Numbers to know
| Fact | Detail |
|---|---|
| Bones in an adult | 206 (a baby is born with more than 270, and some join together as the child grows) |
| Muscles | more than 600 |
| Teeth | 20 milk teeth in a child, 32 permanent teeth in an adult |
| Ribs | 12 pairs (24 ribs) |
| Spine | 33 vertebrae, but the lower ones fuse, so an adult spine has 26 bones |
| Heart | Four chambers; beats about 60 to 100 times a minute in an adult at rest |
| Blood in an adult | about 5 litres |
| Normal body temperature | about 37 °C (98.6 °F) |
| Brain | weighs about 1.3 to 1.4 kg in an adult |
| Water in the body | about 60% of an adult body weight |
| Small intestine | about 6 to 7 metres long, where most food is absorbed |
Biggest, smallest and busiest
| Question | Answer |
|---|---|
| Largest organ | Skin |
| Largest internal organ | Liver |
| Longest and strongest bone | Femur (thigh bone) |
| Smallest bone | Stapes, in the middle ear |
| Organs that filter the blood | Two kidneys |
| Organs that take in oxygen | Two lungs |
Blood
| Part | Job |
|---|---|
| Red blood cells | Carry oxygen using haemoglobin |
| White blood cells | Fight germs |
| Platelets | Help blood to clot at a cut |
| Plasma | The liquid part; carries food, waste and hormones |
The four main blood groups are A, B, AB and O. Group O negative can be given to people of any group, and AB positive people can receive from any group.
Path of food
- Mouth: teeth chew food and saliva starts digesting starch.
- Food pipe (oesophagus): carries food to the stomach.
- Stomach: churns food with acid and enzymes.
- Small intestine: digestion is completed and nutrients enter the blood.
- Large intestine: absorbs water; the rest leaves the body as waste.
Senses and systems
| Sense or system | Organs |
|---|---|
| Sight | Eyes |
| Hearing | Ears |
| Smell | Nose |
| Taste | Tongue |
| Touch | Skin |
| Digestive system | Mouth, stomach, intestines, liver |
| Respiratory system | Nose, windpipe, lungs |
| Circulatory system | Heart and blood vessels |
| Nervous system | Brain, spinal cord and nerves |
| Skeletal system | Bones and joints |
| Excretory system | Kidneys, ureters, bladder |