Essay 5

Do not memorise these answers! These are guidelines. Be creative, devise your own expression and organisation! You can elaborate on the points in your own language.
Remember that there is no 'perfect' answer - a little shortfall in content is easily compensated by presentation.
You should aim at writing an essay in this examination in approximately 20 minutes.

Functions of the bony pelvis.

Developmentally the bony pelvis is the girdle of the lower limb. Anatomically however, it also serves as the wall of the extension of the abdominal cavity and the birth canal in the female.

As the pelvic girdle, the pelvis is formed by the two hip bones and the sacrum which is a part of the vertebral column. The hip bone has ventral (pubis and ischium) and a dorsal element (ilium). Broadly speaking ventral and dorsal muscles of the thigh region are attached to these parts, though the vertebral column also gives attachment to the psoas major and the sacrum to the piriformis muscle.

As a container of the organs, the bony pelvis has significant gaps which are bridged by muscles and ligaments. Thus, the sacrospinous and sacrotuberous ligaments 'convert' the sciatic notches into foramina. The greater sciatic foramen is closed largely by the piriformis muscle. The obturator muscles close the foramen of the same name. These muscles also provide compressible soft tissue cushions for the pelvic walls. Higher up, the large iliacus muscle covers the inner surface of the ilium.

The lower opening of the pelvic wall is closed by a relatively thin but strong sheet of muscle, the pelvic diaphragm. Integrity of the diaphragm is a very important factor in retaining pelvic viscera in place.

In the female the pelvis serves as the birth canal. Under the influence of hormones the connective tissue become somewhat lax and the pelvis can be 'stretched' , even though slightly. Anatomically, the dimensions of the female pelvis are designed to suit this process - a more circular inlet, deeper anteroposterior dimension and ischial tuberosities that are farther apart contribute to these adaptations.