ilium

The broad, flaring portion of the hip bone, distinct at birth but later becoming fused with the ischium and pubis; it consists of a body, which joins the pubis and ischium to form the acetabulum and a broad thin portion, called the ala or wing, bordered superiorly by a thicker crest. The body transmits the weight of the trunk to the femur, while the ala and crest provide for muscle attachment and protect abdominopelvic viscera. SYN: os i. [TA], flank bone, iliac bone, os iliacum. [L. groin, flank]

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il·i·um 'il-ē-əm n, pl il·ia -ē-ə the dorsal, upper, and largest one of the three bones composing either lateral half of the pelvis that in humans is broad and expanded above and narrower below where it joins with the ischium and pubis to form part of the acetabulum

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n.

the haunch bone: a wide bone forming the upper part of each side of the hip bone (see also pelvis). There is a concave depression (iliac fossa) on the inside of the pelvis; the right iliac fossa provides space for the vermiform appendix.

• iliac adj.

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il·i·um (ilґe-əm) pl. ilґia [L.] TA alternative for os ilium.