Chapter 34: Male genitalia
The male genital organs comprise the testes and epididymides, ductus deferentes, seminal vesicles and ejaculatory ducts, prostate, bulbo-urethral glands, and penis (fig. 34-1). Spermatozoa, formed in the testes and stored in the epididymides, are contained in the semen, which is secreted by the testes and epididymides, seminal vesicles, prostate, and bulbo-urethral glands. The spermatozoa, on leaving the epididymides, pass through the ductus deferentes and ejaculatory ducts to reach the urethra. The complete pathway is as follows (figs. 34-1 and 34-2): (1) convoluted seminiferous tubules, (2) straight seminiferous tubules, (3) rete testis, (4) efferent ductules of testis, (5) lobules (or cones) of epididymis, (6) duct of epididymis, (7) ductus deferens, (8) ejaculatory duct, (9) prostatic urethra, (10) membranous urethra, and (11) spongy urethra.
The testis is an ovoid gland that produces spermatozoa and secretes steroid hormones. In late fetal life, the testes descend from the posterior abdomen through the inguinal canal and so reach the scrotum. The left testis is usually lower than the right. Failure of descent of a testis is termed cryptorchidism (cryptorchism) (Gk, "hidden testis"). A testis may descend to an anomalous site, e.g., the perineum (ectopia testis). The testis has superior and inferior poles, medial and lateral surfaces, and anterior and posterior margins.
The testis is covered by the tunica vaginalis, which is an embryologic derivitive of peritoneum. Beneath the visceral layer, a connective tissue coat, the tunica albuginea, sends fibrous septa into the interior, and these converge posteriorly to form the mediastinum testis. Efferent ductules connect the testis with the head of the epididymis.
The epididymis (fig. 34-2) is applied to the posterior margin of the testis and comprises a head, body, and tail. A recess of the tunica vaginalis, termed the sinus of the epididymis, extends between the body of the epididymis and the lateral surface of the testis (fig. 34-2A and C).
The efferent ductules of the testis form lobules (or cones) in the head of the epididymis, and these drain into the duct of the epididymis, which descends through the body and tail of the organ and becomes the ductus deferens. Small embryonic remnants may be found: the appendix testis at the superior end and the appendix of the epididymis on the head of that organ.
The testis and epididymis are supplied by the testicular artery (fig. 34-2C), and their veins drain into the pampiniform plexus, which forms the bulk of the spermatic cord. The veins of the pampiniform plexus often become varicose, a condition termed varicocele. Lymphatics accompany the testicular vessels and drain into the lumbar (aortic) nodes.
A ductus (formerly called vas, hence vasectomy) deferens (fig. 34-2) is continuous from the epididymis to the ejaculatory duct. The ductus deferens extends from the tail along the medial side of the epididymis and becomes surrounded by the pampiniform plexus of veins as it becomes incorporated into the spermatic cord, where it can be felt as a firm cord. After its passage through the inguinal canal, it leaves the spermatic cord and hooks posterior to the inferior epigastric artery. It then enters the pelvis, crosses anterior to the ureter, runs along the opsteior aspect of the bladder, and becomes expanded as the ampulla. Finally, it joins the duct of the seminal vesicle to form the ejaculatory duct. Embryonic remnants include superior and inferior aberrant ductules and the paradidymis (fig. 34-2B).
The seminal vesicles (fig. 34-3) are two saccular pouches on the posterioinferior aspect of the bladder (see fig. 33-2). They produce much of the semen. They are immediateley anterior to the rectum, and their superiormost parts are covered by peritoneum. Each vesicle consists of a coiled tube that ends as a duct and joins the ductus deferens to form the ejaculatory duct. The two ejaculatory ducts penetrate the prostate and open on the colliculus seminalis into the prostatic urethra.
The spermatic cord extends from the deep inguinal ring, where the ductus deferens begins to acquire its coverings, to the posterior border of the testis. It consists of the ductus deferens and associated arteries (including the testicular artery), nerves, and lymphatics; the pampiniform plexus of veins; and remnants of the processus vaginalis of the periotoneum. The three coverings derived from the fasciae associated with the external and internal oblique muscles of the abdomen and the transversalis fascia (see fig. 25-7) are the external spermatic, cremasteric, and internal spermatic fasciae, respectively. The cremasteric fascia contains bundles of skeletal-type muscle known collectively as the cremaster and supplied by the genital branch of the genitofemoral nerve. Contraction results in elevation of the testis and can often be produced by gently stroking the skin of the medial side of the thigh (cremasteric reflex).
