sentence: All organs are surrounded by capillaries, and are made up of tissues.
sentences_before: In biology, an 'organ system' is a group of organs that work together to perform one or more functions. Organs make up an organism. In the human body, major systems are the circulatory system, the respiratory system, the nervous system and the digestive system. There is also the muscular system, and the skeletal system.
concept_name: organ
headings: Organ system