Human Body for Exams: Key Numbers, Organs and Glands
A one-page revision of the human body for SSC and railway science: key numbers, blood and blood groups, digestion, the brain, and the endocrine glands and their hormones.
By the World MCQ Forum India Editorial Team · 27 October 2026 · 2 min read
Questions on the human body appear in almost every general science section. Most of them test a short list of facts. This page collects them in one place so you can revise them quickly.
Key numbers
| Fact | Value |
|---|---|
| Bones in an adult | 206 (about 300 at birth) |
| Chromosomes in a body cell | 46 (23 pairs) |
| Normal heart rate (adult, resting) | about 72 beats a minute |
| Normal blood pressure | about 120/80 mm Hg |
| Normal body temperature | about 37 °C (98.6 °F) |
| Blood in an adult | about 5 litres |
| Life of a red blood cell | about 120 days |
| Normal blood pH | about 7.4 (slightly alkaline) |
Biggest, smallest and longest
| Question | Answer |
|---|---|
| Largest organ | Skin |
| Largest internal organ / largest gland | Liver |
| Longest bone | Femur (thigh bone) |
| Smallest bone | Stapes (in the ear) |
| Largest artery | Aorta |
Blood
- Red blood cells carry oxygen using haemoglobin, which contains iron.
- White blood cells fight infection.
- Platelets help blood to clot; vitamin K is also needed for clotting.
| Blood group | Can give to | Can receive from |
|---|---|---|
| O negative | Everyone (universal donor) | O negative only |
| AB positive | AB positive only | Everyone (universal recipient) |
Digestion in order
- Mouth: saliva’s amylase starts digesting starch.
- Stomach: hydrochloric acid and pepsin start digesting protein.
- Small intestine: digestion is completed with bile (made by the liver) and pancreatic juice; villi absorb the digested food.
- Large intestine: absorbs water.
The brain
| Part | Controls |
|---|---|
| Cerebrum (largest part) | Thinking, memory, senses, voluntary actions |
| Cerebellum | Balance and coordination |
| Medulla oblongata | Breathing, heartbeat, swallowing (involuntary actions) |
| Hypothalamus | Hunger, thirst, body temperature; links to the pituitary |
The basic unit of the nervous system is the neuron; the basic unit of the kidney is the nephron. Exams like to swap these two.
Glands and hormones
| Gland | Hormone | What it does |
|---|---|---|
| Pituitary (“master gland”) | Growth hormone and others | Controls other glands and growth |
| Thyroid | Thyroxine | Controls metabolism; needs iodine (lack causes goitre) |
| Adrenal | Adrenaline | “Fight or flight” response |
| Pancreas | Insulin | Lowers blood sugar; lack causes diabetes |
The pancreas is both an endocrine gland (insulin into the blood) and an exocrine gland (digestive juice into the intestine).
Vitamin deficiencies
| Vitamin | Deficiency disease |
|---|---|
| A | Night blindness |
| B1 (thiamine) | Beri-beri |
| C | Scurvy |
| D | Rickets |
| K | Poor blood clotting |
Common traps
- Universal donor vs recipient: O negative gives to all; AB positive receives from all.
- Bile is made in the liver, stored in the gall bladder.
- Neuron vs nephron: nervous system vs kidney.
Practise with our human body set and the biology and health set.