Sphincter ani internus muscle
- Sphincter ani internus muscle
Muscle infobox
Name = Sphincter ani internus muscle
Latin = musculus sphincter ani internus
GraySubject = 120
GrayPage = 426
Caption = Coronal section through the anal canal. B. Cavity of urinary bladder V.D. Ductus deferens. S.V. Seminal vesicle. R. Second part of rectum. A.C. Anal canal. L.A. Levator ani. I.S. Sphincter ani internus. E.S. Sphinear ani externus.
Caption2 = Coronal section of rectum and anal canal.
Origin =
Insertion =
Action = keep the anal canal and orifice closed, aids in the expulsion of the feces
Blood =
Nerve = Pelvic Splanchnic (S4)
MeshName =
MeshNumber =
DorlandsPre = m_22
DorlandsSuf = 12550809
The Sphincter ani internus (or internal anal sphincter) is a muscular ring which surrounds about 2.5 cm of the anal canal; its inferior border is in contact with, but quite separate from, the Sphincter ani externus.
It is about 5 mm thick, and is formed by an aggregation of the involuntary circular fibers of the intestine. Its lower border is about 6 mm from the orifice of the anus.
Actions
Its action is entirely involuntary. It helps the Sphincter ani externus to occlude the anal aperture and aids in the expulsion of the feces. It is innervated by parasympathetic nerves from S2, S3, and S4. It is not innervated by the pudendal nerve, which is a somatic nerve.
=Additional
External links
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* (NormanAnatomyFig|rectum)
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Sphincter ani externus muscle — Muscle infobox Name = Sphincter ani externus muscle Latin = musculus sphincter ani externus GraySubject = 120 GrayPage = 425 Caption = Caption2 = Coronal section through the anal canal. B. Cavity of urinary bladder V.D. Ductus deferens. S.V.… … Wikipedia
Sphincter ani — can refer to: * Sphincter ani externus muscle * Sphincter ani internus muscle … Wikipedia
musculus sphincter ani internus — noun an internal ring of smooth muscle formed by circular fibers of the rectum • Hypernyms: ↑smooth muscle, ↑involuntary muscle • Part Holonyms: ↑anal sphincter, ↑sphincter ani, ↑musculus sphincter ani … Useful english dictionary
sphincter ani — noun the sphincter muscle of the anus • Syn: ↑anal sphincter, ↑musculus sphincter ani • Hypernyms: ↑sphincter, ↑anatomical sphincter, ↑sphincter muscle • Part Holonyms: ↑ … Useful english dictionary
musculus sphincter ani — noun the sphincter muscle of the anus • Syn: ↑anal sphincter, ↑sphincter ani • Hypernyms: ↑sphincter, ↑anatomical sphincter, ↑sphincter muscle • Part Holonyms: ↑anus … Useful english dictionary
sphincter muscle of anus internal — musculus sphincter ani internus … Medical dictionary
Anal sphincter muscles — can refer to:* Sphincter ani externus muscle * Sphincter ani internus muscle … Wikipedia
sphincter — A muscle that encircles a duct, tube, or orifice in such a way that its contraction constricts the lumen or orifice. SYN: musculus s. [TA], s. muscle [TA]. [G. sphinkter, a band or lace] s. of ampulla s. of hepatopancreatic ampulla. anatomic s.… … Medical dictionary
Muscle — is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart… … Medical dictionary
Levator ani — Infobox Muscle Name = Levator ani Latin = musculus levator ani GraySubject = 119 GrayPage = 422 Caption = Left Levator ani from within. Caption2 = Coronal section through the anal canal. B. Cavity of urinary bladder V.D. Ductus deferens. S.V.… … Wikipedia
