Histology
The Female Reproductive System
The Female Reproductive System
(Genital System)
The female reproductive system consists of
- 2 ovaries
- 2 oviducts (uterine or fallopian tubes)
- The uterus
- The vagina
- The external genitalia
- and Mammary glands
Its functions are:- to produce female gametes (oocytes).
- to hold a fertilized oocyte.
- to produce sexual hormones.
- nutrition of the fetus and newborn.
Ovaries:- ovaries are almond-shaped bodies(3cm long, 1.5 cm wide,
and 1 cm thick), located in the pelvic cavity.
- Their surface is covered by a simple squamous or cuboidal
epithelium called germinal epithelium.
- Under the germinal epithelium, the stroma forms a layer of
dense connective tissue called the tunica albuginea,
which is responsible for the whitish color of the ovary.
- Underneath the tunica albuginea is the cortical region.
The follicles are embedded in the connective tissue
(stroma) of the cortical region. This stroma is composed of
spindle-shaped fibroblasts.
- The most internal part of the ovary is the medullary
region, containing a rich vascular bed within a loose
connective tissue.
- One section is attached to the broad ligament by the
mesovarium and another section to the uterine wall by an
ovarium ligament.
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Histology
The Female Reproductive System
Ovarian follicles:
- An ovarian follicle consists of an oocyte surrounded by
one or more layers of follicular (granulosa) cells.
A- Primordial follicles:- are formed during fetal life.
Each consists of a primary oocyte (is a spherical cell
about 25 ) enveloped by one layer of flattened follicular
cells.
B- Growing follicles:- follicular growth is beginning in puberty and stimulated
by follicle-stimulating hormone (FSH).
- follicular cells divide and form a single layer of cuboidal
cells, the follicle is then called a unilaminar primary
follicle.
- The follicular cells continue to proliferate and form a
stratified follicular epithelium or granulosa layer, the
follicle is then called a multilaminar primary or preantal
follicle.
- A thick amorphous layer, the zona pellucida is secreted
and surrounds the oocyte.
- As the follicles grow, increase in size and number of
granulosa cells.
- Liquid begins to accumulate between the follicular cells.
- The spaces that contain this fluid coalesce, and the
granulosa cells reorganize themselves to form a larger
cavity, the antrum. The follicles are then called
secondary or antral follicles.
- Follicular fluid contains many products such as steroids
(progesterone, androgens, and estrogens).
- some cells of the granulosa layer concentrate at a certain
point on the follicular wall called cumulus oophorus,
which contains the oocyte.
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Histology
The Female Reproductive System
- A group of granulosa cells concentrate around the oocyte
and form the corona radiata. These cells accompany the
oocyte when it leaves the ovary.
- The fibroblasts of the stroma differentiate to form the
theca interna and the theca externa (theca, meaning
box).
- The cells of the theca interna are synthesize a steroid
hormone (androstenedione) that is transported to the
granulosa layer.
-
The cells of the granulosa are synthesize an enzyme,
aromatase, that transforms androstenedione into estrogen.
Estrogen returns to the stroma surrounding the follicle,
enters the blood vessels, and is distributed throughout the
body.
- during each menstrual cycle, usually one follicle grows
much more than the others, and becomes the dominant
follicle. The other follicles enter atresia. This follicle, the
mature or graafian follicle is so large (about 2.5 cm in
diameter) that it protrudes from the surface of the ovary
and can be detected with ultrasound.
- The whole process of growth from primordial to mature
follicle lasts about 90 days.
Follicular Atresia :Most ovarian follicles undergo atresia, in which follicular
cells and oocytes die and are disposed of by phagocytic cells.
Follicles at any stage of development may undergo atresia.
Follicular atresia take place from before birth until a few years
after menopause.
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Histology
The Female Reproductive System
Ovulation:- Ovulation consists of the rupture of part of the wall of the
mature follicle and liberation of the oocyte.
- It takes place in the middle of the menstrual cycle, ie,
around the fourteenth day of a 28 day cycle.
