The mechanism of pelvic support in women: Deductions from a study of the comparative anatomy and physiology of the structures involved

The pelvic outlet in quadrupeds is directed backward and the viscera are thus constantly supported by the ventral half of the bony ring itself. Rotation of the pelvis in man has changed its axis so that the outlet points downward and back. In this case the contents come to lie over the orifice and their weight must be supported by the structures which bridge the gap. If one accepts the idea that the stresses of respiration, evacuation, and reproduction are similar for all vertebrates, one may assume that evolutionary changes in the pelvis of man are for the purpose of counteracting the stress of gravity now acting on its contents through the unprotected outlet. This essay will present the evolutionary facts of the case as they appear from the descriptions of a number of anatomists and clinicians who have studied the female pelvis in man and other mammals. The conclusions of these scientists about the contribution of various elements in the supporting mechanism will be reviewed. Finally, the physiology of the adult tissues derived from mesoderm will be examined with special reference to their capacity for the job of support which is under discussion.