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.
During contraction of sphincter/circular muscles, the lumen associated with the sphincter constricts (closes). This constriction is caused from the shortening of the sphincter muscle. While relaxation of a sphincter muscle causes the lumen to open, which is caused by the lengthening of the associated sphincter muscle.phincters prove effective in the mediation of the entrance or release of liquids and solids; this is evident, for example, in the blowholes of numerous marine mammals. Many sphincters are used every day in the normal course of digestion and vision.