Pelvic Floor and Peritoneum - 6/28

Question 1

External Anal Sphincters

Answer 1

O:
Skin and fascia surrounding anus and coccyx via anococcygeal ligament

In:
Passes around lateral aspects of anal canal, inserting into perineal body

Inn:
Inferior anal nerve, branch of pudendal nerve (S2–S4)

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

Question 2

Bulbospongiosus

Answer 2

O:
Male: median raphe on ventral surface of bulb of penis and perineal body
Female: perineal body

In:
Male: Inserting into perineal membrane, dorsal aspect of corpora spongiosum and cavernosa, and fascia of bulb of penis

Female: Inserts onto pubic arch and fascia of corpora cavernosa of clitoris

Inn:
Muscular (deep) branch of perineal nerve, branch of pudendal nerve (S2–S4)

Act:
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 vestibular gland

Question 3

Ischiocavernousus

Answer 3

O:
Internal surface of ischiopubic ramus and ischial tuberosity

In:
Embraces crus of penis or clitoris, inserting onto inferior and medial aspects of crus and to perineal membrane medial to crus

Inn:
Muscular (deep) branch of perineal nerve, branch of pudendal nerve

Act:
Maintains erection of penis or clitoris by compressing outflow veins and pushing blood from root of penis or clitoris into body

Question 4

Superficial Transverse Perineal

Answer 4

O:
Internal surface of ischiopubic ramus and ischial tuberosity; compressor urethrae portion only

In:
Passes along superior posterior border of perineal membrane to perineal body

Inn:
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)

Act:
Support and fix perineal body (pelvic floor) to support abdominopelvic viscera and resist increased intraabdominal pressure