SECONDARY SEXUAL CHARACTERISTICS
The secondary sexual characteristics of females include growth of pubic hair,
development of mammary glands, development of the pelvic girdle, and deposition of fat
in the mons pubis and labia majora.
Secretion of milk begins after parturition. Stimulation from suckling helps to
maintain the normal rate of milk secretion. At the time of menopause, breast tissue
becomes less prominent.
Section V. THE HUMAN MALE GENITAL (REPRODUCTIVE) SYSTEM
PRIMARY SEX ORGANS (TESTES)
The primary sex organ of the human male is the testis. See Figure 6-5 for an
illustration of the male genital system. The testes are egg-shaped.
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 (see
below). 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 millions continuously produce the spermatozoa. One
such cell may eventually fertilize an ovum of a human female. The testes also produce
male sex hormones, called androgens.
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 1 1/2 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 that
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.