The Prepuce

The prepuce (Præputium), popularly called the “sheath,” is a double invagination of the skin which contains and covers the free or prescrotal portion of the penis when not erect. It consists of two parts, external and internal. The external part or sheath extends from the scrotum forward close to the umbilicus, where the external layer is reflected ventrally and laterally, forming the thick margin of the preputial orifice (Ostium præputiale); dorsally it is directly continuous with the integument of the abdominal wall. It is marked by a median raphé præputii, a continuation of the scrotal raphé. At the lower margin of the preputial orifice there are often in the stallion two papillæ, which are rudimentary teats or nipples. The internal layer passes backward from the preputial orifice a distance of about six to eight inches (ca. 15 to 20 cm.), lining the cavity of the external prepuce, and is then reflected forward until it approaches the orifice, where it is again reflected backward. It thus forms within the cavity of the sheath a secondary tubular invagination, the prepuce proper, in which the anterior part of the penis lies. This tubular cavity is closed behind by the reflection of the internal layer on to the penis to form the penile layer of the prepuce. Its orifice is surrounded by a thick margin, the preputial ring (Annulus præputialis), which is connected ventrally with the outer part of the sheath by the preputial frenum (Frenulum præputii).

The arrangement differs from that found in man in the fact that the inner part of the prepuce as described above is equivalent to the entire human prepuce. This part, the prepuce proper, is well seen on sagittal sections, and can be demonstrated by pulling the penis, inclosed in this prepuce, out of the cavity of the sheath; the arrangement of the free part of the penis and prepuce is then like that in man. (In paraphimosis the penis is strangulated by the preputial ring.)

Structure.—The external skin of the prepuce resembles that of the scrotum. The inner layers of skin are hairless, variable in color, and often irregularly pigmented; they form irregular folds, and are supplied with numerous large sebaceous glands and coil glands, which reach their greatest size at the preputial ring. Beyond this the glands are absent, and the skin resembles a non-glandular mucous membrane. The secretion of the preputial glands (Glandulæ præputiales), together with desquamated epithelial cells, forms the fatty smegma præputii, which has a strong unpleasant odor, and often accumulates in considerable amount. Beneath the skin is a large amount of loose connective tissue, except over the glans penis, where the skin is closely attached to the tunic of the corpus spongiosum. The external part of the prepuce is strengthened by a layer of elastic tissue, derived from the abdominal tunic, and termed the suspensory ligament.

Vessels and Nerves.—The arteries are branches of the external pudic artery, and the veins go chiefly to the external pudic vein. The lymphatics go to the superficial inguinal and lumbar lymph glands. The nerves are derived from the pudic, ilio-hypogastric, and ilio-inguinal nerves.