Between the perineal membrane and the membranous layer of superficial fascia is the superficial perineal pouch. The principal structures in this pouch are the erectile tissues of the penis and clitoris and associated skeletal muscles.
Structures in the superficial perineal pouch
The superficial perineal pouch contains: erectile structures that join together to form the penis in men and the clitoris in women, and skeletal muscles that are associated mainly with parts of the erectile structures attached to the perineal membrane and adjacent bone.
Each erectile structure consists of a central core of expandable vascular tissue and its surrounding connective tissue capsule.
Two sets of erectile structures join to form the penis and the clitoris.
A pair of cylindrically shaped corpora cavernosa, one on each side of the urogenital triangle, are anchored by their proximal ends to the pubic arch. These attached parts are often termed the crura (from the Latin for “legs”) of the clitoris or the penis. The distal ends of the corpora, which are not attached to bone, form the body of the clitoris in women and the dorsal parts of the body of the penis in men.
The second set of erectile tissues surrounds the openings of the urogenital system.
In women, a pair of erectile structures, termed the bulbs of the vestibule, are situated, one on each side, at the vaginal opening and are firmly anchored to the perineal membrane (Fig. 5.71A). Small bands of erectile tissues connect the anterior ends of these bulbs to a single, small, pea-shaped erectile mass, the glans clitoris, which is positioned in the midline at the end of the body of the clitoris and anterior to the opening of the urethra.
In men, a single large erectile mass, the corpus spongiosum, is the structural equivalent to the bulbs of the vestibule, the glans clitoris, and the interconnecting bands of erectile tissues in women (Fig. 5.71B). The corpus spongiosum is anchored at its base to the perineal membrane. Its proximal end, which is not attached, forms the ventral part of the body of the penis and expands over the end of the body of the penis to form the glans penis. This pattern in men results from the absence of a vaginal opening and from the fusion of structures across the midline during embryological development. As the originally paired erectile structures fuse, they enclose the urethral opening and form an additional channel that ultimately becomes most of the penile part of the urethra. As a consequence of this fusion and growth in men, the urethra is enclosed by the corpus spongiosum and opens at the end of the penis. This is unlike the situation in women, where the urethra is not enclosed by erectile tissue of the clitoris and opens directly into the vestibule of the perineum.
The clitoris is composed of two corpora cavernosa and the glans clitoris (Fig. 5.71A). As in the penis, it has an attached part (root) and a free part (body).
Unlike the root of the penis, the root of the clitoris technically consists only of the two crura. (Although the bulbs of the vestibule are attached to the glans clitoris by thin bands of erectile tissue, they are not included in the attached part of the clitoris.)
The body of the clitoris, which is formed only by the unattached parts of the two corpora cavernosa, angles posteriorly and is embedded in the connective tissues of the perineum.
The body of the clitoris is supported by a suspensory ligament that attaches superiorly to the pubic symphysis. The glans clitoris is attached to the distal end of the body and is connected to the bulbs of the vestibule by small bands of erectile tissue. The glans clitoris is exposed in the perineum and the body of the clitoris can be palpated through skin.