Penis and Prepuce

The penis is the male organ of copulation and is composed of erectile tissue that encases the extrapelvic portion of the urethra (Fig. 66-1). The penis of the horse is musculocavernous and can be divided into three parts: the root, the body or shaft, and the glans penis. The penis originates caudally at the root, which is fixed to the lateral aspects of the ischial arch by two crura (leg-like parts) that converge to form the shaft of the penis. The shaft constitutes the major portion of the penis and begins at the junction of the crura. It is attached caudally to the symphysis ischii of the pelvis by two short suspensory ligaments that merge with the origin of the gracilis muscles (Fig. 66-2). The glans penis is the conical enlargement that caps the shaft. The urethra passes over the ischial arch between the crura and curves cranioventrally to become incorporated within erectile tissue of the penis. The mobile shaft and glans penis extend cranioventrally to the umbilical region of the abdominal wall. The body is cylindrical but compressed laterally. When quiescent, the penis is soft, compressible, and about 50 cm long. Fifteen to 20 cm lie free in the prepuce. When maximally erect, the penis is up to three times longer than when it is in a quiescent state. Erectile Bodies