External sphincter muscle of female urethra

External sphincter muscle of female urethra
Sagittal section of the lower part of a female trunk, right segment. (Sphincter not labeled)
Muscles of the female perineum. (Urethral sphincter not labeled)
Details
NerveSomatic fibers from S2-S4 through Pudendal nerve
ActionsConstricts urethra and vagina, maintains urinary continence
Identifiers
Latinmusculus sphincter urethrae externus urethrae femininae
TA98A09.2.03.006F
TA22422
FMA19778
Anatomical terms of muscle

The external sphincter muscle of female urethra is a muscle which controls urination in females. The muscle fibers arise on either side from the margin of the inferior ramus of the pubis. They are directed across the pubic arch in front of the urethra, and pass around it to blend with the muscular fibers of the opposite side, between the urethra and vagina.

The term "urethrovaginal sphincter" ("sphincter urethrovaginalis") is sometimes used to describe the component adjacent to the vagina.[1][2][3] TA: A09.5.03.006F, FMA: 30439

The "compressor urethrae" is also considered a distinct, adjacent muscle by some sources,[4][5] TA: A09.5.03.005F, FMA: 30438

Function

The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system. The external sphincter muscle prevents urine leakage as the muscle is tonically contracted via somatic fibers that originate in Onuf's nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle.[5][6]

Voiding urine begins with voluntary relaxation of the external urethral sphincter. This is facilitated by inhibition of the somatic neurons in Onuf's nucleus via signals arising in the pontine micturition center and traveling through the descending reticulospinal tracts.

See also

References

Public domain This article incorporates text in the public domain from page 431 of the 20th edition of Gray's Anatomy (1918)

  1. ↑ Kyung Won, PhD. Chung (2005). Gross Anatomy (Board Review). Hagerstown, MD: Lippincott Williams & Wilkins. p. 262. ISBN 0-7817-5309-0.
  2. ↑ Rahn DD, Marinis SI, Schaffer JI, Corton MM (2006). "Anatomical path of the tension-free vaginal tape: reassessing current teachings". Am. J. Obstet. Gynecol. 195 (6): 1809–13. doi:10.1016/j.ajog.2006.07.009. PMID 17132484.
  3. ↑ Umek WH, Kearney R, Morgan DM, Ashton-Miller JA, DeLancey JO (2003). "The axial location of structural regions in the urethra: a magnetic resonance study in nulliparous women". Obstet Gynecol. 102 (5 Pt 1): 1039–45. doi:10.1016/j.obstetgynecol.2003.04.001. PMC 1226706. PMID 14672484.
  4. ↑ Adam Mitchell; Drake, Richard; Gray, Henry David; Wayne Vogl (2005). Gray's anatomy for students. Elsevier/Churchill Livingstone. p. 396. ISBN 0-443-06612-4.
  5. 1 2 Jung J, Ahn HK, and Huh Y (September 2012). "Clinical and Functional Anatomy of the Urethral Sphincter". Int Neurourol J. 16 (3): 102–106. doi:10.5213/inj.2012.16.3.102. PMC 3469827. PMID 23094214.
  6. ↑ Shah AP, Mevcha A, Wilby D, Alatsatianos A, Hardman JC, Jacques S, Wilton JC (November 2014). "Continence and micturition: An anatomical basis" (PDF). Clin. Anat. 27 (8): 1275–1283. doi:10.1002/ca.22388. PMID 24615792. S2CID 21875132.


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