Human body systems.
Human body systems.
Credit: Image via Shutterstock

The human body is everything that makes up, well, you. The basic parts of the human body are the head, neck, torso, arms and legs.

[Image Gallery: The BioDigital Human]

Our bodies consist of a number of biological systems that carry out specific functions necessary for everyday living.








The reproductive system allows humans to reproduce. The male reproductive system includes the penis and the testes, which produce sperm. The female reproductive system consists of the vagina, the uterus and the ovaries, which produce eggs. During conception, a sperm cell fuses with an egg cell, which creates a fertilized egg that implants and grows in the uterus. [Related: Awkward Anatomy: 10 Odd Facts About the Female Body]





Humans have five vital organs that are essential for survival. These are the brain, heart, kidneys, liver and lungs.

The human brain is the body's control center, receiving and sending signals to other organs through the nervous system and through secreted hormones. It is responsible for our thoughts, feelings, memory storage and general perception of the world.

The human heart is a responsible for pumping blood throughout our body.

The job of the kidneys is to remove waste and extra fluid from the blood. The kidneys take urea out of the blood and combine it with water and other substances to make urine.

The liver has many functions, including detoxifying of harmful chemicals, breakdown of drugs, filtering of blood, secretion of bile and production of blood-clotting proteins.

The lungs are responsible for removing oxygen from the air we breathe and transferring it to our blood where it can be sent to our cells. The lungs also remove carbon dioxide, which we exhale.

  • The human body contains nearly 100 trillion cells.
  • There are at least 10 times as many bacteria in the human body as cells.
  • The average adult takes over 20,000 breaths a day.
  • Each day, the kidneys process about 200 quarts (50 gallons) of blood to filter out about 2 quarts of waste and water
  • Adults excrete about a quarter and a half (1.42 liters) of urine each day.
  • The human brain contains about 100 billion nerve cells
  • Water makes up more than 50 percent of the average adult's body weight

You use your eyes to see, your ears to hear and your muscles to do the heavy lifting. Well, sort of. In fact, most body parts are far more complicated than that, while some seem to have no business being inside there at all.
An illustration showing the different systems of the human body.
0 of 10 questions complete
Ready for Med School? Test Your Body Smarts
An illustration showing the different systems of the human body.
0 of questions complete

Editor’s Note: If you’d like more information on this topic, we recommend the following book (available on

Systems of the human body

Parts of the human body