the end of the menstrual cycle, the endometrium breaks down. (This produces a "flow"
of blood and cellular elements (menses) in a process known as menstruation.)
(2) Amniotic sac and placenta. When the embryo passes into the uterine
cavity from the uterine tube, it "burrows" into the endometrium. Later, a fluid-filled sac
(the amniotic sac) surrounds the embryo. The embryo floats free, surrounded by
amniotic fluid. The embryo has an umbilical cord that originates in the center of its
anterior abdomen. The umbilical cord is attached to the wall of the uterus by a special
structure known as the placenta.
(3) Cervix. The cervix, the inferior end of the uterus, is inserted into the top
of the vagina. Through the center of the cervix is the cervical canal. Its wall consists
primarily of circular muscle tissue, which holds the opening closed until time for
parturition (giving birth). During the initial stage of parturition, the cervical musculature
dilates (stretches) to form an opening for the passage of the newborn (to be).
c. Vagina. The vagina is a tubular structure that extends from the cervix of the
uterus to the exterior of the perineum. After the vagina receives the male penis, the
semen is discharged into the upper recess opposite the opening of the cervix. At
parturition, the vagina forms the birth canal through which the newborn passes to the
d. External Genitalia. The opening of the vagina and of the urethra are
covered by the external genitalia. Included among the external genitalia are two pairs of
folds--the major and minor labia. Also included is the clitoris, a small structure
comparable to the male penis but without the urethra.
9-16. SECONDARY SEXUAL CHARACTERISTICS
The secondary sexual characteristics of the female are those features designed
to make a female attractive to the male. These features include a higher-pitched voice,
hair distribution, and body softness and shape.
9-17. THE FEMALE BONY PELVIS
The female bony pelvis is an important consideration in childbirth.
a. Several studies have been concerned with the spatial relationships of the
female bony pelvis. One of the most extensive is the Caldwell-Moloy Classification of
Female Pelvis. This study categorizes female pelvis by shape. It illustrates those types
that are better and those that are less well suited for childbirth.
b. Just before childbirth, the phenomenon of "relaxation" occurs. In this
phenomenon, the ligaments of the bony pelvis and perineum become quite stretchable.
This increases the diameters of the birth canal.