Levator ani
188339
220586159
2008-06-20T16:00:34Z
72.214.122.62
/* Origin and insertion of fibers */
{{Infobox Muscle |
Name = Levator ani |
Latin = musculus levator ani |
GraySubject = 119 |
GrayPage = 422 |
Image = Gray404.png |
Caption = Left Levator ani from within. |
Image2 = Gray1079.png |
Caption2 = 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]]. |
Origin = inner surface of the side of the lesser pelvis|
Insertion = |
Blood = |
Nerve = '''[[pubococcygeus]]''' and '''[[iliococcygeus]]''':
*[[levator ani nerve]] ([[sacral spinal nerve 4|S4]])
*[[inferior rectal nerve]] from [[pudendal nerve]] ([[sacral spinal nerve 3|S3]], [[sacral spinal nerve 4|S4]])
*[[coccygeal plexus]]<ref name=Moore217>Essential Clinical Anatomy. K.L. Moore & A.M. Agur. Lippincott, 2 ed. 2002. Page 217 </ref>
<br> '''[[puborectalis]]''':
*[[sacral spinal nerve 3|S3]], [[sacral spinal nerve 4|S4]].
*[[levator ani nerve]] <ref>{{cite journal | author = Wallner C, Maas C, Dabhoiwala N, Lamers W, Deruiter M | title = Evidence for the innervation of the puborectalis muscle by the levator ani nerve. | journal = Neurogastroenterol Motil | volume = 18 | issue = 12 | pages = 1121–2 | year = 2006 | pmid = 17109696 | doi = 10.1111/j.1365-2982.2006.00846.x}}</ref>
|
Action = supports the viscera in [[pelvic cavity]]|
MeshName = |
MeshNumber = |
DorlandsPre = m_22 |
DorlandsSuf = 12549567 |
}}
The '''Levator ani''' is a broad, thin [[muscle]], situated on the side of the [[pelvis]].
It is attached to the inner surface of the side of the lesser pelvis, and unites with its fellow of the opposite side to form the greater part of the floor of the pelvic cavity.
It supports the viscera in pelvic cavity, and surrounds the various structures which pass through it.
In combination with the [[Coccygeus muscle]], it forms the [[pelvic diaphragm]].
==Parts==
The levator ani is divided into two parts:
* [[Iliococcygeus muscle]]
* [[Pubococcygeus muscle]]
The pubococcygeus muscle comprises the puborectalis, the levator prostatae in the male, and the pubovaginalis in the female.
==Origin and insertion of fibers==
The Levator ani arises, in front, from the posterior surface of the superior ramus of the [[pubis (bone)|pubis]] lateral to the [[symphysis pubis|symphysis]]; behind, from the inner surface of the spine of the [[ischium]]; and between these two points, from the [[obturator fascia]].
Posteriorly, this fascial origin corresponds, more or less closely, with the tendinous arch of the pelvic fascia, but in front, the muscle arises from the fascia at a varying distance above the arch, in some cases reaching nearly as high as the canal for the obturator vessels and nerve.
The fibers pass downward and backward to the middle line of the floor of the pelvis; the most posterior are inserted into the side of the last two segments of the [[coccyx]]; those placed more anteriorly unite with the muscle of the opposite side, in a median fibrous raphé (anococcygeal raphé), which extends between the coccyx and the margin of the [[anus]].
The middle fibers are inserted into the side of the [[rectum]], blending with the fibers of the Sphincter muscles; lastly, the anterior fibers descend upon the side of the prostate to unite beneath it with the muscle of the opposite side, joining with the fibers of the [[Sphincter ani externus]] and [[Transversus perinei]], at the central tendinous point of the [[perineum]].
The anterior portion is occasionally separated from the rest of the muscle by connective tissue.
From this circumstance, as well as from its peculiar relation with the [[prostate]], which it supports as in a sling, it has been described as a distinct muscle, under the name of ''Levator prostate''.
In the female the anterior fibers of the Levator ani descend upon the side of the [[vagina]].
