Body Layout

Here is your body.

Taken apart and laid on the table at real size. Learn what each part does, and the signals it sends when something isn’t right. Your body talks. This is how to listen.

General information, not medical advice. The signs follow UK guidance from the NHS. In an emergency, call an ambulance.

The flat lay

All 34 parts, side by side at real size.

Skin

Card 001 of 034, integumentary system. On its tag: Dermadon.

The largest organ you have, and the only one you can see. Spread flat, it would cover about two square metres. It keeps water in and germs out, holds your temperature steady, and is packed with nerves that feel touch, heat and pain. The outer layer is always being replaced: you shed tens of thousands of dead cells every minute.

Watch your moles: Keep an eye on your moles. One that grows, changes colour or gets a ragged edge is worth showing a doctor. More on NHS.

≈ 2 m²: surface
≈ 4 kg: weight
4–6 weeks: to renew the outer layer

Brain

Card 002 of 034, nervous system. On its tag: Cerebrax.

The control centre: every thought, feeling and movement starts here. About 86 billion nerve cells pass signals to each other through trillions of connections. The brain is only around 2% of your body weight, yet it burns about 20% of your energy, even at rest. The wrinkled folds on its surface pack more of it into your skull.

Spot a stroke: If a face droops on one side, an arm won’t lift or speech goes slurred, it could be a stroke. Every minute counts: call an ambulance. More on NHS.

≈ 1.4 kg: weight
86 billion: neurons
20%: of your energy

Lungs

Card 003 of 034, respiratory system. On its tag: Bellows.

Two spongy bags that swap the air you breathe for the oxygen you need. Air goes down the windpipe and splits into ever smaller tubes that end in about 480 million tiny air sacs. There, oxygen slips into your blood and carbon dioxide slips out. The left lung is a little smaller, to leave room for the heart.

A cough that lingers: Most coughs clear up on their own within a few weeks. One that’s still hanging on after three weeks needs a closer listen. More on NHS.

≈ 20,000: breaths a day
480 million: air sacs
≈ 70 m²: inner surface

Heart

Card 004 of 034, circulatory and lymphatic system. On its tag: Thumpra.

A muscle about the size of your fist that never takes a break. Four chambers squeeze in turn to push blood around two loops: one through the lungs to pick up oxygen, one out to the rest of you. Each beat is set off by an electrical spark from its own built-in pacemaker.

Heart attack warning: A crushing pain in the chest, perhaps spreading to the arm, neck or jaw, could be a heart attack. Call an ambulance, don’t drive yourself. More on NHS.

≈ 300 g: weight
100,000: beats a day
≈ 7,000 L: pumped a day

Liver

Card 005 of 034, digestive system. On its tag: Regenix.

Your biggest internal organ, and a chemical factory. It cleans toxins out of your blood, makes bile to break down fat, stores sugar and vitamins for later, and builds the proteins that help your blood clot. It can also regrow: lose more than half of it and it can grow back to full size.

A yellow tinge: When the whites of your eyes or your skin turn yellow, your liver may be struggling. Get medical advice the same day. More on NHS.

≈ 1.5 kg: weight
500+: jobs
regrows: from a fraction

Gallbladder

Card 006 of 034, digestive system. On its tag: Bilbo.

A small pouch tucked under the liver that stores bile. Between meals it holds the bile the liver makes and concentrates it. When you eat something fatty it squeezes, sending bile into the gut to break the fat down. You can live without it: the liver then simply drips bile straight in.

Pain under the ribs: A severe pain under your right ribs or in the middle of your tummy, lasting more than half an hour, can mean gallstones. Get medical advice the same day. More on NHS.

≈ 50 mL: holds
≈ 8 cm: long
optional: you can live without it

Stomach

Card 007 of 034, digestive system. On its tag: Churnox.

A stretchy, muscular bag where digestion gets going. It churns food with acid strong enough to eat through some metals, plus enzymes that start breaking down protein. A layer of mucus stops it from digesting itself, and its lining replaces itself every few days. Folds on the inside let it stretch to hold a big meal.

Bleeding inside: Throwing up blood, or something that looks like coffee grounds, is often a sign of bleeding inside. Always get help, and call an ambulance if you feel faint. More on NHS.

≈ 1.5 L: a full meal
pH 1.5–3.5: acid
2–4 hours: to empty

Pancreas

Card 008 of 034, digestive system. On its tag: Insulix.

A gland behind the stomach with two jobs. It makes digestive juices that break down fat, protein and carbohydrate in the gut. Scattered through it are about a million tiny islands of cells that release insulin and glucagon, the hormones that keep your blood sugar in balance.

A thirst that won’t quit: Thirsty all the time, peeing more, unusually tired? A simple blood test can rule out diabetes. More on NHS.

