Anatomy6- Male Reproductive Organs

Learning Objectives

  • Identify the anatomy and neurovascular supply of the male reproductive organs:

    • Penis

    • Scrotum

    • Testes

    • Epididymis

    • Ductus deferens

    • Prostate gland

    • Seminal glands

  • Explain the path of sperm from the testis to the urethra.

  • Describe the innervation and mechanisms involved in the erection of cavernous tissue, emission, and ejaculation in males.

  • Apply knowledge of male reproductive anatomy to clinical scenarios.

Presentation Sources

  • This material is prepared from diverse anatomical resources, including:

    • Snell’s Clinical Anatomy

    • Moore’s Clinical Anatomy

    • Gray’s Anatomy

    • Complete Anatomy

    • Netter’s Anatomy

  • Images referenced accordingly

  • All information and images are intended for educational purposes.

Overview of Male Reproductive Organs

  1. Penis

  2. Scrotum

  3. Testes and Epididymis

  4. Spermatic cord

  5. Prostate gland

  6. Bulbourethral glands

  7. Seminal vessels

Review: Male Urethra

  • Length: 20 cm

  • Composed of 4 parts:

    1. Preprostatic (intramural): Extends between the internal urethral orifice and prostate

    2. Prostatic: Passes through the prostate gland

    3. Membranous: Goes through the deep perineal pouch, surrounded by the external urethral sphincter

    4. Spongy (penile): Traverses the corpus spongiosum

Penis: Structure

  • The penis serves two primary functions:

    • Micturition (urination)

    • Sexual intercourse

  • Anatomical composition:

    • Erectile tissue

    • Muscles

    • Fascial coverings

    • Vascular structures

  • Structural distinctions:

    • Root: Fixed structure located in the superficial perineal pouch, contains three erectile tissues and two muscles

    • Body: Free segment consisting of three erectile tissues enveloped by three fascial layers and skin

    • Glans: Expanded part of the corpus spongiosum.

Penis: Erectile Tissue

  • Function: Fills with blood during sexual arousal.

  • Components of erectile tissue:

    • Crura: Attached to the ipsilateral ischial ramus, covered by ischiocavernosal muscles

    • Bulb: Forms the corpus spongiosum ventrally, which eventually extends to form the glans

Penis: Muscles

  • Bulbospongiosus muscles: Contract to expel residual semen and urine from the spongy urethra, aid in maintaining erection.

  • Ischiocavernosus muscles: Contract to push blood from the cavernous spaces in the crura into the corpora cavernosa.

Penis: Fascia

  • Two fascial coverings for each mass of erectile tissue:

    • Superficial fascia (Colles fascia): Continuous with Scarpa’s fascia

    • Deeper fascia (Buck’s fascia): Continuity with the deep perineal fascia, encapsulates all three erectile tissues

  • Tunica albuginea: A thick layer beneath Buck’s fascia, individually encasing each cavernous body.

Penis: Ligaments

  • Suspensory ligament: Connects the erectile bodies to the pubic symphysis

  • Fundiform ligament: Arises from the linea alba, encircles the penis, and attaches to the symphysis pubis.

Penis: Vasculature

  • Blood supply: Originates from the internal pudendal artery and consists of:

    1. Dorsal arteries

    2. Deep arteries

    3. Bulbourethral arteries

  • Venous drainage:

    1. Deep dorsal vein of the penis drains into the prostatic venous plexus

    2. Superficial dorsal veins drain skin and subcutaneous tissues.

Penis: Nerve Supply

  • Erection (Point): Primarily regulated by parasympathetic nerves (pelvic splanchnic nerves).

  • Ejaculation (Shoot): Influenced by sympathetic nervous system (pudendal nerve).

  • Provides deep sensation; skin and root innervated by the ilioinguinal nerve.

Scrotum

  • Anatomical characteristics:

    • A cutaneous sac that anchors the testes to the lower part of the spermatic cord

    • Primary function: Temperature regulation for optimal sperm production

  • Structural layers:

    • Superficial skin

    • Deeper dartos fascia

  • Musculature:

    • Dartos muscle: Smooth muscle fibers found within dartos fascia

    • Cremaster muscle: Involved in elevating the testes.

  • Contents: Includes testis, epididymis, and spermatic cord.

Testes

  • Description: Oval-shaped gonads suspended from the abdomen by the spermatic cord.

