WebLecture-Pelvis-Lec36

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I. Orientation of Pelvis

II. Osteology

III. Joints

IV. Ligaments

V. Pelvic Musculature

VI. Perineum

WebLecture Slide 36

The perineum is that region inferior to the pelvic diaphragm and extends to the skin of the buttocks, thighs and external genetalia. The skeletal limits of the perineum are the same skeletal boundaries as those of the pelvic outlet. The anterior limit is the pubic arch. The lateral boundaries follow the pubic and ischial rami to the ischial tuberosity and follows the sacrotuberous ligament to the tip of the coccyx. The perineum is often described as diamond shaped made up of two triangles, the urogenital triangle anteriorly and the anal triangle posteriorly. This lateral view emphasizes the angle that exists between the urogenital triangle, anteriorly, and the anal triangle posteriorly.

Quicktime Movie 36

The diamond shaped (though not planar) perineum extends from the pubic arch to the ischial tuberosity to the sacrum to the contralateral ischial tuberosity and back to the pubic arch. These bony landmarks are easily palpated on yourself, or your cadaver. The diamond is broken into two triangles by a line drawn from right to left ischial tuberosity. When viewed laterally the differing orientation of the planes of the anal triangle and the urogenital triangle can be appreciated. The urogenital triangle is commonly refered to as the urogenital (or UG) diaphragm, but the 38th edition of Gray's Anatomy (Williams et al., 1995) state that the muscles of the urogenital region "do not form a diaphragmatic sheet, but extend through the visceral outlet into the lower reaches of the pelvic cavity; thus the is no urogenital diaphragm as such" (Williams et al., 1995: 832). We therefore refer to this region as the urogenital triangle but be prepared to seee it refered to as the urogenital diaphragm in most anatomy text books.

Williams, PL, Banniser, LH, Berry, MM, Collins, P, Dussek, JE, Dyson, M, Ellis, H, Gabella, G, Salmons, S, Soames, RW, Standring, SM 1995 Gray's anatomy. 38th edition. Churchill Livingstone, New York.

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