produces energy for survive without
proteins to be used both the cell by breaking a nucleus?
down nutrients via
Golgi apparatus Prokaryotic cells are much more basic than their
Named after the Italian eukaryotic counterparts. Up to 100 times
biologist Camillo Golgi, Small and spherical.
this organelle contains smaller and mainly comprising species of
bacteria, prokaryotic cells have fewer functions
than other cells, so they do not require a nucleus
to act as the control centre for the organism.
Instead, these cells have their DNA moving
around the cell rather than being housed in a
nucleus. They haye nochloroplasts, no
membrane-bound organelles and they don't
orundertake cell division in the form mitosis or
meiosis like eukaryotic cells do.
Prokaryotic cells divide asexually with DNA
molecules replicating themselyes in a process
known as binary fission.
at are stem ce •
Understand how these building blocks bring new life
Stem cellsare incredibly proliferation- while others suchas Cloning cells
special because they nerve cells don't divideatall.
have the potential to Scientists can reprogram
becomeany kind of cell Thereare twostem cell types, as cells to forget their
in the body, from red blood cells to Professor Paul Fairchild, co-director current role and become
brain cells.They are essential to life of the OxfordStem Cell Institute at pluripotent cells again
andgrowth, as they repalr tissues Oxford MartinSchoolexplains: - indistinguishable from
and replace dead cells.Skin, for "Adult stem cellsare multipotent, early embryonic stem cells. These
example, isconstantly replenished which means theyare able to are called induced pluripotent stem
byskinstemcells. produce numerouscells that are cells (IPSCs) and can be used in areas
Stem cells begin their life cyc le as
generic, featureless cells that don't loosely related, suchas stem cells in of the body where they are needed,
contain tissue-specific structures, the bone marrowcangeneratecells
such as theability to carryoxygen. that make up the blood; hesays. "In taking on the characteristics of
Stem cells become specialised contrast, pluripotentstem cells, nearby cells.
through a process called found within developing embryos,
differentiation. This Is triggered by are ableto makeany one ofthe IPSCs are more reliable than stem
signals inside and outside the cell. estimated 210 cell types that make cells grown from a donated embryo
lntemalsigna Is come from strands up the human body."
of DNA that carry information for a II because the body is ITl()(e likely to
cellularstructures, while extemaI This fascinating ability to accept stem cells generated by itself.
signals include chemicals from transform and divide bas made
nearby cells. Stem cells can stem cells a rich source for medical IPSCs can treat degenerative
replicate many times - known as research. Once their true potential
has been harnessed, they could be conditions such as Parkinson's
used to treat a huge range of
diseases and disabilities. disease and baldness, which are
caused by cells dying without being
replaced. The IPSCs fill those gaps,
restoring the body's systems.
Professor Fairchild says IPSCs could
help find a cure for certain disorders:
"By deriving these cells from
individuals with rare conditions, we
are able to model the condition in the
laboratory and investigatethe effects
of new drugs on that disease."
STRANGE VVhathappensifyou Answer:
BUT TRUE halve a flatwor1n?
FlatWOI'ms have the ability to (egenefate ofgans.
A LIFE DIVIDED A It dies B It becomes two flatwonns
C One half lives while the other dies which is an Invaluable skill fOf' Sllr'Vfvat. Thetefon~.
If you cut one in half. Its pluripotent stem cells
activate and create two flatworms. We'd father
you didn't try this, though!
I•U•Jtl•I!JirW•ll,.!JP Stem cells have been used to restore the sight of patients suffering from certain forms of blindness
How to grow a stem cell
Fertilised human embryos that and put them into a culture dish. divide theyare placed into multiple
have been donated for research This is filled with a culture dishes, each tryingto completean
have plenty ofstem cells inside medium,which isa mixtureof embryonicstem cellline.lfa line is
them as the cells are yet to fully nutrientsthat encourages the cells completed, it can then be used for
form. Scientists extract the cells to divide and grow. As the ceUs further research and development.
The bone marrow contains both active cells
and stem cells that are waiting to develop.
Platelets Multipotent Haematopoietic stem cell
If you cut yourself, these This stem cell in an adult Stem cells Inside the bone marrow are
is multipotent, so can called haematopoietic stem cells.
blood cells clump together, become any blood-
stopping the blood flowing Chemical exchange
out of your body. related cell.
,....-- When needed, chemicals from
surrounding cells alter DNA
strands inside the stem cell.
I Myeloid Lymphoid
progenitor cells progenitor cells
neutrophils These are the stem cells These are the stem cells that
that become red blood tum into white blood cells,
These are essential for responsible for battling disease.
ceUs, among others.
stopping infections from 023
spreading in the body.
• Olfactory bulb
The abilityto smell is one of our This area olthe brain iswhere si!Jlals are
most crucial senses and can
influence the food we eat and ~and smel ispercei\led. Othe<
the people we date...
animals......., a much largerarea asthey
Smell, or olfaction to use the proper
terminology, is a very dl reel sense, can pe ceNe widerraM}bd511ds and
in that we actually breatheIn use theirsense olsmel more.
substance that we smell. These hit the
olfactoryepithelium, a mucus Theoltactory""""" pass
membranein the nasal cavity, which inlonnation about the particles
contains millions ofolfactory receptor sensed in the nasal cavity to the
neuron cells. Each of these sensory
brain,where thesesi!Jlals are
eel Is is coveredinsmall hal r-llke
structures, calledcilla, which react to the
odour and sendsigna Is to the olfactory nerve,
which relays this information to the braInso it Is then
perceivedas smell. Humans can recognise around
to,ooo different odours and no two Individuals can
senseanything exactly the same.
...._ _.,_.......••••• ~halhowndwlWOit•• Nasal cavity -~:.::.
~only·-- This iswhereairand
Smell affects taste tftaosoopie molecuk!s of
sU>stanceswe areto smel
2 Ththuman-loacbllllvlho ente<. /IJr is p!Aied into this
malnorpnl_ ln_...,. """' to pass through into the
-......- . ......--ra~abucll ...onl)l Ungs by the body's
Olfactory epithelium +--+-......_~ ~Mr-M.,.-..;;;;
This is where the olfactory
neow cells are located. In a
. .......a:~ human. this area is around
--5 Saaseof su el
ie . .uwes~sn ·.~....,- · Cells smell
tlwlinttw-.. ... The patch ofsensory cells located in the nasal
cavity are made up ofseveral different parts
Mucosa lines the epitheiun inside the nasal cavity andcatches the
oclol.r particlesto be sensed by the receptor lli!U'Oil cells.
Olfactory receptor neli"'O1 eels -----------,
These a r e - - e e l s thatarestinUatedbythe
eiia. They then send .,...._ ll'roughtothebrain.
These sense the particles in <W. There are S.20olthese
- - - - - - - - - - - t lif\1on each olfactory ner\1! cell which linethe epitheilm.
•••••••• • •••••••••• •••• ••••
: 3 4 s•••••••
STOP Around 2501.> of ~le Otl..,.. factors Taste buds are not : You can lose yoar Butterflies taste
contribute to flavour only on the tongue sense of taste with their feet
FACTS 1are 'supertasters' : 2 tt's notall aboutjusttaste buds. •
Thingstastedifferent to some • Factors such as temperature. As wt>ll ashaving around 8,000 tfyou happentosuffera serious Notall species taste things in
TASTE because theyare supertasters •••••• taste bodson thehuman •••••• headinjury, neurological cisorder the sameWiJY ashumans.
smell andeven hearing can tongue, h~Snans alsohave rx E'\'en dental problems. then Butterlles' taste sensors. for
and experiencetaste these can severely affect~ example.areactually located
contribute toa thing's flavour them on the rodoftheirmooth ability totastethingsproperty.
signiftcantly more intensely in theirfeet!
than 'nOI'TTlal' people. alongside taste. and oesophagus.
l•li•Jm1!]1:w.mp The tongue contains obout B,ooo taste buds
Discover howwe distinguish
Taste budsare sensoryorgans that are found in the little
bumps (or papillae)on the tongue. The tongue contains
about8,oootaste budsand they're replaced approximately
every two weeks. Sensitivemicroscopic hairs on the taste
buds(microvilli) pic!< up dissolved chemicals from foodandsend
electricalsignals to the brain that distinguishes between five different
tastes: sweet, bitter, savoury(umami),saltyand sour. Varying
sensitivity to these tastes occursacross the whole ofthe tongue. But
taste budsalone cannot tell us the exactflavour offood. Other factors
suchassmell, spiciness, temperatureand texture also contribute to the
eventual taste. So ifyou hold your nose while you eat then your brain
won't getthe full tastestory!
"Factors such os smell,
spiciness and texture also
contribute to taste"
five Taste QUalities are found in all areas of Your taste budshaw
n the tongue, although some regjons are very tiny. sensitive hairs
more sensitive than others.
Building an in-depth map ofthe tongue called miaovili which
send messages to your
There is generalagreement that humans have five basic tastes,
although the fifth taste 'primary' has only been recently offidally brain about how
recognised.Sweetness, bitterness, sournessand saltiness werejoined
bysavouriness in 2002.Severalothersensations that the tongue can something tastes.
recognise have beenidentified butare not classifiedas tastes.
SWeetnessis associated primarily with simplecarbohydrates-ofwhichsugaris --
oneofthe most common.The way sweetness is detected is complexand only
recently has the current model of multiple bindingsites between the receptors •
and sweetsubstance itselfbeen proposedand accepted. Asweet taste infers that
the substanceis high inenergyandstudies have shown that newborns in 025
particular, who need a high calorieintake to grow, demonstrate a preference for
sugarconcentrationssweeter than lactose, which is found in breast milk.
