Anatomical and physiological characteristics of pelvic muscles in the female rabbit (Oryctolagus cuniculus)

Abstract

In mammals, the pelvic striated muscles have been linked to the regulation of urinary functions and little is known about the involvement of this muscle in reproductive functions. The objective of this study was to use surgical and electrophysiological techniques to determine the anatomical features and innervation of iliococcygeus and pubococcygeus muscles in adult female rabbits and characterize the reflex electromyographic (EMG) activity in response to genital stimulation. Results show that the iliococcygeus and pubococcygeus are long bilateral muscles with fibers attached to the ilium bone. The muscle fibers are not attached to the pelvic viscera but they run adjacent to the vagina and rectum to be inserted into the sacral vertebrae. The iliococcygeus and pubococcygeus muscles are innervated by branches arising from S3 and S4. The reflex EMG activity was obtained during stimulation of the vaginal orifice skin and the perineal and pelvic vagina. Abdominal vaginal stimulation did not cause an EMG response. Cervical stimulation produced a temporary inhibition in the activity of the iliococcygeus and pubococcygeus. These findings extend the poor descriptions of innervation and anatomy of the striated pelvic musculature shown in the textbooks and atlas of rabbits. They also suggest that the iliococcygeus and pubococcygeous muscles can be activated by reflex action during reproductive processes such as mating and parturition.