Urethra has two sphincter muscles: external urethral sphincter and internal urethral sphincter. The term sphincter urethrae refers to the external urethral sphincter muscle. It surrounds the urethra in the deep perineal pouch.
Origin and Insertion:
It arises from the pubic arch on the two sides and passes medially to encircle the urethra.
Sphincter urethrae muscle is innervated by the perineal branch of the pudendal nerve.
Sphincter urethrae compresses the membranous part of the urethra, so that urine outflow is stopped. During micturition, it relaxes and thus the passage for outflow of urine from the body is opened. Sphincter urethrae muscle provides the means for voluntary control of micturition.