Membranous part. The membranous part of the urethra is narrow and passes through the deep perineal pouch (Fig. 5.45B). During its transit through this pouch, the urethra, in both men and women, is surrounded by skeletal muscle of the external urethral sphincter.
Spongy urethra. The spongy urethra is surrounded by erectile tissue (the corpus spongiosum) of the penis.