==Innervation==
The levator ani muscles are mostly innervated by the [[pudendal nerve]], [[perineal nerve]] and [[inferior rectal nerve]] in concert.<ref name=grigorescu> {{cite journal |author=Grigorescu BA, Lazarou G, Olson TR, ''et al'' |title=Innervation of the levator ani muscles: description of the nerve branches to the pubococcygeus, iliococcygeus, and puborectalis muscles |journal=Int Urogynecol J Pelvic Floor Dysfunct |volume=19 |issue=1 |pages=107–116 |year=2008 |pmid=17565421 |doi=10.1007/s00192-007-0395-8}}</ref> In addition, [[sacral spinal nerves]] ([[sacral spinal nerve 3|S3]], [[sacral spinal nerve 4|S4]]) innervate the muscles directly as well (in ~70% <ref name=grigorescu/> of people). Sometimes (in ~40% <ref name=grigorescu/> of people) the inferior rectal nerve innervates the levator ani muscles independently of the pudendal nerve.
==Tail-wagging in animals==
The levator ani muscles, in quadruped animals with tails, are responsible for moving the tail around in the act of "wagging." These muscles are not as strong as their human equivalents, as tail-wagging is less demanding than the support function that the muscles serve in humans.<ref>Sloan, Ethel (2001, p. 53). ''Biology of Women'', Wisconsin: CENGAGE Delmar Learning. ISBN 0766811425 (excerpt available [http://webtools.delmarlearning.com/sample_chapters/0766811425_02.pdf here])</ref>
==Levator Ani Syndrome==
'''Levator Ani Syndrome''' (also known as '''levator syndrome''' and '''proctodynia''') is episodic [[rectum|rectal]] pain, caused by spasm of the levator ani muscle. The [[etiology]] is unknown.
[[Symptom]]s include a dull ache high in the rectum and a feeling of constant rectal pressure or burning. The pain may also be felt in the low [[pelvis]] or [[perineum]].
The discomfort may be relieved by walking or pelvic tightening exercises similar to [[Kegel exercise]]s. Other treatments include [[massage]] of the muscle, warm baths, [[muscle relaxant]] medications, and [[biofeedback]]. Electrical stimulation of the levator ani muscle has been used to try to break the spastic cycle. Injection of [[botulinum toxin|botulinum toxin A]] has also been used.
Variants of levator ani syndrome include [[proctalgia fugax]] (fleeting pain in the rectum) and [[coccydynia]] (pain in the [[coccyx|coccygeal]] region). Proctalgia fugax and levator ani syndrome have not been found to be of psychosomatic origin, although stressful events may trigger attacks.
==See also==
*[[Coccygectomy]]
==Additional images==
<gallery>
Image:Gray236.png|Right hip bone. Internal surface.
Image:Gray402.png|Coronal section of pelvis, showing arrangement of fasciæ. Viewed from behind.
Image:Gray406.png|Muscles of male perineum.
Image:Levator ani.png
Image:Gray539.png|The arteries of the pelvis.
Image:Gray837.png|Sacral plexus of the right side.
Image:Gray1076.png|Iliac colon, sigmoid or pelvic colon, and rectum seen from the front, after removal of pubic bones and bladder.
Image:Gray1077.png|The posterior aspect of the rectum exposed by removing the lower part of the sacrum and the coccyx.
Image:Gray1136.png|Male pelvic organs seen from right side.
</gallery>
==References==
{{reflist}}
==External links==
* {{GPnotebook|-60096433|Levator ani muscle}}
* {{GPnotebook|-53477317|Pubovaginalis muscle}}
* {{MuscleLoyola|pubv}} (Pubovaginalis)
* {{SUNYAnatomyFigs|41|05|00}} - "Muscles of the female superficial perineal pouch."
* {{SUNYAnatomyFigs|42|04|00}} - "Muscles of the male superficial perineal pouch."
* {{SUNYAnatomyLabs|43|16|01|02}} - "Muscles of the Pelvic Diaphragm"
* {{SUNYAnatomyImage|9|0|72}}
* {{SUNYAnatomyImage|9|0|89}}
* {{SUNYAnatomyImage|9|8|71}}
* {{ViennaCrossSection|pelvis/pelvis-e12-15}}
* {{NormanAnatomy|perineum}} ({{NormanAnatomyFig|analtriangle3}})
* [http://www.chronicprostatitis.com/spasm.html Male chronic pelvic pain site]
* [http://www.merck.com/mmpe/sec02/ch020/ch020g.html Merck Manual article on levator ani syndrome]
{{Gray's}}
{{Muscles of trunk}}
[[Category:Muscular system]]
[[de:Musculus levator ani]]
[[it:Muscolo elevatore dell'ano]]
[[la:Musculus levator ani]]
[[pl:Mięsień dźwigacz odbytu]]