The largest oil spill to occur in the United States so far was the Exxon Valdez spill into Prince William Sound, Alaska, in March 1989. The Exxon Valdez, a medium-sized oil tanker, ran aground on a reef to cause this spill of almost 11 million gallons of crude oil.
Sphincters, composed of skeletal muscles, regulate movement through our digestive and urinary systems, thus, controlling swallowing, defecation and even urination. Skeletal muscle contraction generates heat, which helps to maintain body temperature.
sphincter-a ring of muscle that contracts to close an opening. anatomical sphincter, sphincter muscle. muscle, musculus-one of the contractile organs of the body. physiological sphincter-a sphincter that is not recognizable at autopsy because its resting arrangement cannot be distinguished from adjacent tissue. anal sphincter, musculus sphincter ani, sphincter ani-the sphincter muscle of the anus.