THE PENIS 





to the base of the prostate. The posterior surface rests upon the rectum, from which 

 it is separated by the rectovesical fascia. The upper extremities of the two vesicles 

 diverge from each other, and are in relation with the ductus deferentes and the 

 terminations of the ureters, and are partly covered by peritoneum. The lower 

 extremities are pointed, and converge toward the base of the prostate, where each 

 joins with the corresponding ductus deferens to form the ejaculatory duct. Along 

 the medial margin of each vesicle runs the ampulla of the ductus deferens. 



Each vesicle consists of a single tube, coiled upon itself, and giving off several 

 irregular cecal diverticula ; the separate coils, as well as the diverticula, are connected 

 together by fibrous tissue. When uncoiled, the tube is about the diameter of a 

 quill, and varies in length from 10 to 15 cm.; it ends posteriorly in a cul-de-sac; 

 its anterior extremity becomes constricted into a narrow straight duct, which 

 joins with the corresponding ductus deferens to form the ejaculatory duct. 



Structure. The vesiculse seminales are composed of three coats: an external or areolar coat; 

 a middle -or muscular coat thinner than in the ductus deferens and arranged in two layers, an 

 outer longitudinal and inner circular; an internal or mucous coat, which is pale, of a whitish 

 brown color, and presents a delicate reticular structure. The epithelium is columnar, and in 

 the diverticula goblet cells are present, the secretion of which increases the bulk of the seminal 

 fluid. 



Vessels and Nerves. The arteries supplying the vesicula? seminales are derived from the 

 middle and inferior vesical and middle hemorrhoidal. The veins and lymphatics accompany 

 the arteries. The nerves are derived from the pelvic plexuses. 



The Ejaculatory Ducts (Ductus Ejaculatorii) (Fig. 1153). 



The ejaculatory ducts are two in number, one on either side of the middle line. 

 Each is formed by the union of the duct from the vesicula seminalis with the ductus 

 deferens, and is about 2 cm. long. 

 They commence at the base of 

 the prostate, and run forward 

 and downward between its mid- 

 dle and lateral lobes, and along 

 the sides of the prostatic utricle, 

 to end by separate slit-like ori- 

 fices close to or just within the 

 margins of the utricle. The ducts 

 diminish in size, and also converge, 

 toward their terminations. 



Structure. The coats of the ejacula- 

 tory ducts are extremely thin. They 

 are: an outer fibrous layer, which is 

 almost entirely lost after the entrance 

 of the ducts into the prostate; a layer 

 of muscular fibers consisting of a thin 

 outer circular, and an inner longitu- 

 dinal, layer; and mucous membrane. 



Ejaculatory duct 





Prostatic utricle 

 Urethral crest 

 Prostatic urethra 



FIG. 1153. Vesiculse seminales and ampullse of ductus defer- 

 entes, seen from the front. The anterior walls of the left ampulla, 

 left seminal vesicle, and prostatic urethra have been cut away. 



The Penis. 



The penis is a pendulous organ suspended from the front and sides of the pubic 

 arch and containing the greater part of the urethra. In the flaccid condition it is 

 cylindrical in shape, but when erect assumes the form of a triangular prism with 

 rounded angles, one side of the prism forming the dorsum. It is composed of 

 three cylindrical masses of cavernous tissue bound together by fibrous tissue and 

 covered with skin. Two of the masses are lateral, and are known as the corpora 

 cavernosa penis; the third is median, and is termed the corpus cavernosum urethras 

 (Figs. 1154, 1155). 



