Ischiopubic ramus
Ramus ischiopubicus
Definition
The ischiopubic ramus is a fused bony structure resulting from the joining of the inferior ramus of the pubis with the ischial ramus. It forms the lower boundary of the obturator foramen in the hip bone.
The ischiopubic ramus consists of two borders (upper and lower) and two surfaces (inner and outer):
The upper border constitutes the lower margin of the obturator foramen and serves as an attachment site for the obturator membrane.
The lower border contributes to the pubic arch, which, along with the corresponding ischiopubic ramus on the opposite side, shapes the front margin of the pelvic outlet. Notably, the lower border of the ischiopubic ramus (and pubic arch) provides attachment for two important fascial structures: the fascia lata and Colle's fascia (the membranous layer of superficial fascia) of the perineum.
The outer surface gives rise to the obturator externus, as well as the adductor muscles, including adductor brevis, gracilis, and adductor magnus.
The inner surface can be divided into three zones: the upper zone gives origin to the obturator internus muscle, the middle zone provides origin for the deep transverse perineal muscles and is associated with the dorsal nerve of the penis and internal pudendal vessels, and the lower zone provides attachment to the perineal membrane and the underlying crura of the penis/clitoris, ischiocavernosus, and superficial transverse perineal muscles.
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Text written by Muhammad A. Javaid, MD, PhD © 2023 IMAIOS.
Drake, R.L., Vogl, A.W. and Mitchell, A.W.M. (2009). ‘Chapter 5: Pelvis and Perineum’ in Gray’s anatomy for Students. (2nd ed.) Philadelphia PA 19103-2899: Elsevier, pp.408 & Fig: 5.3.
Standring, S. and Gray, H. (2016). ‘Chapter 80: Pelvic girdle, gluteal region and thigh’ in Gray’s anatomy The anatomical Basis of Clinical Practice. (41st ed.) New York: Elsevier, pp. 1341-1343.
