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Organs and systems, vitamins and minerals, blood, and common diseases with their causes.
30 of 30 the human body
Pumps blood around the body
A muscular organ with four chambers (two atria, two ventricles) that beats about 60–100 times a minute at rest. The right side pumps blood to the lungs; the left side pumps oxygen-rich blood to the body.
Exchange oxygen and carbon dioxide
Air passes through the trachea and bronchi into millions of tiny air sacs (alveoli), where oxygen enters the blood and carbon dioxide leaves it. The right lung has three lobes, the left two.
Control centre of the nervous system
Has about 86 billion neurons. The cerebrum controls thinking and voluntary movement, the cerebellum balance and coordination, and the brainstem breathing and heartbeat.
Largest internal organ
Makes bile to digest fats, stores glycogen and vitamins, removes toxins, and makes blood-clotting proteins. It can regrow after part of it is removed.
Filter the blood and make urine
Each kidney has about a million filtering units (nephrons). They remove waste and extra water and help control blood pressure. Dialysis does this job when they fail.
Largest organ of the body
Protects against germs, controls body temperature through sweat, and makes vitamin D in sunlight. Its colour comes from the pigment melanin.
Makes insulin and digestive enzymes
Its islets of Langerhans make insulin and glucagon, which control blood sugar. When it makes too little insulin, diabetes results.
206 bones in an adult
Supports and protects the body and makes blood cells in the bone marrow. The femur (thigh bone) is the longest bone; the stapes in the ear is the smallest. Babies are born with about 270 bones that fuse over time.
Controls metabolism
A butterfly-shaped gland in the neck that makes thyroxine, which needs iodine. Iodine deficiency can cause goitre, a swelling of the thyroid; this is why salt is iodized.
The 'master gland'
A pea-sized gland under the brain that controls other glands, and makes growth hormone.
Carry oxygen
Contain haemoglobin, an iron-rich protein that carries oxygen. They are made in bone marrow and live about 120 days; adult human RBCs have no nucleus.
Fight infection
Part of the immune system. Lymphocytes make antibodies; others swallow germs. A very high count can signal infection or leukaemia.
Help blood clot
Tiny cell fragments that clump together to stop bleeding. In dengue fever the platelet count can fall dangerously low.
A, B, AB and O
Discovered by Karl Landsteiner (1901). O negative is the 'universal donor'; AB positive is the 'universal recipient'. The Rh factor makes a group positive or negative.
For eyesight and skin
Found in carrots, liver, milk and green leafy vegetables. Deficiency causes night blindness.
For nerves and energy
Found in whole grains, beans and meat. Deficiency causes beriberi, once common where people ate mostly polished rice.
For red blood cells and nerves
Found mainly in animal foods. Contains cobalt. Deficiency causes pernicious anaemia.
For gums, skin and healing
Found in citrus fruits, guava and tomatoes; destroyed by heat. Deficiency causes scurvy, which once killed many sailors.
For strong bones
Made in the skin in sunlight and found in fish and eggs; helps the body absorb calcium. Deficiency causes rickets in children and osteomalacia in adults.
For blood clotting
Found in green leafy vegetables and made by gut bacteria. Newborns are given a vitamin K injection to prevent bleeding.
Needed for haemoglobin
Found in meat, lentils and spinach. Deficiency causes iron-deficiency anaemia, very common among women and children in Pakistan.
For the thyroid and for bones
Iodine deficiency causes goitre. Calcium, from milk and dairy, builds bones and teeth; long-term lack contributes to osteoporosis.
Caused by a parasite (Plasmodium)
Spread by the bite of the female Anopheles mosquito. Causes cycles of fever and chills. Treated with drugs such as chloroquine and artemisinin; Ronald Ross showed mosquitoes transmit it (1897).
Caused by a virus
Spread by the Aedes aegypti mosquito, which bites in the daytime and breeds in clean standing water. Can cause a dangerous drop in platelets. Common in Pakistan after the monsoon.
Caused by bacteria
Caused by Mycobacterium tuberculosis, discovered by Robert Koch (1882); spreads through the air and mainly affects the lungs. The BCG vaccine protects children; it is cured with a six-month course of antibiotics.
Caused by a virus
Poliovirus spreads through contaminated water and food and can cause permanent paralysis. Prevented by vaccines (Salk's injected vaccine, 1955; Sabin's oral drops, 1961). Pakistan and Afghanistan are the last countries where wild polio still spreads.
Caused by bacteria in dirty water
Typhoid (Salmonella Typhi) and cholera (Vibrio cholerae) spread through contaminated food and water. Cholera causes severe diarrhoea; oral rehydration solution (ORS) saves lives. Pakistan has had outbreaks of drug-resistant (XDR) typhoid.
Viruses that damage the liver
Spread through infected blood, such as reused syringes and unsafe transfusions. Pakistan has one of the world's highest rates of hepatitis C. There is a vaccine for hepatitis B, and hepatitis C can now be cured with tablets.
Too much sugar in the blood
Type 1: the pancreas makes no insulin. Type 2 (most common): the body does not use insulin well, linked to weight and inactivity. Insulin was discovered by Banting and Best in 1921.
Caused by a virus
A highly contagious disease that causes fever and a red rash; it can be deadly for young children. Prevented by the MMR or measles vaccine.
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