a. Location. The paired testes lie within the scrotum. The scrotum is a sac of
loose skin attached in the pubic area of the lower abdomen. The scrotum provides a
site cooler than body temperature to maintain the viability of the spermatozoa.
However, when the air is too cold, muscles and muscular fibers draw the testes and
scrotum closer to the body to maintain warmth. Otherwise, the scrotum hangs loosely.
The tunica vaginalis is a serous cavity surrounding each testis.
b. Functions. The testis produces the male sex cells called spermatozoa
(spermatozoon, singular). The spermatozoa are continuously produced by the millions.
One such cell may eventually fertilize an ovum of a human female. The testes also
produce male sex hormones called androgens.
8-15. SECONDARY SEX ORGANS
a. Epididymis. The epididymis is a coiled tube whose function is to aid in the
maturation of spermatozoa. Its coiled length is only about one and one-half inches. Its
uncoiled length is about 16 feet. When coiled, it extends downward along the posterior
side of each testis. Its lining secretes a nutritive medium for spermatozoa. It receives
spermatozoa from the testes in an immature state. As the spermatozoa pass through
the nutrient, they mature.
b. Ductus (Vas) Deferens. The ductus deferens is a transporting tube which
carries the mature sperm from the epididymis to the prostate. Each tube enters the
abdomen through the inguinal canal. Each passes over a ureter to reach the back of
the urinary bladder and then down to the prostate gland.
c. Seminal Vesicles. Lying alongside each ductus deferens as it crosses the
back of the bladder is a tubular structure called the seminal vesicle. The seminal
vesicle produces a fluid which becomes part of the ejaculate.
d. Ejaculatory Duct. Each ductus deferens and its corresponding seminal vesicle
converge 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 sperma-
tozoa and seminal vesicle fluid.
e. Prostate Gland. As the urethra leaves the urinary bladder, its first inch is
surrounded by a chestnut-size gland called the prostate gland. The prostate gland
provides an additional fluid to be added to the spermatozoa and seminal vesicle fluid.
f. Penis. As the urethra leaves the abdomen, it passes through the penis, the
male organ of copulation.