Supplementary Material for: Comparative Anatomy of the Ovine and Female Pelvis

Background: Pelvic organ prolapse affects half of
vaginally parous women. Several animal models are used to study its
pathophysiology and treatment. Sheep are interesting because they
develop spontaneously prolapse with similar risk factors as women and
can be used for vaginal surgery. This study describes ovine pelvis
anatomy and compares it to women's pelvis to provide anatomical tools
for translational researchers. Methods: MRI, pelvic
dissections, and histology were used for detailed macro- and microscopic
analysis of relevant anatomical structures in 6 nulliparous ewes. Results:
Although sheep are quadrupeds, the gross and microscopic anatomies are
similar to the female pelvis. Principal differences are the shape and
its orientation, the absence of the sacrospinous ligament and the
internal obturator. The levator ani (except for the puborectalis) and
the coccygeus muscle are present, yet the latter is more developed -
coinciding with the tail. The dimensions and morphology of the ovine
vagina is comparable. The retropubic and the rectovaginal space are
accessible transvaginally. There is a wide expression of estrogen
receptors with low or absent immunoreactivity in the urethral
epithelium, bladder, anus and internal anal sphincter. Conclusion: The ovine pelvic floor has many anatomical and ultrastructural similarities to the female pelvic floor.