The organs and blood vessels The human body is an amazing natural machine. If you give it food, water, air and warmth, it can walk, talk, think and produce more of its own kind. Flesh and bones, blood and organs, act together to make the body and create a moving, feeling and intelligent being. Whether awake or asleep, your body’s working parts continue to function. The digestive organs, including the stomach, intestines and liver, sort out the nutrients—the substances useful to the body—from the food you have eaten. Your body has a constant need for oxygen, so you breathe air, your lungs alternately absorbing oxygen and expelling carbon dioxide. Your heart never stops beating, pumping blood, which carries nutrients and oxygen to all parts of your body. Your brain is constantly active, controlling digestion, breathing and heartbeat, and many other things besides.
Organs and systems
The body’s main working parts, such as the brain, heart, lungs and stomach, are called organs. Like all the body's organs, they are formed from various types of tissue. All the tissues in the human body are themselves made up from tiny building blocks, called cells. There are more than 100 million million cells in the body.Systems within the bodyDifferent groups of organs work together as systems. For example, the heart, the body-wide network of tubes, called blood vessels, and the red liquid called blood, together form the circulatory system. There are a number of major systems.
The skeletal system supports the body. The muscular system enables movement. The circulatory system carries essential nutrients, hormones and oxygen to all body parts and collects waste materials for disposal. The digestive system breaks down food and absorbs nutrients into the bloodstream. The nervous system is the body’s main control system. The urinary system removes wastes. The respiratory system takes in oxygen from the air and expels waste carbon dioxide. The endocrine system releases hormones that control several body processes. The reproductive system enables humans to produce offspring.
Support, movement and protection
The body is supported by a strong, flexible framework of bones called the skeleton. Bones are connected to each other by moveable joints that allow body parts, such as the arms and legs, to move freely. Bones and their joints each have different purposes. The skull, for example, supports and protects the brain, while the 27 bones in the hand give it great dexterity.
Muscles, bands of tissue connected to the bones by tough cords called tendons, provide the power for movement. The brain gives the muscles a signal to contract (shorten), pulling a bone into position.
Wrapped around your organs, bones and muscles is the skin, the body’s waterproof outer wrapping. The skin protects the body from harmful rays, helps control the body temperature and is extremely sensitive to touch and pain.
Consultant: Richard Walker