Bitterness can bedetected in very low levelsand isgenerally perceived to bean
unpleasant orsharp taste. Many toxicsubstances in nature are known to be bitter
and there is an argument proposed byevolutionaryscientists that bitterness
sensitivity is an evolutionarydefence mechanism. Humans, however, have now
developed various techniques to make previous inedible bittersubstancesedible
through redudng their toxidty, often through cooking.
The taste ofsaltiness is produced by the presenceofsodiumions, orother
closely related alkali metal ions. Potassiumand lithium producea similar taste as
they are most closely related to sodium.
Sournessdetectsaddity. Thewaywe measure the degree ofsournessis through
rating soursubstancesagainst dilute hydrochloric. The mechanism involved in
detectingsourness issimilar to saltinessin that taste is caused bya concentration
ofions- in this case hydrogen ions. Savouriness isthe newestof the recognised
basic tastes and the taste Is produced by fermented oraged foods. Glutamateis a
common compound that can cause this taste and consequentlysavourinessis
consideredfundamental to Eastern cuisine.
umon tonsils explained
What purpose do these fleshy lumps
inthe back of our throats serve?
Where you can find
the three pairs of
tonsils in your head
Tonsilsare the small masses of Palatine tonsils Ungual tonsils Pharyngeal tonsils
flesh found In pairsat the back of
the throats of many mammals. In These are the best·known pair The lingual tonsils are found at These areotherwise knownas
humans the word isactually used the rearof your tongue -one at the adenoids and are located
to describe three sets ofthis spongy lymphatic of tonsis, as they~e clearly at the back ofthe sinuses.
tissue: the lingual tonsils, the pharyngeal visible at the back of yourthroal either side in your lower jaw.
tonsilsand the more commonly recognised
palatine tonsils. Lots of bed rest, fluids Tonsillitis in focus
The palatine tonsils are the oval bits that and pain relief like
hang down from either side at the back ofyour paracetamol are all Tonsillitis is usually caused by certain bacteria
throat - you can see them Ifyou open your recommended for (eg group A beta-haemolytic streptococci) and
mouth wide in the mirror. Although the full treating tonsillitis
purpose of the palatl ne tonsi Is isn't yet sometimes viral infections that result in a sore
understood, because they produce antibodies and swollen throat, a fever, white SPOts at the
and because of their prominent position in the back of the throat and diffoculty swallowing.
throat, they're thought to be the first line of
defenceagainst potential infection in both the Usually rest and a course of antibiotics will see it
respiratoryand digestive tracts.
The pharyngeal tonsUsarealso known as the off, but occasionally the infection is very severe
adenoids. These are found tucked away in the and can potentially cause serious problems, or
nasal pharynx and serve a similar purpose to reoccurs very frequently. In these cases a
thepalatine tonsils but shrink inadulthood.
The lingual tonsils are found at the back of tonsillectomy may be considered - a surgical
the tongue towards the root and, ifyou poke
your tongue right out, you should spot them. procedure where the tonsils are removed.
These are drained very effidently by mucous
glandsso theyvery rarelyget infected. The adenoids are less commonly infected but,
when they are, they become inflamed and swell
026 to obstruct breathing through the nose and
interfere with drainage from the sinuses, which
can lead to further infections. In younger people,
constant breathing through the mouth can
stress the facial bones and cause deformities as
they grow, which is why children will sometimes
have their adenoid glands removed.
I•U•JW•1!113N•l!i'i> The vocal cords remain open when you breathe, but dose completely when you hold your breath
, , , , , , ------·~----------~.-r--~
The vocal cords and larynx in_particular Tongue ---.1 Theepiglottis stopsfood
have evolved over time to enable humans to This musde,situated in the entering the trachea
produce a dramatic range ofsounds orderin mouth, can affect and
change sound as it travels uP I
to communicate- but how do theywork? from the vocal cords and out Vocal cords openwhen
through the mouth. breathing. butare pulled
Vocal cords, also known as As alrIs expelled from the lungs, the Trachea ----.....J
vocal folds, are situated In
the larynx, which Is placed vocal foldsvibrateandcollide to produce The vocal cords are situated
at the top ofthe trachea. a range ofsounds.Thetypeofsound
Theyare layers of mucous membranes emitted Is effected byexactly how the at the top of the lr.IC'-
thatstretchacross the larynx and control folds collide, moveandstretchasair wNch is where air from the
howair isexpelled from the lungs In
order to make certain sounds.The passesover them.An individual kNlgs traYels uPthrough
primary usage ofvocal cords within 'fundamental frequency' (theirstandard from thechest.
humansisto communicateand It Is pitch) Isdetermined by the length. size Vocal cords -----!......_-..-..~.
hypothesised that human vocal cords and tension of their vocal cords.
Movementof thevocal folds iscontroUed These layers of I1'AICOUS
actually developed to the extent we see by thevagus nerve, and soundisthen
merrba.esstretch acaoss ,,,, , ,
now to facilitateadvanced levelsof further fine-tuned to form words and the larynx and they open,
communication In response to the sounds that we can recognise by the doseandvibrate 10 produce
larynx, tongueand lips. Fundamental
formation ofsocialgroupings during dille ent sounds.
phasesofprimate,and specifically frequency in malesaveragesat125Hz.
human, evolution. andatztoHzin females. Children have a I
higher average pitchataround300Hz.
This is a flap of skln that 1
Male voices are oftenmuch lower than voices has beenstudied In relation to shuts off the trachea when 1
femalevoices.This is primarilydue to sexual success, and individuals with
thedllfe.rent sizeofvocaIfolds present lower voices have beenseen to be an individual is swallowing I
in each sex, with males havinglarger moresuccessful in reproduction.The food. It steps food and liquids
foldsthat create a lowerpitched sound, reason proposed for this is that a tower 'going down the wrong way'. .--~
and females havingsmaller folds that
createa higher pitch sound. The tone voice may Indicatea higher level Oesophagus _ _..
oftestosterone present In a male.
averagesizefor malevocal cords are This tube, situated ~nd
between17and 25mm,a nd females the lr.IC'- is where
are normally between12.5and 17.5mm.
From the rangeInsize, however. males food and liquid traYels
can beseen to have quite high pitch down to the slomad1.
voices, and femalescan have quite low ~ --------~~--~
~are essential for the
The other major biological
difference that effects pitch Is that production ofSl>«'ific
males generally have a largervocaI S<U1ds, like 'b' C< '))'.
tract, which can further lower the tone
oftheir voice Independent ofvocal ~~ ------~~_.
cord size.The pitchand tone ofmale
box, this protects the trachea
and is heavly ir1IIOived In
contn>&lg pitch and vOOme.
Theweal cords are situated
within the larynx.
most fascinating organ of oil
The human brain is the most
mysterious- and complex-
entity in the known universe
It's a computer, a thinking machine, a pinkorgan, and avast
collectionof neurons- but how does It work?The human brain is
amazingly complex-in fact. morecomplex lhananythlnginthe
known universe. The brain effortlesslyconsumes power, stores
memories, processes thoughts, and reacts to danger.
Insomeways, the human brain isllkea carengine.Thefuel- whlchcould
be the sandwich you had for lunch ora sugardoughnut for breakfast- causes
neurons to lire Ina logical sequenceand to bond with other neurons. This
combinationof neurons occursincredibly fast, but the chain reaction might
help you composea symphonyor recall entire passagesofa book, help you
pedal a bike or write an email to a friend.
Sdentistsarejustbeglnni ng to understand how these brain
neurons work-they have not figured out how they trigger a reaction
when you touch a hot stove, for example, or why you can re-generate
braincells when you work outat the gym.
TheconnectionsInside a braInare verysi mliar to the Internet- the
connecllonsareconstantlyexchanging information. Yet, even the internet
is rathersimplisticwhen compared to neurons. Thereare ten to 10oneurons,
and each one mal<es thousands ofconnections. This is how the brain
processes information, ordetermines how to move an arm and grip a surface.
These calculations, perceptions, memories, and reactions occuralmost
instantaneously, and notjusta few times per minute, but millions. According
tojim Olds, research directorwith George Mason University, if the internet
were as complexas oursolarsystem. then the brain would beas complexas
ourgalaxy. In other words, we have a lot to learn. Sdence has notgiven up
trying. and has made recentdiscoveriesabout howwe adapt, learn new
information, and canactually Increase braincapability.
In the most basicsense, our brainis the centreofall inputand outputs in the
human body. Dr PaulaTallai,aco-directorof neuroscienceat Rutgers
University, says the brain Is constantly processingsensoryinformation- even
from infancy. "It'seasiest to think of the brain in terms oflnputsandoutputs;
saysTallal."Inputsare sensory information, outputsare how our brain
organises that informationand controls our motorsystems.·
Tallalsaysoneof the primaryfunctions of the brain is in learning to predict
whatcomes nexL In her research for ScientificLearning, she has found that
young childrenenjoy having the same book read to them again andagain
because that is how the brain registers acoustic cues that form into phonemes
(soundsl to becomespoken words.
