Internal urethral sphincter

Internal urethral sphincter
Internal urethral sphincter
	The urinary bladder, with the position of the internal urethral sphincter shown as the internal urethral orifice.
Details
Origin	The inferior ramus of the pubic bone
Insertion	Perineal raphe
Nerve	Sympathetic fibers from T10-L2 through the inferior hypogastric plexus then vesical nervous plexus
Actions	Constricts proximal urethra, maintains urinary continence
Identifiers
Latin	musculus sphincter urethrae internus
TA98	A09.2.03.009; A09.4.02.013
TA2	3444, 3428
FMA	45769
	Anatomical terms of muscle

The internal urethral sphincter is a urethral sphincter muscle which constricts the internal urethral orifice. It is located at the junction of the urethra with the urinary bladder and is continuous with the detrusor muscle,^[1]^[2] but anatomically and functionally fully independent from it.^[3] It is composed of smooth muscle, so it is under the control of the autonomic nervous system, specifically the sympathetic nervous system.

^ Jung J, Ahn HK, and Huh Y (September 2012). "Clinical and Functional Anatomy of the Urethral Sphincter". International Neurourology Journal. 16 (3): 102–106. doi:10.5213/inj.2012.16.3.102. PMC 3469827. PMID 23094214.
^ Sam P, LaGrange CA (February 2019). "Anatomy, Abdomen and Pelvis, Sphincter Urethrae". StatPearls [Internet]. PMID 29494045.
^ Dorschner W, Stolzenburg JU, Neuhaus J (2001). "Structure and function of the bladder neck". Advances in Anatomy, Embryology, and Cell Biology. 159: III–XII, 1–109. doi:10.1007/978-3-642-56879-4. ISBN 978-3-540-67998-1. PMID 11417142. S2CID 36907268., page 29, Preview Amazon.