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PinkMonkey Online Study Guide-Biology

(C) Pelvic Girdle or Hip Bone (Figure 20.18). (1) The hip bone is a large irregular bone expanded both above and below but constricted in the middle. Each hip bone consists of three fused bones- (a) Ilium (b) Pubis and (c) Ischium. (2) The ilium is expanded and projects upwards, having an iliac crest at the upper border. The lower border is smaller and forms part of the articular surface of the acetabulum. (Gluteal muscles are attached to external side). On the inner side of ilium is the iliac fossa and iliac tuberosity. (3) The pubis forms an anterior part of the hip bone and articulates with the opposite bone forming cartilaginous-joint called the ’pubic symphysis’. The rami of the pubis and ischium form the greater part of the obturator foramen, through which passes the obturator nerve, artery and vein downwards from the pelvis to the thigh. (4) The ischium is a large, expanded bone on the postero-inferior part of the hip bone. It bears a large ischial tuberosity, which supports the body weight in sitting posture. (5) The acetabular cavity is cup-shaped and faces laterally, downwards and forwards. It articulates with the head of the femur. The ilium, ischium and pubis contribute to its formation. (6) Obturator foramen is a large opening between the pubis and ischium below and the acetabulum in front. It is large and oval in males, small and triangular in females. (7) In females the pelvis is more circular, thinner, lighter with less prominent muscular impressions and having all diameters comparatively large.

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Table of Contents

20.0 - Introduction
20.1 - Axial Skeleton
20.2 - Appendicular Skeleton

Chapter 21


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