Info

Figure 18-3 Anatomy of erection.

the membranous portion, and the cavernous (anterior) portion. The short posterior portion passes through the prostate gland. The common ejaculatory duct and several prostatic ducts enter at the distal end of this portion. The external urethral sphincter surrounds the membranous urethra, and on either side lie Cowper's bulbourethral glands. The anterior urethra is the longest portion and passes through the corpus spongiosum. The ducts of Cowper's glands enter the anterior urethra near its proximal end.

The scrotum is the pouch containing the testes; it is suspended externally from the perineum. The scrotum is divided into halves by the intrascrotal septum, one testis lying on each side. The wall of the scrotum contains involuntary smooth muscle and voluntary striated muscle. A major role of the scrotum is temperature regulation of the testes. The testes are maintained about 2° C lower than the temperature of the peritoneal cavity, a condition necessary for spermatogenesis. The size of the scrotum is variable according to the individual and his response to ambient temperature. During exposure to cold temperatures, the scrotum is contracted and very rugate. In a warm environment, the scrotum becomes pendulous and smoother.

The testes, or testicles, are ovoid, smooth, and approximately 1.5 to 2 inches (3.5 to 5 cm) in length. The left testicle commonly lies lower than the right. The testes are covered with a tough fibrous coat called the tunica albuginea testis. Each testicle has a long axis directed slightly anteriorly and upward and contains long, microscopic, convoluted seminiferous tubules that produce sperm. The tubules end in the epididymis, which is comma-shaped and located on the posterior border of the testis. It consists of a head that is swollen and overhangs the upper pole of the testicle. The inferior portion, or tail, of the epididymis continues into the vas deferens. The testicular artery enters the testicle in its posterior mid-portion. The veins draining the testicle form a dense network called the pampiniform plexus, which drains into the testicular vein. The right testicular vein drains directly into the inferior vena cava, whereas the left drains into the left renal vein. The lymphatic drainage of the testes is to the preaortic and precaval nodes, not to the inguinal nodes. This is important to recognize because the testes are embryologically intra-abdominal organs, and neoplasms and inflammations of the testis produce adenopathy of these nodal chains. In general, inguinal adenopathy is rare.

The relationship of the testicle and epididymis is illustrated in Figure 18-4.

The vas deferens is a cordlike structure, easily felt in the scrotum. The vas deferens, testicular arteries, and veins form the spermatic cord, which enters the inguinal canal. The vas deferens passes through the internal ring and, after a convoluted course, reaches the fundus of the bladder. It passes between the rectum and the bladder and approaches the vas deferens

Pampiniform plexus

Vas deferens-fk

Vas deferens-fk

Epididymis

Testicle

Ejaculatory duct i

Epididymis

Testicle

Figure 18-4 Anatomy of the testicle and epididymis.

Vas deferens Epididymis r,

Testicle

Seminal vesicle Prostate gland Cowper's gland

Ejaculatory duct i

Seminal vesicle Prostate gland Cowper's gland

Urethra

Figure 18-5 Sources and direction of seminal fluid flow.

Urethra

Figure 18-5 Sources and direction of seminal fluid flow.

of the opposite side near the seminal vesicles. Near the base of the prostate, the vas deferens joins with the duct of the corresponding seminal vesicle to form the ejaculatory duct, which passes through the prostate gland to enter the posterior urethra.

The prostate gland is about the size of two almonds, or approximately 1.5 inches (3.5 cm) long by 1.2 inches (3 cm) wide. Traversing the gland in the midline is the posterior urethra. On either side is an ejaculatory duct. The prostate is commonly divided into five lobes. The posterior lobe is clinically important because prostate carcinoma frequently affects this lobe. In the presence of cancer, the midline groove between the two lateral lobes may be obliterated. The middle and lateral lobes are above the ejaculatory ducts and are typically involved in benign hypertrophy. The anterior lobe is of little clinical importance.

The sources and direction of seminal fluid flow in the male genitalia are illustrated in Figure 18-5.

The descent of the testes is important to review at this time. In the normal full-term male newborn, both testes are in the scrotum at birth. The testes descend to this position just before birth. About the 12th week of gestation, the gubernaculum develops in the inguinal fold and grows through the body wall to an area that will ultimately lie in the scrotum. This tract marks the location of the future inguinal canal. A dimple called the processus vaginalis forms in the peritoneum and follows the course of the gubernaculum. By the 7th month of gestation, the processus vaginalis has reached the aponeurosis of the external oblique muscle. Each testis then begins its descent from the abdominal cavity through the internal ring to lie in the abdominal wall. During the 8th month, the testes descend along the inguinal canal;at birth, they are in the scrotum. At birth, the gubernaculum is barely distinguishable, and the processus vaginalis becomes obliterated within the spermatic cord. In about 5% of male infants, there is imperfect descent of the testis (cryptorchidism). The descent of the testes is illustrated in Figure 18-6.

The genital development stages for boys are illustrated in Figure 24-44 (and discussed in Chapter 24, The Pediatric Patient).

Processus vaginalis

12 WEEK OLD FETUS

5 Secrets to Lasting Longer In The Bedroom

5 Secrets to Lasting Longer In The Bedroom

How to increase your staying power to extend your pleasure-and hers. There are many techniques, exercises and even devices, aids, and drugs to help you last longer in the bedroom. However, in most cases, the main reason most guys don't last long is due to what's going on in their minds, not their bodies.

Get My Free Ebook


Post a comment