·we learn to put things togetherso that they become smoothsequences;
shesays.Thesesmooth sequencesare observable in the brain, interpreting
Spennwhale Mouse lemur Elephant
The sperm whale has Thes mallest pr'imate At 10.5 poonds
evolved the largest brain brain is owned by the (4.78kg) it'scertalnlya
ever toexist on our pygmy mouse lem.~r of big one.The b<aln of
plane~ w<!igling as the elephant makes up
weighs in a t just 0 .004 1~ than 0.1 per cent of
much as nine kilogr'CIO"'s
pounds(2g). Its body w<!lght.
ltU•JU•11J!3N•IW The overage human brain is 14omm wide x 167mm long x 93mm high
, - - - - Cerebral cortex Functions of
The 'grey matter' of the brain cootrols cerebral
cognition, motoractivity, sensation, and
The cerebral cortex is the wrinkling
other higher level functions. Includes part ofour brain that shows up when
the association areas which help
process infO<mation. These
association areas are what
distinguishes the ho.man
brain from other brains.
suc:llas taste, hearing, and l~ex you see pictures ofthe brain
might help usdetennine movements ------ ' SN!Ietal""""'"'""' .---- Parietal lobe
Where the brainsenses
langu-and tt-e toneci touch and anytling that
solving \ interacts with the surface
of the skin, makes us
aware of the feeings
Prefrontal cortex 1 - - - - - - -Temporallobe
Executivefunctions such asCOft'1:llex. What cistinglishes the t.Jman
plannilg, memorising. social and verbal
ad\tanoed Uinking and interactions. tn L___ _ _Anaslyosuinsdosf and interpretwhatother parts
adults, helps usdeteNrinewhetheran of the brain are hearing,
actionmakes senseorisdangerous. sensing, ortasting and
"In a sense, the main function of
the brain is in ordering information
- interpreting the outs1oe world and
making sense of it"
the outside world and maldngsense of it. The brain them (or even faster in some cases).This means
is actually a seriesofinterconnected that when you reach out to opena door,your
'superhighways'or pathways that move 'data' from brain has already predeterminedhow to move
one part of the body to another. your elbowand clasp your hand around the door
handle - maybe evensimulated this movement
Tallalsaysanotherway to thinkabout the brain
is by lower and upperareas. Thespinalcord moves more than once. before you evenactuallyperform
information up to the brainstem, then up into the the action.
cerebral cortex which controls thoughts and Another interestingaspect to the brain is that
memories. Interestingly, the brain really does work
likea powerful computerin determining not only therearesomevoluntarymovements and some
movements but registering memories that can be involuntary. Somesections of the brain might
controla voluntary movement- suchas patting
According to Dr Robert Melillo,a neurologist your knee to a beat. Anothersectioncontrols
involuntary movements, suchas the gait ofyour
and the founder ofthe Brain Balance Centers walk- which is passeddown from your parents.
(www.brainbalancecenters.com), the brain Reflexes, long-term memories, the pain reflex -
actual ly predeterminesactions and calculates the theseareall aspects thatare controlled bysections
results abouta half-second before performing
in the brain.
Neurons, nerves and the spinal--c-o-r-d--------------------------------
Anet.I'OO is a l'lei'"Ye ceiiW1 Neurons fire like electrical circuits
the bran thatC<W1 be Neuronsarea kind ofcell In the brain (humans have many cellsin
activated (l.ISUaly by the body, Includingfat cells, kidney cells, and gland cells). Aneuron
glucose) toCOIOIOCt with is essentiallylikea hub thatworks with nearby neurons to generate
an electrical and chemicaIcharge. Drlikosky of theSwedish
- netronS and form a Medical Inslltutesaysanother way of thinking about neurons is
bond that trigger-s an that they are lil<ea basl<etball and the connections(calledaxons)
action in the brain. are lll<e electrlca Iwires that connect to otherneurons. This creates
a kind ofcircuit In the human body.Tallal explained that input
~ r-:-- Neu-otransmitter from the five sensesIn the bodycause neurons to fire.
A neurotransmitter is the "The more oftena collectionof neurons are stimulated together
• electnH:hemical cn:u~ In lime, the more likely they are to bind togetherand the easierand
easier it becomesfor that pattern ofneurons to lire insynchronyas
that carries the signal from well as sequentially; saysTallal.
one neuron to another
along the axon.
.-- A thin synapse
A thin synapse
(measuring just a few
carried aklng the axon in
the brain, forms the
"The brain - a fragile Brain
organ that weighs TrackVis generates unique maps of the brain
about 1,500 grams" TrackVis isa free program used by neurologists to seea map of the brain that shows
the fibre connections.On every brain, these neural pathways help connectone partof
the brain to another so that a feeling you experience In one partofthe braincan be
transmittedand processed byanother partof the brain(one that may dectde the touch
isharmful or pleasant).TrackVis uses fM Rl readings onactual patients to generate the
colourfuland eye-catchingImages. To construct the maps, the programcan take
several hours to determine exactly how the fibres are positioningin the brain.
brain U.COiiiJ1 2 . . . . ..., ....-
Ifyou could hold it inyour hand... I1I1I.!.I'.E.I..•..... 1•.1.~. .. - -•
Inpictures, the human brain often looksplnkandspongyz __... . .lllilp5h~--
According to Dr Wllliam Ukosky, a neurologist at theSwedish - -••---•
Medical Institute(www.swedlsh.org),the brain Isactually I,CIOO,..aoHcs pox 7 m
quite different from what most people think. Llkosky
described thebrainasbelng not unlike fetacheeseln tlllll...... tau • I tit
appearance-afragile organ that weighsaboult,5Q()grams
andsagsalmostlikea bagfilled with water. In theskull, the --- --- -.•.-"--·................,......_
brain Is highly protected and has hard dssue, but most ofthe ._,.,..
fatty tissueinthe brain-which helps passchemicalsand
othersubstances through membranes-Is considerably
STOP 100,000 miles of 2!••••••••IH.lletahdeabcrh.e...n.I.o) t 3•••••••••••••••••The brain consists •••••••• Your brain uses :ZOO!c> s•••••••••••••••••The brain has trillions
of60%t.rt of power of c:onnections
FACTS 1blocid vessels Aheadache actualyOCOJrs : 4 The brain is ~ite ~eedy; it
Thereare a staggering Your brainis 60 per cent fat Thebrainhas trillions of
THE BRAIN lOO,OOOmHesofblood ••••••• in bloodvessels around the -which helps canywater and : usesabout20 per-centofthe oonnections.. much
protein through membranes to more than the internet,
...essels in the brain, that is blain.not around the brai'l brain ceUs. keeping everything ••••• power in yourbody thatis
enough towrap around and morethan can
Earth four times. itself. The brain cannotfeel any ticking over. generated from food ounendy becounted
p a i n whatsoever.
ltU•JU•11J!3N•IW The adult human brain weighs about 1.4kg [or three pounds)
How do Nerve transmissions - - - - - - - - - -+ Nerve triggers
Some """"' transmiss<ons trawl great When many neli'OI1s are activated together
distances through the human body, at the same time, the nerve is excited - this
others lriM!I short distances - both use is when we might feel the sensation of
a de-polarisation tocreate the circuit. •• •• touch or a distinct smel.
De-polarisation is like a wound-._., • •
spring that releases stored energy oooe •• • •
work? - • ..• • • • • • •• ••• •
Myelinated and • ••••
Nerves carry signals throughout the un-mylinated - - -• •• . . -.•••• • • •• .•.••.•.• .
body- a chemicalsuperhighway • • • • • • •• •
Nerves are the transmission cables that carry brainwaves in the • • •• •• •••• • •
human body, saysSol Diamond, an assistant professor at the Thayer Some nerves are fTIY"linated • • •
School ofEngineeringat Dartmouth. According to Diamond, nerves • • • •• •
communicate thesesignals from one point to another, whether from (orinsulated) with fatty tissue
that appea<swhite and forms a •• • • - .• • • • •• •
slowerconnection overa •• ••
longerdistance. Others are •
un-myelinated and are
un-insulated. These nerves
your toenail up to yourbrain or from the sideofyour head. tr.M!I shorterdistances.
sp• Spinal cord core
The spinal cord actually In the core ofthe spinal cord, grey matter
is part ofthe brain and - fike the kind in the outer layer of the
plays a major role
brain - is forprocessing nervecellssuch
Scientistshave known for the
past100years or so that the as touch, pain and m ovement
spinalcord isactuallypart of
the brain. According to - - - - - - Nell'ogenesis
Melillo, while the brain has
grey matter on the outside According to Tallal, by repeating brain
(protected by the skull)and activities such as memorisation and
protected white matter on
the inside, the spina lcord is pattern recognitioo, you can grcwv nevv
the reverse: the grey matter is
inside the spinal cord and the brain cells in the spinal cord and brai"t
white matter is outside.
;....._ _ _ _ _ _ _ _ Neuroplasticity
Grey matter cells
In the spinal oord and in the brain, cells
Grey matter eels in the spinal oord can rejuvenate over tWne when you
camot regenerate, w hich iswhy
people w ith a serious spilalcord injury exe.-cise and become strengthened. This
cannotrecover over a period oftime. process iscal~ neuroplasticity.
White matter cellscan re-generate.
White matter cells==------:;T;.....-:::;;;;;'T---'
White m atteroells in the spinal cord
carry the electro-chemical pulses up to
the brain. For example, when you are
kicl<ed in the shin, you feel the pain in
the shin and your brain then tells you
to m ove yourhand toaN~ that area.
Inside the human eye
This pit at the centre of the
back of the eye is rich in light
receptors and is responsible
for sharp central vi.slon.
Uncovering one ofthe most complex Optic nerve
constructs in the natural world
Signals from the retina
travel to the brain via the
optic nerve, a bundle of
fibres that exits through
the back of the eye.
The structure of the human eye is so ofthe pupil.The lightfirst passes
complex that It's hard to believe that
it's not the product of intelligent th rough a tough protective sheet
design, but by looking at the eyes of calledthe cornea, and then moves into
otheranimals, scientists have shown that it the lens. This adjustable structure
evolved very gradually from a simple light-dark bends the light, focusing it down to a
sensor over the course ofaround 100 million pointon the retina, at the back oftheeye.
years. II functions in a very similar way to a
camera, with an openingthrough which the Theretina is covered Inmillionsof
light enters, a lens forfocusingand a light-
sensitive membrane at the back. light-sensitive receptorsknownas rods
Theamountoflightthat enters the eye is and cones. Each receptorcontains
controlledbythe circularand radial musclesin pigmentmolecules,which change
the iris, which contractand relax toalterthesize shape when they are hit by light,
triggeringan electrical message
tllat travels to the brain via the
Seeing in three dimensions
Each eye sees a slightly different image, allowing t he brain to perceive depth
Oureyes are only able to produce two-dimensional images, butwith some clever
processing, the brain Is able to build these Rat pictures into a three-dimensional
view. Our eyes are positioned about five centimetres (two inches) apart, so each sees
the world from a slightly different angle. The brain compares the two pictures,
using the dmerences to create the illusion ofdepth.
