The Human Body in Numbers: Facts Every Quiz Player Should Know

Questions about the human body appear in almost every science round, and for a good reason: the answers are precise, memorable and a little surprising. This guide gathers the facts that are asked most often and arranges them by body system, so that each new fact has somewhere to fit.

Bones and Muscles

• An adult has 206 bones. A newborn baby has many more, close to 300, because several bones fuse together as a child grows.
• The longest and strongest bone is the femur, in the thigh.
• The smallest bone is the stapes, in the middle ear. It is only a few millimetres long.
• Humans have 12 pairs of ribs.
• The body has more than 600 muscles. The largest is the gluteus maximus, and the masseter, the muscle that closes the jaw, is among the strongest for its size.
• Tooth enamel is the hardest substance in the human body.

The Heart and Blood

• The heart has four chambers: two atria at the top and two ventricles below.
• It beats about 100,000 times a day.
• An adult has roughly five litres of blood.
• Arteries carry blood away from the heart, and veins carry it back.
• Red blood cells carry oxygen using a protein called haemoglobin. They are made in the bone marrow and live for about 120 days.
• White blood cells fight infection, and platelets help blood to clot.
• The four main blood groups are A, B, AB and O. People with O negative blood are called universal donors, and those with AB positive are called universal recipients.

The Brain and Nerves

• The adult brain weighs about 1.4 kilograms.
• Although it is only about two percent of body weight, it uses around a fifth of the body's energy.
• The cerebrum is the largest part and handles thinking, memory and speech.
• The cerebellum, at the back, controls balance and coordination.
• The brainstem controls automatic functions such as breathing and heartbeat.
• Nerve cells are called neurons, and the brain contains tens of billions of them.

Breathing and Digestion

• The right lung has three lobes and the left has two, leaving room for the heart.
• The muscle beneath the lungs that drives breathing is the diaphragm.
• The small intestine is actually the longer one, about six to seven metres. The large intestine is only about a metre and a half. The names refer to their width, not their length.
• The stomach produces hydrochloric acid to help break down food.
• The liver is the largest internal organ and can regrow after part of it is removed.
• The two kidneys filter waste from the blood and produce urine.

Skin and the Senses

• The skin is the largest organ of the body.
• In the eye, light is focused on the retina, which contains two types of cells. Rods work in dim light, and cones detect colour.
• The three tiny bones of the ear are the malleus, incus and stapes, commonly called the hammer, anvil and stirrup.
• The inner ear is responsible for balance as well as hearing.
• No two people have the same fingerprints, not even identical twins.

Glands and Hormones

• The pituitary gland, at the base of the brain, is known as the master gland because it controls many others.
• The pancreas produces insulin, which regulates blood sugar.
• The thyroid gland, in the neck, controls the rate at which the body uses energy.
• The adrenal glands, above the kidneys, release adrenaline in moments of fear or excitement.

Vitamins and What Happens Without Them

• Vitamin A: a shortage causes night blindness.
• Vitamin B1: a shortage causes beriberi.
• Vitamin C: a shortage causes scurvy, once common among sailors on long voyages.
• Vitamin D: a shortage causes rickets, which weakens the bones. The body makes this vitamin when skin is exposed to sunlight.
• Vitamin K: needed for blood to clot.
• Iron: a shortage causes anaemia.
• Iodine: a shortage causes goitre, a swelling of the thyroid gland.

Numbers to Remember

• Normal body temperature: about 37 degrees Celsius
• Adult teeth: 32, following 20 milk teeth
• Chromosomes: 23 pairs
• Water: roughly 60 percent of body weight
• Resting heart rate: usually between 60 and 100 beats a minute

Common Myths

• Different parts of the tongue taste different flavours. The old tongue map is wrong. All tastes can be detected across the whole tongue.
• Humans have only five senses. We also sense balance, temperature, pain and the position of our own limbs.
• Hair and nails keep growing after death. They do not. The skin dries and shrinks, which makes them appear longer.

This article is general knowledge for quiz practice and is not medical advice. For any question about your own health, speak to a qualified doctor.

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