a. Male. In the male, the actual reproductive cells are the spermatozoa (sperm).
The spermatozoa are produced in the seminiferous tubules of the testes. In the testes,
germinal cells produce spermatozoa by a process called spermatogenesis. Once
formed, the spermatozoa travel into another portion of the testes called the epididymis.
The spermatozoa are stored in the epididymis until they mature. From the epididymis,
the spermatozoa travel in two ducts called the vas deferens. The vas deferens unite
with the urethra. In the vas deferens, the spermatozoa are joined by a fluid produced by
the seminal vesicle. This fluid, together with the secretions of the prostate gland and
the bulbo-urethral gland which flow into the urethra, compose the semen that nourishes
the spermatozoa and provides the electrolytes and proper pH In the proper
concentration range. The vas deferens is separated from the urethra by the ejaculatory
duct (a muscular sphincter). During the process of ejaculation, the sphincter relaxes
and the spermatozoa are propelled by powerful peristaltic waves. At the onset of
puberty in the male, the pituitary gland produces follicle-stimulating hormones (FSH)
which stimulate the seminiferous tubules to undergo spermatogenesis and produce
spermatozoa. At the same time, the pituitary gland releases interstitial cell-stimulating
hormones (ISCH or LH), that stimulate the interstitial cells in the testes to produce
androgens. Androgens are masculinizing hormones. The principal androgen is
testosterone. Testosterone, in turn, stimulates the secondary sexual characteristics of
the male. These androgens are produced throughout the male's life.
b. Female. In the female reproductive system, the ovaries produce the egg cell
or ovum. The ovum then passes the short distance between the ovary and the fallopian
tube (in the abdominal cavity) and enters the fallopian tube (oviduct). The ovum then
travels down the oviduct by peristalsis and ciliary movement of the cells lining the
oviduct. The fallopian tubes connect the ovaries with the uterus. The uterus is a pear-
shaped organ in the center of the female reproductive system. It is lined with a tissue
called the endometrium. The base of the uterus is a diaphragm-like structure called the
cervix. Below the cervix is a muscular tube called the vagina.
(1) Hormone production. The production of hormones in the female is
considerably more complex than in the male. The hormones of the female reproductive
system do not remain at a constant level, as in the male, but are in a cyclic balance.
Each cycle takes, on the average, 28 days. To understand this cycle properly, one
should first consider the production of the ovum in more detail. The ovaries are
composed of several hundred thousand ova. These are surrounded by granulosa cells.
This combination is called a primary follicle. Under the influence of hormones, the
follicle enlarges and begins to secrete a fluid that fills the cavity inside the follicle,
creating an antrum (cavity) in the follicle. Numerous follicles enlarge at the same time
until one follicle ruptures. The remaining follicles then return to their normal state. The
ova, which is released then migrates through the abdominal cavity until it reaches the
fallopian tube. The ovum then takes from three to seven days to reach the uterus.
However, the ova must be fertilized within 24 hours after it is released. Thus, the ova
must be fertilized while it is in the oviduct. Occasionally, more than one follicle ruptures
at the same time and more than one ova are released. This is the chief cause of
multiple births. Pituitary gonadotropins function in the process of releasing ova.