Due to the positioning of our eyes,
when objects are closer than about
5.5m (18ft) away, each eye sees a
slightly different angle.
··.~ Comb ined image
The incoming signals from both Retina Iris
eyes are compared in the brain, and
The retina is covered in This circular rnusde
the subUe differences are used to receptors that detect light. controls the si2e of
It is highly pigmented, the pupil, allowing it
create a three-dimensional image. preventing the light from to be closed down in
scattering and ensuring a bright light, or opened
Try it for yourself crisp image. wide in the dark.
By holding your hand in front of
your tace and dosing one eye at a
time, it is easy to see the different
20 views perceived by each eye.
~~~82 Tarsier 2.BIGGER Ostrich Colossal squid
AN EYE FOR SIZE The eyes of these tiny Ostriches are the largest Uttle is known about
primates are as big as these mysterious
IMng birds and also have
the.kbtains, so as a creatur'~, but they have
result, they have the largest eyes of any eyes the sizeof Footballs
living land animal,
developed extremely - tOO largest knoWn in the
measuring an l.nc:redible
good nightvision. ..__ _......;"-_.._ _ __.. Scm (21n) In dlamet..-. animal ldngdom.
[t!f•1\1!I!J!3~[•1~!l? 285 million people in the world ore estimated to be visually impaired and 39 million of them ore blind
. - - - - - - - - - - Ciliary body Vision problems
This tissue surrounds the The most common problems
lens and contains the with our eyesight
muscles responsible for
changing its shape. Farsightedness (hyperopia)
lf the eye is too short, the cornea is too flat, or if
- - - Sclera the lens sits too far bad<, incominglightis
focused behind the retina, making nearby
A tough white membrane objects appear blurry, particularly in thedark.
known as the sclera helps
to maintain the eye's Nearsightedness (myopia)
lf the eyeis too long, or the cornea and lens are
spherical shape. too curved, the light is focused before ithits
the backof the eye, and then starts to defocus
again as it reaches the retina, making distant
objects difficult to see.
This rare condition is often linked to a gene on
the X-chromosome and occurs more commonly
in men than inwomen.Adefectin the cone
cells ofthe eye reduces the numberofcolours
that can be detected.
The eyes are shielded by several layers of protection.
They are almost complet ely encased in bone at the
back and insulated from shock by layers of muscle
and connective t issue. The front is kept moist with
tears and constantly w iped by the eyelids, while the
hairs of the eyebrows and eyelashes cat ch any debris
that might fall in.
Tears are produced here
and wash across to the
inner corner of the eye,
helping to clean and
nourish the surface.
Lens Pupil Comea Eyebrows Eyelashes •
The lens is responsible for The pupil is a hole that The pupil and iris are The arch of the eyebrows Eyelashes not only catch
focusing the light, and can allows light to reach helps to keep sweat and dust before it enters the
change shape to the back of the eye. covered in a tough, rain away from the eyes, eye, they are also sensitive,
accommodate objects transparent channelling it down the like whiskers, and the
near and far from the eye. membrane, which sides of the face. slightest unexpected touch
provides protection triggers a protective blink.
and contributes to
focusing the light.
The human ear performs a
range offunctions, sending
messages to the brainwhen a
sound is made while also
providingyour bodywith a
about the human earls that sound Is all
about movement. Whensomeone
kind ofmovement. the airaround them Is
disturbed, creatingasound wave ofalternating
high and low frequency.These waves are detected
by the earand interpreted by the bralnaswords,
fluid-filled channelsand highly sensitivecells, the
earhas external, middleand Internal parts.The
outerearconsistsofa skin-covered flexible cartilage
flap called the ·auricle', or'plnna'.This feature Is
shaped to gathersound wavesand amplify them
before they enter the earfor processingand
transmission to the brain.The first thing a sound
wave entering the earencounters is the sheet of
tightly pulled tissue separating the outerand
middle ear. This tissue Is the eardrum, or tympanic
membrane, and itvlbratesassound waves hit it.
Beyond the eardrum, in the air-filled cavity of the
middle ear, are three tiny bonescalled the 'ossicles'.
These are the smallest bones In your enUre body.
Sound vibrations hitting the eardrum pass to the
first ossicle, the malleus(hammer). Next the waves
proceedalong the incus(anvll) and then on to the
(stapes) stirrup.Thestirrup pressesagalnsta thin
layerof tissue called the 'oval window', and this
membrane enablessound waves to enter the
The inner ear is home to the cochlea, which
consistsofwatery ducts that channel the vibrations,
as ripples, along the cochlea'sspiraling tubes.
Running through the middle of the cochlea Is the
organofCorti, which is lined with minutesensory
hair cells that pick upon thevibrations and
generate nerve impulses thataresentto the brainas
electricalsignals. The braincan Interpret these
loss••••• ••••••••••••••••• ••••••••••••• Wax essential • s me••••••••••••••••Making dizzy
•: 2 3 • 4••••••••• Waxdeansandh.Jbrieatesthe Inflammation o f the i m e r ear due
STOP 1Hearing range Underwater hearing Hearing outer auditory canal, toviraVbacterialconditionssuch as
H...-nan ears can hear sounds
FACTS with frequencies between 20Hz Hl.ma"'scanhear much The mostcommon causesof transportilgdirtand dead labyri'lthitis can cause dizziness
and 20.000Hz. The abi~tytohear hir;tler-pitched sounds hearing lossareageflg and skin awayfrom the ear. tf and nausea. When balance is
HUMAN EARS frequenciesaboveand belowttis (200.000Hz) whenunder water. noise.. As weage. ourabHityto exc.es.sivewax isa problem,
because wecan 'hear'w ith our heat souOOswith h;ghe< consult )'CIIIdoctor. affected, sufferers may rotbeable
islinked to the sizeofthecells towalk orstand.
and sensitivity. bones. bypassing theouterear frequencies deteriorates- thisis :
known as 'presbycusis'.
ltU•JU•11J!3N•IW The eardrum needs to move less than the diameter of o hydrogen atom in order for us to perceive sound
Abony snail-shaped structure, Thevesti rsystem
the cochlea receives vibrations
Inside the innerearare the vestibule Semicircularcanal
from the ossicles and and semicircularcanals, which
feature sensorycells. From the These three loops positiooed
at right angles to eachother
semicircular canals and are fuD of fluid that transports
maculae, informationabout sound vibrations to the crista.
which way the head is ,......- Vestibular nerve
moving is passed to
receptors, whichsend Sends infonnation
electrical signals about equilibrium from
to the brainas
nerve impulses. to the brain.
Asensayarea ~~l-~t::=:==:~~--~~ Vestibwe
~ in Inside the fluid-filled
tiny hairs. vestibules are two
chambers (the utricle
and saccule), both of
C~a --------------------------~ which contain a
structure called a
At thee nd ofeach semicircular canal macula, which is
covered in sensory
there are tiny hair-filled sensory receptors
A sense of balance
The vestibularsystemfunctions to give detect acceleration lie, movement ofyour
you a senseofwhich wayyour head Is head) in three different directions due to
pointingin relation togravity. Itenables the positioningof the loops along
you to discern whetheryour head is different planes. Like the organofCorti,
upright or not, as well as helping you to thesemicircularcanalsemploy tiny hair
maintain eyecontact withstationary
objectswhile your head is turning. cells to sense movement Thecanalsare
connected to the auditory nerve at the
Also located within the innerear, but
back of the brain.
less to dowith soundand more Yoursenseof balance issocomplex
concerned with the movement ofyour
head, are the semicircular canals. Again that thearea ofyour brain that's
filled with fluid, these loopingducts act
dedicated to this one role involves the
like internalaccelerometers that can same numberofcellsas the rest ofyour
braincells put together.
structures that are so
versatile they enable us
to eat a well varied diet
1be b"Ollble .,..~"' Theprimaryfunctionof the teeth firstappearatslx months old From ancient times healers havesought
teeth Is to crunchand chew and are replaced bysecondary teeth after to treat and replace the teeth with false
with food. For this reason, teeth sixorsevenyears.Someanlmalsdevelop ones. Examples ofthis pmcticecan be
• are made ofstrong only onesetof teeth, while sharks, for seenfromancient Egyptian timesand
Tooth decay, also often instance, grow a newsetof teeth every today, wesee revolutionary new
substances -namelycalcium, techniquesin the form of dental
known as dental caries, phosphorusand various mineral salts. two weeks. Implants, whicharesecureddeepwithin
affects the enameland The main structure of the tooth Is the bone of thejaw.
dentine ofa tooth, breaking dentine, this itsell Is enclosedina shiny With humans, tooth loss can occur
down tissue and creating substance calledenamel.Thisstrong through accident, gum disease or oldage. , - - - - - Pulp
fissures in the enamel. '!Wo whltecoatingls the hardest material Enamel - - -..... The pulp nouislles the
typesofbacterla-namely found In the human body. dentineand keeps the
Streptococcus mutansand The white, outers<rlace "" tooth healthy - the pulp is
Humans have different types of teeth the soft tissue of the tooth,
Lactobacillus- are that function In various ways. Incisors of the tooth. This can be which is protected by the
responsible for tooth decay.
tear at food, suchas the residue found dearly seen when dentine and enamel.
