Muscles of the Pelvic floor

Question 0

bulbospongiosus of female

Answer 0

Origin: perineal body
Insertion: passes on each side of lower vagina, enclosing bulb and greater vestibular gland; inserts onto pubic arch and fascia of corpora cavernosa of clitoris
Innervation: muscular (deep) branch of perineal nerve, branch of pudendal nerve (S2-S4)
Action: supports and fixes perineal body/pelvic floor; “sphincter” of vagina; assists in erection of clitoris (and bulb of vestibule); compresses greater vestibular gland

Question 1

ischiocarvernosus

Answer 1

Origin: internal surface of ischiopubic ramus and ischial tuberosity
Insertion: embraces crus of penis or clitoris, inserting onto inferior and medial aspect of crus and to perineal membrane medial to crus
Innervation: muscular (deep) branch of perineal nerve, branch of pudendal nerve
Action: maintains erection of penis or clitoris by compressing outflow veins and pushing blood from root of penis or clitoris into body

Question 2

superficial transverse perineal body

Answer 2

Origin: internal surface of ischiopubic ramus and ischial tuberosity; compressor urethrae portion only
Insertion: passes along superior posterior border of perineal membrane to perineal body and external anal sphincter
Innervation: muscular (deep) branch of perineal nerve, branch of pudendal nerve (S2-S4); dorsal nerve of penis or clitoris, terminal branch of pudendal nerve (S2-S4)
Action: support and fix perineal body (pelvic floor) to support abdominopelvic viscera and resist increased intra-abdominal pressure

Question 3

external anal sphincter

Answer 3

Origin: skin and fascia surrounding anus and coccyx via anococcygeal ligament
Insertion: passes around lateral aspects of anal canal, inserting into perineal body
Innervation: inferior anal nerve, branch of pudadendal nerve (S2-S4)
Action: constricts anal canal during peristalsis, resisting defecation; supports and fixes perineal body/pelvic floor

Question 4

obturator internus

Answer 4

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 emur in acetabulum

Question 5

bulbospongiosus of male

Answer 5

Origin: median raphe on ventral surface of bulb of penis and perineal body
Insertion: surrounds lateral aspects of bulb of penis and most proximal part of body of penis, inserting into perineal membrane, dorsal aspect of corpora spongiosum and cavernosa, and fascia of bulb of penis
Innervation: muscular (deep) branch of perineal nerve, branch of pudendal nerve (S2-S4)
Action: supports and fixes perineal body/pelvic floor; 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