Pelvis - Anatomy & Physiology

Pelvic Girdle

Pelvis - Wikimedia Commons 2008

Two symmetrical halves: hip bones (ossa cosarum) meet at pelvic symphysis ventrally and articulate with sacrum dorsally
Hip Bones:
- Three bones develop from separate ossifications within a single cartilage plate
- Ilium: craniodorsal, extends obliquely forward from hip to articulate with sacrum
  - Cranial wing varies between species
  - Dorsally, forms sacral tuber more prominent in large animals than dogs and cats
  - Ventrally, forms tuber coxae, or the point of the hip
  - Margin of the wing is known as the iliac crest
  - Body is deeply excavated for attachment of the gluteus medius
  - Greater Sciatic Notch on dorsal border of the wing is cut away at its junction with the shaft to allow the sciatic nerve passage en route to the hind limb
- Pubis : extends medially from the joint to form cranial pelvic floor
  - L-shaped to give two branches: cranial (acetabular) and caudal (symphysial)
- Ischium: caudal, forms most of pelvic floor
  - Ischial tuberosity is formed by the caudolateral corner of the horizontal plate of the ischium
- The Pelvic Symphysis comprises both pubis and ischium
- The Acetabulum provides the socket to the joint of the hip, and is comprised of all three bones of the pelvis
Species differences:
- Larger species have a more vertical ilium, bringing the sacroiliac joint (and with it the weight of the trunk) closer to the hip
- Smaller species have an oblique ilium

Pelvic Symphysis, Gray's Anatomy - Wikimedia Commons 2008

Pelvic Symphysis: secondary cartilaginous joint that ossifies with age and may expand in parturition
Sacroiliac joints: synovial joints combined with fibrous joints
- Transmits the weight of the trunk to the hindlimbs
Sacrotuberous ligament varies tremendously between species, caudal edge is palpable
- Dog: stout cord extending between the sacrum and lateral ischial tuberosity
- Cat: not present
- Ungulates: Sacrosciatic ligament expands to a broad sheep