The human body contains trillions of cells, 78 different organs, and more than 60,000 miles of blood vessels if you stretched them end-to-end. Incredibly, all of these cells, vessels, and organs work together to keep you alive.
Each organ belongs to one of ten human body systems. These body systems are interconnected and dependent upon one another to function. Your heart does not beat unless your brain and nervous system tell it to do so. Your skeletal system relies on the nutrients it gains from your digestive system to build strong, healthy bones.
A body system is a group of parts that work together to serve a common purpose. Your cardiovascular system works to circulate your blood while your respiratory system introduces oxygen into your body.
Each individual body system works in conjunction with other body systems. The circulatory system is a good example of how body systems interact with each other. Your heart pumps blood through a complex network of blood vessels. When your blood circulates through your digestive system, for example, it picks up nutrients your body absorbed from your last meal. Your blood also carries oxygen inhaled by the lungs. Your circulatory system delivers oxygen and nutrients to the other cells of your body then picks up any waste products created by these cells, including carbon dioxide, and delivers these waste products to the kidneys and lungs for disposal. Meanwhile, the circulatory system carries hormones from the endocrine system and the immune system’s white blood cells that fight off infection.
Each of your body systems relies on the others to work well. Your respiratory system relies on your circulatory system to deliver the oxygen it gathers, while the muscles of your heart cannot function without the oxygen they receive from your lungs. The bones of your skull and spine protect your brain and spinal cord, but your brain regulates the position of your bones by controlling your muscles. The circulatory system provides your brain with a constant supply of oxygen-rich blood while your brain regulates your heart rate and blood pressure.
Even seemingly unrelated body systems are connected. Your skeletal system relies on your urinary system to remove waste produced by bone cells; in return, the bones of your skeleton create a structure that protects your bladder and other urinary system organs. Your circulatory system delivers oxygen-rich blood to your bones. Meanwhile, your bones are busy making new blood cells.
Working together, these systems maintain internal stability and balance, otherwise known as homeostasis. Disease in one body system can disrupt homeostasis and cause trouble in other body systems. If you become ill with the AIDS virus that affects your immune system, for example, you may develop pneumonia in your respiratory system, a yeast infection in your reproductive system, Candida that affects your esophagus in your digestive system, or the skin cancer known as Kaposi’s sarcoma.