Deep to these layers, the testis and epididymis are covered by a double serous layer, the tunica vaginalis testis, derived embryologically from the processus vaginalis of the peritoneum (see fig. 25-11). The potential cavity between the parietal and visceral layers of some part of the processus vaginalis (usually the tunica) may become distended with fluid, a condition termed hydrocele. Although the commonest type of hydrocele is in the tunica around the testis, a remnant of the processus may form an encysted hydrocele of the spermatic cord.
Prostate (fig. 34-3)
The prostate is a fibromuscular, pelvic organ surrounding the male urethra and containing glands that contribute to the semen. It is situated posteior to the pubic symphysis and anterior to the rectum, through which it can be palpated. The prostate presents a base, an apex, and anterior, posterior, and two inferolateral surfaces. The base is continuous with the bladder, although it is separated by a slight groove. The apex is the most inferior part. The anterior surface is narrow, and the inferolateral surfaces are related to the superior fascia of the pelvic diaphragm. The posterior surface is triangular and presents a median groove (see figs. 33-2A. and 34-3B). The normal prostate can be palpated per rectum as an elastic swelling with a median groove ending above in a notch. The superior part of the posterior surface is covered by the seminal vesicles and the ampullae of the ductus deferentes.
The prostatic glands within the organ open chiefly by ductules into the prostatic sinuses of the urethra. The main glands, situated laterally and posteriorly, are those involved in carcinoma.
The prostate increases rapidly in size at puberty. During the fifth decade, it either begins to atrophy or undergoes benign hypertrophy.
Access to the prostate may be gained by one of the following routes: transvesical, retropubic, perineal, or urethral (see fig. 34-1).
Although the fetal prostate consists of several lobes, these are not distinguishable in the adult. In a study by J. E. McNeal (J. Urol., 107: 1008-1016, 1972) it was emphasized that (1) the prostatic lobes of the fetus do not persist in the adult; (2) the urethral glands, which form a central zone, are not really a part of the prostate; (3) the prostatic urethra comprises a superior portion distinguished by the urethral glands and a "preprostatic sphincter;" (4) "benign prostatic hypertrophy" is really benign peri-urethral hyperplasia, being confined to the central zone and superior portion of the prostatic urethra; (5) the preprostatic sphincter is important in maintaining continence; and (6) the peripheral zone is the site of carcinoma. Nevertheless, right and left
lobes, united in front by a muscular isthmus, are often postulated. The portion of the prostate that extends anteriorward from the superior part of the posterior surface and lies between the ejaculatory ducts and the urethra is commonly known as the middle (or median) lobe. Enlargement of the so-called middle lobe may accentuate the uvula of the bladder, which then acts as a valve over the internal urethral orifice, thereby blocking the passage of urine.
The superior fascia of the pelvic diaphragm forms the sheath or fascia of the prostate and is continued over the bladder (see fig. 38-2). The sheath, which is attached to the pubis by ligamentous and smooth muscle fibers, is separated from the capsule of the prostate anteriorly and laterally by the prostatic venous plexus. Beneath the capsule, the compressed outer zone of an enlarged prostate may form a "false capsule."
The prostate is supplied mainly by the inferior vesical artery of the internal iliac artery. The prostatic venous plexus drains into the internal iliac veins and communicates with the vertebral plexus, thereby allowing neoplastic spread to the vertebrae. The lymphatics end mostly in the internal iliac nodes, although some end in the external iliac nodes.
34-1 What is meant by descent of the testis?
34-2 What is the tunica vaginalis testis?
34-3 List some embryonic remnants related to the testis, epididymis, and ductus deferens.
34-4 What is a varicocele?
34-5 What is the spermatic cord?
34-6 What is the key feature of the normal prostate as palpated per rectum?
34-7 What are the surgical approaches to the prostate?
34-8 Where is the middle (or median) lobe of the prostate?
34-9 Where is the uvula of the bladder?
34-10 What are the coverings of the prostate?
Figure 34-1 Male reproductive system. The approaches to the prostate are (1) transvesical, (2) retropubic, (3) perineal, and (4) urethral. M, middle lobe of the prostate (which may produce a uvulvil); L, median groove between the lateral lobes of the prostate.
Figure 34-2 The testis and epididymis. A, Right testis, lateral aspect. B, Ductal system. (See text.) C, Horizontal section, showing the tunica vaginalis. The numbers 1 to 7 refer to the parts listed in the text.
Figure 34-3 The prostate. A, Coronal scheme, showing the seminal vesicles and colliculus seminalis. Cf. fig. 33-2C. The depression on each side of the urethral crest is termed the prostatic sinus. B, Horizontal section.