Anatomy of Urogenital Triangle in Vishram Singh's Textbook

Urogenital Triangle

• Presents penis and scrotum in males and external genitalia, and orifices of urethra and vagina in females.
• Contains superficial and deep perineal pouches.
• Components include perineal membrane, superficial and deep perineal pouches, external genitalia, and openings of urethra and vagina.

Perineal Body

• Fibromuscular tissue located at the junction between the urogenital triangle and anal triangle.
• In front of the anal canal (between the vagina and anal canal in females).
• Multiple muscles attach to it, including superficial and deep transverse perineal, bulbospongiosus, external anal sphincter, levator ani, and longitudinal coat of the anal canal.

Perineal Membrane

• Thin, tough fascia that encloses the urogenital triangle and provides a foundation for attachment of erectile bodies of the external genitalia.
• Laterally attaches to ischiopubic rami and its posterior margin fuses with the perineal body.
• Perforated by the urethra in males and by the urethra and vagina in females.

Urethral Sphincters

• Layers of the perineum from deep to superficial:
  • Floor of the pelvic cavity = roof of the perineum
  • Deep transverse perineal muscle, external urethral sphincter in the deep perineal pouch
  • Perineal membrane enclosing the urogenital triangle, leaving openings for the urethra (and vagina in females)

Perineal Pouches

• Deep perineal pouch:
  • Contains deep transverse perineal muscle and external urethral sphincter
• Superficial perineal pouch:
  • Contains superficial transverse perineal muscle and erectile tissues

Anal Triangle

• Definition: borders anterior - horizontal plane between ischial tuberosities, posterior - coccyx, inferior/lateral - sacrotuberous ligaments
• Contents:
  • Anal canal (in the center)
  • Ischiorectal fossae (on each side)
  • Pudendal canal and its neurovascular bundle
• Skin is innervated by inferior rectal nerve (S2-4) and direct perineal branches off S4

Ischioanal Fossa

• Two fossae that communicate posterior to the anal canal (posterior recesses)
• Above the urogenital diaphragm, extending forward as (anterior recesses)

Pudendal Canal and Pudendal Nerve

• Pudendal canal is located in the lateral wall of the ischiorectal fossa, from the lesser sciatic foramen to the deep perineal pouch.
• Contains:
  • Pudendal nerve (branches into dorsal nerve of penis and perineal nerve)
  • Internal pudendal vessels
• Pudendal nerve:
  • Origin: S2-S4
  • Main nerve of the perineum
  • Sensory from external genitalia and anus
  • Afferent component of erection and motor to external urethral and external anal sphincters, levator ani, bulbospongiosus, and ischiocavernous mm