Human Body: Organs, Systems and Key Facts for Job Tests

The human body is one of the most popular topics in the Everyday Science section of police, FIA, teaching, clerk and PSC tests. Questions are usually short and factual: which organ does what, which gland makes which hormone, which is the largest or smallest part. This note groups the most useful facts in one place so you can revise quickly.

1. Major Body Systems at a Glance

System	Main organs	Main function
Digestive	Mouth, stomach, small and large intestine, liver, pancreas	Breaks down food and absorbs nutrients
Circulatory	Heart, blood vessels, blood	Transports oxygen, nutrients and wastes
Respiratory	Nose, trachea, lungs	Gas exchange (oxygen in, carbon dioxide out)
Excretory	Kidneys, ureters, bladder	Removes liquid waste and balances water
Nervous	Brain, spinal cord, nerves	Controls and coordinates the body
Skeletal	Bones, joints	Support, protection and movement
Endocrine	Glands such as thyroid, pituitary, pancreas	Release hormones

2. The Heart and Blood

• The human heart has four chambers: two atria (upper) and two ventricles (lower).
• Arteries carry blood away from the heart; veins carry blood towards the heart; capillaries are the tiny vessels where exchange takes place.
• A normal resting heart rate for an adult is about 60 to 100 beats per minute.
• Normal body temperature is about 37 °C (98.6 °F).

Blood components

• Red blood cells (RBCs) carry oxygen with the help of haemoglobin. They are made in the bone marrow and live for about 120 days.
• White blood cells (WBCs) fight infection.
• Platelets help blood to clot.
• Plasma is the liquid part of blood.
• Blood group O negative is called the universal donor, and AB positive the universal recipient.

3. Digestive System

• Digestion of starch begins in the mouth, because saliva contains the enzyme amylase.
• The stomach produces hydrochloric acid and digests proteins.
• Most digestion and absorption of food takes place in the small intestine.
• The large intestine absorbs water.
• The liver is the largest internal organ and the largest gland. It produces bile, which helps digest fats.
• The pancreas produces digestive enzymes and the hormone insulin.

4. Respiratory and Excretory Systems

• Gas exchange happens in tiny air sacs of the lungs called alveoli.
• The diaphragm is the main muscle used in breathing.
• The kidneys filter blood and form urine. The functional unit of the kidney is the nephron.
• The skin is the largest organ of the body.

5. Skeleton and Muscles

• An adult human has 206 bones.
• The femur (thigh bone) is the longest and strongest bone.
• The stapes, a tiny bone in the middle ear, is the smallest bone.
• An adult has 32 teeth; children have 20 milk teeth.
• The gluteus maximus (buttock muscle) is the largest muscle in the body.

6. Endocrine Glands and Hormones

Gland	Hormone / role
Pituitary	Called the "master gland"; controls many other glands
Thyroid	Thyroxine, which controls metabolism
Pancreas	Insulin, which controls blood sugar
Adrenal	Adrenaline, for "fight or flight" responses

A shortage of insulin causes diabetes.

7. The Brain

• Cerebrum: the largest part; controls thinking, memory and voluntary actions.
• Cerebellum: maintains balance and coordination.
• Medulla oblongata: controls involuntary actions such as breathing and heartbeat.

8. Quick Revision Tips

1. Learn each organ together with its single most important function.
2. Make small tables for glands and hormones; they are asked again and again.
3. Revise "largest / smallest / longest" facts the night before the test.
4. Practise with timed questions after every topic.

Practise What You Learned

Test yourself with our Everyday Science MCQs, then try the Daily Quiz to keep your revision regular. You can also read our note on Vitamins: Sources and Deficiency Diseases for related health questions.