L6.3 Pelvic walls, muscles and fascia

Question 1

Layers of the pelvic wall

Answer 1

1. Bones
2. Muscles
3. Pelvic fascia
   
   • Parietal layer of peritoneum
   • Somatic N & parietal vessels
4. Pelvic viscera

Question 2

Location of the piriformis and obturator internus

Answer 2

• Piriformis:
  
  • Mid 3 sacrum → through GSF → ex rotation of hip
• Obturator internus
  
  • Obturator foramen → through LSF (b/w ischial spine and tuberosity by sacrospinous ligament) → ex rotation of hip

Question 3

Obturator fascia

Answer 3

• Covers obturator internus twds INF bony attachment
• Thickened at the middle of O.I → called the tendinous arch → where perineum attaches

Question 4

Levator ani fascia

Answer 4

• Superior fascia of L.Ani joins Obturator fascia at tendinous arch
• Perineum beneath, also joins at tendinous arch
• Is the pelvic diaphragm, projects twd midline (pelvic floor is like a hammock)
  
  • Important for rotation of fetal head

Question 5

Pudendal canal

Answer 5

• Found b/w L.Ani and O.I
• VAN found in canal → supplies pelvic floor

Question 6

Pelvic floor

Answer 6

• L.Ani + coccygeus
• Raphe → Tendinous line where muscles attach in the middle
• Pelvic floor is always under pressure

Question 7

Components of levator ani

Answer 7

• Attaches to perimeter of pelvic wall (LAT + POS)
• 3 components:
• Pubococcygenus (Has puborectalis)
  
  • On perineum side → the sacrotuberous ligament
  • On pelvic side → a muscle
• Iliococcygeus
• (ischio)coccygeus (POS)

Question 8

Puborectalis

Answer 8

• Voluntary control with maturity
• Passes around anal canal → maintain fecal continence
  
  • Pulls rectum twds pubis → kinking it
  • Rectum straightens only during defecation
• Merges with deep part of external anal sphincter

Question 9

Other smaller components of levator ani

Answer 9

• Puboanalis
• Pubovesicalis
• Pubourethralis
• Pubovaginalis
• Puboprostaticus

Question 10

Perineal body

Answer 10

• Fibrous mass at the junction b/w urogenital and anal triangle, essential for integrity of pelvic floor (esp in females)
• Perineal body (larger in females than males)
  
  • Component of L.Ani merge with perineal body and helps stabilises pelvic floor

Question 11

Function of the pelvic floor

Answer 11

• Supports pelvic viscera
• Raising pelvic floor → to increase intra-abdominal pressure
  
  • Assists Continence and defecation
• Childbirth → L.Ani at the plane of least dimension
  
  • Creates gutter to enable flexion & rotation of fetal head

Question 12

BS to the pelvis

Answer 12

• Internal iliac A (ex iliac goes into limbs)

Question 13

NS to the pelvis

Answer 13

• S2,3,4 (*supplies the floor of the arse)
• Pudendal (S2-3) from blelow (major supply)
  
  • From pelvic cavity (with SUP gluteal A) enters GSF → Enters gluteal region → Exit LSF to pelvic floor
  • Ischial spine = Major landmark
• Well protected
  
  • Except for trauma from perineum (INF) - i.e. Falling onto a beam
  • Anaesthetised during childbirth

Question 14

How is the stability of the vagina increased?

Answer 14

• Increase abdominal pressure → pushes uterus down → kinked fwd in relation to vagina

Question 15

Weakness of the pelvic floor

Answer 15

• Injury following childbirth
• May result in prolapse
  
  • Uterus through vagina
• Cystocoele - Bladder herniate into vag
• Urethrocoele - Herniation of bladder intro urethra
• Rectocoele - Rectum herniation into POS vag wall