the pelvis Flashcards
2 functions of the pelvis
- girdle for lower limb attachment - force transduction
- basin to hold pelvic viscera
force transduction
allows force to be transduced from the ground through bone
pelvic girdle is made up of
sacrum and 2 os coxa
os coxa
three bones that fuse during development
broad pelvis
distance covered by momentum moving over a fixed limb is larger
increased the efficiency in bipedalism
distance between acetabulum and the scare-iliac joint is short
centre of mass is vertically closer to the hip joint - easier to control and balance
rickets
issues with the composition of the bone of the pelvis
bones can bend in pathological ways due to force transduction
pelvic inlet/brim defines
true pelvis - beneath it
false pelvis - above it
pelvic brim is the same as
pelvic inlet
sacral promontory
part of the S1 vertebral body protruding into the pelvis
pubic symphysis
anterior mechanical link between limbs
weaker than posterior link
bone on with side (pubic bone), N plate cartilage and fibrous cartilage in the middle
capsular ligaments thickened at the top and the bottom - superior and inferior pubic ligament
joint cavities
- can be due to trauma
- common in multiparous women
- fibrous cartilage tears
sacroiliac joint
synovial joint
auricular surfaces articulate
auricular cavity - not fully connected
capsular ligaments in the sacroiliac joint
ventral sacroiliac - thin
dorsal interosseous sacroiliac - very thick, resists more forces
sacrospinous ligament
between sacrum and spine off the ischium
sacrotuberous ligament
from the sacrum to the ischial tuberosity
iliolumbar
between L5 and the ilium
coronal and forntal stability
keystone principle
SI joint can slip in the coronal plane - wedges itself
resisted by dorsal interosseous and iliolumbar ligament
more slip of the SI joint
means more tension on the ligaments
holds ileum to sacrum more securely
limits further movement
functional leg length discrepency
changes in where the joint is positioned
causes difference in legs length due to SI joint
lumbosacral joint and sagittal stability
joint is steeply sloped
60 degrees for males and up to 80 in females
force on lumbar to slip anteriorly
resistance to lumbar slipping
dorsal ligaments
iliolumbar ligaments
neural arch components (articular processes)
prevent arteries displacement
tendency of the sacrum to rotate forwards relative to the ilium is resisted by
dorsal interosseous SI ligament
sacrotubuerous ligament
sacrospinous ligament
greater sciatic foramen is formed by
sacrotuberous ligament
lesser sciatic foramen is formed by
sacrospinous ligament
what plugs up the obturator foramen
obturator muscles - internal and external
internus tendon passes through lesser sciatic foramen
what covers obturator internus muscle
obturator fascia
forms attatchemtn for the pelvic diaphragm
what passes through the obturator canal
obturator nerve and vessels
what passes through the greater sciatic Foramen
- piritoforms muscle
- sciatic nerve
- gluteal nerves and vessels
- pudendal nerves and vessels
what passes through the lesser sciatic foramen
- obturator inernus tendon
- pedundal nerve and vessels
what closes the pelvic outlet
pelvic floor - levator ani
- all support abdomino pelvic viscera
- elevates anal canal
- made from 3 muscles - used to be 4
levator ani is made up of
- pubococcygeus
- iliococcygeus
- puborectalis
sexual dimorphism in male pelvis
external features related to load bearing and muscle attachment tend to be bigger
sexual dimorphism in female pelvis
internal diameters are larger
- predict likelihood of successful vaginal delivery
- creates larger and rounder pelvic cavity
male pelvis internal morphology
has less variation - not an evolutionary pressure
bipedalism changes pregnancy centre of mass issues
increased tendency to fall forwards
the hormone relaxin makes ligament stretchier - decreases joint stability
lordotic curve supports baby weight
lordotic curve
adaptation made to avoid and reduce pressure of prolapse due to upright body position
