Section I. THE FEMALE
1-3. INTERNAL FEMALE
The internal organs of the female consists of the uterus,
vagina, fallopian tubes, and the ovaries (see figures 1-1 and 1-2).
a. Uterus. The uterus is a
hollow organ about the size and shape of a pear. It serves two important
functions: it is the organ of menstruation and during pregnancy it receives the
fertilized ovum, retains and nourishes it until it expels the fetus during
(1) Location. The uterus is located between the urinary
bladder and the rectum. It is suspended in the pelvis by broad ligaments.
(2) Divisions of the uterus. The uterus consists of the body
or corpus, fundus, cervix, and the isthmus. The major portion of the uterus is
called the body or corpus. The fundus is the superior, rounded region above
the entrance of the fallopian tubes. The cervix is the narrow, inferior outlet
that protrudes into the vagina. The isthmus is the slightly constricted
portion that joins the corpus to the cervix.
(3) Walls of the uterus (see figure 1-3). The walls are thick
and are composed of three layers: the endometrium, the myometrium, and the
perimetrium. The endometrium is the inner layer or mucosa. A fertilized egg
burrows into the endometrium (implantation) and resides there for the rest of
its development. When the female is not pregnant, the endometrial lining
sloughs off about every 28 days in response to changes in levels of hormones
in the blood. This process is called menses. The myometrium is the smooth
muscle component of the wall. These smooth muscle fibers are arranged. In
longitudinal, circular, and spiral patterns, and are interlaced with
connective tissues. During the monthly female cycles and during pregnancy,
these layers undergo extensive changes. The perimetrium is a strong, serous
membrane that coats the entire uterine corpus except the lower one fourth and
anterior surface where the bladder is attached.
(1) Location. The vagina is the thin in walled muscular tube
about 6 inches long leading from the uterus to the external genitalia. It is
located between the bladder and the rectum.
(2) Function. The vagina provides the passageway for
childbirth and menstrual flow; it receives the penis and semen during sexual
c. Fallopian Tubes (Two).
(1) Location. Each tube is about 4 inches long and extends
medially from each ovary to empty into the superior region of the uterus.
(2) Function. The fallopian tubes transport ovum from the
ovaries to the uterus. There is no contact of fallopian tubes with the
(3) Description. The distal end of each fallopian tube is
expanded and has finger-like projections called fimbriae, which partially
surround each ovary. When an oocyte is expelled from the ovary, fimbriae
create fluid currents that act to carry the oocyte into the fallopian tube.
Oocyte is carried toward the uterus by combination of tube peristalsis and
cilia, which propel the oocyte forward. The most desirable place for
fertilization is the fallopian tube.
d. Ovaries (2) (see figure
(1) Functions. The ovaries are for oogenesis-the production of
eggs (female sex cells) and for hormone production (estrogen and
(2) Location and gross anatomy. The ovaries are about the size
and shape of almonds. They lie against the lateral walls of the pelvis, one on
each side. They are enclosed and held in place by the broad ligament. There
are compact like tissues on the ovaries, which are called ovarian follicles.
The follicles are tiny sac-like structures that consist of an immature egg
surrounded by one or more layers of follicle cells. As the developing egg
begins to ripen or mature, follicle enlarges and develops a fluid filled
central region. When the egg is matured, it is called a graafian follicle, and
is ready to be ejected from the ovary.
(3) Process of egg production--oogenesis (see figure 1-5).
(a) The total supply of eggs that a female can release has
been determined by the time she is born. The eggs are referred to as "oogonia"
in the developing fetus. At the time the female is born, oogonia have
divided into primary oocytes, which contain 46 chromosomes and are
surrounded by a layer of follicle cells.
(b) Primary oocytes remain in the state of suspended
animation through childhood until the female reaches puberty (ages 10 to 14
years). At puberty, the anterior pituitary gland secretes
follicle-stimulating hormone (FSH), which stimulates a small number of
primary follicles to mature each month.
Figure 1-4. Human ovary.
(c) As a primary oocyte begins dividing, two different
cells are produced, each containing 23 unpaired chromosomes. One of the
cells is called a secondary oocyte and the other is called the first
polar body. The secondary oocyte is the larger cell and is capable of
being fertilized. The first polar body is very small, is nonfunctional,
and incapable of being fertilized.
(d) By the time follicles have matured to the graafian
follicle stage, they contain secondary oocytes and can be seen bulging
from the surface of the ovary. Follicle development to this stage takes
about 14 days. Ovulation (ejection of the mature egg from the ovary)
occurs at this 14-day point in response to the luteinizing hormone (LH),
which is released by the anterior pituitary gland.
(e) The follicle at the proper stage of maturity when
the LH is secreted will rupture and release its oocyte into the
peritoneal cavity. The motion of the fimbriae draws the oocyte into the
fallopian tube. The luteinizing hormone also causes the ruptured
follicle to change into a granular structure called corpus luteum, which
secretes estrogen and progesterone.
(f) If the secondary oocyte is penetrated by a sperm, a
secondary division occurs that produces another polar body and an ovum,
which combines its 23 chromosomes with those of the sperm to form the
fertilized egg, which contains 46 chromosomes.
(4) Process of hormone production by the ovaries.
(a) Estrogen is produced by the follicle cells, which are
responsible secondary sex characteristics and for the maintenance of these
traits. These secondary sex characteristics include the enlargement of
fallopian tubes, uterus, vagina, and external genitals; breast development;
increased deposits of fat in hips and breasts; widening of the pelvis; and
onset of menses or menstrual cycle.
(b) Progesterone is produced by the corpus luteum in
presence of in the blood. It works with estrogen to produce a normal
menstrual cycle. Progesterone is important during pregnancy and in preparing
the breasts for milk production.
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