An organ is a collection of tissues that work together to perform one or more specific functions in the body. The liver, for example, is an organ that detoxifies the blood and stores nutrients. Organs are composed of various types of tissue, each with a unique function. The four main types of tissue found in organs are: epithelial, connective, muscle, and nervous.
Epithelial tissue covers the surface of organs and body cavities and forms glands. Connective tissue binds organs to each other and provides support. Muscle tissue contracts to move organs and produce force. Nervous tissue transmits signals between different parts of the body and coordinates organ function.
Organs can be divided into two main categories: internal and external. Internal organs are located within the body cavity and include the heart, lungs, kidneys, spleen, pancreas, bladder, uterus, ovaries, testes, prostate gland, and digestive tract (stomach and intestines). External organs are located outside of the body cavity and include the skin; hair; nails; eyes; ears; nose; mouth; hands; feet; arms; legs; breasts; genitals; anus