Next we’ll take a further look at the bones of the pelvis. For a start, we need to understand something about the word “pelvis”. The pelvis is commonly used as the short name for two different things: the bony pelvis, and the pelvic cavity.
This is the bony pelvis, consisting of the sacrum, and the two hip bones. This is the pelvic cavity: it’s the deep and narrow space that’s enclosed by the sacrum, the lower parts of the hip bones, and by ligaments and muscles that we’ll see in the next section. The pelvic cavity is continuous with the abdominal cavity here, at the pelvic brim, which we’ll return to in a minute.
To understand the abdomen, we need to understand the upper and anterior parts of the bony pelvis. We took a good look at the sacrum in the first section of this tape. The only parts of it that we’ll mention here are the most anterior part, the promontory, and this broad part, the ala or wing of the sacrum
Now we need to take a look at some important features of the hip bone. The hip bone is also known as the innominate bone. It develops by the fusion of three originally separate bones, the massive ischium below and behind, the more lightly constructed pubis below and in front, and the broad ilium above. We’ll look at the ilium first
The thick lower part of the ilium is the body. The broad expanse of bone that fans out above the body is the ala, or wing of the ilium. The concavity on the inner surface of the ala is known as the iliac fossa. This roughened area, the auricular surface, articulates with the sacrum, forming the sacro-iliac joint
The broad, roughened edge of the ala ...