The penis is composed mainly of the two corpora cavernosa and the single corpus spongiosum, which contains the urethra (Fig. 5.71B.) As in the clitoris, it has an attached part (root) and a free part (body):
The root of the penis consists of the two crura, which are proximal parts of the corpora cavernosa attached to the pubic arch, and the bulb of the penis, which is the proximal part of the corpus spongiosum anchored to the perineal membrane.
The body of the penis, which is covered entirely by skin, is formed by the tethering of the two proximal free parts of the corpora cavernosa and the related free part of the corpus spongiosum.
The base of the body of the penis is supported by two ligaments: the suspensory ligament of the penis (attached superiorly to the pubic symphysis), and the more superficially positioned fundiform ligament of the penis (attached above to the linea alba of the anterior abdominal wall and split below into two bands that pass on each side of the penis and unite inferiorly).
Because the anatomical position of the penis is erect, the paired corpora are defined as dorsal in the body of the penis and the single corpus spongiosum as ventral, even though the positions are reversed in the nonerect (flaccid) penis.
The corpus spongiosum expands to form the head of the penis (glans penis) over the distal ends of the corpora cavernosa (Fig. 5.71B).
Erection of the penis and clitoris is a vascular event generated by parasympathetic fibers carried in pelvic splanchnic nerves from the anterior rami of S2 to S4, which enter the inferior hypogastric part of the prevertebral plexus and ultimately pass through the deep perineal pouch and perineal membrane to innervate the erectile tissues. Stimulation of these nerves causes specific arteries in the erectile tissues to relax. This allows blood to fill the tissues, causing the penis and clitoris to become erect.
Arteries supplying the penis and clitoris are branches of the internal pudendal artery; branches of the pudendal nerve (S2 to S4) carry general sensory nerves from the penis and clitoris.
The greater vestibular glands (Bartholin’s glands) are seen in women. They are small, pea-shaped mucous glands that lie posterior to the bulbs of the vestibule on each side of the vaginal opening and are the female homologues of the bulbo-urethral glands in men (Fig. 5.71). However, the bulbo-urethral glands are located within the deep perineal pouch, whereas the greater vestibular glands are in the superficial perineal pouch.
The duct of each greater vestibular gland opens into the vestibule of the perineum along the posterolateral margin of the vaginal opening.
Like the bulbo-urethral glands in men, the greater vestibular glands produce secretion during sexual arousal.
The superficial perineal pouch contains three pairs of muscles: the ischiocavernosus, bulbospongiosus, and superficial transverse perineal muscles (Fig. 5.72 and
Table 5.6). Two of these three pairs of muscles are associated with the roots of the penis and clitoris; the other pair is associated with the perineal body.
The two ischiocavernosus muscles cover the crura of the penis and clitoris (Fig. 5.72). Each muscle is anchored to the medial margin of the ischial tuberosity and related ischial ramus and passes forward to attach to the sides and inferior surface of the related crus, and forces blood from the crus into the body of the erect penis and clitoris.
The two bulbospongiosus muscles are associated mainly with the bulbs of the vestibule in women and with the attached part of the corpus spongiosum in men (Fig. 5.72).