Unit 3 - Thorax, Abdomen, Pelvis, and Perineum: Muscles of the Pelvic Wall (Parietal Muscles) (Ex. III)

Question 1

obturator internus

Answer 1

O: inner surface of obturator membrane and bony boundaries
I: greater trochanter, M surface of femur
Inn: direct branches from S plexus (L5-S1)
A: hip joint - external (M) rotation, adduction, and extension of flexed hip (also active in abduction, depending on joint’s position)

Question 2

piriformis

Answer 2

O: pelvic surface of sacrum
I: apex of greater trochanter of femur
Inn: direct branches from S plexus (S1-S2)
A: hip joint - external (M) rotation; stabilization, extension and abduction of flexed hip