The organs in the human body work together to form nine major organ systems in the body:
- digestive system - digestion breaks down food so it can be absorbed. It takes place mainly in the stomach and small intestine. Digested food is absorbed into the blood system.
- respiratory system - takes in oxygen and remove carbon dioxide. Air enters the lungs by movement of the rib muscles and diaphragm. Oxygen is absorbed into the blood system.
- circulatory system - transports nutrients and wastes around the body in the blood. The heart pumps the blood around the body.
- skeletal system - main job of the skeleton is support. Some bones provide protection to delicate organs (e.g. skull protects the brain.
- muscle system - muscles (in pair) are attched to bones around joints to cause movement when they contract and relex.
- reproductive system - producing offspring. Eggs are produced by the ovaries and sperms are produced by the testes to fertilise the eggs.
- nervous system - contains five sense organs: eyes, ears, nose, tongue and skin. These organs contain nerves which send messages to the brain and the brain responds by sending messages to the muscles. The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain. The brain and spinal cord together make up the central nervous system (CNS)
- gland system - pancreas, thyroid, testes (male) and ovaries (female) are glands that produce hormones to control growth, sexual characteristics and other bodily functions such as menstruation.
- excretory system - remove waste substances from the body, some are poisonous. Waste material is filtered out of the body by the kidneys and store in the bladder and passes out as urine.
The human body contains 13000 million nerve cells and 100,000km of blood vessels. The major organs in the humman body and their functions are:
- Brain - controls the nervous system.
- Heart - pumps blood around the body. It takes one minute to make a full cycle.
- Lungs - the breathing organs.
- Liver - processes and stores some food in the blood.
- Kidneys - control the loss of water and waste from the body. Each kidney can filter 1.3 litres of blood every minute.
- Skin - largest organ in the human body. It has an area of about 2m2.