Male internal urethral sphincter
Sphincter internus urethrae masculinae
- Latin synonym: Musculus sphincter internus urethrae masculinae; Musculus sphincter supracollicularis
- Synonym: Internal sphincter of male urethra; Supracollicular sphincter muscle; Preprostatic sphincter muscle; Lissosphincter muscle
- Related terms: Internal urethral sphincter; Supracollicular sphincter; Preprostatic sphincter
Definition
The internal sphincter muscle of urethra is a urethral sphincter muscle which constricts the internal urethral orifice. It is the junction of the urethra with the urinary bladder. The muscle is made of smooth muscle, so therefore it is under involuntary control. It is kept tonically contracted by Lumbar plexus of the sympathetic nervous system.
Function :
- Prevent urine leakage as the muscle is contracted via sympathetic stimulation (via the Inferior hypogastric plexus).
- During ejaculation, the contraction of the muscle prevents reflux of semen in the urinary bladder.
References
This definition incorporates text from the wikipedia website - Wikipedia: The free encyclopedia. (2004, July 22). FL: Wikimedia Foundation, Inc. Retrieved August 10, 2004, from http://www.wikipedia.org
