MALE REPRODUCTIVE ORGANS The testes or testicles are the glands in which the male repro ductive cells are formed. They lie, one on each side, in the scro tum surrounded by the tunica vaginalis (see COELOM AND SEROUS MEMBRANES). Each is oval, about one and a half inches long and has a strong fibrous coat (tunica albuginea), from which septa penetrate into the substance, dividing it into lobules in which the seminiferous tubes are coiled. It is estimated that the total length of these seminiferous tubes in the two glands is little short of a mile. (See fig. I.) Posteriorly, the fibrous sheath is thickened, and contains a plexus of tubules (rete testis) (see fig. I), into which the seminif erous tubes open. In this way the secretion of the gland is car ried to its upper and back part, whence from fifteen to twenty small tubes (vasa eflerentia) pass to the epididymis. Each of these is convoluted before opening (coitus vasculosus).
Microscopically, the seminiferous tubules consist of a base ment membrane surrounding several layers of epithelial cells, some of which are constantly being transformed into spermatozoa or male sexual cells.
The epididymis (see fig. I) is a soft body lying behind the testis; it is enlarged above to form the globus major or head, While below is a lesser swelling, the globus minor or tail. The whole epididymis is made up of a convoluted tube about soft. long. Between the globus major and the testis two small vesicles (hydatids of Morgagni) are often found.
The vas deferens is the continuation of the tube of the epidi dymis and starts at the globus minor; it runs up on the inner (mesial) side of the epididymis to the external abdominal ring. On its way up it is joined by testicular arteries, veins, lymphatics and nerves to form the spermatic cord. After entering the external abdominal ring, these structures pass obliquely through the ab dominal wall, lying in the inguinal canal for an inch and a half, until the internal abdominal ring is reached. Here they separate and the vas passes down the side of the pelvis and turns inward to meet its fellow at the back of the bladder, just above the prostate. The whole length of the vas is 1 2 to i8in. and it is re markable for the thickness of its muscular walls, which gives it the feeling of a piece of whipcord when rolled between the finger and thumb.
A little above the globus major a few scattered tubules are found in children in front of the cord ; these form the rudimentary structure known as the organ of Giraldes or paradidymis.
The vesiculae seminales are muscular sac-like diverticula, one on each side, from the vasa deferentia. They are about sin. long and run outward behind the bladder and parallel to the upper margin of the prostate for some little distance, but usually turn upward near their blind extremity. When unravelled each is about 5in. long, sharply bent upon itself two or three times. Where the vesiculae join the ampullae of the vasa deferentia the ejacu latory ducts are formed; these are narrow and thin-walled, and run, side by side, through the prostate to open into the floor of the prostatic urethra.
The prostate is situated just below the bladder and traversed by the urethra; it is somewhat conical with the base upward in contact with the bladder. Vertically and transversely it measures about an inch and a quarter, antero-posteriorly it is only about three-quarters of an inch, though its size is liable to great varia tion. It is enclosed in a fibrous capsule from which it is separated by the prostatic plexus of veins anteriorly.
Microscopically, it consists of masses of long, slender, slightly branching glands, embedded in unstriped muscle and fibrous tis sue; these glands open by delicate ducts (about twenty in num ber) into the prostatic urethra.
The male urethra begins at the bladder and runs through the prostate and perineum to the penis, which it traverses as far as the tip. It is divided into a prostatic, membranous and spongy part, and is altogether about 8 inches in length. The prostatic urethra is about an inch and a quarter long, and a longitudinal ridge is seen in its posterior wall (verumontanum), on each side of which the numerous ducts of the prostate open. Near the lower part of the verumontanum is a little pouch, the utriculus masculinus, about one-eighth of an inch deep, the opening of which is guarded by a delicate membranous circular fold, the male hymen. Close to the opening of the utriculus the ejaculatory ducts open into the urethra by very small apertures. The part of the urethra above the openings of these ducts really belongs to the urinary system only, though it is convenient to describe it here. After leaving the prostate the urethra runs more f or ward for about three-quarters of an inch, lying between the two layers of the triangular ligament, both of which it pierces. This is known as the membranous urethra, and is very narrow, being gripped by the compressor urethrae muscle.