L8.1 Perineum

Question 1

Region of the perineum

Answer 1

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

Question 2

Features of the perineum

Answer 2

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

Question 3

Significance of the angulation of the vaginal and anal canal

Answer 3

• Forms functional sphincters

Question 4

Development of the urogenital/GI system

Answer 4

• 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

Question 5

Perineal membrane

Answer 5

• 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

Question 6

Deep perineal pouches

Answer 6

• 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

Question 7

Superficial perineal pouch

Answer 7

• 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

Question 8

Clitoris

Answer 8

• 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

Question 9

What happens when the bulbs are damaged

Answer 9

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

Question 10

Features of the female external vaginal components

Answer 10

• 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

Question 11

Ischio (rectal) anal fossa

Answer 11

• 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)

Question 12

External anal sphincter

Answer 12

• 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)

Question 13

Nerves of the perineum

Answer 13

• 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