Tooth decay occursafter on bones, while bicuspids have long
repeated contact with acid· sharp structures that are also used for looking in the mouth. Bone
producing bacteria. ripping. Bicuspids tear and crush while
Environmental factors also molars,which have a flatter surface, Cementum --...,...;;P!II( The bone acts
have a strongeffecton dental grind the food beforeswallowing.This The root coating, k asan
health.Sucrose, fructose and aids digestion. Because humans have a i1111pcw ta It
glucose createlarge problems varied army of teeth (called collective protects the root anchor lor the
within the mouth, and diet dentition) we are able to eata complex canal and the tooth and
canbe an important factor In nerves. tt is keepstheroot
dlet of both meat and vegetables. Other coronected to the 5eCU'e witiW1
maintaining good oral health. species, suchasgrazlnganimals, have jav.boc "' throujl t h e jawbone.
The mouth containsan specific types of teeth. Cows, for example, collagen fibres.
enormous variety of bacteria, have large fiat teeth, which restricts them Blood vessels
to a simplediet.
which collectsaround the and nerves --_..:...~~T-~
teeth and gums.This Is visible Teeth have many functions, insome
inthe form ofa sticky white cases they aid hunting but theyalso have The blood........ts
substancecalled plaque. strongpsychological connotations. Both and ner wescany
Plaque Is known as a bio!Um. animalsand humans baretheir teeth
After eating, the bacteria In mxxtat
when faced with an aggressivesituation. llOlWislwnent tothe
the mouth metabollsessugar, Teethare the most enduringfeatures of
which subsequentlyattacks the human body. Mammals are toothand ....,
described as 'diphyodont', which means sensi!Neto
the areas around the teeth. they develop two sets of teeth. Inhumans pre5Slftand
1. Hippopotamus 2. Piranha 3. Hamster
A hippopotamus has an Piranha teeth are very sl'l'\2lll A membetof the rodent family,
eoor'mous mouth that can but can be extr'emely shar'p and the hamster has teeth that
toeasur'e up to 1.2 meues grow continuously. They
ate often used by the local
wide. They areequipped with populationsof South America lher'efore need to9rind thelt
a pair ofhuge and ve.ry tocreate a vatietyoftools teeth ona har'd substance to
dangerous inclsots. and weapons.
ltU•JU•11J!3N•IW The ancient Egyptians hod severe problems with their teeth. They invented the world's first dental bridge
The upperand lower areas ofthe mouth canine
are known as the maxilla and the
mandible. The upperarea of the mouth
called the upper arch ofthe mouth,
while the mandible is the v-shaped bone
that carries the lowersetof teeth.
long, pointed teeth that are
used forholding and tearing at
the food within the mouth.
Wisdom teeth -------------
Usually appear between the
agesof 17 and 25, and often
erupt in a group of four.
The tooth is a complexstructure.The Mandible First and second of
enamelat the surface of the tooth is highly Alookinsideyour towerjawbone Theapproximate
The premolar or bicuspids are ages atwhich the
visible while the dentine is a hard but Lateral and central incisors _ _ _ _ _..... permanentteeth
porous tissue found under the enameL located between the canine begin to erupt
The gums providea secure hold for the Incisor comesfrom the latin V'JOrd 'to Age&
tooth, while the root is anchored right cut',they are used to grip and bite. and molar teeth. They are
used for chewing. First molar
into thejawbone. In the centreofthe tooth
there is asubstancecalled 'pulp' which Age7
contains nerves and blood vessels, the
pulp nourishes the dentine and keeps the Central incisor
tooth healthy. Age9
Tooth formationbegins before birth.
Normally thereare20 primary teeth
jhuman baby teeth) and later, 28 to 32
permanent teeth, which includes the Second premolar
wisdom teeth. Of the primary teeth, ten Agell
are found in the maxilla jtheupperjaw)
and ten in the mandible jlowerjaw), while Canine
the mature adult has16permanent teeth
in the maxilla and16in the mandible.
or not at all
Explore one ofthe most complex and functional areas ofthe human body
The human neck is a perfect blend Get it in the neck Oesophagus Larynx
ofform and function. It has several
specific tasks (eg making it possible We show the major features that are pack ed This pipe comects the This serves two rna.il
into this junction between the head and torso mouth to the stomach,
to turn our heads to seeI, while and is collapsed llltil functions: to connect tile
Sympathetic trunk Cartilage ---.. youswalow mouth to tile trachea, and
servingas a conduit for other vital activities (eg sOf'I"K?thing,when its to generate your voice.
connecting the mouth to the lungsj. These special nerves run This tough tissue muscular walls stretch.
alongs<de tile spinal cord, and protects tile delicate Carotid artery
The anatomical design of the neck would airways behind,
impress modern engineers. The flexibility of control svveatalg,heart rate including the larynx. These arteries transmit
the cervical spine allows your head to rotate, and breathing, among other
flex and tilt many thousands of times a day. oxygenated blood from
vital functioos. tile heart to the brain.
The muscles and bones provide the stre ngth There are twoof them
and flexibility required, however the really Phrenic nerve Vertebra ---"""
impressive design comes with the trac hea, Cri!:lrt and left), i1 case one
oesophagus, spinal cord, myriad nerves and These important These bones provide
the vital blood vessels.These structures must SlJilpoft to p.......,rn tile neck becomes blocked.
all find space and function perfectlyat the same nerves come off the
time. They must also be able to maintain their third, fourth and fifth collapsi"lg, hold"" tile skul
shape while the neck moves. neckwrtebrae, and and protect the spinal
These structuresare all highly adapted to innervate tile cord within.
achieve their aims.The trachea is protected by
a ring ofstrongcartilage so It doesn't collapse, ~whidl
while a llowing enough flexibility to move when keeps- breathing
stretched.Above this, the larynx lets air move
over the vocal cords so we can speak.l'arther (without - havi1g to
back, the oesophagus is a muscular tube which think about it).
food and drink pass through en route to the
stomach. Within the supporting bones of the
neck sits the s pinal cord, which transmits the
vital nerves allowing us to move and feel. The
carotid arteries and jugular veins, meanwhile,
constantly carry blood to and from the bra in.
How does the head Spinal cord _ _ _ _ __..;;;
connect to the neck?
Shielded by thewrtebrae.
They are connected at the bottom of the skull the spinal cord sends
and at the top of the spinal column. The first molD<sq,als daMl nerves
vertebra is called the atlas and the second is and receives sensory
called the axis. Together these form a special i"lforrnalion from all
pivot joint that grants far more movement than around the body.
other vertebrae.The axis contains a bony
projection upwards, upon which the atlas
rotates, allowing the head to tum. The skull sits
on top of slightly flattened areas of the atlas,
providing a safe platform for it to stabilise on,
and allowing for nodding motions. These bony
connections are reinforced with strong muscles,
adding further stability. Don' t forget that this
amazing anatomical design still allows the vital
spinal cord to pass out of the brain. The cord sits
in the middle of the bony vertebrae, where it is
protected from bumps and knocks. It sends out
nerves at every level (starting right from the top)
granting control over most of the body.
Thegiraffe has the
longest oeck ol any land
animal today. However,
amazingly, ithas the same
nurrber of neck vertebrae
as~ do- seven.
l.U•Jt(•l!-rW•mG> The hyoid bone at the front of the neck is the only one 1n the body not connected to another bone
Just say no...
The physiology that lets
us shake our heads
The """""""' of .-J---~T:h-i' s~
the odontoid P"9 articulates (ma..oes)
allows for rotation around the odontoid
of the skull alxM! it.
Odontoid - -
process projects through iL
This bony projection ~~---- Axis
is parallel with the In the spinal column, this
is the second vertebra,
longitudinal axis which provides the
of the spine. stability for the required
Tum )'OU' head leftand feel the
right of )'OU' neck - this is the The first neck (cervical)
muscle doing the turr*>g. vertelra is what
pem its the nodding
The second c:eMcal Whenyou shrug)'0\1'
shoUders this !woad
vertebra alows rotation muscle !e<ISeS up
of the head. Sowhen between)'0\1'
you're shaking )'OU' head shoulderand neck.
to say no, you hiM! got
' - -- Jugular vein this bone to thank. Cervical plexus
These ~~esse4s These nervesprovide
sensation tothe skin and
from the neck, alsocontrol the fine
ret:uming it to
Vertebrae create a
cage of bones to
spN cord withh
Seventh cervical Splenius capitis
This rnJSde is anexa11 !pie
This is the bony
~at the ofoneofthemany
bottooI of )'0\1' neck, strap.Jiloe rniSdes which
whchyou can feel; COilbol the mUtitudeof
fine l1'lOIIerTiel1! ofthe
doctors use it as a ldndof
landmark so theycan head and neck.
locate the other vertebrae.
