Lab 21: Perineum/External Genitalia

Bulbospongiosus muscle

Ischiocavernosus muscle

Superficial Transverse Perineus

Superficial Transverse Perineus

Perineal Membrane (Female)

Perineal Membrane (Male)

Perineal Body

Urogenital Diaphragm

UGD

UGD

Urogenital triangle

Colle’s Fascia (Superficial Perineal Fascia)

Superficial Perineal Space

Ischioanal Fossa (male)

Ischioanal Fossa (female)

Pudendal Canal (atlas view p. 217)

Pudendal Canal

Corpus cavernosum

Corpus spongiosum

Corpus spongiosum

Suspensory Ligament of Penis

Deep Fascia of Penis (Buck’s Fascia)

Buck’s fascia

Buck’s Fascia

Perineal Fascia

Tunica albuginea

Crus of Penis

Left crus of penis

Bulb of Penis

Bulb of penis

Perineal membrane

Mons pubis

Clitoris

Glans clitoris

Glans clitoris

Clitoris

Body of Clitoris

Prepuce of clitoris

Labia majora

Labia majora

Labia minora

Labia minora

vestibule

Female Urethral Orifice Description: • External orifice of urinary tract Function: • Male: discharge of urine and semen • Female: discharge of urine

Crus of Clitoris Description: • Paired, erectile body attached to ischiopubic ramus • Becomes corpus cavernosum in body of clitoris • Covered by ischiocavernosus muscle Function: • Engorged with blood during sexual response

Vestibular Bulb Location: • Perineum (urogenital triangle) Description: • Paired erectile bodies • Covered by bulbospongiosus muscle Function: • Engorges with blood during sexual response

Greater Vestibular Gland Location: • Perineum (urogenital triangle) • Lateral to vaginal opening Description: • Paired, mucus-producing gland • Duct opens into vestibule Function: • Lubrication of vaginal opening, especially during sexual response Also known as: • Bartholin's gland

Perineal Membrane Location: • Perineum (urogenital triangle) Description: • Sheet of deep fascia • Stretches across pubic arch • Pierced by urethra (both sexes) and vagina Function: • Forms part of pelvic floor • Forms boundary between superficial and deep parts of urogenital triangle Also known as: • Inferior fascia of urogenital diaphragm

Perineal Body Location: • Perineum (midline) • Between anus and bulb of penis/posterior wall of vagina Description: • Subcutaneous collection of fibrous and muscular tissue Function: • Supports pelvic viscera • Provides attachment for several perineal muscles (superficial and deep transverse perineal muscles, external anal sphincter, and bulbospongiosus muscle) Comment: • In female, may be incised surgically (episiotomy) to prevent tearing of perineal tissues during vaginal delivery

Internal Pudendal Artery Origin: • Internal iliac Course: • Exits pelvis via greater sciatic foramen • Exits gluteal region via lesser sciatic foramen • Lies in lateral wall of ischio-anal fossa • Courses anteriorly to external genitalia Distribution: • Anal canal • External genitalia (both sexes) Branches: • Inferior rectal • Perineal • Dorsal artery of penis/clitoris • Deep artery of penis/clitoris Comment: • Does not supply testes

Inferior Rectal Artery Origin: • Internal pudendal Course: • Crosses medially through adipose tissue of ischio-anal fossa Distribution: • Anal canal (muscles and lining) • Perianal skin Comment: • Anastomoses with middle and superior rectal arteries, and with contralateral inferior rectal artery

Perineal The perineal artery (superficial perineal artery) arises from the internal pudendal artery, and turns upward, crossing either over or under theTransversus perinæi superficialis, and runs forward, parallel to the pubic arch, in the interspace between the Bulbocavernosus and Ischiocavernosus, both of which it supplies, and finally divides into several posterior scrotal branches which are distributed to the skin and dartos tunic of the scrotum

Dorsal Artery of Penis • Paired arteries on dorsal surface course length of body of penis Supplies skin of penis

Deep Artery of Penis The deep artery of the penis (artery to the corpus cavernosum), one of the terminal branches of the internal pudendal, pierces the inferior fascia, and, entering the crus penis obliquely, runs forward in the center of the corpus cavernosum penis, to which its branches are distributed

Pudendal Nerve Ventral rami of S2-4 spinal nerves

Inferior Rectal Ventral rami of S2-4 spinal nerve Motor: • External anal sphincter General sensation: • Lining of lower part of anal canal (i.e., inferior to pectinate line) • Perianal skin

Perineal (superficial and deep nerves)

Posterior Scrotal/Labial Nerve They are branches of the perineal nerve, which is itself is a branch of the pudendal nerve. The pudendal nerve arises from spinal roots S2 through S4, travels through the pudendal canal on the fascia of the obturator internus muscle, and gives off the perineal nerve in the perineum. The major branch of the perineal nerve is the posterior scrotal/posterior labial.

Dorsal Nerve of Penis/Clitoris Contributions: • Ventral rami of S2-4 spinal nerves Comment: • Terminal branch of pudendal nerve • Forms dense network of sensory nerve endings (especially in glans) important in sexual response