A human body system consists of specific cells, tissues and organs that work together to perform specific functions. These systems work together to maintain your overall health. Your body systems include the endocrine, nervous, musculoskeletal, urogenital, respiratory, circulatory, immune and digestive systems, as well as the skin and related structures.
The integument covers and protects the body and is the first line of defense against the environment and germs. This system includes your skin, hair, nails and sweat glands. Your skin, hair and nails are largely protective, while sweat glands help control your body temperature and assist with waste excretion. Additionally, receptors in your skin provide information about touch, heat, cold and pain.
The bones, cartilage, ligaments and muscles of your musculoskeletal system give your body shape and support and enable voluntary movement. In addition to protecting internal organs, your bones serve as attachment points for your muscles, produce blood cells and act as calcium and phosphorus storage banks.
The nervous system includes your brain, spinal cord, nerves and sense organs, such as your eyes and ears. This system receives, transmits and integrates information from inside and outside the body. Your brain and spinal cord specifically form the central nervous system, while the peripheral division of the nervous system includes sensory organs and all the nerves that connect your spinal cord to the rest of your body.
The respiratory system includes your lungs and airways. This system enables gas exchange between your blood and your body's external environment. Specifically, it absorbs oxygen and gets rid of other gases, such as carbon dioxide.
The circulatory system consists of cardiovascular and lymphatic divisions. The cardiovascular division transports materials within your body and includes your heart, blood and blood vessels. The lymphatic division maintains fluid balance and defends you against disease. It includes the lymph glands and vessels and the spleen, thymus and tonsils.
Your mouth, esophagus, stomach and bowels make up the digestive system. These structures and organs enable you to take in and digest food and absorb nutrients into the bloodstream for use by the body. Your salivary glands, liver, gallbladder and pancreas facilitate these processes by releasing digestive juices into your digestive system.
The urogenital system includes the reproductive organs and urinary system. The testes, ovaries and their associated structures enable reproduction. In the urinary division, your kidneys, bladder and their associated ducts enable removal of excess water, metabolic waste and unneeded substances from your body.
The endocrine system consists of a network of glands that release hormones to regulate various body functions. The system controls growth, metabolism and sexual development and function. Components of this system include the pancreas, testes and ovaries and the pituitary, adrenal, thyroid, parathyroid and pineal glands.
The immune system protects your body against harmful organisms, such as bacteria and viruses. The immune system includes the lymph nodes and an array of specialized cells that patrol your body organs and tissues and fight invading germs. Immune cells produce many types of specialized proteins that aid in the protective function of this system.