What is the Human Body?

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The human body

The human body is a living machine made of many parts that work together so you can move, think, and stay alive. At the smallest level it is built from tiny units called cells, which group up to form tissues, organs, and whole body systems.[13][19]

Basic structure

The body has a central trunk (chest, abdomen, and pelvis) with a head at the top and two arms and two legs attached. Inside is an internal framework of bones (the skeleton) that gives shape, lets you stand upright, and protects soft organs like the brain, heart, and lungs.[19][20]

Organs and systems

Organs are specialized body parts, like the heart, lungs, stomach, and kidneys, each doing a particular job. Groups of organs and tissues that work together for a common purpose are called systems, such as the circulatory system for moving blood or the digestive system for handling food.[12][20][13][19]

Main body systems

Some key systems are:

Circulatory: heart and blood vessels move blood to deliver oxygen and nutrients and carry away waste.[20][19]

Respiratory: nose, windpipe, and lungs bring oxygen in and push carbon dioxide out so cells can release energy from food.[19][20]

Digestive: mouth, stomach, intestines, and helpers like the liver and pancreas break food into small pieces the body can use.[20][19]

Nervous: brain, spinal cord, and Nerves act as the control network, sensing the world and sending signals to the rest of the body.[19][20]

Musculoskeletal: bones, joints, and muscles let you sit, stand, and move and also store minerals and produce blood cells.[13][20]

Outside layer and defenses

The skin, along with hair and nails, forms a protective covering that keeps the inside in, keeps many harmful things out, and helps control body temperature by sweating. The immune system uses cells and organs like lymph nodes and the spleen to recognize and fight Germs like bacteria and viruses.[13][20]

Control and balance

Chemical messengers called hormones, made by glands like the thyroid, adrenals, and pancreas, help control growth, energy use, stress responses, and reproduction. All systems constantly send information back and forth so the body can keep a stable internal state (things like temperature and blood sugar), even when the outside world changes.[20][13][19]

References and Further Reading