Scapula Collarbone ---....,
Without a skeleton, we would not Carpals
be able to live. It is what gives us
our shape and structure and its
presence allows us to operate
on a daily basis. Italso is a
fascinating evolutionary link
to all other living and
The human skeleton Is crucial 4. Radius/Ulna - - - - --1
for us to live. It keepsourshape
and muscle attached to the The raciusa1d.ma arethebones
skeletonallows us the ability to situated in the forearm. They
move around, whilealso protectingcrucial connect the wrist and the elbow.
organs that we need to survive.Bonesalso
produce blood cells within bone marrow 5. Ribcage - - - - - - - - - - . - J
and store minerals we need released ona
This stru<:tJ.n ofmany single rib bones creates a
daily basis. protective barrier for organs situated in the chest
As a fully grown adult you will have cavity. They join to the vertebrae in the spine at the
back of the body, and the sternum at the front
around2o6 bones, but you are born with
over 270, which continue to grow, makes up bone, osseous tissue, is
actually mineralised calcium
strengthenand fuse after birth until phosphate, but other forms of tissue such
around18 infemales and 20 In males. as marrow, cartilageand blood vessels are
Human skeletonsactual ty do vary between also containedIn the overallsrructure.
sexes instructurealso. One of the most Many individuals think that bonesare
obviousareas is the pelvisas a female must solid, butactually inner bone is porousand
full ofllttle holes.
beable to give binh, and therefore hips are
comparativelyshallowerand wider. The As weage, so do our bones. Even though
craniumalso becomes more robust In cellsare constantly being replaced, and
males due to heavy muscleattachmentand therefore no cell in our bodyis more than
20years old,theyare not replaced with
a male's chinIs often more promin.ent. perfect, brand-new cells.The cellscontain
Femaleskeletonsaregenerally more errors in their DNAand ultimatelyour
delicate overall. However, although there bones therefore weaken as we age.
are several methods, sexingcan be difficult Conditionssuch asarthritisand
becauseofthelevel ofvariatlonwe see osteoporosis canoften becaused by ageing
within thespecies. and reduced movementability.
Bonesare made up ofvarious different
elements. Inutero, the skeleton takes
shapeas cartilage, which then starts to
calcifyand develop durlnggestatlonand
following birth.The primaryelementthat
HHEEAADD2 1. Snails 2.Snake 3.Giraffe
SKELETONS Exoskeletons are often The skeleton ofa snake Consideting the size of a
seen in animals. These <l(e is one of thes trangest.
fjraffe's neck. you'd expect
bulky, tough outer layer'S Becauseofhow it moves,
lt has more joints in the it to have morecetVical
that fli'Otect the in<ivlrual, vertebrae than a human,
Instead of the body, prlmaflly ll<!rtebrae.
and has no Hmlls. but It only has seven - the
endoskeletons we have.
ltU•JU•11J!3N•IW Around five per cent of o/1 onimols hove backbones and ore therefore classified as vertebrates
Inside our ilow our joints work
The types of joints 1n our body explained
Whether it's a complete break or 1. Ball and socket joints 3. Skull sutures
How the human just a fracture, botfi can take time
skeleton works ond to heal properly Both the hip and the shoulder joints are Although not generally
ball and socket joints. The femur and
keeps us upright Ifyou simplyfracture the bone, you mayjustneed to keep it humerus have ball shaped endings, which thought of as a 'joint', all the
straightand keep pressureoff it until it heals. However, if tum in a cavity to aUow mOl/em""" cranial sutures present from
!.Cranium you breakit into more than one piece, you may need metal
pins inserted into the bone to realignitor plates to cover the 2. Vertebrae w here bones have fused in
The cranium, also known as breakin orderfor it to heal properly.The bone heals by childhood are in fact
producing new cellsand tiny blood vessels where the Vertebraefit togetherto
the skull, is where the brain fracture or break has occurredand these then rejoin up. For immoveable joints.
and the majority of the most breaksorfractures, a castexternal to the body will be support the body and allow
putonaround the bone to take pressureoff the bone to bending mCM!flleflts. They
sensory organs are located. ensure that no more damage is doneand the breakcan heal.
are joined by cartilage
2. Metacarpals "The skull is actually
seven separate plates and are classified as
The loog bones in the when we ore born,
which fuse together" semi·mobile joints.
hands are called
metacarpal~ and are
the equivalent of
metatarsals in the
located close to the
up the fingers.
..___ _ _ _ 3. Vertebrae Skull 4. Hinged joints 5. Gliding joints 6. Saddlejoints
There are three main kinds of When we are born, many ofour Both elbows and knees Some movement can Theonlyplacewe see
bones are still somewhat softand are hingedjoints. These
vertebrae (excluding the sacrum and are notyet fused- this process be aDowed when flat this joint in humans is
occurs rater during our childhood jointsonly allow timited bones 'glide1 across
ooocyx) - cervical, thoracic and each other. The w rist the thumb. Movement
lumbar. These vary in strength and The primary reasons for the cranium in particular not to be movement inone bones - the carpals -
fully fused at birthis to allow the skull to Oexas the baby is direction. The bones fit is limited in rotation,
structure as they carry different bornandalso to aUow the extreme rate ofgrowth that operate like this,
occursin the first fewyears ofchildhoodfollowing birth. togetherand are moved m oved by ligam ents. but the thumb can
pressure wittin the spine. The skull is actually insevenseparate plates when we are moveback, forwand
bornand over the first two years these piecesfuse together by m uscles.
G. Pelvis slowlyand ossify.The platesstartsuturing together early and to the sides.
on, but the anterior fontanel - commonly known as the soft
This is the transitional joint between spot- will take around18 months to fully heal. Some other
the trunk of the body and the legs. It bones, suchas the five bones locatedin the sacrum, don't
fully fuse until late teens orearly twenties, but the cranium
isone ofthe key areas in which we becomesfully fused byaroundage two.
can see the skeletal differences
between the sexes.
This is the largest and longest single
bone in the body. It connects to the
pelvis with a ball and socketjoint.
- - - - - - 8. Fibula/Tibia Baby Six year old Adult
These two bones form the lower skull
leg bone and connect to the knee 041
joint and the foot.
These are the five long bones in
the foot thataid balance and
m ovem ent. Phalanges located
close to the metatarsals are the
bones which are present in toes.
uscles ex ined
Muscles are essential for us to
operate on a daily basis, but how
are they structured and how do
they keep us moving
Amuscle is a group oftissue fibres that 6. Abdominal muscles
contractand release to control
movementswithin the body. We have 'Abs' are often bui~ up by body
bt.llders and support the body core.
threedilferent types of muscles In our Theyare also referred to as core
bodies-smooth muscle, cardlacmuscleand muscles and are important in
skeletal muscle.Skeletal muscle, aIso known as sportssuch as rowing and yoga.
striated muscle, iswhat we would commonly
perceiveas muscle, this beingexternal muscles that 7. Quadriceps
areattached to the skeleton, such as bleepsand The large fleshy muscle
deltoids.These muscles are connected to the group O<>V<!t"ing the front
skeleton with tendons.Cardiac muscle concerns the and sides of the thig h.
bean. which iscrucial as it pumps bloodaround the
8. Gluteus maximus
body, supplyingoxygenand ultimatelyenergy to
muscles, which allows them to ope.rate. Smooth The biggest muscle in the body,
muscle, which Is normallysheet muscle, Is this is prinarilyused to move
primarily involved in muscle contractionssuch as the thighs backand forth.
bladdercontroland oesophagus movements. These
9. Hamstrings ------~~¥.
are often referred to as involuntaryas we have little
or no control over these muscles' actions. Refers to one of the three
Muscles control most functions within our posterior th9l n-.JSdes. or tothe
bodies; release of waste products, breathing.
tendonsthat mal<eup the boo ders
seeing. eatingand movement to name buta few. d thespace beiW1d the knee.
Actual musclestructure Is quite complex, and each
muscle is made up ofnumerous fibres which work
together to give the musclestrength. Muscles
increase in effectivenessand strength through
exerciseandgrowthand the main way this occurs
Is through small damage caused byeach repetition
ofa muscle movement, which the body then repairs
More than 64o muscles are actually present
acrossyourenttre body to enableyour limbs to
work, control bodilyfunctionsand shape the body
"More than 300 individual
muscles ore present
across your body to
enable your limbs to work"
1. Gluteus 2. Stapedius 3. Masseter
maximus The smallest llk.lscle In the muscle
body is the stapedius.
The~uteus maxii'OUS.the which is situated in the This isvery much dependant
buttock, isthe largest middle earand helps mO\IE!
musde. lt Isa superf;cial the tiny llooeos which aide on how you define strength.
The masseter (jaw) muscle
muscle that helps control OUr' heaflng. can exert the highest dir'ect
thigh movement. forceon an object.
ltU•JU•11J!3N•IW Skeletal muscles account for around 40 per cent of your total body moss
- - 1. Deltoids What affects our How the
These musclesstretchacross Bicepsand triceps are a pairofmuscles that work together
How strongwe are is a combination to move the arm up and down. As the bicepcontracts, the
the shoulders a1d aid lifting. ofnature and nurture tricepswill relax and stretch outand consequentlythearm
will move upwards. When the arm needs to move down,
- - - 2. Trapezius Musclestrength refers to theamount offorce that a muscle the opposite will occur- with the triceps contractingand
can produce, while operatingat maximum capadty, in one the bicep relaxing and beingforciblystretchedout by the
large, superficial muscle at the contraction. Sizeand structure of the muscle is important triceps. The bicep isso named a flexor as it bendsa joint,
back of the neck and theupper formusclestrength, with strength being measured In and triceps would be the extensoras itstraightens thejoint
part of thethorax, or chest. several ways. Consequently, it is hard to definitivelystate out. Neither ofthese muscles can push themselvesstraight,
which muscleisactuallystrongest. they depend on the other to oppose their movements and
- - - 3. Pectoralis major stretch them out Many muscles thereforework in pairs,
We have two types ofmuscle fibre- one thatsupports so-called antagonisticmuscles.
Commonly knownas the 'pees', long, constant usage exertinglow levels ofpressure, and
this group of muscles stretch one that supports brief, high levelsofforce. The latteris L Tricep relaxes - - - - - -..,
acrossthe chest. used during anaerobic activityand these fibres respond
better to muscle bullding. 2. Bicep contracts
Geneticscanaffect muscle strength, as can usage, diet
These ann muscles work and exercise regimes. Contractions ofmuscles cause
together to lift the ann up and down. injuriesin themuscle fibres and it is the healing of these
Each one contracts, causing movement thatactually create musclestrengthas the injuriesare
in the opposite direction to the other. repaired and overallstrengthen the muscle.
