ABSTRACT
The pelvic floor musculature is essential to the maintenance of the plane of the pelvic floor and to the normal anatomical relationships of the anorectum, vagina, and uterus, and bladder and urethra. The latter reach the levator ani and puborectalis muscles via their visceral surfaces. Histological studies of the three major muscles of the pelvic floor, i.e., the external anal sphincter, the puborectalis, and the levator ani, revealed changes consistent with denervation and reinnervation. Denervation of the pelvic floor muscles has been associated with straining at stool and with constipation. The functional disturbance is often initiated by difficult childbirth, and has been shown to be related to stretch-induced injury to the pelvic floor innervation, especially of the pudendal nerves. These concepts form the basis of the neurogenic theory of stress incontinence, a disorder that is usually associated with weakness of the pelvic floor.
