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Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: S:Sphincter Ani Externus

Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: S

Sphincter Ani Externus

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD

Peer Review Status: Internally Peer Reviewed
This muscle shows considerable individual variations in structure

Peikert, Platzek, Besséde and May studied the relationship between the bulbospongiosus muscle and the external anal sphincter. They reported that the perineum contains several fascial layers composed of elastic and collagen fiber including bundles of smooth muscle fibers. The bulbospongiosus was found subdivided into a ventral and dorsal portion, which developed into four variants. The ventral insertion formed a morphological unity with the ischiocavernosus muscle while the dorsal origin had a variable relation to the external anal sphincter (5 variants). A muscle- or connective tissue-like connection was frequently present between the muscles, otherwise they were completely independent. The authors conclude that the ventral fiber group of bulbospongiosus form a functional and morphological unit. The bulbospongiosus and external anal sphincter remain independent muscles, however their frequent connection could have clinical implications for perineal surgery and anogenital disorders.


References

Macalister, A. (1875) Additional observations on muscular anomalies in the human anatomy. (Third series with a catalogue of the principal muscular variations hitherto published.) Trans. Roy. Irish Acad. Sci. 25:1-130, 1875.

Anson, B.J. Ed. Morris' Human Anatomy, 12th Ec. The Blakiston Division, McGraw-Hill Book Company, New York, 1966.

Gardner, E., Gray, D.J. and R. O'Rahilly, Anatomy, 3rd Ed. W.B. Saunders Company, Philadelphia, 1969

Gegenbaur, C. Lehrbuch der Anatomie des Menschen, 3rd Ed. V. Wilhelm Engelmann. Leipzig, 1888.

Henle, J. Handbuch der Systematischen Anatomie des Menschen, 3 volumes. von Friedrich Vieweg und Sohn, Braunschweig, 1868.

Huber, C.G., Ed. Piersol's Human Anatomy, 9th Ed. L.B. Lippincott Company, Philadelphia, 1930.

Hyrtl, J. Lehrbuch der Anatomie des Menschen, 19th Ed. Wilhelm Braumüller, Wien, 1887.

Jackson, C.M., Ed. Morris' Human Anatomy, 9th Ed. P. Blakiston's Son & Co., Inc., Philadelphia, 1993.

Kopsch, F. Rauber's Lerbuch der Anatomie des Menschen. Georg Thieme, Leipzig, 1908.

Latarjet, A. Testut's Traite D'Anatomie Humaine, 9th Ed. G. Doin & Cie., Paris, 1948.

Peikert, K., Platzek, Besséde, T. and C. A. May. (2015) J. Urol. 193: 1433-1440.

Schaefer, E.A., Symington, J. and T.H. Bryce, Eds. Quains's Anatomy, 11th Ed. Longmans. Greem, and Co., London, 1923.

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