5. Latissmus dorsi
Also referred toas the 'lats', these
musdes are again buit up during
>Neight training and are used to
pull down objects from abow.
"Tendons ottoch muscles 3. Arm aJrls ..
such os biceps to bones,
allowing muscles to move L Bicep relaxes
elements of our body" 3. Arm extends ~
What are muscles made up of?
Musclesare made up ofnumerous cylindrical Bloodvessels and nerves also run through
fibres, which work together to contractand the connective tissue to give energy to the 2. Tricep contracts
control partsofthe body. Musclefibres are muscle andallow feedback to besentto the
bound together by the perimysium intosmall brain.Tendonsattach musclessuchas biceps What is a pulled muscle,
bundles, which are then grouped together by and triceps to bones, allowing muscles to
the epimysium to form theactual muscle. move elementsofour bodyas wewish.
Epimysium Blood vessel Perimysium and how does it ha111Je11?
The external layer that covers the This providesoxygen a1d allows This layer groups Theyhurt like crazyso here'swhy
together muscle fibres it's important to warmup
muscle overall and keeps the bundles the musde to access energy for
within the muscle.
of muscle fibres together. musde operation.
Apulled muscle is basicallya tear in muscle fibres. Sudden
movements commonlycause pulled muscles, and often,
when an individual bas not warmed up appropriately
beforeexerciseoris unfit, a tear can occuras the muscle is
not prepared for usage. The most common muscle to be
pulled is the hamstring, Go... run...
which stretchesfrom gettothe
~------~--~--~-------- A~~~ the buttock to the knee. dlopperl
Myofibrils are constructed Apulled muscle may
of filaments, whichare resultinswellingand
made up of the proteins
actin and myosin.
days before the fibres
repair themselves. To
......---~;:=~- ------.!..:::-:;:..:....;....!2:~;;::..----- Endomysium prevent pulling
muscles, warming up
' _,... ' - - - - - - - Myofibril This layer SUI'I'<Ulds is recommended
- - - Tendon each singular muscle
beforeany kind of
These attach muscle to bones, w hich in located within the single muscle fibres, fibre and keeps the
turn enables the muscles to move parts nnyofibril.s are bll'ldles ofactonnyosin nnyofilril filaments
of the body around (off image). filaments. They are crucial forcontraction. grouped together.
kin colour 1 Skin grafts
Skin co Melanin and skin colour
What is melanin and how does Keratinocytes Suface Keratinocytes
it affect the tone of our skin?
Theseprotecti\lecells are procLad Basal skin eels rt\inJfacbnd in the Thekeramocytes of
The light-absorbing pigment melanin Is a in the lowerlaye<s of theepidemis.
chemical substance that gives your skin Its They take up the meliw:losomes lowerlaye<s d theePderm6!70W ~- skinned
natural colouring. Skin can vary from very dark procLad by themelanocytes.
brown toalmostcompletelywhlte due to a tlvough the skin tothe surface. where people take up fewer
combination ofyourgenesand Inherited tra itsand the DARK they are ewntuaty sloo.9>ed lmlrf. melanosomes.
amount ofsunlight to which you're exposed.
Skin colourdiffers from person to person depending on ~ UGHT
the concentration of melanin present In their skin and Its
distribution throughout the skin's layers. Basically, those •• .•::;t.=•::~S
with less melanin have Ughtersldn, while those with more .• •
of the pigment have darker skin. Melanin Is produced by ~ ••
specialisedskin cells caned melanocytes In the lower ~.
layers of the epidermis and is contained Insidea
meianosome bya very thin membrane. • I
Exposure tosunllght stlmulatesthe production of
melanin granules. The meianosomes containing the Dendrite Melanocyte
melanin then move out towards the skin's protective
keratlnocyte cellsalong branch cellscalled dendrites. Melanin is made in the melanocytes. Thosewilh ligiUrskin have fewer
Melanin is then stored In the nuclei of the keratlnocytes dendrites in theirlowerlaye<s and
where itacts as a natural protectoragainst theeffeetsofthe PeqJiewilh darlo!r skin, or those melao•• toke<atinocytes.
Sun'sultravioietrays. Keratlnocytes make up the bulk their melanocytesare
- around 95 percent-of the outer layers of thesklnand who ille in regia IS wi!hgealer
form the barrier between the bodyand the outside world. alsolessactNe
They take up melanin which canabsorbcancer-<auslng UV stright exposu-e. havemore Melanosomes
radiation soit doesn't get Into the body's Internal tissues.
active melanocytes. These pad<els d melanin release The meliw:losomes infl!l>ter skin
melanin !JGr1Uies ilto the ke<atinocytes. release far fewermelanin granoAes.
Howsking work Skin graft surgery
When our body's largest organ is damaged, '-- Stitching
sometimes it needs a helping hand to heal
Smal skin grafts
Skin grafting isa medicalprocedure where a Asterile gali2E are stitched while
portion ofskin Is removed and stitched onto is applied while the
skin attaches and biggerareas
another partof the body. Thereare many require stapling.
cosmeticand medica lreasons why this anew blood
might be necessary: serious burns, surgery, tattoo supply estabishes.
removal and some medical conditions (skin canceror
diabetes, for example) might all necessitate skin grafting. Donor skin --~
Autograftsaresldn grafts taken from the patient's own Thedooorskin is
body, usually the buttocks, neck or back of the arm. I1!ITll>lle(j and then
Dependingon the sizeof the area that It's removed from, appied to the
it's then stitchedorstapled closedagalnandthe new
sldnapplied to the Injuredarea.Allograftsand
xenografts, meanwhile- taken from other humans and
animals, respectively -are temporary grafts.
But perhaps most InterestingIs thearttfldal'sldn'
called Integra, made ofanima Icollagen that gives the
damaged partan organicscaffoldingfor new skin to
grow into. This Is usually used In cases ofextreme burns
where there isn'tenough healthyskin for an autografL
STOP Bacteria thrive •••••••• You shed skin 3•••••••••••••••••Skin varies drastically • 4skin••••••••••••••••As we~ s•••••••••••••••••We have billions
in thickness th"1ns ' of sweat glands
FACTS 1on human skin everyday!
Every~are inch ofan normal : 2 Every 24 hours. you will lose Skin isarol.nd lmmthickon Skin thinsovertimeand begins Each square inchof
SKIN human'sskin has anaverageol : your uppennost layer ofdead your eyelids,but on yourfeet toloosen, which iswhere
32 milion bacteria onit... no healthy skincontainsclose
••••• skinoells, helping tokeep your ttwsthickness increasesto wrinkles COI'lle from. and why to 650 sweatglands, which
matterhoiN manybathsor 3rrm. giving )01.1much more are essential for keeping
skin fresh and dean andable protectionwhere needed. people opt f<>< plastk;S<.<g<.'ry
showersyou havea day! lo 1><-eathe. in laterlife. )'OUCool.
ltU•JU•11J!3N•IW? All mammals hove hair on their skjn, including marine mammals which appear hairless
Find out more about the largest organ inyour body...
Ourskin is the largestorganinour bodies with an 1. Epidennis 3. Nerve ending .---- 5. Subcutaneous
average individualskin'ssurfacearea measuring This is the top, protective layer. It Situated within the dermis, nerve
around two square metresand accountingfor up iswaterproof andprotects the The layer of fat found in the
to 16 percentoftotal body weight. It is made up of body against UV light, disease and endings allow us tosense temperature, hypodennis that is present to
three distinct layers. Theseare the epidermis, the dermis and
the hypodermis and they all have differing functions. dehydration among other things. pain and pressure. Thisgives us p"""'nt heat lossand protect
informationon ourenvironment and bone and m.tscle from
Humans are rare in that we cansee these layersdistinctly. 2. Dennis
The epidermis is the top, waterproofing layer. Alongside stops us hurmg ourselws. damage. It is also a reserve
The layer that nourishesand energy source.
helping to regulate temperature ofthe body, the epidermis helps maintain the epidennis,
also protectsagainst infection as itstops pathogensentering the dermis houses hair ~ regulation, this is
roots. nerve endings where sweat is
the body. Although generally referred to as onelayer, it is
actually made up offive. The top layersare actually dead and sweatglands. secreted to cool the
keratin-filled cells which prevent water Jossand provide body downwhen it is
protectionagainst the environment, but the lower levels, •
where new skincellsare produced, are nourished by the becomingtoohot.
dermis. In otherspecies, suchas amphibians, the epidermis How your
consists ofonlylive skincells. Inthese cases, the skin is skin works
generally permeableandactuallymay bea major The skin is made of many more
respiratory organ. elements than most people imagine
The dermis has the
connective tissue and nerve
endings, contains hair
follicles, sweat glands,
vessels. The top layer of the
dermis is ridged and
with the epidermis.
hypodermis is not actually
skin, its purpose is to
connect the upper layers
ofskin to the body's
muscle. Bloodvessels and
nerves pass through this
layer to the dermis. This
layer is also crucialfor
regulation, as it
contains 50 percent
ofa healthy adult's
body fat in
tissue. These kinds of
layers are not often
humans beingone offew
that you can see the distinct
layers within theskin. Notonly
does the skinoffer protection for
muscle, boneand internalorgans, butitis
our protective barrieragainst the
insulation, excretionofsweatand sensationare justa
few more functions ofskin.
How does this condition cause intense
inflammation ofjoints and the eventual
destruction ofcartilage tissue?