- In the human, usually only one oocyte is liberated by the
ovary during each cycle, but sometimes no oocyte is
ovulated at all. Sometimes 2 or more oocytes can be
expelled at the same time, and if they are fertilized there
may be 2 or more fetuses.
- The stimulus for ovulation is a surge of luteinizing
hormone (LH) in response to high levels of circulating
estrogen produced by the growing follicles.
- An indication of ovulation is a local change in color and
translucence of the follicular wall.
- The fimbriae is the first part of the oviduct. It is very close
to the surface of the ovary and receive the ovum.
- The ovum (oocyte) remains viable for an estimated
maximum of 24 hours, if the ovum is not fertilized, it
degenerates and is phagocytized.
Corpus luteum:- After ovulation, the granulosa cells and the cells of the
theca interna of the ovulated follicle form a temporary
endocrine gland called the corpus luteum (yellow body).
- The granulosa cells called granulosa lutein cells with the
characteristics of steroid- secreting cells. Cells of the theca
interna also giving rise to theca lutein cells.
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Histology
The Female Reproductive System
- Also under stimulus by LH, the cells of the corpus luteum
begin secreting progesterone and estrogens.
-
the corpus luteum is programmed to secrete for 10-12
days. If pregnancy does not occur, the cells of the corpus
luteum degenerate by apoptosis.
-
The decreasing secretion of progesterone is menstruation.
- After the corpus luteum degenerates, the concentration of
blood steroids decreases and FSH is liberated, stimulating
the growth of another group of follicles, beginning the
next menstrual cycle.
- The fibroblasts invade the area and produce a scar of dense
connective tissue called corpus albicans (white body,
because of the large amount of collagen).
- If pregnancy occurs, the embryo synthesize a hormone
called human chorionic gonadotropin (HCG). This
hormone rescues the corpus luteum from degeneration,
causes stimulates secretion of progesterone. It persists for
4-5 months and degenerates and is replaced by a corpus
albicans .
Oviducts :- The oviducts are two muscular tubes of great mobility (12
cm in length).
- The uterine tubes are divided into four regions:
1. infundibulum: extending from infundibulum fingerlike
processes called fimbriae.
2. ampulla
3. isthmus
4. intramural region
- The wall of the oviduct is composed of 3 layers:1. a mucosa: simple columnar epithelium
(contain folds)
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Histology
The Female Reproductive System
and lamina propria
2. a thick muscularis composed of smooth
muscle : -inner circular layer
-Outer longitudinal layer
3. a serosa
- The epithelium contains 2 types of cells : once has cilia, the
other is secretory.
-Fertilization usually occurs in the ampulla. When
fertilization does not take place, the oocyte undergoes
autolysis in the oviduct. Once fertilized, the oocyte, now
called a zygote and is transported to the uterus, a process that
lasts about 5 days.
Uterus :-The uterus is a pear shaped organ that consists of :1. a body (corpus), which lies above a
narrowing of the uterine cavity (the internal
os).
2. a lower cylindrical structure, the cervix,
which lies below the internal os.
3. the fundus (dome-shaped part) of the
body of the uterus.
-the wall of the uterus is formed of 3 layers:1. endometrium (mucosa)
2. myometrium (a thick tunic of
smooth muscle)
3. perimetrium :serosa or adventitia
depending on the part of the uterus.
Myometrium:
The myometrium (Gr. mys, muscle,+metra, uterus) is composed
of bundles of smooth muscle fibers separated by connective
tissue.
During pregnancy the myometrium goes through a period of
great growth. After pregnancy, there is destruction of some
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Histology
The Female Reproductive System
smooth muscle cells, reduction in the size of others. The uterus
is reduced in size almost to its prepregnancy dimensions.
Endometrium:the endometrium consists of :- epithelium (ciliated and secretory simple columnar cells)
- a lamina propria containing simple or branched tubular uterine
glands.
Its subdivide into 2 zones
- the basalis: is the deepest one, it contains lamina propria
and the beginning of the uterine glands.
- the functionalis contains the remainder of the lamina
propria and of the glands, as well as the surface epithelium
the blood vessels supplying the endometrium called arcuate
arteries. From these vessels, 2 sets of arteries arise to supply
blood to the endometrium :
- straight arteries which supply the basalis.
