*Ribs,
sternum,
infrasternal angle and costal margin: The abdomen extends as far superiorly as the seventh costal cartilage. Therefore, ribs 7-12 and the inferior portion of the sternum are important bony landmarks and serve to protect some of the abdominal viscera. The structures that mark the inferior border of the rib cage, the infrasternal angle and costal margin, overlie parts of the liver, stomach, and transverse colon.
*Iliac crests, anterior superior iliac spines, and posterior superior iliac spines: These structures mark points in the inferior portion of the abdomen. The most superior portion of the iliac crest lies at the L4 level. A plane between the two crests separates the RL, U, and LL regions from the RI, H, and LI regions (see above).
*Pubic crests and pubic tubercle: These structures mark the most inferior portion of the abdomen and the entry into the pelvic region. They are especially important when considering the structures of the inguinal ligament.
*Sacrum and sacral promontory: The sacrum, along with the two os coxae, make up the skeletal "pelvis". It is comprised of five fused vertebrae, though occasionally the fusion is incomplete. The sacral promontory is an anterior projection at the superior end of the sacrum. (Latin, coxa = hip, os sacrum = holy bone).
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