High-Yield Points:
• Caudal limit of abdomen = pelvic inlet (sacral promontory dorsally + ilium laterally + cranial border of pubis ventrally).
• Floor of abdominal cavity = abdominal wall muscles (no bone).
• Tuber coxae (hook bone) + tuber ischiadicum (pin bone) form palpable bony landmarks of the abdominal-pelvic boundary.
• Important for pelvimetry (heifer breeding fitness).

BONY BOUNDARIES — A SUMMARY

The abdomen is the largest body cavity, but it is not entirely bony — only the dorsal and cranio-lateral walls are skeletal. The floor and lateral walls are muscular (the abdominal wall). The cavity is bounded:
• Cranially — by the diaphragm (attaches to the costal arch and the sublumbar regions).
• Dorsally (Roof) — by lumbar vertebrae and their psoas musculature.
• Laterally cranially — by the last 3-4 ribs and costal arch.
• Laterally caudally and ventrally — by abdominal wall muscles.
• Caudally — by the pelvic inlet (entrance to the pelvic cavity).

Pelvic inlet:
• Dorsal limit: sacral promontory (cranial border of S1).
• Lateral limits: shafts of the ilium (terminal line / iliopectineal line).
• Ventral limit: pectineal eminence and cranial border of pubis.
The dimensions of the pelvic inlet (conjugate diameter, transverse diameter) are measured by pelvimeter in heifers before first breeding to predict dystocia.

Tuber coxae (hook bone) and tuber ischiadicum (pin bone) are the two prominent palpable angles of the bony pelvis used for body condition scoring, conformation evaluation, and reference points in nerve blocks (paravertebral block uses tuber coxae line for landmarks).