Inferior ramus of the ischium

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Bone: Inferior ramus of the ischium
Right hip bone. External surface.
Latin ramus inferior oss. ischii
Gray's subject #57 235

The Inferior Ramus of the ischium (ascending ramus) is the thin, flattened part of the ischium, which ascends from the superior ramus, and joins the inferior ramus of the pubis—the junction being indicated in the adult by a raised line.

The outer surface is uneven for the origin of the obturator externus and some of the fibers of the adductor magnus; its inner surface forms part of the anterior wall of the pelvis.

Its medial border is thick, rough, slightly everted, forms part of the outlet of the pelvis, and presents two ridges and an intervening space.

The ridges are continuous with similar ones on the inferior ramus of the pubis: to the outer is attached the deep layer of the superficial perineal fascia (fascia of Colles), and to the inner the inferior fascia of the urogenital diaphragm.

If these two ridges be traced downward, they will be found to join with each other just behind the point of origin of the transversus perinæi; here the two layers of fascia are continuous behind the posterior border of the muscle.

To the intervening space, just in front of the point of junction of the ridges, the transversus perinæi is attached, and in front of this a portion of the crus penis vel clitoridis and the ischiocavernosus.

Its lateral border is thin and sharp, and forms part of the medial margin of the obturator foramen.

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.