Select the description below that illustrates a difference hetween a sphincter and circular muscle: A) A sphincter is composed of smooth muscle while circular muscle is composed of skeletal muscle tissu B) A sphincter is a thickening of circular muscle that can prevent the movement of digesting materials while circular muscle is involved in propulsion digesting material C) Sphincters are found throughout the Gl tract while circular muscle is found only in the proximal portion of the Gl tract D) Sphincters are found in the proximal portion of the GI tract while circular muscle is found in the distal portions

B)

Explanation:

A sphincter is a thick circular muscle that normally holds a natural body passage or orifice constricted and relaxes as needed by normal physiological function. Circular muscles are the muscle layer that encircles the body between the epidermis and the longitudinal layer of muscles.

The mucosa of muscularis consists of a smooth muscle and is most common in the stomach. The circular muscle layer prevents food from flowing backward within the muscularis externa (propulsion), while the longitudinal layer shortens the tract while a sphincter prevent the movement of digesting materials.

Hence, the correct option is B.

the correct answer is d