Penis

The penis is composed of the two corpora cavernosa attached posteriorly to the rami of the ischia and pubes and terminating in blunt ends anteriorly, and the corpus spongiosum, commencing at the bulb, at the central point of the perineum posteriorly, and ending in the glans anteriorly. The glans is the extended corpus spongiosum and covers the ends of the corpora cavernosa. Its extended rim is called the corona glandis and the groove immediately behind, the neck, or col-lum glandis. In the centre of each corporus cavernosum runs an artery (Fig. 469). The skin is thin, loose, free from hair except at the root, and has beneath it some fibres of the dartos. It projects over the glans, forming the prepuce and is attached at the neck or collum glandis and underneath as far forward as the urethra, forming the fraenum. The connective tissue beneath the skin is loose and free from fat. A fibrous sheath (Buck's fascia) surrounds the corpora cavernosa and corpus spongiosum and binds the three together. It is continuous posteriorly with the suspensory ligament and the deep layer of the superficial fascia (Colles's fascia).

Fig. 469.   Structure of the penis.

Fig. 469. - Structure of the penis.

Anteriorly it ends at the collum glandis. The corpora cavernosa and corpus spongiosum have each a separate fibrous sheath which separates the two corpora cavernosa forming the septum pectiniforme: it is incomplete anteriorly, allowing the blood of the two corpora cavernosa to mingle. The separate sheath of the corpus spongiosum is not as marked as those of the corpora cavernosa. The single dorsal vein of the penis runs in the median line with an artery to each side and the dorsal nerves still farther out. They all lie between the fascial covering of the corpora cavernosa beneath and the fibrous sheath above.

The lymphatics of the prepuce and skin drain into the inguinal nodes, those of the glans empty into the nodes in and just above (inside the abdomen) the crural canal; one radicle enters through the inguinal canal running posterior to the cord. As the lymphatic radicles anastomose at the root of the penis a lesion on one side of the organ may involve the lymphatic nodes in the opposite inguinal region.

Practical Considerations

The opening of the prepuce is often constricted, so that the glans cannot be uncovered. This condition is called phimosis. A certain amount is normal in young children. At times the prepuce becomes adherent to the glans but it can usually be separated by a blunt instrument without cutting. When the sulcus is reached an accumulation of smegma is seen. This is produced by the subaceous glands of the corona and collum glandis and under surface of the prepuce. In performing circtimcision the prepuce should not be drawn too far forward or too much of the skin and not enough of the mucous surface will be removed; a common mistake. It is sufficient to remove the skin and mucous membrane two-thirds of the way back to the sulcus and then bring the ends of the incision gradually down and forward to meet at the lower angle of the meatus (Fig. 470). By doing this the fraenum is not cut and troublesome bleeding from the little artery it contains is avoided. The laxity of the skin, especially of the prepuce, favors rapid swelling. When a contracted prepuce is forcibly drawn behind the glans it constricts the veins and the part beyond the constriction swells rapidly. This is called paraphimosis. To relieve it an incision is made through the skin directly across the constricting band and the prepuce can then be pulled forward over the glans.

Extravasation of urine may invade the penis beneath the fibrous sheath but does not invade the glans because the sheath stops at the collum glandis.

Fracture or rupture of the corpora cavernosa may occur from violence. The extrav-asated blood is absorbed and the laceration heals with a scar. In erection this part does not expand, hence deformity and distortion with interference of function may result. Chordee. - When the urethra is inflamed the exudate may involve the corpus spongiosum surrounding it and prevent it from expanding. In erection the organ assumes a downward curve, a condition designated as chordee. It disappears with the subsidence of the inflammation.