bony pelvis Flashcards
the bony pelvis overview
a. composed of the hip bone , sacrum and coccyx b. the pelvis has the ASIS and pubic tubercules
the pelvic brim
the pelvic inlet marks the boundary between the greater pelvis and lesser pelvis boarders of the pelvic brim
boarders of the pelvic inlet
- posterior: sacral promontory
- lateral: arcuate line on the inner surface of the ilium and the pectineal line on the superior pubic ramus
- anterior- pubic symphysis
The pelvic inlet determines the size and shape of the birth canal, with the prominent ridges key areas of muscle and ligament attachment.
Some alternative descriptive terminology can be used in describing the pelvic inlet:
Linea terminalis – the combined pectineal line, arcuate line and sacral promontory.
Iliopectineal line – the combined arcuate and pectineal lines. This represents the lateral border of the pelvic inlet.
the greater pelvis ( false pelvis) and the lesser pelvis ( true pelvis )
greater pelvis ( false pelvis)
- expanded portion of the bony pelvis superior to pelvic brim : deep in male ; shallow in female
- lowest part of abdominal cavity with superior part of bony pelvis providing protection to lower abdominal vicera
lesser pelvis ( true pelvis)
- bony pelvis inferior to pelvic brim
- open to abdominal cavity superiorly but closed inferiorly by the pelvic diaphragm
- has inferior part of the bony pelvis protecting the pelvic organs and providing skeletal support for perineum
the pelvic outlet
the pelvic outlet is located at the end of the lesser pelvis and the beginning of the pelvic wall
the borders are:
- posterior- the tip of the coccyx
- lateral: the ischial tuberocities and the inferior margin of the sacrotuberous ligament
- anterior : the pubic arch
traumatic pelvis fractures
Because the pelvis functions as a rigid ring of bone, traumatic injury frequently causes a fracture in two places: a site where traumatic force is applied and 180° opposite that site. If an individual falls on the greater trochanter or falls from a height and lands on his feet, the head of the femur may be driven through the acetabulum into the pelvic cavity. Pelvic fractures may injure pelvic organs, including the urinary bladder and reproductive organs, and cause hemorrhage from pelvic blood vessels and resultant shock. The majority of bleeding often results from venous plexus injury. A full bladderis more likely to rupture than an empty one, and urethral injuries are more likely in males. During surgical repair, screws must be carefully placed to avoid injuring the internal iliac artery and veinlying against the inner surface of the bone.
avulsion fractures
in skelletally immature patients, avusion fractures at the sites of muscle attachments are common. frequent sites of avusion fractures include anterior superior iliac spine (sartois) anterior inferior iliac spine (rectus femoris) and ischial tuberocity ( hamstrings)
the fetal head rotates 90 degrees during birth as maximum diameter changes transverse at pelvic inlet to anteroposterior at pelvic outlet
the midpelvic diameter is the narrowest point of the birth canal and the point of greatest difficulty during labor
joints of the pelvis
sarcoiliac joint
only joint between the axial skeleton and pelvic gridle
transfers all the weight of upper body to lower extremities
reinforced by strong ligaments and so stable that bone on either side of joint is more likely to fracture than joint is to dislocate
joints of the pelvis
pelvi symphysis
midline joint between bodies of two pubic bones
fibrocartilogous disc connecting surfaces covered by hyaline membrane
reinforced by superior pubic and inferior arcuate pubic ligaments
relatively immobile except in latter stages of pregnancy , when hormones cause ligaments to loosen
hemoral changes during pregnancy relax the pelvic ligaments and pubic symphysis allowing for enlargement of the birth canal
