Histologic Anatomy of the Anterior Vagina and Urethra

Vaginal and urethral histology is important to understanding the pathophysiology of the pelvic floor.

En bloc removal of 4 female cadaveric pelvises was performed, with 18 to 25 serial sections obtained from each. The vaginal and urethral lengths were divided into distal and proximal sections; urethra was divided into anterior and posterior segments as well. Innervation and vasculature were qualified as small and large and quantified per high-power field.

The mean vaginal length was 7.45 cm, and the mean urethral length was 3.38 cm. A distinct vaginal fibromuscular layer was noted, without evidence of a dense sheet of continuous collagen. An epithelial, lamina propria, and muscular layer surrounded the urethral lumen. Adipose and loose fibroconnective tissue separated the urethra from the anterior vagina in 41% of slides. Nerves and vasculature were concentrated in the lamina propria. More small nerves and vessels were grossly seen compared with larger counterparts in both the vagina and urethra. No significant differences in layer thickness, innervation, or vasculature were observed along the vaginal length. The posterior urethra had greater innervation than did the anterior (P = 0.012). The distal posterior urethra had more large vessels than did the proximal posterior urethra (P = 0.03). No other differences were noted in urethral sections.

A vaginal fibromuscular layer was confirmed, refuting a true fascia. Innervation and vasculature were quantitatively the same along the anterior vagina. However, the posterior urethra had greater innervation than did anterior and is most innervated proximally. Nerve and vascular histology may relate to pelvic floor disorder etiology.