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.
1 The internal sphincter muscle of urethra: located at the bladder's inferior end and the urethra's proximal end at the junction of the urethra with the urinary bladder. 2  The internal sphincter is a continuation of the detrusor muscle and is made of smooth muscle, therefore it is under involuntary or autonomic control.