≈ 15 cm: long
≈ 1.5 L: juice a day
1 million: hormone islets

Spleen

Card 009 of 034, circulatory and lymphatic system. On its tag: Recyclops.

The blood’s filter and recycling plant, high on your left side. It pulls worn-out red blood cells out of circulation and recycles their iron. It also stores white blood cells and helps fight some infections. Like the gallbladder, it is one of the organs you can live without.

After a knock to the side: After a hard knock to your left side, pain behind the ribs, dizziness or a racing heart can mean a damaged spleen. Get to hospital straight away. More on NHS.

≈ 150 g: weight
120 days: red cell lifespan
fist: sized

Kidneys

Card 010 of 034, urinary system. On its tag: Twinbean.

Two bean-shaped filters, best seen from your back. Each one holds about a million microscopic filters called nephrons. Together they filter all of your blood many times a day, keep what you need, and send waste and extra water down to the bladder as urine. They also help control your blood pressure.

Pain that comes and goes: Pain in your side or lower back that comes and goes, and can be severe, may be a kidney stone. If it’s bad, get medical advice the same day. More on NHS.

≈ 180 L: filtered a day
1–2 L: urine a day
2 × 1 million: nephrons

Small intestine

Card 011 of 034, digestive system. On its tag: Noodlor.

A long, coiled tube where your food is absorbed into your blood. Almost all the goodness in what you eat is taken in here. Its inner wall is covered in millions of tiny finger-like villi, which gives it a huge surface for something that fits in your belly. Food takes a few hours to wind through it.

When it won’t settle: An upset stomach usually settles within a week. Diarrhoea that runs on for longer than that is worth getting medical advice about. More on NHS.

≈ 6 m: long
≈ 30 m²: inner surface
2–6 hours: transit

Large intestine

Card 012 of 034, digestive system. On its tag: Colossus.

The last stretch of the gut, framing the small intestine. It soaks up water and salts from what is left of your food and turns it into stool. It is also home to most of your gut bacteria, trillions of microbes that digest fibre, make vitamins and train your immune system.

Don’t be embarrassed: Blood in your poo, or toilet habits that change and stay changed, are worth mentioning, even if it feels awkward. More on NHS.

≈ 1.5 m: long
trillions: of bacteria
10–60 hours: transit

Bladder

Card 013 of 034, urinary system. On its tag: Tankard.

A stretchy storage tank for urine. Urine trickles down from the kidneys all day. The bladder’s muscular wall relaxes to fill up, and stretch sensors tell your brain when it is time to go, usually when it is about half full.

Red means report: Seeing blood in your pee, even a little and even without pain, always needs checking. Get medical advice the same day. More on NHS.

400–600 mL: capacity
≈ 250 mL: first urge
6–8: trips a day

Skull

Card 014 of 034, skeletal system. On its tag: Craniac.

A helmet for the brain, made of 22 bones. Eight bones form the vault around the brain and fourteen shape the face. They lock together at wiggly joints called sutures. Only one of them, the lower jaw, can move.

After a blow to the head: After a blow to the head, being sick is a reason to get medical advice. Struggling to stay awake, speak or walk? Call an ambulance. More on NHS.

22: bones
1: that moves
sutures: zip it together

Rib cage

Card 015 of 034, skeletal system. On its tag: Cagey.

A flexible cage around the heart and lungs. Twelve pairs of ribs curve round from the spine. The top seven attach straight to the breastbone, the next three join through cartilage, and the last two float free. Every breath lifts and widens the whole cage.

When breathing hurts: A sharp stab every time you breathe in, after a fall or a blow to the chest, can mean a cracked rib. If breathing gets harder, call an ambulance. More on NHS.

24: ribs
7 + 3 + 2: true, false, floating
every breath: it moves

Spine

Card 016 of 034, skeletal system. On its tag: Stackbone.

A stack of 33 vertebrae with the spinal cord running through it. It holds you upright yet lets you bend and twist, thanks to cushioning discs between the bones. Its gentle S-curve works like a spring that absorbs the shock of every step. The bottom nine vertebrae are fused into the sacrum and tailbone.

A rare emergency: Back pain together with numbness around your bottom or trouble peeing is rare, but an emergency. Get to hospital straight away. More on NHS.

33: vertebrae
24: can move
S-curve: built-in suspension

Pelvis

Card 017 of 034, skeletal system. On its tag: Hipster.

The bowl that connects your spine to your legs. It carries the weight of your whole upper body down to your hips, cradles the bladder and lower gut, and anchors some of your strongest muscles. The ball-and-socket hip joints sit on either side.

After a fall: Can’t stand or put weight on a leg after a fall, with pain in the hip or groin? It may be broken. Don’t try to walk it off. More on NHS.

2 + 2: hip bones, sacrum, coccyx
ball: and socket hips
bowl: for organs

Arms and hands

Card 018 of 034, skeletal system. On its tag: Grabbit.

