(1) Testes. The testes are the primary organs of reproduction in the male.
The male testes correspond to the female ovaries. Located in the scrotum, the testes
are oval structures enclosed in a fibrous capsule. A dense layer of white fibrous tissue
called the tunica albuginea covers the testes. This tissue layer extends inward and
divides each testis into a series of internal compartments called lobules. Each of the
200 to 300 lobules contains one to three tightly coiled tubules called the seminiferous
tubules. These tubules produce sperm by a process called spermatogenesis.
Interstitial cells within the testes produce testosterone, the hormone that is essential for
the development of the male secondary sex characteristics. Growth of hair on the face
and body, deepening of the voice, and an increase in skeletal muscle mass do not
occur in a male whose body does not produce testosterone.
(2) Epididymis. At the upper and posterior part of each testes is located an
epididymis, an elongated triangular tube which is 16 to 20 feet in length. Each of these
two tubes is tightly coiled. Sperm mature in the epididymis tubes. These tubes link the
testes proper with the ductus deferens. Sperm are stored in the epididymis tubes until
they are ejaculated and enter the ductus (vas) deferens.
(3) Ductus (vas) deferens. At the tail of the epididymis, the epididymis
becomes less coiled, its diameter increases, and the tube becomes known as the
ductus (vas) deferens. Vas deferens are muscular tubes about 48 centimeters (18
inches) long. Two vas deferens, one from each epididymis tube, lead up through the
inguinal canal into the pelvic cavity, cross to the inferior surface of the urinary bladder,
and unite with the ducts of the seminal vesicles to form the ejaculatory ducts.
(4) Seminal vesicles. The seminal vesicles are two glandular pouches
located behind and below the urinary bladder. These tubular structures secrete a
substance that activates the spermatozoa in the semen. The secretions contain
fructose and prostaglandins. Fructose energizes the sperm, and prostaglandins assists
ejaculation and stimulates uterine contractions. Thus, both fructose and prostaglandins
help sperm move to the uterine tubes where fertilization occurs. Additionally, seminal
fluid is slightly alkaline and the seminal vesicles' secretions help protect sperm against
the acid secretion of the vagina. Secretion of the seminal vesicles makes up 60 percent
of the ejaculate. See figure 1-9.
(5) Ejaculatory duct. Each ductus deferens and its corresponding seminal
vesicle coverage to form a short tube called the ejaculatory duct. The ejaculatory duct
opens into the urethra within the prostate gland. The ejaculatory duct carries both
sperm and seminal vesicle fluid.