Rheumatoid arthritis Is a response, but It Is thought that it Extreme swellingand
chronicand progressive Involvesa body'sgeneticsusceptibility
dlseasethateffects many Inflammationcaused by
to certain vtruses. Regardless however,
peoplearound the world. rheumatoidarthritis
Through inflammation throughout onceactivated bysucha cause, a series
the connective tissues of the body, It of Immune system reactions proceed to
individuals'joints.The disease develops cause unwanted/abnormal levels of
when a person's bodygeneratesan destruction within the body.
autoimmune response- a mlsta i<en Inflammation is caused bya heavily
body'sown tissues- that attacks Itsjoint abnormal Interaction between B-cells
and T-cells (see 'Cellular-level
components rather than the hostile development' boxout below),a complex
process that causesa variety ofproteins,
As of now, scientistsare unsure of
what instigates the autoimmune antibodies and othercells to be released
which breakdown jointcartilage
The cellular mechanisms, proteins and antibodies
involved in the development ofrheumatoid arthritis
Ek:els Osteoc:lasts T-cells
8-oells are lymphocytes (white bloodeels) that make Osteoclasis areterminaly <ifferentiatedcells of the Similar to 8-<:ells, T-<:ellsdiffer in the fact that they
ao1ttxxles tocombat antigens. These cells lntemaise macrophage lineage that re-abso<b bone matrlx. ln hM! $I)OOial receptors on their Slriace. Theyassist
antigens befooe preserting them toT-eels.
rfleuTiatoid arthritis, they aid jointdestruction. the matl.l'ationof8-oells into plasma cells.
-· .. •., •••••
· · · ~··· ·
Plasma eels L - - - - - - - - - Macrophages ' - - - - - - - - - Synovial membrane
Plasma cells deoelop when 8-oells areactivated t.nder The role cl the macrophage is toengulf and digest The s}'nOIIial ,.,..,b .... isthesoft tissue that ines the
stiroolation byT-<::el5. Theyare a larger and""'"' ......... debis and ~d--OS, stilrulate 8-oells and non-<:artiaginc surfaces withinjoints. Wdh rheunatoid
SPOOialised~oell release enzymes and "'oo,;, 15.
I•U•JW•1!113N•l!i'i> Bone morrow constitutes approximately 4"/o of the total body moss of humans
ns1• eour nes
Learn how bone marrow can transform cells into whatever the body needs
The skeleton is not only used as the cells in the blood, from oxygen-carrying red In an adult human, most of the long bones are
body's main structural support, itis blood cells to bacteria-munching macrophages. filled with yellow bone marrow - mostly made
also home to the largest collective up offat cells - howeverthis can be converted to
reserve ofadu lt stem cells within us. The majority of these stem cellsare contaIned red marrow for blood cell productionshould an
Bone marrow is a soft tissue present inside all in the red marrow, which gains its colour from a emergency arise.
the long bones of the limbs, a nd inside Hat rich network of blood vessels. The stem cells are
bones such as the pelvis, s kull a nd ribs and it is supported by a range ofothercells collectively Bone marrow also containsa second,
jam-packed with haematopoietic stem cells. known as stroma. Thestromal cells provide the less-studied population ofstem cells known as
These cells are only partly committed to their right microenvironment for the development of mesenchyma Istem cells (MSCs). These are able
development pathway, so depending on the stem cells into the blood's components, making to produce the basic elements that make up the
signals they receive, can become any of the a range of growth factors to encourage cells to con nective tissues of the body, including fat
differentiate down the correct path. cells. bone cells and fibroblasts.
Bone marrow in context The origins of blood
What is going on i nside one of the long bones in our legs? See how bone marrow is a f actory capable of producing
Compact bone 1. Haematopoietic
Compressed layersof stem cell
mineralisedboneon Thisstemcell In red bone
Osteon ___, MeduUary cavity
ofcell dependingon the
The c o m p a c t bone Ourlong bonesale signals it receives.
thatsupportsthe legis mostly bollow,and the
madeupofseve-a! bonemarrowIsstored 2. Common
coocentrtcsystems, m yeloid progenitor
layers of bone.
to becominga particular
typeofcell Eachstep In
Blood supply -~ Bone marrow 3. Common
Thestemcellsare In an adult, mostofthe lymphoid progenitor
medullarycavity Is I!Ued Oncean HSC becomesa
the bone marrow;only withyellowmarrow, \!~=-- lymphoidprogenitor, ills
fully developed cells can whilethe red marrowIs
enter the bloodstream. restricted to the ends of committed tobecominga
the bones. m a k e antibodies~
4 . Macrophage 4 . Dendritic cell
Whichcell thecommon Theseplayavitalrole In
myeloid progenitor the Immunesystem.
what the body needs. flaggingother Immune
4 . Erythrocyte cells totakeaction.
Endosteum Red bloodcellsare 4. Platelet
the most common
TheInnersurface ofthe ThesearesmallcellfragmentS InvolvedInblood
bonelsllnedwlth typeofblood cell and clotting.andarecreated by bagmentatlonofhuge
cacryoxygenaround cellscalled megakaJYOCY!eS.
calledosteoblasiS, the body.
supportthestem cells. !:
").._ __,._ Spine curvature L-rnof·l
• Asyoulook at the human sph1e,you can n:r:oJ
seesomedlstlnctcurves. The primary
• reasons for theseare to help distribute -a
\ weight throughout the spine and support :r-:tr-
aspects of the body. The cur~~e most
familiar to usIs the lumbarcurve, ro
between the ribs and pelvis. This
develops when we start to wall< at about caAr'
12-18months and helps with weight
distribution during locomotion. Prior to :r:oJ
thlswe develop the cervical curve, which
allows us to supportthe weight of our
head at around three-four months, and
two smallerless-obvious curves In the
spine(the thoradc and pelvic curves)are
developed during gestation.
The humanspinalcord Isan Immensely
complexstructure made up ofnervecells
anda largeamount ofsupporting.
protectl~~e ttssue.ltsplltslnto)l different
from thebraln to between the first and
second lumbarvertebrae. Although more
commonly referred to In respect of the
brain. there Is both white and grey matter
presentin the centreof the spinal cord.
White matter contalnsaxons tracts
surrounded by fats. and blood ~~esselsto
protect them. Thegreymattercontalns
more of the neural cell bodies, such as
dendrites, more axons and glial cells.
Spinalcord Injuries are normally
Intervertebral discs and vertebrae to
breal<, they can plercethesplnal cord,
which can result In lossoffeellng. Cord
severance may result In paralysis.
... ' • . - - -·- --Vi _ - ~- b'
• •• - . - .• - 0-ric·
•• ~ 10
• • •f rtl
• ...r.......:_ .,..,. 'fi,;o::-;r:...~ ·~
How is the skull
a-or ~ ~ ~f ;! ~CT~~~~~a~:;:.or~.rg..uc~~~...~g!~l.!!""
attached to the
spine? 0. 1~11
The sl<uU is connected to the spl ne by the Ill
atlanto-occipital joint, which Is created
byCt(atlas)and the occipital bone £ - Hn0
situated at the base of the cranium ~-
(slruiQ. ThJsuniquevertebra has no
'body' and actually lool<s more IU<e a 11ng ;;I "U1'
than any othervertebra. Itsits at the top c:0
of the cervical vertebrae and connects
with the occipital bonevia an eUlpsoldal c:
joint, allowing movementsuchas
noddJngor rotation of the head.An l1l
eiUpsoldalJol ntiswherean ovoid
connection (In this case tile ocdpital -- Hp-HiB"f..f.. !.,'.l.:~r
bone) is placed Into an elliptical cavity (C1 ~~~i~l~~~~5~i' ~
vertebrae~ The restofthecervical V1 l-·
vertebraealsoworl< to support the weight
ofthe head. 1J
Skull Neck ~.g.ti ~~ iH ~!~1l1!".ii~i""g''·:i~,?..W.
surround the The bones C)
which connects olthe neck
the brain to (cervlca
nre p.1rt ol
eart attacks exp-la--in--e-d----------------------------------------------
What causes heart attad<s and
how do they kill?
A heart attack, also known asa generation ofcoronaryartery disease (CAD). ~- . -----------m~~
This is where arteries are constricteddue to -* ·---- •
when a blockage stops blood plaque build-upsand this layer then
oxygenating the heart muscle. If ruptures. Blood plateletsmake their way to 1
this is notcorrected quickly, the muscle the siteofrupture and start to form blood
tissue that is lackingoxygen can become clots. IIthese clots become too large, the
damaged, or indeed die. Thescaleof Impact narrowedarterywill blockand a heart
on the individual's health aftertheattack Is attack occurs. Heartattacks canalso be
dependant on how long the blockageoccurs caused bycoronaryartery spasms,
for, what arteryItaffected and what
treatment was received. Following the buttheseare rare.
Although some people
initialattack, heart failure orarrhythmlas
can occur, both ofwhich may prove fatal to will begenetically
the victim. However, given the right predisposed to heart
treatment many sullerersgo on to rna ke attacks, Individuals
good recoveries and can eventually return
can reduce risk by
to their normal activities. keeping theirweight
The most common reason for heart
attacks worldwide in humans Is the theyeat, not smokingand
L Coronary arteries 4. Blockage occurs
These are thearteries that ...,py the heart Either tlvough eYCA!Ss dotti og or 1\.nherdeposit buikkJp,a
blod<age can oca.r. This meansblood flow cannot get tiYough
wilh blood. They are crucial to lco<!prog the
Ill aland the lack ofoxygen resUts in heart tissuedying.
and oxygen to
Coronary 3. Plaque rupture
Plaque becomes hardened as
it builds up, and it can rupture.
If it ruptures, platelets gather
toclot around therupture.
which can cause a blockage
Heart muscle - -
5. Dead tissue -------- L - - - Dead heart muscle '----- 2. Plaque build-up
Dueto alack ofoxygen.~ Plaque, made upof inllanmatorycels,
sections of heart rrusde candie off.
This can redJce effectiveness of the Jll'oteins, fatty deposits and calcit.m.
muscle asa whole following reecM!fY. narrows the artery and means thatooly
a redJced blood flow can get throug:l.