WebLecture-Pelvis-Lec21

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I. Orientation of Pelvis

II. Osteology

III. Joints

IV. Ligaments

V. Pelvic Musculature

VI. Perineum

WebLecture Slide 21

The piriformis muscle is a strong lateral rotator of the thigh and is also a muscle of particular importance in gaining orientation during dissection of the pelvis and perineum. It is a large muscle that can be as thick as a fat cigar when measured from anterior to posterior and covers the lateral portions of sacral vertebrae 2, 3, and 4 just lateral to the pelvic foramina of these vertebrae. Originating on the pelvic (anterior) surface of the sacrum, the piriformis muscle leaves the pelvis via the greater sciatic foramen (which it nearly fills) and attaches to the medial side of the superiormost point of the greater trochanter of the femur. The piriformis is innervated by sacral nerves 1 and 2 through small branches of the sacral plexus (not shown). The pudendal nerve (sacral nerve segments 2, 3, and 4) is shown in this picture to provide orientation. Realise that the pudendal nerve is just one named nerve of the sacral plexus. Its isolated appearance here is instructional, but not realistic.

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