  • Function: Sperm and testosterone production.

  • Composition: Includes intricate tubules (seminiferous tubules and rete testis) and secretory cells (Leydig and Sertoli cells).

  • Parenchyma is protected by the tunica albuginea, covered almost entirely by the tunica vaginalis.

Epididymis

  • Structure: A heavily coiled duct located posterior to the testes.

  • Function: Storage and maturation of spermatozoa.

  • Parts: Distinguished into head, body, and tail, draining into the ductus deferens.

Blood Supply to Testis and Epididymis

  • Primarily supplied by paired testicular arteries.

  • Form anastomoses with the main testicular artery, incorporating:

    • Branches of the cremasteric artery

    • Artery of the vas deferens

  • Testicular veins:

    • Formed from the pampiniform plexus

    • Left testicular vein: Drains into the left renal vein

    • Right testicular vein: Drains directly into the inferior vena cava (IVC).

Varicocele

  • Definition: A tortuous dilation of the veins draining the testes, more common on the left side.

  • Characteristics: Described as a “bag of worms” in the scrotum due to the enlargement of veins.

Spermatic Cord

  • Description: A bundle comprising arteries, nerves, pampiniform plexus, ductus deferens, lymphatic vessels, and tunica vaginalis.

  • Pathway: Extends through the inguinal canal to the scrotum, dispersing contents around the testes.

  • Contains three layers:

    1. External spermatic fascia (derived from external oblique muscle)

    2. Cremaster muscle (from internal oblique muscle)

    3. Internal spermatic fascia (from transversalis fascia).

Spermatic Cord Coverings

  • Covering details:

    1. External spermatic fascia: Continuous with external oblique muscle

    2. Cremaster muscle: Derived from the internal oblique muscle, involved in the cremasteric reflex to elevate the testes.

    3. Internal spermatic fascia: Formed from transversalis fascia.

  • The cremaster muscle is innervated by the genital branch of the genitofemoral nerve.

Contents of the Spermatic Cord

  • Blood Vessels:

    • Testicular artery

    • Cremasteric artery and vein

    • Artery to vas deferens

    • Pampiniform plexus of testicular veins

  • Nerves:

    • Genital branch of genitofemoral nerve

    • Autonomic nerves

  • Other structures:

    • Vas deferens

    • Processus vaginalis

    • Lymphatics.

Testicular Torsion

  • Condition: Representing the twisting of the spermatic cord upon itself.

  • Symptoms: Sudden severe pain in the affected testis, leading to the affected testis lying higher than the normal side.

  • Clinical significance: Considered a surgical emergency due to potential strangulation of the testicular artery, resulting in necrosis of the testis.

  • Causes include spasm of cremasteric muscle fibers or a loose testicle within a large tunica vaginalis.

Vas Deferens

  • Description: A thick, straight muscular tube responsible for conveying sperm from the epididymis to the ejaculatory duct.

  • Structure: Comprised of three layers of smooth muscle:

    • Inner: Longitudinal

    • Intermediate: Circular

    • Outer: Longitudinal

  • Features: Rich autonomic innervation ensures rapid movement of sperm towards the ejaculatory duct.

Vas Deferens Anatomical Course

  • Course:

    1. Tail of epididymis

    2. Through inguinal canal

    3. Following the lateral pelvic wall near the ischial spine

    4. Turning medially to pass between the bladder and ureter

    5. Descending along the posterior surface of the bladder

    6. Joining the seminal vesicle to form the ejaculatory duct.

Seminal Vesicles

  • Description: Glandular structures measuring 5 cm in length, situated between the bladder and rectum.

  • Function: Contributes to the formation of the ejaculatory duct alongside the ductus deferens, draining into the prostatic urethra.

  • Secretion: Comprises approximately 70% of semen volume, containing alkaline fluid, fructose, prostaglandins, and a clotting factor essential for semen functionality.

Bulbourethral Glands (Cowper’s Glands)

  • Description: Pea-shaped exocrine glands located posterolateral to the membranous urethra.

  • Function: Produce a lubricating mucus secretion with glycoproteins, contributing to the final volume of semen.

Prostate

  • Function: The largest accessory gland in the male reproductive system, secreting proteolytic enzymes into the semen.

  • Location: Positioned inferior to the external urethral sphincter (EUS), with levator ani muscle located inferolateral and the rectum positioned anteriorly.