Built for reach and fine control. One bone in the upper arm, two in the forearm that roll around each other so you can turn your palm, and 27 in each hand. Your hands alone hold about a quarter of all your bones.

Pins and needles: Pins and needles in your fingers that keep coming back, often worse at night, may be a trapped nerve in your wrist. More on NHS.

27: bones per hand
54: in both hands
2: forearm bones that roll

Legs and feet

Card 019 of 034, skeletal system. On its tag: Femurai.

The longest, strongest bones you have. The thigh bone, or femur, is the longest bone in your body: about a quarter of your height, and stronger than concrete. Each foot has 26 bones arranged in arches that spring with every step. Hands and feet together hold more than half of your skeleton.

Clot warning: One leg swollen, throbbing and red or darker could be a blood clot. Get medical advice today, or call an ambulance if you’re breathless. More on NHS.

≈ ¼: of your height: the femur
26: bones per foot
106 / 206: in hands and feet

Eyes

Card 020 of 034, nervous system. On its tag: Peepers.

Two balls of jelly that turn light into pictures for your brain. Light passes through the clear cornea and the lens, which focus it onto the retina at the back. There, about 120 million light-sensitive cells turn it into signals for the brain. Each eye is only about 2.5 cm across, and the muscles that move it are among the fastest in your body.

Sight in danger: Flashes of light, new floaters or a shadow creeping across your sight can mean a detaching retina. Get medical advice straight away. More on NHS.

≈ 2.5 cm: across
120 million: light-sensitive rods
≈ 7 g: each

Tongue

Card 021 of 034, digestive system. On its tag: Lickety.

A bundle of muscles you taste, talk and swallow with. It is made of eight muscles with no bone inside, which is why it can bend into almost any shape. Its surface is covered in small bumps that hold thousands of taste buds, each one renewed every week or two. It also pushes food to the back of your mouth to be swallowed.

A sore that stays: Most mouth ulcers heal within a couple of weeks. A sore or patch that’s still there after three should be checked. More on NHS.

8: muscles
2,000–4,000: taste buds
1–2 weeks: to renew a taste bud

Thyroid gland

Card 022 of 034, endocrine system. On its tag: Butterfly.

A butterfly-shaped gland in your neck that sets your body’s pace. It wraps around the front of your windpipe and releases hormones that control how fast your body uses energy. They affect your heart rate, your temperature, your weight and even your mood. It needs iodine from your food to make them.

A lump in the neck: A new lump or swelling at the base of your neck, where a tie knot would sit, is one to have examined. More on NHS.

≈ 5 cm: across
≈ 20 g: weight
iodine: to make its hormones

Diaphragm

Card 023 of 034, respiratory system. On its tag: Domo.

A dome of muscle under your lungs that does most of your breathing. When it tightens, it flattens and pulls down, drawing air into your lungs; when it relaxes, it springs back up and air flows out. It works automatically, day and night, but you can also control it. A hiccup is a sudden spasm of it.

Hiccups that won’t stop: Hiccups are harmless, until they won’t stop. Two days of them is a reason to ask a doctor why. More on NHS.

≈ 20,000: contractions a day
1–2 cm: it moves at rest
up to 10 cm: in a deep breath

Adrenal glands

Card 024 of 034, endocrine system. On its tag: Rush.

Two small glands on top of your kidneys that handle stress. In a fright they release adrenaline in seconds, which speeds up your heart, sharpens your senses and sends energy to your muscles. Over longer stretches they make cortisol, which helps manage stress, blood sugar and blood pressure. Each one weighs only a few grams.

Tired for no reason: Worn out, losing weight and craving salt, with no clear reason why? Ask your doctor about your adrenal glands. More on NHS.

≈ 5 g: each
seconds: for adrenaline to act
2: one on each kidney

Thymus

Card 025 of 034, circulatory and lymphatic system. On its tag: Coach.

A small gland behind your breastbone that trains your immune cells. In childhood it is where T cells, a kind of white blood cell, learn to tell your own body apart from invaders. It is largest just before puberty, then slowly shrinks and turns to fat, but the T cells it trained protect you for life.

Muscles that fade: Eyelids that droop by evening, double vision, or muscles that tire far too fast are worth describing to a doctor. More on NHS.

T cells: trained here
puberty: when it’s largest
≈ 30 g: at its biggest

Appendix

Card 026 of 034, digestive system. On its tag: Tagalong.

A small, finger-shaped pouch at the start of the large intestine. For a long time it was thought to do nothing at all. It is now known to hold a store of gut bacteria and some immune tissue, which may help your gut recover after an illness. You can live perfectly well without it.

Low on the right: Pain that starts by your belly button and moves low on the right, getting worse, may be appendicitis. Get help now, or call an ambulance if it’s severe. More on NHS.

