Male Reproductive System and Embryology

Male Reproductive System

• Functions include reproduction, sexual intercourse, and urination.
• Parts include internal and external genitalia.
• Learning objectives include understanding male genitalia development, anatomy of external genital organs, male urethra, and internal genital organs.
• Organs of the male reproductive system include testes, epididymis, seminal vesicle, ductus deferens, spermatic cord, ejaculatory duct, prostate, male urethra, bulbourethral glands, male urethra, and scrotum. The penis is also a key organ. These structures are involved in sperm production, maturation, conduction, and sexual intercourse.

Embryology

• Gonads differentiate into testes due to Y chromosome/TDF.
• Leydig cells and Sertoli cells are key for this process.
• Mesonephric (Wolffian) ducts form epididymis, vas deferens, and seminal vesicles.
• Mullerian ducts degenerate.
• Testosterone and DHT are key hormones driving development.
• The penis develops from genital tubercle/urethral folds.
• The descent of the testes to the scrotum occurs around the 28th week. The gubernaculum is critical for the process.
• The gubernaculum and related connective tissues direct testicular movement and hold them in place.
• Retroperitoneal connective tissue and the primordial scrotum facilitate testis descent.
• Peritoneal diverticulum is the processus vaginalis.

Ectopic Testis

• Ectopic testis are abnormal locations of the testes.
• Locations include abdominal, femoral, and pubopenile.

Penis

• Parts include the root, body, and glans.
• The root comprises crura and bulb of penis.
• Ischiocavernosus and bulbospongiosus muscles are critical for erection and ejaculation.
• The body includes corpora cavernosa (x2) and corpus spongiosum. The corpus spongiosum contains the urethra.
• Tunica albuginea covers the cavernous bodies.
• Deep fascia (Buck's fascia) is a key layer.
• Arteries include dorsal and deep penile arteries.
• Veins include deep and superficial dorsal veins.
• Nerves include the dorsal nerve of the penis and pudendal nerve (S2-S4).
• Suspensory and fundiform ligaments support the penis.

Mechanism of Erection

• Erection involves the relaxation of helicine arteries and smooth muscles, leading to blood flow into cavernous spaces.
• Key neurotransmitters and hormones involved include acetylcholine, dopamine, ATP, adenosine, VIP, peptides, adrenomedullin, CGRP, prostanglandins, and endocannabinoids.

Penile fracture

• Penile fracture is an injury to the suspensory ligaments, penis fascia, or surrounding tissue. This leads to a visible deformation, like an "eggplant" form.

Male Urethra

• Length: 18-22 cm.
• Sections: intramural (preprostatic), prostatic, intermediate (membranous), and spongy (cavernous).
• Sphincters: internal and external urethral sphincters are important.

Scrotum

• Cutaneous sac containing the testes, with pigmented skin and dartos muscle.
• Separating right and left compartments is the septum of the scrotum.
• The dartos muscle controls the skin wrinkling of the scrotum.

Testes

• Male gonads producing sperm and testosterone.
• Tunica vaginalis (closed peritoneal sac) partially surrounds the testes.
• Tough fibrous layer/tunica albuginea surrounds the testes, forming lobules.
• Seminiferous tubules, straight tubules, rete testes, and efferent ductules are important structures.

Testes Vascularization

• Testicular arteries arise from the abdominal aorta.
• Right testicular veins drain into the inferior vena cava.
• Left testicular veins drain into the renal vein.

Testicular torsion

• A twisting or rotation of the testis, decreasing blood flow.

Epididymis

• Elongated structure behind the testis.
• The duct of epididymis has tight convolutions.
• The head, body, and tail connect to the ductus deferens.

Ductus Deferens

• Thick-walled, cord-like structure carrying sperm.
• Continuation of the epididymis.
• Part of the spermatic cord, crossing the external iliac vessels and lateral pelvic wall.
• Joins the seminal vesicle duct to form the ejaculatory duct.

Spermatic Cord

• Collective name for structures supporting the testes.
• Includes vas deferens, testicular artery and vein, lymphatic vessels, nerves, and ilioinguinal and genital branch of genitofemoral nerve.

Seminal Vesicles

• 5 cm long; between bladder fundus and rectum.
• Covered by peritoneum of rectovesical pouch.
• Secrete fructose-rich fluid and coagulating agent.

Ejaculatory Ducts

• 2.5 cm long.
• Union of seminal glands ducts & ductus deferens.
• End near the prostatic utricle.

Prostate

• Walnut-sized accessory gland.
• Glandular/fibromuscular part.
• Lobules (isthmus, median, posterior, lateral) are significant.
• Prostatic capsule, venous plexus, and sheath (visceral layer of pelvic fascia) are important.

Bulbo-urethral Glands

• Pea-sized glands within external urethral sphincter.
• Opening into proximal spongy urethra.

Innervation

• Sympathetic (T12-L2, hypogastric pelvic plexuses) and parasympathetic (S2-S4, pelvic splanchnic nerves) innervations are important for male reproductive system functions.
• Pudendal nerve and other components are also key for sensitive control.