L8.1 Perineum Flashcards Preview

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Flashcards in L8.1 Perineum Deck (13):

Region of the perineum

  • Perineum is best seen with legs open, separates into urogential triangle and anal triangle (located behind
    • Perineum is the region below the pelvic floor


Features of the perineum

  • Perineum is the site of anchoring for penis and clitoris
  • Anal triangle is slightly angulated POS
  • Triangles divided by line across the ischial tuberosities

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Significance of the angulation of the vaginal and anal canal

  • Forms functional sphincters


Development of the urogenital/GI system

  • Common ejection chamber for urogential system and GI tract
    • Cloaca
      • Made up of endoderm
      • Has cloacal sphincter (mesoderm)
      • Skin has a rich sensory NS
        • Internally different NS and BS
    • Partition during development (rectovesical septum)
      • Urogenital and anal

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Perineal membrane

  • Perineum has strong support from perineal membrane
  • Has deep perineal pouch
    • Where skeletal muscles forms sphincters around urethra and vagina
    • Allows attachment of external genitalia

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Deep perineal pouches

  • External urethral sphincter
    • Made up of skeletal muscles (slow twitch fibres)
    • Able to maintain tone 24/7
      • Relaxed to allow micturition
  • Additional sphincter components in Females
    • Sphincter urethrovaginalis
      • Surrounds urethra and goes on to support the vagina (active muscular support)
      • Goes in front of vagina
    • Compressor urethrae

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Superficial perineal pouch

  • Superficial urogenital muscles
  • Bulbspongiosus
    • Contracts to expel the last drop of urine
    • Attaches to the fibrous N - the perineal body
  • Perineal body
    • Common sites of attachment for muscles of perineum
  • Roots of external genitalia



  • Clitoris is deisnged similarly to the penis
    • Made up of bulb on each side
    • Crura (homologues of corpus cavernosum in male)
    • Erectile tissues
    • Glands
    • Bulb


What happens when the bulbs are damaged

  • Leads to Extravasation of urine into extraperitoneal tissue of the pelvic cavity
  • Damaged by falling onto a beam


Features of the female external vaginal components

  • Vulva
    • External genitalia in female
  • Labium majora
    • Homologue of the scrotum in males
  • Labium minora
    • Homologue of the spongy urethra in males
  • Glands is ANT to urethra (which is just behind the clitoris)
    • Glands open up into area called vestibule
  • Hymen
    • Partitioning the opening of the vagina

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Ischio (rectal) anal fossa

  • Contains fat and pudendal N (gives off INF rectal N) to external anal sphincter
  • Allws rectum and anua to distent to allow defaecation
  • Abscess formation (typically have to be removed)

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External anal sphincter

  • Deep part
  • Superficial part
    • Attach to perineal body
    • Forms the raphe to the tips of the coccyx
    • Stabliises the perineal body
  • Subcutaneous part
    • Guards the most superficial part of the anal canal
  • Innervated by INF rectal N (branch from S4)

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Nerves of the perineum

  • INF retal N (S4) comes from pudendal N
    • Pudendal N (S2, 3, 4)
      • Supply branches to perineum, rectum, L.A
      • Into pelvic cavity via GSF and exits LSF
        • Not prone to compression or entrapment
        • INF to the pelvic floor