Last updated: 3 October 2026
Questions on the human body are asked in almost every General Science section. This chapter collects the numbers and facts that come up most often.
Important numbers
| Fact | Value |
|---|
| Bones in an adult | 206 |
| Teeth in an adult | 32 (milk teeth: 20) |
| Chromosomes | 46 (23 pairs) |
| Normal body temperature | 37 °C (98.6 °F) |
| Normal blood pressure | About 120/80 mm Hg |
| Normal heart rate | About 72 beats per minute |
| Chambers of the heart | 4 |
| Life span of a red blood cell | About 120 days |
Largest and smallest
| Question | Answer |
|---|
| Largest organ | Skin |
| Largest internal organ | Liver |
| Largest gland | Liver |
| Longest bone | Femur (thigh bone) |
| Smallest bone | Stapes (in the ear) |
| Largest cell (in females) | Ovum |
Blood
- Red blood cells carry oxygen with the help of haemoglobin; they are made in the bone marrow.
- White blood cells fight infection; platelets help blood to clot.
- Blood groups (A, B, AB, O) were discovered by Karl Landsteiner.
- O negative is the universal donor and AB positive the universal recipient.
Glands and hormones
| Gland | Hormone / role |
|---|
| Pituitary | Called the "master gland"; growth hormone |
| Thyroid | Thyroxine; lack of iodine causes goitre |
| Pancreas | Insulin (from the islets of Langerhans); lack of insulin causes diabetes |
| Adrenal | Adrenaline: the "fight or flight" hormone |
Units of body systems
| System | Basic unit |
|---|
| Nervous system | Neuron |
| Kidney | Nephron |
| Lungs | Alveoli (air sacs) |
Quick revision
- Adult bones: 206. Smallest: stapes. Longest: femur.
- Largest organ: skin. Largest gland: liver.
- Universal donor: O negative. Universal recipient: AB positive.
- Insulin is made in the pancreas.
- Pituitary is the master gland.
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