anatomy of the pelvis Flashcards
what bones make up the bony pelvis?
right and left hip bone and the sacrum
where does the bony pelvis join anteriorly and posteriorly?
anteriorly - pubic symphysis
posteriorly - sacro-iliac joint
what kind of a joint is the sacro-iliac joint?
Partially cartilaginous, partially synovial
what bones make up the bony pelvis?
ilium, ischium and pelvis
what holds together the bones of the acetabulum?
triradiate cartilage
what is the triradiate cartilage?
Y shaped cartilage between the bones
what is the ASIS in vertical alignment with?
pubic symphysis
what is ASIS?
Bony protuberance found where the iliac crest ends. Attachment of sartorius and inguinal ligament.
what is AIIS and what muscle attaches to it?
just below ASIS. Attachment of rectus femoris muscle of quadriceps.
what is the pubis?
V shaped bone made up of the superior and inferior pubic ramus
what attaches to the pubic tubercle?
inguinal ligament
what foramen is pubis the border of?
obturator foramen
what muscles attach to the ischial tuberosity?
hamstrings
what are the borders of the pelvic inlet?
pubic symphysis, iliopectineal lines, sacral promontory.
what makes up the borders of the pelvic outlet?
pubic arch, ischial tuberosity, coccyx
what cavity is the pelvic cavity continuous with?
abdominal cavity
what is the true/lesser pelvis?
region of the pelvis between the inlet and outlet, containing pelvic organs only
what is the false/greater pelvis?
region of the pelvis above the inlet which also contains abdominal organs
what are the functions of the pelvis?
weight bearing
locomotion
child bearing (women)
do males or females have the largest pelvic outlet?
females
describe the female pelvis?
- Has to be adapted for child birth
- Wide sub-pubic angle (greater than 80°)
- Wide pelvic inlet and outlet
- Bones have thin and light structure
describe the male pelvis
- Larger muscles attaching to them thicker bones, but narrow bony pelvis
- Narrow sub-pubic angle (less than 70°)
- Narrow pelvic inlet and outlet
- Thick and heavy structure
how can you tell the difference between a male and female pelvis?
look at the angle under the pubic symphysis
• Female pelvis: angle between the thumb and the index finger is the angle under PS
• Male pelvis: angle between the index and middle finger is the angle under PS
what methods can be used to measure the pelvis?
radiography
manually
where is the smallest distance within the pelvic inlet?
between sacral promontory and pubic symphysis
fixed bony distance
what is the smallest distance of the pelvic outlet?
interspinous distance
Distance between the ischial spines on each side
Not a fixed distance
what are the 4 shapes of the female pelvis?
o Android
o Anthropod – oval pelvic inlet
o Gynecoid – most common. Has a round pelvic inlet and outlet. Ideal shape for child bearing (hence why it’s so common)
o Platypelloid – oval pelvic inlet
what is the most common shape of the female pelvis?
gynecoid
where does the sacrotuberous ligament attach?
sacrum to ischial tuberosity
where is the lesser sciatic foramen?
between sacrospinous and sacrotuberous ligament
where does the sacrospinous ligament attach?
attached from outer edge of sacrum/coccyx to spine of the ischium
where is the greater sciatic foramen?
between sacrospinous ligament and bony pelvis
what muscle passes through the greater sciatic foramen?
piriformis
what passes through the greater sciatic foramen under the piriformis muscle?
inferior gluteal neurovascular passes through along with pudendal nerve
describe the pathway of the pudendal nerve
- Leaves the pelvis via the greater sciatic foramen
* Enters the perineum through the lesser sciatic foramen
what passes through the greater sciatic foramen above the piriformis muscle?
superior gluteal neurovascular bundle
where is the sacroiliac ligament?
situated in deep depression between sacrum and ilium
what does relaxin do and when is it released?
During pregnancy, the hormone relaxin causes ligaments to relax, permitting a 10-15% increase in pelvic diameter.
what is the inferior border of the external oblique muscles?
inguinal ligaments
what does the inguinal ligament attach to?
ASIS and the pubic tubercle
where is the obturator membrane found?
almost completely closes off the obturator foramen
what passes through the obturator foramen and where do these structures go?
Obturator artery, nerve and vein pass through this foramen towards the medial compartment of the thigh
what structures pass through the greater sciatic foramen?
- Gluteal arteries, veins, nerves
- Sciatic nerve
- Pudendal nerve
- Internal pudendal artery
what passes through the lesser sciatic foramen?
- Pudendal nerve
* Internal pudendal artery
what are the nerve roots of the pudendal nerve?
S2-S4 somatic
what does pudendal nerve innervate?
Provides motor and sensory innervation to the perineum
what does the abdominal aorta divide into?
common iliac arteries
what do the common iliac arteries divide into?
external and internal iliac arteries
what are the 4 major arteries that leave the pelvis?
superior gluteal artery
inferior gluteal artery
obturator artery
internal pudendal artery
why are there different arteries within the pelvis in men and women?
because they have different viscera
what are the arteries in the pelvis of women and what do they supply?
superior vesicular arteries - supply the bladder
uterine artery - going to the uterus
middle rectal artery - goes towards the rectum
what is the main branch of the uterine artery and what does it supply?
vaginal branc
supplies the vagina
what does the superior rectal artery branch off?
inferior mesenteric artery
what does the inferior rectal artery branch off?
pudendal artery
what are the arteries in the pelvis in males?
superior vesicular arteries
inferior vesicular arteries
middle rectal artery
what do the inferior vesicular arteries supply?
the inferior portion of the bladder
supplies the prostate gland
what is the pelvic floor?
a muscular sheet which closes the pelvic outlet. Slightly curved
what is above and below the pelvic floor?
Main pelvic cavity above, the perineum below.
what makes up the pelvic floor?
• Made up by levator ani muscles, coccygeus muscles and their covering fascia. Incomplete anteriorly (urethra/vagina)
what muscles make up the levator ani?
puborectalis
pubococcygeus
iliococcygeus
coccygeus/ischiococcygeus
what is the puborectalis?
muscular sling from bone around rectoanal junction Muscle fibres go from pubic bone, looping around the rectum and going back to the pubic bone
what is the function of the puborectalis muscle?
maintain anal angle at the ano-rectal junction (kinks the rectum to create a right angle - important for anal continence)
o During defecation there is relaxation of the puborectalis muscle which will straighten out the recto-anal angle.
where is the pubococcygeus muscle found?
Muscle fibres which go from pubic bone and extend back to the coccyx and back to the pubic bone on the other side.
where is the coccygeus muscle found?
muscle which goes from the ischial spine to the coccyx
where is the piriformis found?
originates at the sacrum, passes through greater sciatic foramen to attach to the posterior aspect of the femur
where is the obturator internus found?
leaves pelvis through lesser sciatic foramen. Covers obturator foramen. Enters gluteal region to attach onto the posterior aspect of femur
