Pelvic anatomy Flashcards
three main components of the bony pelvis?
- two hip bones (aka innominate or pelvic bones)
- sacrum
- coccyx
functions of the pelvis?
- Transfer of weight from the upper axial skeleton to the lower appendicular components of the skeleton, esp during movement.
- Provide attachment for muscles and ligaments of locomotion.
- Contains and protects the abdominopelvic and pelvic viscera.
The osteology of the pelvic girdle allows the pelvic region to be divided into two:
- ?
- ?
The junction between the greater and lesser pelvis is known as what?
- Greater pelvis (false pelvis): superiorly, provides support of the lower abdominal viscera (e.g. ileum and sigmoid colon).
- Lesser pelvis (true pelvis): inferiorly, contains the pelvic cavity and pelvic viscera.
Junction = pelvic inlet (its size its marked by its edge, the pelvic brim)
State which bony components make up the borders of the pelvic inlet.
(posterior, lateral and anterior)
- Posterior: sacral promontory and sacral ala
- Lateral: arcuate line on the inner surface of the ilium, and the pectineal line on the superior pubic ramus (iliopectinal line)
- Anterior: pubic symphysis.
Borders of the pelvic outlet? (posterior, lateral and anterior)
- Posterior: tip of coccyx
- Lateral: ischial tuberosities and sacrotuberous ligament
- Anterior: pubic arch (the inferior border of the ischiopubic rami).
The angle beneath the pubic arch is known as what? How does it differ between men and women?
the sub-pubic angle (greater size in women)
How is the female pelvis adapted for childbirth?
- most women have a gynaecoid pelvis (c.f. male android pelvis)
- gynaecoid: wider and broader structure yet lighter in weight; oval-shaped inlet (c.f. heart-shaped android pelvis); less prominent ischial spines (= greater bispinous diameter); greater angled sub-pubic arch (>80-90 degrees); shorter, more curved sacrum with less pronounced sacral promontory
In addition to the bony adaptations, the ____ and ____ ligaments can stretch under the influence of ____ and increase the size of the outlet further.
sacrotuberous
sacrospinous
progesterone
The lesser pelvis is the bony canal through which the fetus has to pass during childbirth. It is therefore of great importance to determine the diameter of this canal and therefore the childbearing capacity of the mother.
The diameter can be determined by a pelvic examination or radiographically. Which 2 measurements are of importance?
- Obstetric Conjugate: minimum AP diameter of the pelvic inlet (narrowest fixed distance that the foetus would have to negotiate). Sacral promontory > midpoint of the pubic symphysis. Can’t be taken clinically, due to the presence of the bladder.
- Diagonal Conjugate: sacral promontory > inferior border of pubic symphysis. Can be measured manually via the vagina.
In addition to measuring the diagonal conjugate, a mid-pelvis check is carried out.
What is this?
testing for straight side walls and measuring the bispinous diameter (narrowest part of the pelvic canal).
The width of the subpubic angle at the pelvic outlet can be determined by the distance between the ischial tuberosities.
The hip bones have which three main articulations?
- Sacroiliac joint: with sacrum
- Pubic symphysis: between left and right hip bones.
- Hip joint: with head of femur
The hip bone is comprised of which three parts?
- ilium
- pubis
- ischium.
(together they form the acetabulum)
Immediately above the acetabulum, the ilium expands to form the wing (or ala).
Describe the 2 surfances of the wing of the ilium
- Inner surface: concave, produces the iliac fossa (site of origin of the iliacus muscle).
- External surface (gluteal surface): convex, provides attachments to the gluteal muscles.
NB: superior margin of the wing is thickened, forming the iliac crest. It extends from ASIS to PSIS
On the posterior aspect of the ilium there is an indentation known as the __ __ __
greater sciatic notch
The Pubis
- is the most ____ portion of the hip bone.
- Consists of which 3 components?
- Pubic body: located medially, articulates with the opposite pubic body at the __ __.
- Together, the superior and inferior rami enclose part of the ____ foramen
- what passes through this?
6.
- anterior
- body, superior ramus and inferior ramus
- pubic symphysis
- obturator
- obturator nerve, artery and vein pass through to reach the lower limb.