An organ system in biology is a group of organs that work together for one purpose. If any one of these organs were to fail, it would cause a substantial amount of stress on the other organs, and may even cause an entire system to shut down, with the ultimate result often proving to be fatal. The interdependency of these organs on one another are critical for normal life functions. For example, the digestion that takes place in the stomach, part of the digestive organ system, would be useless if the intestines failed to operate adequately.

The human body has ten organ systems. These systems are classified according to what they do. These systems are: digestive, excretory, respiratory, circulatory, skeletal, nervous, muscular, reproductive, endocrine and integumentary. There are ailments that are often associated with each that take different skills to heal. Some doctors specialize in the treatment of conditions affecting certain organ systems. For example, a urologist is likely to treat those having problems with the urinary portion of the excretory system, or those who need treatment for a reproductive system problem.

Most of these systems are self explanatory in what they do. The circulatory system, for example, is responsible for circulating blood throughout the body. The excretory system is responsible for getting rid of waste. The endocrine organ system and the integumentary organ system are two that some people may not be as familiar with. The endocrine system is responsible for communication in the form of cells that produce hormones. Several organs make this possible. The integumentary system is the one that deals specifically with the skin, hair and other protective outer parts of the body.

It may be possible to function without some parts of the organ system, but never without the main function. In the case of the integumentary system, for example, it would be impossible to sustain life without skin. It is quite possible, however, to sustain life without hair. Though it should be noted hair, or fur, may be more important for some species than it would be others. Therefore, how each organ system reacts, and its importance, is somewhat dependent on the species.

Most forms of animal life have multiple organ systems. There are a few animals, such as the jellyfish, which are considered animal life that have no organ system, at least not in the traditional sense. The only system that may be considered an organ system in a jellyfish is the digestive system.