The main organs of the muscular system include skeletal muscles, smooth muscles and cardiac muscles. A complete muscle that is made up of connective tissues, muscle fibers, nerve tissues and blood tissue is considered an organ. The organs are responsible for governing nearly all movement in the body as well as managing posture and body temperature. Skeletal muscles are the most abundant organs in the muscular system. These muscles provide contraction and extension movements to the limbs, provide strength and support for the body, as well as protecting the internal organs. The muscles are connected to tendons, skeletal tissues or ligaments. Cardiac muscles are found in the heart. They have the ability to stretch for long periods of time. The cardiac organs in the muscular system are involuntary and contract automatically. Internal organs, such as the bladder, urethra, blood vessels, parts of the digestive system including the esophagus, stomach and intestines, as well as uterus in women, are lined with smooth muscles. Like the heart muscles, the smooth muscles are also automatic.