A muscle that encircles a tube or orifice is:
A)Circumflex
B)A sphincter
C)Periorbital
D)Perisacral
E)A band

Question

Quizplus · Accepted Answer

Derived from the Greek word for a band, a sphincter is a band of muscle that encircles a tube or orifice; when it contracts, the opening squeezes closed. Sphincters are generally composed of smooth, involuntary muscle, but some also have skeletal muscle as well, allowing a degree of voluntary control, for example, to hold back the voiding of feces or urine.

A Muscle That Encircles a Tube or Orifice Is