Walls and Floor of the Pelvis Flashcards
What converts the greater and lesser sciatic notches to the greater and lesser sciatic foramina?
Sacrotuberous and sacrospinous ligaments
Other than creating the sciatic foramina, what else do the sacrotuberous and sacrospinous ligaments add to the structure of the pelvis?
Obturator membrane
How does the obturator membrane change the obturator foramen?
Converts big obturator foramen into small residual passage = obturator canal
Located superiorly
What is the origin of obturator internus?
Internal aspect of obturator membrane and margins of obturator foramen
Spares obturator canal
Extends up a little bit to bony side wall of pelvis
Which muscle is on the lateral wall of the pelvis?
Obturator internus
Which muscle is on the posterior wall of the pelvis?
Piriformis
What forms the functional part of the pelvic floor?
Levator ani
How does obturator internus exit the pelvis into the gluteal region?
Fibres converge
Exit through lesser sciatic foramen
Pick up gemellus on either side
What is the insertion of obturator internus?
Greater trochanter of femur
What is the origin of piriformis?
Middle 3 pieces of anterior surface of sacrum
How does piriformis exit the pelvis and enter the gluteal region?
Fibres converge on greater sciatic foramen and exit there
What is the relationship between piriformis and obturator internus in the gluteal region?
Piriformis superior to obturator internus
What closes off the pelvic outlet?
Levator ani
What is the pelvic floor?
Entire muscular diaphragm separating pelvic viscera from exterior
Is all of the pelvic floor functional?
No
Functional part = can lift
Called levator ani
What is the attachment of the pelvic floor?
Has one continuous attachment to each side wall of pelvis
- Internal surface of pubic bone
- Across obturator internus as far as ischial spine
Where do the fibres from either side of the pelvic floor meet?
Fibres meet in middle and interdigitate at white line = midline raphe
How does the pelvic floor attachment divide obturator internus?
Half of obturator internus above attachment, and half below
What is the extent of the midline raphe?
Extends from tip of coccyx to anorectal junction
Therefore called anococcygeal raphe
What are the three component parts to the pelvic floor, from anterior to posterior?
Pubococcygeus
Iliococcygeus
Ischiococcygeus
What is the origin of the pubococcygeus?
Pubic bone
What is the relationship between pubococcygeus and obturator internus?
Pubococcygeus extends a little bit onto front of obturator internus
Do all the fibres of pubococcygeus interdigitate at the anococcygeal raphe?
No
What do the most anterior fibres of pubococcygeus sling around?
Anorectal junction
Some fibres blend in with it