The levels of organization of multicellular living organisms re: cells make tissues, tissues make organs, organs make organ systems, and organ systems make the organism. A body system is defined as a group of organs and tissues that work together in order to perform one or more vital function of the organism. The organ systems are: the digestive system, the endocrine system, the nervous system, the circulatory system, the excretory system, the reproductive system, the respiratory system, the lymphatic system, the muscular system, the skeletal system, and the integumentary system.
Mechanical systems are also made of smaller parts that form a larger structure. Mechanical systems are also similar to body systems because their smaller parts help the overall production of the mechanical system. Likewise, if a smaller part is either a mechanical system or an organism (such as a body system) is not functioning to par, then its overall function suffers.