Male urethra
1, bladder; 2, prostate; 3, colliculus; 4, orifice of the sinus pocularis; 5, orifices of the prostatic ducts; 6, orifices of Cowper’s glands; 7, corpus cavernosum urethræ; 8, corpora cavernosa penis; 9, præputium; 10, glans; 11, fossa navicularis.
Urethra.—The urethra is divided into three parts, the prostatic, the membranous and the cavernous parts. The prostatic part is the widest portion of the entire urethra. It is surrounded by an unstriped muscular layer and the muscles of the prostate. The membranous part is the narrowest, shortest, and most thin-walled portion of the three parts of the urethra. It is entirely surrounded by the muscular fibres of the diaphragma urogenitale, which takes here a circulatory course. It is in this way situated on the border-line of the abdominal cavity and the exterior, within the abdominal wall. The cavernous portion of the urethra is surrounded by the corpus cavernosum urethrae. This portion shows two dilatations, one in the bulbous part, just anterior to the termination of the membranous part, where the ducts of the two Cowper’s glands open; the other dilatation is near the end, behind the meatus, forming the so-called fossa navicularis. The meatus itself is the narrowest part of the entire urethra. Numerous mucous crypts, the glands of Littré and certain lacunae, the largest among them near the fossa, open into the lumen of this part of the urethra. The entire urethra is lined with a cylindrical epithelium, except at the fossa navicularis. The latter is covered by a layer of pavement epithelia. The length of the urethra is about 18 centimeters. In the usual state the urethra possesses only a virtual lumen, i. e., the walls touch each other.
CUT IX.
Schema of sagittal cut through penis. After Testus.
1, bladder; 2, vas deferens; 3, colliculus; 4, prostate; 5, urethra; 6, bulbus urethræ; 7, symphysis.
Prostate.—The prostate is a gland, chestnut-like in shape. Its greatest diameter is in average about 4 centimeters. The diameter from the base to the apex is about 3 centimeters. The thickness of the prostate is about 2 centimeters, and its weight is about 18 grammes. The upper broad margin, the basis, is adjacent to the bladder, the lower, narrower end, or the apex, rests on the diaphragma urogenitale. It thus lies completely within the abdominal cavity. The anterior surface is connected with the lower end of the symphysis pubis by the ligamenta puboprostatica, the posterior surface is connected with the rectum by loose connective tissue. The prostate is lobulated and generally divided into three lobes, a median and two lateral lobes. The prostate embraces the neck of the bladder and the first portion of the urethra.
The structure of the prostate is a framework of muscular fibres, in which are embedded numerous racemous glands. The latter collect and open into the prostatic ducts. The main substance of the prostate is glandular. The mucous lining of the prostate, which forms at the same time the mucous membrane of the prostatic urethra, shows upon the posterior wall a linear elevation of the mucous membrane which covers a fold of erectile tissue, the so-called colliculus seminalis.
CUT X.
