(1) During the first eight weeks, the developing organism is known as an
embryo. During this time, the major systems and parts of the body develop.
(2) During the remainder of the pregnancy, the developing organism is
known as the fetus. During this time, growth and refinement of the body parts occur.
(3) Parturition is the actual delivery of the fetus into a free- living state. The
delivery of the fetus is followed by a second delivery-- that of the placenta and fetal
f. Menstruation and Menopause. About two weeks after an ovum is released,
if it is not fertilized, menstruation occurs. Menstruation involves the loss of all but the
basal layer of the endometrium. This process includes bleeding. It first occurs at
puberty and lasts until menopause (45 to 55 years of age). After menopause, pregnan-
cy is no longer possible.
8-12. 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.
8-13. MAMMARY GLANDS
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 promi-
Section IV. THE HUMAN MALE GENITAL (REPRODUCTIVE) SYSTEM
8-14. PRIMARY SEX ORGANS (TESTES)
The primary sex organ of the human male is the testis. See figure 8-5 for an
illustration of the male genital system. The testes are egg-shaped.