Pelvic Wall

Question 1

Levator ani

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 increase in intra-abdominal pressure

Question 2

Coccygeus (ischiococcygeus)

Answer 2

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 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

Question 4

Piriformis

Answer 4

Origin : pelvic surface of 2-4th 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 and abducts hip joint; assists in holding head of femur in acetabulum

Question 5

External anal sphincter

Answer 5

Inferior anal nerve, branch of pudendal nerve (S2-S4)

Constricts anal canal during peristalsis, resisting defecation; supports and fixes perineal body/pelvic floor

Question 6

Bulbospongiosus

Answer 6

Deep branch of perineal nerve, branch of pudendal nerve (S2-S4)

Supports and fixes perineal body/pelvic floor

Male: compresses bulb of penis to expel last drops of urine/semen; assists erection by compressing outflow via deep perineal vein and by pushing blood from bulb into body of penis

Female : sphincter of vagina; assists in erection of clitoris and bulb of vestibule; compresses greater vestibule gland

Question 7

Ischiocavernosus

Answer 7

Deep branch of perineal nerve
Maintains erection of penis or clitoris by compressing outflow veins and pushing blood from root off penis or clitoris into body

Question 8

Superficial and Deep transverse perineal body

Answer 8

Muscular branch of perineal nerve; dorsal nerve of penis or clitoris , terminal branch of pudendal nerve

Supports and fix perineal body (pelvic floor) to support abdominopelvic viscera and resist increased intra-abdominal pressure

Question 9

External urethral sphincter

Answer 9

Muscular branch of perineal nerve; dorsal nerve of penis or clitoris, terminal branch of pudendal nerve

Compresses urethra to maintain urinary continence

Female : urethrovaginal sphincter portion also compresses vagina