lesson 32

The female gonad, one of a pair of reproductive glands in women. The ovaries are located in the pelvis, one on each side of the uterus. Each ovary is about the size and shape of an almond. The ovaries produce eggs (ova) and female hormones.

The cortex is the site of the ovarian follicles, each of which
consists of one developing ovum surrounded by numerous small
follicular cells. The ovary does not have a system of tubules like the
testis; eggs are released one at a time by the bursting of the follicles
(ovulation).

Most primary follicles degenerate with no further development.
In a few, however, the granulosa cells secrete pools of estrogen-rich
follicular fluid. These pools grow and merge until they form a
single fluid-filled cavity, the antrum. The follicle is now called a
secondary (antral) follicle. This is the state of development when
menstruation ends around day 5. (Day 1 of the cycle is regarded as
the first day of menstruation.)

When the oocyte is expelled, the follicle collapses and bleeds
into the antrum. As the clotted blood is slowly absorbed, granulosa
and theca interna cells multiply and fill the antrum, and a dense bed
of blood capillaries grows amid them. The ovulated follicle has now
become a structure called the corpus luteum,35 named for a yellow
lipid that accumulates in the theca interna cells (see fig. 26.12).
These cells are now called lutein cells. The corpus luteum secretes
a large amount of progesterone, which stimulates the uterus to prepare
for possible pregnancy.

A hormone produced in the human placenta that maintains the corpus luteum during pregnancy

An ovulated oocyte is received into the uterine tube, also called the
oviduct or fallopian37 tube (see fig. 26.11). The tube is a ciliated
canal about 10 cm long leading from the ovary to the uterus. At the
distal (ovarian) end, it flares into a trumpet-shaped infundibulum38
with feathery projections called fimbriae39 (FIM-bree-ee); the middle
and longest part of the tube is the ampulla; and the segment near
the uterus is a narrower isthmus. The uterine tube is enclosed in the
mesosalpinx40 (MEZ-oh-SAL-pinks), which is the superior margin
of the broad ligament.

In about 1 out of 300 pregnancies, the blastocyst implants somewhere
other than the uterus, producing an ectopic14 pregnancy. Most cases
begin as tubal pregnancies, implantation in the uterine tube. This usually
occurs because the conceptus encounters an obstruction such as
a constriction resulting from earlier pelvic inflammatory disease, tubal
surgery, previous ectopic pregnancies, or repeated miscarriages. The
uterine tube cannot expand enough to accommodate the growing
conceptus for long; if the situation is not detected and treated early, the
tube usually ruptures within 12 weeks, potentially killing the mother.
Occasionally, a conceptus implants in the abdominopelvic cavity,
producing an abdominal pregnancy. It can grow anywhere it finds an
adequate blood supply—for example, on the outside of the uterus, colon,
or bladder. About 1 pregnancy in 7,000 is abdominal. Abdominal
pregnancy is a serious threat to the mother’s life and usually requires
abortion, but about 9% of abdominal pregnancies end in live birth by
cesarean section.

32% of all cases of infertility are attributed to Fallopian tube blockage. Tubal blockages can prevent the egg and sperm from meeting, thus impairing fertilization, or can prevent the movement of a fertilized egg into the uterus. It is possible to have bilateral or unilateral Fallopian tube blockage, spasms of the tubes, mucus plugs, fluid buildup (hydrosalpinx) or scar tissue in the Fallopian tubes.

bacterial STD affects 3-5 million people per year

Untreated can cause infection to spread to uterine tubes and cause tubal blockages and tubal scarring

Can lead to increased cases of ectopic pregnancy

The uterus41 is a thick muscular chamber that opens into the roof
of the vagina and usually tilts forward over the urinary bladder (see
figs. 26.11 and 26.13). Its function is to harbor the fetus, provide
it with a source of nutrition (the placenta, composed partially of
uterine tissue), and expel the fetus at the end of gestation (pregnancy).
It is somewhat pear-shaped, with a broad superior curvature
called the fundus, a midportion called the body (corpus), and
a narrow inferior end called the cervix. The uterus measures about7 cm from cervix to fundus, 4 cm wide at its broadest point on the
fundus, and 2.5 cm thick, but it is somewhat larger in women who
have been pregnant.

