What Are the Nine Body Systems?

Within the study of biology, the human body hosts nine distinct systems, comprising different organs that support each other in the performance of a specific bodily function. Together, these nine systems work with one another to keep the body operating at a level of peak performance.

Nine Systems of the Human Body

• The nine systems of the human body are the circulatory system, the digestive system, the endocrine system, the muscular system, the nervous system, the reproductive system, the respiratory system, the skeletal system and the urinary system. Each has a specific function in the body.

Skeletal, Muscular and Nervous Systems

• The skeletal system consists of bones, tendons and ligaments, shaping the body and shielding organs from harm. The muscular system consists of tissues and muscles that control the body's movements, including skeletal muscles (which connect with the skeletal system to help the body move), smooth muscles (which move involuntarily, and are located inside certain organs) and the cardiac muscle, which is only found in the heart. The nervous system consists of the brain, the spinal cord and nerves that travel throughout the body, sending, receiving and processing nerve impulses.

Circulatory, Endocrine and Respiratory Systems

• The circulatory consists of the heart, which pumps blood through the body in veins and arteries. The endocrine system is comprised of glands that produce hormones, which are chemicals that control body functions such as metabolism and sexual development. The respiratory system brings air into the body, filters it in the lungs, passes oxygen into blood stream and expels carbon dioxide.

Digestive, Urinary and Reproductive Systems

• The digestive system includes the organs that break down food into vitamins, minerals, protein, fats and carbohydrates the body can use and that then eliminate waste, such as the stomach and intestines. The urinary system eliminates liquid waste; the kidneys remove waste from the blood and send it to the bladder to be expelled as urine. Finally, the reproductive system is made up of the genitals, with a female's egg fertilized by a male's sperm within the female fallopian tube before traveling to the uterus, which hosts the developing fetus for nine months.