Osteology of the Pelvis Flashcards
What are the functions of the pelvis?
- Weight transfer – from axial to lower appendicular skeleton
- Withstand compression and other forces
- Provide attachment for powerful muscles
Name the bones that make up the bony pelvis in a mature person?
- Hip bones
- Ilium
- Ischium
- Pubis
- Sacrum – 5 fused sacral vertebrae
- Coccyx – 4 fused coccygeal vertebrae
Describe the bones of the bony pelvis in an infant?
hip bones consist of 3 separate bones (ilium, ischium and pubis) united by cartilage at acetabulum
- Fuses at Puberty
Another name for hip bones in an infant is?
coxal bones or innominate bones
Name the 4 pelvic joints?
1. Pubic symphysis – joins two hip bones together 2. Sacroiliac joint – joins hip bones to sacrum 3. Lumbosacral joint – joins vertebrae to sacrum 4. Sacrococcygeal joint – joins sacrum to coccyx
Name the parts of the ilium?
- ala – wing
- Iliac crest
- Anterior and posterior superior + inferior iliac spines
- Iliac fossa
- Body – forms acetabulum
Name the parts of the ischium?
- Body – forms the acetabulum
- Ramus – forms obturator foramen
- Ischial tuberosity
- Ischial spine – posterior projection between body and ramus
- Lesser sciatic notch – concavity between ischial tuberosity and spine
Name the parts of the pubis?
- superior ramus – form acetabulum
- Inferior ramus – form obturator foramen
- Pubic crest – anterior thickening of the body
- Pubic tubercle – lateral prominent bump
- Pecten tubercle (Pectineal line of pubis) – oblique ridge on the ramus
The bony pelvis is divided into what 2 regions?
- Greater pelvis (false pelvis, pelvis major)
- Lesser pelvis (true pelvis, pelvis minor)
- separated by an oblique plane that forms the pelvic inlet
Describe the location of the greater pelvis and its contents?
- Superior to pelvic inlet
- Location for abdominal viscera
e. g. ileum and sigmoid colon
What are the boundaries of the greater pelvis?
- Anteriorly – abdominal wall
- Posterior laterally – iliac fossa
- Posteriorly – L5 and S1 vert.
- Inferior – pelvic inlet
Describe the location of the lesser pelvis and its contents?
- Between pelvic inlet and outlet
- Forms the pelvic canal (birth canal)
- Location of pelvic viscera e.g. urinary bladder + reproductive organs
- Major obstetrical and gynecological significance
Describe the boundaries of the lesser pelvis?
- Bounded by pelvic surfaces of hip bones and sacrum + coccyx
- Limited inferiorly by musculofascial pelvic diaphragm
Note: this is true pelvic cavity - abdominopelvic cavity
Describe the pelvic inlet (oblique plane)?
- passes from the sacral promontory to terminal lines (lineae terminales)
- Its edges (or rim) forms the pelvic brim
- Oblique plane forms an angle of 55 degrees to the horizontal
What are the boundaries to the pelvic inlet?
- Anterior - superior margin of pubic symphysis
- Posterior - sacral promontory + sacral ala
- Lateral - Arcuate line of ilium + pectineal line on superior pubic ramus
- Inferior- pelvic diaghram
What are the boundaries of the pelvic outlet?
- Anterior – inferior margin of the pubic symphysis (pubic arch)
- Anterolateral – inferior rami of pubis and ischial tuberosities
- Posterolateral– sacrotuberous ligament
- Posterior – tip of coccyx
Describe the pelvis orientation in anatomical position?
Anterior superior iliac spines and anterior aspect of pubic symphysis lie in the same vertical plane
Note: Pelvic canal curves obliquely posteriorly
What is the pubic arch?
formed by the conjoint rami of pubis and ischium of the two sides
What is the subpubic angle?
The rami meet at pubic symphysis to form the Subpubic angle
Compare the general structure of the bony pelvis of a male and female?
male - thick and heavy
female - thin and light
Compare the greater pelvis of a male and female?
male - deep
female - shallow
Compare the lesser pelvis of a male and female?
male - narrow and deep
female - wide and shallow
Compare the shape of the pelvic inlet of a male and female?
male - heart shaped
female - oval and rounded
Compare the pelvic outlet of a male and female?
male - comparatively small
female - comparatively large
