Reproductive Systems—purpose is to pro-
duce gametes (egg and sperm), to ensure
fertilization, and in women to provide a site
for the embryo-fetus
Meiosis—the cell division process that pro-
duces gametes
- One cell with the diploid number of chromosomes
(46) divides twice to form four cells, each with the
haploid number of chromosomes (23). - Spermatogenesis takes place in the testes; a contin-
uous process from puberty throughout life; each
primary spermatocyte produces four functional
sperm (see Fig. 20–1). FSH and testosterone are
directly necessary (see Table 20–1). - Oogenesis takes place in the ovaries; the process
is cyclical (every 28 days) from puberty until
menopause; each primary oocyte produces one
functional ovum and three non-functional polar
bodies (see Fig. 20–2). FSH, LH, and estrogen are
necessary (see Table 20–3).
Male Reproductive System—consists of the
testes and the ducts and glands that con-
tribute to the formation of semen (see Fig.
20–3)
- Testes (paired)—located in the scrotum between
the upper thighs; temperature in the scrotum is
96 F to permit production of viable sperm. Sperm
are produced in seminiferous tubules (see Fig. 20–4
and Table 20–1). A sperm cell consists of the head,
which contains 23 chromosomes; the middle
piece, which contains mitochondria; the flagellum
for motility; and the acrosome on the tip of the
head to digest the membrane of the egg cell (see
Fig. 20–1). - Epididymis (paired)—a long coiled tube on the
posterior surface of each testis (see Fig. 20–4).
Sperm complete their maturation here. - Ductus deferens (paired)—extends from the epi-
didymis into the abdominal cavity through the
inguinal canal, over and down behind the urinary
bladder to join the ejaculatory duct (see Fig. 20–3).
Smooth muscle in the wall contracts in waves of
peristalsis.
4. Ejaculatory ducts (paired)—receive sperm from
the ductus deferens and the secretions from the
seminal vesicles (see Fig. 20–3); empty into the ure-
thra.
5. Seminal vesicles (paired)—posterior to urinary
bladder; duct of each opens into ejaculatory duct
(see Fig. 20–3). Secretion contains fructose to
nourish sperm and is alkaline to enhance sperm
motility.
6. Prostate gland (single)—below the urinary bladder,
encloses the first inch of the urethra (see Fig.
20–3); secretion is alkaline to maintain sperm
motility; smooth muscle contributes to the force
required for ejaculation.
7. Bulbourethral glands (paired)—below the prostate
gland; empty into the urethra (see Fig. 20–3);
secretion is alkaline to line the urethra prior to
ejaculation.
8. Urethra (single)—within the penis; carries semen
to exterior (see Fig. 20–3). The penis contains
three masses of erectile tissue that have blood
sinuses. Sexual stimulation and parasympathetic
impulses cause dilation of the penile arteries and an
erection. Ejaculation of semen involves peristalsis
of all male ducts and contraction of the prostate
gland and pelvic floor.
9. Semen—composed of sperm and the secretions
of the seminal vesicles, prostate gland, and bul-
bourethral glands. The alkaline pH (7.4) neutral-
izes the acidic pH of the female vagina.
Female Reproductive System—consists of the
ovaries, fallopian tubes, uterus, vagina, and
external genitals- Ovaries (paired)—located on either side of the
uterus (see Fig. 20–6). Egg cells are produced in
ovarian follicles; each ovum contains 23 chromo-
somes. Ovulation of a graafian follicle is stimulated
by LH (see Table 20–3). - Fallopian tubes (paired)—each extends from an
ovary to the uterus (see Fig. 20–6); fimbriae sweep
the ovum into the tube; ciliated epithelial tissue and
peristalsis of smooth muscle propel the ovum
toward the uterus; fertilization usually takes place
in the fallopian tube.
The Reproductive Systems 471STUDY OUTLINE