muscles of the bony pelvis and pelvic viscera

Question 0

coccygeus

Answer 0

Origin: ischial spine
Insertion: inferior end of sacrum and coccyx
Innervation: branches of S4 and S5 nerves
Action: forms small part of pelvic diaphragm that supports pelvic viscera; flexes coccyx

Question 1

levator ani (pubococcygeus and iliococcygeus)

Answer 1

Origin: body of pubis, tendinous arch of levator ani, ischial spine
Insertion: perineal body, coccyx, anococcygeal ligament, walls of prostate or vagina, rectum, anal canal
Innervation: Nerve to levator ani (branches of S4), inferior anal (rectal) nerve, coccygeal plexus
Action: helps support pelvic viscera; resists increases in intra-abdominal pressure

Question 2

piriformis

Answer 2

Origin: pelvic surface of 2nd-4th sacral segments; superior margin of greater sciatic notch and sacrotuberous ligament
Insertion: greater trochanter of femur
Innervation: Anterior rami of S1 and S2
Action: laterally rotates hip joint; abducts hip joint; assists in holding head of femur in acetabulum

Question 3

obturator internus

Answer 3

Origin: pelvic surface of ilium and ischium; obturator membrane
Insertion: greater trochanter of femur
Innervation: nerve to obturator internus (L5, S1, S2)
Action: laterally rotates hip joint; assists in holding head of femur in acetabulum