Pelvis Cavity Walls

Obturator Internus (lateral)

Proximal origin: pelvic surfaces of ilium and ischium; obturator membrane

distal insertion: greater trochanter of the femur

Innervation: nerve to obturator internus (L5,S1,S2)

Action: rotate hips joints laterally, assist head of femur in acetabulum

Piriformis (posterosuperior)

Proximal origin: pelvic surface of S2-S4 segments; superior margin of greater sciatic notch and Sacrotuberous ligament

distal insertion: greater trochanter of the femur

Innervation: anterior rami of S1 and S2

Action: rotate hips joints laterally, abducts and assist head of femur in acetabulum

LEvator Ani (floor)

Proximal origin:body of pubis; tendinous arch of obturator fascia; ischial spine

distal insertion: perineal body coccyx; anococcygeal ligament; walls of the prostate or vagina, rectum and anal canal.

Innervation: nerve to leavtor ani, inferior anal nerve, and coccygeal plexus

Action: forms most of pelvic diaphragm that helps support pelvic viscera and resists increases in intra abdominal pressure.

Coccygeus (floor)

O: ischial spine

I: inferior end of the sacrum and coccyx

N: Branches of S4 and S5 spinal nerves

A: Forms small part of pelvic diaphragm that supports pelvic viscera; flexes coccyx