≈ 9 cm: long
finger: shaped
optional: you can live without it

Teeth

Card 027 of 034, digestive system. On its tag: Chompers.

The hardest parts of your body, built for cutting, tearing and grinding. Each tooth is covered in enamel, the hardest substance your body makes, with softer dentine and a living pulp of nerves and blood vessels inside. Adults have 32: incisors to cut, canines to tear, and premolars and molars to grind. Unlike bone, enamel can’t repair itself.

Bleeding gums: Gums that bleed when you brush are often the first sign of gum disease. Your dentist can help you treat it early. More on NHS.

32: adult teeth
20: baby teeth
enamel: the hardest thing in you

Oesophagus

Card 028 of 034, digestive system. On its tag: Chute.

The muscular tube that carries food from your mouth to your stomach. It doesn’t rely on gravity: waves of muscle squeeze each mouthful down, which is why you can swallow lying down or even upside down. A ring of muscle at the bottom opens to let food in and closes to keep stomach acid out.

Food that sticks: If food keeps feeling stuck on the way down, or swallowing is getting harder, don’t put up with it. Get medical advice the same day. More on NHS.

≈ 25 cm: long
≈ 7 seconds: from mouth to stomach
upside down: you can still swallow

Windpipe

Card 029 of 034, respiratory system. On its tag: Hosepipe.

The tube that carries air from your throat down to your lungs. It is held open by up to twenty C-shaped rings of cartilage, so it never collapses as you breathe. Its lining is covered in tiny hairs that sweep dust and mucus back up, away from your lungs. At the bottom it splits in two, one branch for each lung.

Blood when you cough: Coughing up blood is never something to ignore: get medical advice the same day. More than a few streaks, or breathless? Call an ambulance. More on NHS.

≈ 11 cm: long
16–20: rings of cartilage
2: branches, one per lung

Larynx

Card 030 of 034, respiratory system. On its tag: Voxbox.

Your voice box: the cartilage at the top of your windpipe that makes sound. Air from your lungs passes through two folds of tissue, the vocal cords, and makes them vibrate. Muscles tighten or loosen them to change the pitch. A flap called the epiglottis closes over it every time you swallow, so food goes down the right way.

A voice that won’t recover: A croaky voice after a cold is normal. Hoarseness that hasn’t got better after two weeks is worth showing a doctor. More on NHS.

2: vocal cords
100–200: vibrations a second as you talk
epiglottis: its lid

Salivary glands

Card 031 of 034, digestive system. On its tag: Drool.

Glands under your jaw and tongue that keep your mouth wet. Together with a third pair in your cheeks, they make up to a litre and a half of saliva a day. It softens food so you can swallow it, starts breaking down starch before it reaches your stomach, and protects your teeth by washing away food and neutralising acid.

Swelling at mealtimes: A swelling in your mouth that flares up and hurts whenever you eat can be a stone blocking a salivary gland. More on NHS.

0.5–1.5 L: of saliva a day
2 pairs: shown here
starch: it starts to digest

Pituitary gland

Card 032 of 034, endocrine system. On its tag: Boss.

A pea-sized gland under your brain that tells other glands what to do. It hangs from the base of your brain and sends out hormones that control your thyroid, your adrenal glands, your growth and much more. That is why it is often called the master gland. It takes its own orders from the part of the brain just above it.

Slow, strange changes: Rings that no longer fit, shoes a size up, features slowly growing: changes this gradual are easy to miss, and worth raising. More on NHS.

pea: sized
≈ 0.5 g: weight
8: main hormones

Ureters

Card 033 of 034, urinary system. On its tag: Pipework.

Two thin tubes that carry urine from your kidneys to your bladder. Urine doesn’t just drain down them: their muscular walls squeeze it along in waves, a few times a minute. Where they enter the bladder they cross its wall at an angle, which works as a valve so urine can’t flow back up.

Pain on the move: A sudden, severe pain that spreads from your side down into your groin can be a stone on the move. Get medical advice the same day. More on NHS.

25–30 cm: long
3–4 mm: wide
1–5: waves a minute

Aorta and vena cava

Card 034 of 034, circulatory and lymphatic system. On its tag: Highway.

The two biggest blood vessels in your body. The aorta carries oxygen-rich blood from your heart down through your chest and belly; every artery in your body branches off it. Beside it, the vena cava brings used blood back up to your heart. Here they run from your chest down to where they split for your legs.

A sudden, severe pain: A sudden, severe pain in your belly or back could be a burst aorta, your body’s main blood vessel. Call an ambulance right away. More on NHS.

≈ 2.5 cm: wide: the aorta
≈ 5 L: of blood a minute at rest
2: one out, one back

Back in one piece

Now you know what’s inside, and the signs worth looking out for.