Pelvis - Anatomy & Physiology

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Pelvic Girdle

• 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 Joints and Ligaments

• 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 sheet