Male Genital Organs

A. Testis

Develops retroperitoneally and descends into the scrotum retroperitoneally.
Is covered by the tunica albuginea , which lies beneath the visceral layer of the tunica vaginalis.
Produces spermatozoa and secretes sex hormones.
Is supplied by the testicular artery from the abdominal aorta and is drained by veins of the pampiniform plexus.
Has lymph vessels that ascend with the testicular vessels and drain into the lumbar (aortic) nodes; lymphatic vessels in the scrotum drain into the superficial inguinal nodes.

B. Epididymis

Consists of a head, body, and tail, and contains a convoluted duct about 6 m (20 feet) long.
Functions in the maturation and storage of spermatozoa in the head and body and propulsion of the spermatozoa into the ductus deferens.

C. Ductus deferens

Is a thick-walled tube that enters the pelvis at the deep inguinal ring at the lateral side of the inferior epigastric artery.
Crosses the medial side of the umbilical artery and obturator nerve and vessels, passes superior to the ureter near the wall of the bladder, and is dilated to become the ampulla at its terminal part.
Contains fructose, which is nutritive to spermatozoa, and receives innervation primarily from sympathetic nerves of the hypogastric plexus and parasympathetic nerves of the pelvic plexus.

D. Ejaculatory ducts

Are formed by the union of the ductus deferens with the ducts of the seminal vesicles.
Peristaltic contractions of the muscular layer of the ductus deferens and the ejaculatory ducts propel spermatozoa with seminal fluid into the urethra.
Open into the prostatic urethra on the seminal colliculus just lateral to the blind prostatic utricle (see the section on urethral crest).

E. Seminal vesicles

Are enclosed by dense endopelvic fascia and are lobulated glandular structures that are diverticula of the ductus deferens.
Lie inferior and lateral to the ampullae of the ductus deferens against the fundus (base) of the bladder.
Produce the alkaline constituent of the seminal fluid , which contains fructose and choline.
Have lower ends that become narrow and form ducts, which join the ampullae of the ductus deferens to form the ejaculatory ducts.
Do not store spermatozoa, as was once thought; this is done by the epididymis, the ductus deferens, and its ampulla.

F. Prostate gland

Is located at the base of the urinary bladder and consists chiefly of glandular tissue mixed with smooth muscle and fibrous tissue.
Has five lobes: the anterior lobe (or isthmus), which lies in front of the urethra and is devoid of glandular substance; the middle (median) lobe , which lies between the urethra and the ejaculatory ducts and is prone to benign hypertrophy obstructing the internal urethral orifice; the posterior lobe , which lies behind the urethra and below the ejaculatory ducts, contains glandular tissue, and is prone to carcinomatous transformation; and the right and left lateral lobes , which are situated on either side of the urethra and form the main mass of the gland.
Secretes a fluid that produces the characteristic odor of semen. This fluid, the secretion from the seminal vesicles and the bulbourethral glands, and the spermatozoa constitute the semen or seminal fluid.
Secretes prostate-specific antigen (PSA) , prostaglandins, citric acid and acid phosphatase, and proteolytic enzymes.
Has ducts that open into the prostatic sinus , a groove on either side of the urethral crest.
Receives the ejaculatory duct , which opens into the urethra on the seminal colliculus just lateral to the blind prostatic utricle.

G. Urethral crest

Is located on the posterior wall of the prostatic urethra and has numerous openings for the prostatic ducts on either side.
Has an ovoid-shaped enlargement called the seminal colliculus (verumontanum) , on which the two ejaculatory ducts and the prostatic utricle open. At the summit of the colliculus is the prostatic utricle, which is an invagination (a blind pouch) about 5 mm deep; it is analogous to the uterus and vagina in the female.

H. Prostatic sinus

Is a groove between the urethral crest and the wall of the prostatic urethra and receives the ducts of the prostate gland.

I. Erection

Depends on stimulation of parasympathetics from the pelvic splanchnic nerves, which dilates the arteries supplying the erectile tissue, and thus causes engorgement of the corpora cavernosa and corpus spongiosum, compressing the veins and thus impeding venous return and causing full erection.
Is also maintained by contraction of the bulbospongiosus and ischiocavernosus muscles , which compresses the erectile tissues of the bulb and the crus.
Is often described using a popular mnemonic device: point (erection by parasympathetic) and shoot (ejaculation by sympathetic).

J. Ejaculation

Begins with nervous stimulation. Friction to the glans penis and other sexual stimuli result in excitation of sympathetic fibers , leading to contraction of the smooth muscle of the epididymal ducts, the ductus deferens, the seminal vesicles, and the prostate in turn.
Occurs as a result of contraction of the smooth muscle, thus pushing spermatozoa and the secretions of both the seminal vesicles and prostate into the prostatic urethra, where they join secretions from the bulbourethral and penile urethral glands. All of these secretions are ejected together from the penile urethra because of the rhythmic contractions of the bulbospongiosus, which compresses the urethra.
Involves contraction of the sphincter of the bladder, preventing the entry of urine into the prostatic urethra and the reflux of the semen into the bladder.

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