Male Perineum

Male Perineum Overview - The Southern Frontier

• Diamond-shaped region inferior to the pelvic diaphragm, situated between the proximal thighs.
• Boundaries:
  • Anterior: Pubic symphysis.
  • Posterior: Tip of the coccyx.
  • Anterolateral: Ischiopubic rami.
  • Posterolateral: Sacrotuberous ligaments.
  • Roof: Pelvic diaphragm (Levator ani and Coccygeus muscles).
  • Floor: Skin and perineal fascia.
• An imaginary transverse line joining the anterior parts of ischial tuberosities divides it into:
  • Urogenital triangle (anterior).
  • Anal triangle (posterior).

⭐ The perineal body (central tendon of the perineum) is a key fibromuscular structure located at the midpoint of the line joining the ischial tuberosities, providing crucial support to pelvic viscera.

Urogenital Triangle - Plumbing & Support

• Anterior perineum; borders: pubic symphysis, ischiopubic rami, ischial tuberosities.
• Layers & Contents (Superficial to Deep):
  1. Skin & Colles' Fascia (continuous with Scarpa's fascia of abdomen).
  2. Superficial Perineal Pouch (SPP):
     • Muscles: Ischiocavernosus, Bulbospongiosus, Superficial Transverse Perineal.
     • Erectile Tissues: Crura & Bulb of penis.
     • Neurovasculature: Perineal branches (internal pudendal a. & n.).
  3. Perineal Membrane (PM):
     • Thick fascial sheet; pierced by urethra & neurovasculature.
  4. Deep Perineal Pouch (DPP):
     • Muscles: Deep Transverse Perineal, External Urethral Sphincter.
     • Glands: Bulbourethral (Cowper's) glands.
     • Neurovasculature: Dorsal n. of penis, internal pudendal vessels.
• Key Support: Perineal body (central tendon of perineum).
• Plumbing: Urethra (membranous & spongy parts), Root of penis.

⭐ Straddle injury can rupture the bulbous urethra; urine extravasates into the superficial perineal pouch, scrotum, penis, and anterior abdominal wall (limited by Colles' fascia attachments).

Anal Triangle - Exit Strategy

• Boundaries: Posterior perineum; apex: coccyx; base: line between ischial tuberosities; sides: sacrotuberous ligaments.
• Key Structure: Anal canal & anus.
  • Sphincters:
    • Internal (IAS): Smooth muscle, involuntary.
    • External (EAS): Skeletal muscle, voluntary (inferior rectal nerve from pudendal N.).
• Ischioanal Fossa: Paired, wedge-shaped spaces lateral to anal canal.
  • Contents: Fat (for anal distension), inferior rectal nerves & vessels.
  • Clinical: Common site for ischioanal abscesses.
• Pudendal Canal (Alcock's): In obturator internus fascia (lateral wall of ischioanal fossa).
  • Transmits: Pudendal nerve (S2-S4), internal pudendal artery & vein.

  ⭐ Pudendal nerve (S2, S3, S4) is crucial for EAS motor control and perianal sensation.

Perineal Neurovasculature - Power & Lines

• Core Supply:
  • Nerve: Pudendal N. (from S2,S3,S4 ventral rami).
  • Artery: Internal Pudendal A. (branch of Internal Iliac A.).
  • Vein: Internal Pudendal V. (drains to Internal Iliac V.).
• Path: Travels through the Pudendal (Alcock's) Canal.

  ⭐ Pudendal nerve block: Anesthetic is injected near the ischial spine to block the pudendal nerve. This is crucial for pain relief in obstetric procedures and surgeries in the perineal region.

• Main Branches (Nerve & Artery typically paired):
  • Inferior Rectal N/A: Supplies external anal sphincter & perianal skin.
  • Perineal N/A:
    • Superficial br: Posterior scrotal N/A (sensory to posterior scrotum).
    • Deep br: Muscular branches to urogenital (UG) triangle muscles (e.g., bulbospongiosus, ischiocavernosus).
  • Dorsal N/A of Penis: Sensory to penis skin & glans; Deep Artery of Penis (branch of internal pudendal A.) supplies corpora cavernosa. 📌 Mnemonic (Pudendal Nerve roots): "Sex 2, 3, 4 keeps the penis off the floor."

High‑Yield Points - ⚡ Biggest Takeaways

• Pudendal nerve (S2-S4): chief nerve supply to the perineum.
• Perineum: divided into anterior urogenital triangle & posterior anal triangle.
• Colles' fascia: continuous with abdominal Scarpa's fascia; limits urine extravasation.
• Perineal body: central fibromuscular hub, crucial for pelvic floor support.
• Superficial perineal pouch: contains roots of penis (crura, bulb), ischiocavernosus, bulbospongiosus muscles.
• Deep perineal pouch: houses membranous urethra, external urethral sphincter, bulbourethral glands.
• Ischioanal fossa: fat-filled space lateral to anal canal, common site for abscesses.