St A - Male Reproductive Organs 2

Question 1

Describe the external structure of the Penis

Answer 1

• Superficial (dartos) fascia surrounds the whole penis. The skin double backs on itself to form the foreskin which is continuous with the glans.
• Frenulum ventrally between foreskin and the glans with increased sensation.
• Ventral midline raphe

Question 2

How does smegma form?

Answer 2

Secretions of the sebaceous glands in the foreskin

Question 3

Describe what roots the penis?

Answer 3

• Bulb which continues as the corpus spongiosum

- Left and right crus which attaches to ischiopubic ramus. Continues as corpora cavernosa.

Question 4

Describe features of the corpora cavernosa?

Answer 4

• Divided by a septum which is complete proximally but pectiniform distally.
• Each surrounded by thick tunica albuginea (veins here are compressed during erection to reduce venous drainage),
• Filled with blood during erection

Question 5

Describe features of the corpus spongiousum

Answer 5

• Transmits the urethra,

- Forms glans as a cap over the cavernous bodies.

Question 6

What are the muscles of the root of the penis?

Answer 6

• Ischiocavernosus muscle (surrounds each crus)

- Bulbospongiosus (surrounds the bulb, compresses the urethra during ejaculation and to expel urine.)

Question 7

What are the supportive ligaments of the penis?

Answer 7

• Fundiform and suspensory ligaments

Question 8

Name the different sections of the urethra

Answer 8

• Preprostatic (surrounded by internal urethral sphincter),
• Prostatic (ejaculatory ducts open)
• Membranous (surrounded by external urethral sphincter,
• Spongy (in the bulb of the penis or spongy body)

Question 9

Describe features of the membranous part of the urethra

Answer 9

• Within the striated external sphincter and pubourethral or puboprostatic part of levator ani to resist surges of raised intra-abdominal pressure,
• Sphincter has its base on the perineal membrane and its apex pushing up into the prostatic urethra

Question 10

Describe features of the spongy part of the urethra

Answer 10

• Bulbourethral glands, and scattered glands especially in the navicular fossa. (expansion of the urethra in the glans penis)
• Has 2 curvatures when flaccid (infrapubic - between membranous and bulbar urethra and the prepubic - in spongy). These disappear in erection

Question 11

What are the bulbo-urethral glands (cowper’s gland)

Answer 11

• Located in deep perineal pouch, postero-lateral to membranous urethra,
• Surrounded by transverse fibres of external sphincter.
• Drains into spongy urethra,
• Secretes mucus before ejaculation to neutralize pH of urethra and lubricates urethra

Question 12

What is the lymphatic drainage of the external genitalia

Answer 12

Internal iliac lymph nodes. Prostate may drain to presacral nodes

Question 13

Describe the nerve supply

Answer 13

• Autonomics (PSNS from pelvic splanchnic (S2-4), SNS from superior hypogastric (L1-2),
• Visceral afferents via sacral parasympathetics.
• Somatic afferents via pudendal nerve (S2-4) and its perineal branches (supplies external urethral sphincter)

Question 14

Describe features of errection

Answer 14

• Driven by parasympathetics. It promotes NO release from endothelium leading to vasodilation and engorgement of erectile bodies. Vaso-occlusive mechanism and contraction of muscles in root facilitate erection.

Question 15

Describe features of ejaculation

Answer 15

• Driven by sympathetics,
• It is caused by smooth muscle contraction and rhythmic contractions of bulbospongiosus.
• Arterial vasoconstriction