When pregnancy occurs,
the endometrium is the site of attachment of the embryo and forms
the maternal part of the placenta

The uterine wall consists of an external serosa called the perimetrium,
a middle muscular layer called the myometrium, and an inner
mucosa called the endometrium. The perimetrium is composed
of simple squamous epithelium overlying a thin layer of areolar tissue. The myometrium,43 about 1.25 cm thick in the nonpregnant
uterus, constitutes most of the wall. It is composed mainly of
bundles of smooth muscle that sweep downward from the fundus
and spiral around the body of the uterus. The myometrium is less
muscular and more fibrous near the cervix; the cervix itself is almost
entirely collagenous. The muscle cells of the myometrium are
about 40 μm long immediately after menstruation, twice this long
at the middle of the menstrual cycle, and up to 10 times as long
in pregnancy. The function of the myometrium is to produce the
labor contractions that help to expel the fetus.
The inner lining of the uterus, or mucosa, is called the endometrium.
44 It has a simple columnar epithelium, compound tubular
glands, and a stroma populated by leukocytes, macrophages, and
other cells (fig. 26.18). The superficial half to two-thirds of it, called
the stratum functionalis, is shed in each menstrual period. The
deeper layer, called the stratum basalis, stays behind and regenerates
a new functionalis in the next cycle. When pregnancy occurs,
the endometrium is the site of attachment of the embryo and forms
the maternal part of the placenta.

menstrual cycle, the monthly rhythm of endometrial
buildup, breakdown, and discharge. This cycle averages 28
days long, with day 1 considered to be the first day of visible vaginal discharge of menstrual fluid.

A cycle in which ovulation occurs, characterised by a bi-phasic temperature chart

Ovulation, the release of an oocyte, typically occurs on day 14,
the midpoint of the average cycle

The pre-ovulatory phase characterised by the growth and development of the egg follicles. See menstrual cycle and pre-ovulatory phase

The post-ovulatory phase characterised by the growth and development of the corpus luteum.The phase from ovulation to the onset of the next menstruation.

It has a relatively constant length, usually lasting from 12-16 days

About 3 days before the
menstrual period begins, pituitary secretion of follicle-stimulating
hormone (FSH) stimulates several primordial follicles to develop
into primary follicles.

LH, the other gonadotropin, is
also secreted by the gonadotropes. In females, it stimulates
ovulation (the release of an egg). LH is named for the fact
that after ovulation, the remainder of a follicle develops into a yellowish body called the corpus luteum.11 LH also stimulates
the corpus luteum to secrete progesterone, a hormone
important to pregnancy. In males, LH stimulates the testes to
secrete testosterone.

The premenstrual phase is a period of endometrial degeneration
occuring in the last 2 days or so of the menstrual cycle. When
the corpus luteum involutes, the spiral arteries exhibit spasmodic
contractions that cause endometrial ischemia (interrupted blood
flow). The premenstrual phase is therefore also called the ischemic
(iss-KEE-mic) phase. Ischemia leads to tissue necrosis. As the endometrial
glands, stroma, and blood vessels degenerate, pools of
blood accumulate in the stratum functionalis. Necrotic endometrium
falls away from the uterine wall, mixes with blood and serous
fluid in the lumen, and forms the menstrual fluid

The menstrual phase (menses) begins when enough menstrual
fluid has accumulated in the uterus that it begins to be discharged
vaginally. The first day of external discharge marks day 1 of a new
cycle.

In girls, the third principal
event is menarche65 (men-AR-kee), the first menstrual period.
Menarche does not immediately signify fertility. A girl’s first few
menstrual cycles are typically anovulatory (no egg is ovulated).
Most girls begin ovulating regularly about a year after they begin
menstruating

Around ages
50 to 55, both men and women go through a period of physical
and psychological change called climacteric, although (jokes about
“male menopause” aside) only women experience menopause, the
cessation of menses