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Body Basics

Bones, Muscles, and Joints
Our bones, muscles, and joints form our musculoskeletal system and enable us to do everyday physical activities.

Endocrine System
The endocrine system influences almost every cell, organ, and function of our bodies. It is instrumental in regulating mood, growth and development, metabolism, and sexual function, among other things.

Blood
Without blood, our organs couldn't get the oxygen and nutrients they need, we couldn't keep warm or cool off, we couldn't fight infections, and we couldn't get rid of our own waste products. Find out about the mysterious, life-sustaining fluid called blood.

Digestive System
Most people think digestion begins when you first put food in your mouth. But the digestive process actually starts even before the food hits your taste buds.

Immune System
The immune system is made up of special cells, proteins, tissues, and organs that defend people against germs and microorganisms. It's the body's defense against organisms and substances that invade our systems and cause disease.

Mouth and Teeth
Did you know that your mouth is the first step in the body's digestive process? Or that the mouth and teeth are essential for speech? Learn about the many roles your mouth and teeth play.

Kidneys and Urinary Tract
The kidneys perform several functions that are essential to health, the most important of which are to filter blood and produce urine.

Skin, Hair, and Nails
Our skin protects the network of tissues, muscles, bones, nerves, blood vessels, and everything else inside our bodies. Hair and nails are actually modified types of skin.

Spleen and Lymphatic System
The lymphatic system is an extensive drainage network that helps keep bodily fluid levels in balance and defends the body against infections.

Heart and Circulatory System
The heart and circulatory system (also called the cardiovascular system) make up the network that delivers blood to the body's tissues.

Lungs and Respiratory System
Each day you breathe about 20,000 times. Find out more about the lungs and breathing process.

Female Reproductive System
Why do girls get periods? What goes on when a girl gets pregnant? What can go wrong with the female reproductive system? Find the answers to these questions and more in this article.

Male Reproductive System
What makes up a guy's reproductive system and how does it develop? Can anything go wrong? Find the answers to these questions and more in this article.

Eyes
Although your eyes are small, their structure is incredibly complex. Find out how they work in this body basics article.

Metabolism
Your body gets the energy it needs from food through a process called metabolism. Get all the facts on metabolism in this article.

Brain and Nervous System
If the brain is a central computer that controls all the functions of the body, then the nervous system is like a network that relays messages back and forth to different parts of the body. Find out how they work in this Body Basics article.