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I. Orientation of Pelvis 

II. Osteology 

III. Joints 

IV. Ligaments 

V. Pelvic Musculature 

VI. Perineum

[WebLecture Slide 09 320x240 pixels]
[QT movie]

WebLecture Slide 09

The ilium forms the upper portion of the acetabulum, and is composed primarily of the ala (wing) which has a posterior or gluteal surface and an anterior surface called the iliac fossa.  This large surface is used as a major site of muscle attachment on both the anterior and posterior surfaces. The gluteal surface is marked by lines that are the sites of attachment of the large, gluteal muscles. The iliac fossa provides attachment for the iliacus muscles. The gluteal surface and the iliac fossa are joined along the superior border at the iliac crest which is the site of attachment of many muscles.  Bony landmarks at the anterior extreme of the iliac crest include the anterior superior iliac spine and the anterior inferior iliac spine.  At the posterior border of the crest are the  posterior superior iliac spine and the posterior inferior iliac spine. The inferior border of the ilium, inferior to the inferior posterior iliac spine, makes up a large portion of the greater sciatic notch, the remainer of which is formed by the ischium.  The ischial spine denotes the inferolateral extension of the greater sciatic notch and separates it from the lesser sciatic notch.  

The ischium forms the inferoposterior part of the acetabulum and consists of a body and a ramus. The ramus ascends anteromedially to join the descending ramus of the pubis where it is referred to as the ischiopubic ramus. The ischial tuberosity makes up most of the posterior surface of the ischium, is the site of attachment of many hip muscles and is the structure of primary support during sitting. The ischial spine is located just superior to the ischial tuberosity, faces posteromedially, and denotes the superior border of the lesser sciatic notch.  

The pubis has two rami: a superior ramus which passes from the midline laterally towards the acetabulum and an inferior ramus that passes inferolaterally to join the ischium. The left and right pubic bones join at the midline and form the cartilaginous pubic symphysis. Fusion of the ischium and pubis at the acetabulum and the junction of these two bones along the ischiopubic ramus form a large foramen, the obturator foramen which faces anterolaterally.  

The sacrum and coccyx are series of single vertebrae that fuse to form bony elements. The sacrum and coccyx fuse to one another after age 40. The sacrum is formed from five independent sacral vertebrae. The superior surface of the first sacral vertebrae is called the promontory and articulates with the fifth lumbar vertebrae. The fifth sacral vertebrae artculates with the first coccygeal vertebrae, of which there are three to five. 
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Quicktime Movie 09  
Standard pelvic posture. 

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