Human Body Organs System

Organs Organs , such as the heart, the lungs, the stomach, the kidneys, the skin, and the liver, are made up of two or more types of tissue organized to serve a particular function. For example, the heart pumps blood, the lungs bring in oxygen and eliminate carbon dioxide, and the skin provides a barrier to protect internal structures from the external environment. Most organs contain all four tissue types. The layered walls of the small intestine provide a good example of how tissues form an organ. The inside of the intestine is lined by epithelial cells, some of which secrete hormones or digestive enzymes and others of which absorb nutrients. Around the epithelial layer are layers of connective tissue and smooth muscle, interspersed with glands, blood vessels, and neurons. The smooth muscle contracts to move food through the gut, under control of its associated networks of neurons.   An  organ  is a group of tissues that work together for the overall function of the org...