Scrotum

The scrotum is a cutaneous, fibromuscular sac that houses and protects the testes, epididymides, and the lower ends of the spermatic cords. It provides an external, cooler environment essential for spermatogenesis. The scrotum is divided into two compartments by a central septum and is suspended posterior to the base of the penis. Structurally, it is composed of several layers derived from the abdominal wall during testicular descent. It also contains the dartos muscle, which regulates temperature by altering scrotal surface area through contraction and relaxation.

Structure

The scrotum is a multilayered pouch containing skin, fascia, and smooth muscle. It is divided into two hemispheres by a septum, which is externally marked by the midline raphe. Each compartment contains one testis and its associated structures. The scrotum lacks fat and is highly mobile and distensible.

Layers of the Scrotal Wall

From superficial to deep:

1. Skin: Thin, pigmented, with hair follicles, sebaceous, and sweat glands
2. Dartos fascia: Continuous with Colles and Scarpa fascia; contains the dartos muscle
3. External spermatic fascia: From external oblique aponeurosis
4. Cremasteric muscle and fascia: From internal oblique muscle
5. Internal spermatic fascia: From transversalis fascia
6. Tunica vaginalis (parietal layer): Derived from peritoneum; surrounds testes internally

Surface Features

• Scrotal raphe: Midline ridge indicating underlying septum
• Rugae: Wrinkled surface due to dartos muscle tone

Location

The scrotum is located in the perineal region, posterior and inferior to the penis. It hangs externally from the anterior abdominal wall, allowing it to remain cooler than body temperature, which is essential for normal sperm production.

Direction	Related Structures
Anterior	Penis
Posterior	Perineum and anus
Superior	Pubic symphysis and mons pubis
Deep	Testes, epididymides, spermatic cords

Function

• Thermoregulation: Maintains testes at ~2–3°C below core temperature; critical for spermatogenesis
• Protection: Encases and protects the testes from mechanical trauma and environmental damage
• Compartmentalization: Prevents spread of infection or injury between the two testes via the scrotal septum
• Reflex control: Responds to temperature and stimuli via cremasteric and dartos muscle reflexes

Blood Supply

• Arterial:
  • Anterior scrotal arteries (from external pudendal artery)
  • Posterior scrotal arteries (from internal pudendal artery)
  • Cremasteric artery (from inferior epigastric artery)
• Venous: Mirrors arterial supply; drains into external and internal pudendal veins

Lymphatic Drainage

• Superficial inguinal lymph nodes (unlike the testes, which drain to para-aortic nodes)

Innervation

• Anterior scrotum: Ilioinguinal nerve and genital branch of genitofemoral nerve
• Posterior scrotum: Perineal branches of pudendal nerve and posterior femoral cutaneous nerve

Embryological Origin

• Develops from labioscrotal swellings
• Fused midline raphe forms as genital tubercle elongates
• Homologous to the labia majora in females

Clinical Significance

• Hydrocele: Fluid collection within tunica vaginalis, causing scrotal swelling
• Varicocele: Dilated pampiniform plexus often felt as a “bag of worms” in upper scrotum
• Testicular torsion: Twisting of the spermatic cord; presents with sudden painful scrotal swelling
• Scrotal hernia: Indirect inguinal hernia may descend into the scrotum
• Fournier's gangrene: Rapidly spreading necrotizing fasciitis of scrotum/perineum; surgical emergency
• Scrotal trauma: May lead to hematoma, rupture of tunica albuginea, or testicular fracture