Lecture on the Perineum

Introduction

• Importance of the perineum in medical studies.
• Common challenges in understanding the orientation and structure.
• Focus on boundaries, triangles, and pouches within the perineum.

Boundaries of the Perineum

• Lithotomy View: Looking at the pelvic bone inferiorly.
• Key Structures:
  • Pubic symphysis.
  • Ischio-pubic ramus.
  • Ischial tuberosity.
  • Sacro-tuberous ligament.
• Divides into two triangles: Urogenital Triangle and Anal Triangle.

Division of the Perineum

• Urogenital Triangle:
  • Contains urinary and genital structures.
  • Includes urethra, vagina, bulb, and crust of penis.
• Anal Triangle:
  • Contains anal canal and ischioanal fossa.

Approach to Studying the Perineum

• Traditional approach: Skin to pelvic diaphragm.
• Recommended approach: Superior (pelvic diaphragm) to inferior.

Key Concepts

• Orientation from Inferior to Superior:
  • Inferior structures are superficial.
  • Superior structures are deep.
• Pelvic Diaphragm: Composed of pubococcygeus, iliococcygeus, and ischiococcygeus.

Muscles of the Pelvic Diaphragm

• Levator Ani: Includes pubococcygeus and iliococcygeus (not ischiococcygeus).
• Modifications of Pubococcygeus:
  • Pubourethralis, pubovaginalis, puborectalis.

Urogenital Diaphragm

• Structure: Double-layered.
• Layers:
  • Superior layer.
  • Inferior layer (perineal membrane).

Muscles Associated with the Perineum

• Around Bulb of Penis: Bulbospongiosis.
• Around Crust: Ischiocavernosis.
• Transverse Perineal Muscle: Superficial below perineal membrane.

Perineal Body

• Fibromuscular node for pelvic viscera support.

Pouches

• Deep Perineal Pouch:
  • Boundaries: Superior layer of UGD, perineal membrane, transverse perineal ligament.
  • Contents: Membranous urethra, external urethral sphincter, bulbo-urethral gland, deep transverse perineal muscle.
• Superficial Perineal Pouch:
  • Boundaries: Perineal membrane, colis fascia.
  • Contents: Bulb and bulbospongiosis, crust and ischiocavernosis, superficial transverse perineal muscle, Bartholin’s gland (female).

Injury to Urethra

• Membranous Urethra Injury: Urine in deep perineal pouch.
• Spongy Urethra Injury: Urine in superficial perineal pouch, scrotum, anterior abdominal wall, upper thigh.

Important Points

• Perineal membrane separates deep and superficial pouches.
• Structures piercing the perineal membrane are in both pouches.

Questions

• Perineal body injuries and modifications of pubococcygeus.
• Pouch-specific contents and likely exam questions.

Conclusion

• Understanding perineal structures and boundaries is crucial for medical exams.
• Focusing on unique contents between pouches helps in exam preparation.