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
What genitourinary structures does pubococcygeus sling around in males and females?
Males = prostate Females = vagina
What are the three component parts of pubococcygeus, from anterior to posterior?
Pubovaginalis/puboprostaticus
Puborectalis
Pubococcygeus proper
What does puborectalis do to the rectum and anal canal, and what is the significance of this?
Puborectalis creates angle of rectum on anal canal = anorectal angle/perineal flexure = 80 degrees
Really important functional element of feacal continence
Relax puborectalis > straighten out anorectal angle > defecation
What is the origin of iliococcygeus?
Fascia overlying obturator internus
Where do the fibres of iliococcygeus on either meet?
Anococcygeal raphe
What is the relationship between pubococcygeus and iliococcygeus?
Iliococcygeus underlaps pubococcygeus - can’t see fibres of iliococcygeus meet at midline
Which parts of the pelvic floor make up levator ani?
Pubococcygeus
Iliococcygeus
What is the action of levator ani?
Lift > pelvic floor comes up
What is the size and shape of ischiococcygeus?
Small
Triangular
What are the attachments of ischiococcygeus?
Ischial spine
Sacrum
What does ischiococcygeus do?
Basically some muscle fibres over internal aspect of sacrospinous ligament
Non-functional
What does the pelvic fascia overly, and what is it called?
Parietal fascia lines walls of pelvis
Visceral fascia lines viscera
Describe the consistency of the parietal fascia?
Dense over walls
Loose over floor, because floor needs to lift
What is the consistency of the visceral fascia?
Very loose over expansile portions of pelvic viscera
Dense over fixed portions
What are the spaces in between the walls and viscera filled with?
Very loose connective tissue, also called pelvic fascia
Why does infection spread so easily in the pelvis?
Because of pelvic fascia
What is the relationship between the pelvic fascia and neurovascular bundles?
Fascia condenses around neurovascular bundles heading to structures they supply from walls
Creates many ligaments
Act as surgical landmarks
Major stabilisers of pelvic viscera
Where do the nerves of the pelvis predominantly come from?
Sacral plexus
How is the sacral plexus adhered to piriformis?
Glued down by pelvic fasca
Where do the arteries of the pelvis come from?
Internal iliac artery
What do the veins of the pelvis drain into?
Iliac vein
Which vessel are the common iliac arteries the two terminal branches of?
Abdominal aorta
Into what and where does the common iliac artery divide?
Internal and external iliac arteries at pelvic brim
Where does the external iliac artery go after it splits from the common iliac artery?
Doesn’t enter pelvis and goes beneath inguinal ligament
What are the two divisions of the internal iliac artery?
Anterior division
Posterior division
What do the anterior and posterior divisions of the internal iliac artery give rise to?
Parietal branches
Which division of the internal iliac artery gives rise to visceral branches?
Anterior division
On which side of the pelvic fascia do the vessels lie?
Inside fascia, closer to viscera - pelvic fascia lies in between sacral plexus and vessels
What drapes over the pelvic viscera?
Pelvic peritoneum
What does the pelvic peritoneum invest to the viscera it drapes over?
In part, a serous coat
Where does the pelvic peritoneum reflect off the anterior abdominal wall in males, and then where does it go?
Reflects off roughly at top of pubic symphysis Goes over top of bladder Dips down behind bladder Reflects over rectum Onto posterior abdominal wall
What does the pelvic peritoneum create between the bladder and rectum?
Dependent fold/puhc = rectovesical pouch
How can the bladder be accessed suprapubically if there is peritoneum lining it?
When bladder fills, it pushes up, pushing peritoneal cavity with it
Strips peritoneum off anterior abdominal wall
In babies, if suspecting urinary tract infection, to sample urine, percuss bladder over pubic bone > if dull, bladder expanded, and has pushed peritoneum away from anterior abdominal wall > introduce sterile needle and take sample of urine from bladder
In elderly men with enlarged prostate gland, 1st part of urethra can be compressed > can’t void > bladder fills and fills > can quickly relieve discomfort by inserting needle above pubic bone and drain urine that way
What is the arrangement of the bladder, rectum, and uterus in females?
Bladder in front
Rectum behind
Uterus bet forwards over vagina in between
In females, how does the pelvic peritoneum lie over the viscera?
Peritoneum lines anterior abdominal wall, down to superior aspect of body of pubis
Reflects up over top of bladder - densely adherent
Onto anterior part of uterus - only upper 2/3
Over top and all the way over posterior part of uterus, beyond reach of cervix and superior aspect posterior part of vagina
Back up over rectum
Onto posterior abdominal wall
What are the two dependent folds in the peritoneum of females?
Between bladder and uterus = vesicouterine pouch
Between rectum and uterus = rectouterine pouch = pouch of Douglas
Which pouch in females is the deepest?
Vesicouterine pouch - lowest point of peritoneal cavity in females
How can you feel a burst appendix, for example, in a per vagina exam?
Ruptured appendix > fluid collects in peritoneal cavity
Fluid will gravitate towards pouch of Douglas
When you do per vagina exam, because of angulation of uterus forwards over vagina, which is heading backwards, tip of 2 fingers hit superior part of posterior wall of vagina
Tip of fingers right against pouch of Douglas > can feel free fluid
- Can insert needle and take sample for investigations