- spiral arteries, which bring blood to the functionalis.
Menstrual cycle:- cyclical monthly changes in both structure
and function of female reproductive organs.
Menarche :- is the appearance of the initial menstrual cycle in
the maturing individual.
Menopause:- is the phase when the cycles become irregular and
eventually disappear.
The menstrual cycle:- Estrogens and progesterone control the organs of the
female reproductive system. Even before birth, these
organs are influenced by estrogen and progesterone that
circulate in the maternal blood and reach the fetus through
the placenta.
- After puberty, the ovarian hormones cause the
endometrium to undergo cyclic structural modifications
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Histology
The Female Reproductive System
during the menstrual cycle. The duration of the menstrual
cycle is variable but averages 28 days.
- Menstrual cycles start between 12-15 years of age and
continue until about 45-50. The female is fertile only
during the years when she is having menstrual cycles. This
does not mean that sexual activity is terminated by
menopause- only that fertility ceases.
- The menstrual cycle is taken as the day when menstrual
bleeding appears. The menstrual discharge consists of
degenerating endometrium mixed with blood from the
ruptured blood vessels. The menstrual phase lasts 3-4 days
on average.
The proliferative, follicular, or estrogenic phase: its
include,
-After the menstrual phase uterine mucosa is thin.
- Rapid growth of ovarian follicles.
- Follicles begin to secrete estrogens.
- Cell proliferation of the endometrium.
- The uterine glands are straight tubules.
- The duration is variable, 10 days on average.
The secretory or luteal phase:
- Starts at ovulation and lasts about 14 days.
- The corpus luteum secret progesterone which inhibits the
contractions of smooth muscle cells of the myometrium.
- The glands become highly coiled.
- Growth of the mucosa.
- Embryo transported to the uterus (if fertilization occur ).
The menstrual phase:
- When fertilization do not occur the levels of progesterone and
estrogens in the blood decrease.
- Shedding of part of the mucosa about 14 days.
- Blood vessels rupture and bleeding begins.
- The amount of endometrium and blood lost varies between
women and even in the same women at different times.
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Histology
The Female Reproductive System
- At the end, the endometrium is begin a new cycle as its cells
begin dividing to reconstitute the mucosa.
Placenta:The placenta is a temporary organ and is the site of
physiologic exchanges between the mother and the fetus. It
consists of a fetal part and a maternal part. The placenta is also
an endocrine organ, producing such hormones as estrogens and
progesterone.
Uterine cervix
The uterine cervix is the lower, cylindrical part of the uterus.
1. The mucosa :
The lining a- consists of a mucus-secreting simple columnar
epithelium, and the external aspect is covered with stratified
squamous epithelium.
b- contains the cervical glands(branched)
2. The muscular :
The cervix has few smooth muscle fibers and consists 85% of
dense connective tissue.
At the time of ovulation, the cervical mucous secretions are
watery and allow penetration of the uterus by sperm. In the
pregnancy, the progesterone levels alter the mucous secretions
so that they become more viscous and prevent the passage of
sperm, as well as microorganisms, into the body of the uterus.
The dilation of the cervix that precedes parturition is due to
intense collagenolysis, which promotes its softening.
Vagina:The wall of the vagina is devoid of glands and consists of 3
layers:
- a mucosa:-stratified squamous non keratinized and lamina
propria rich in elastic fibers (cause the elasticity of the vagina).
- muscular layer:- inner circular and outer longitudinal layers of
smooth muscle fibers
- an adventitia
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Histology
The Female Reproductive System
The mucous found in the lumen of the vagina comes from the
glands of the uterine cervix.
External genitalia:The female external genitalia, or vulva, consist of the clitoris,
labia minora, labia majora, and some glands that open into the
vestibulum, a space enclosed by the labia minora. These glands
are glandulae vestibulares majores and glandulae vestibulares
minores.
Mammary glands:-
 Each mammary gland consists of 15-25 lobes of the
compound tubuloalveolar type whose function is to secrete
milk.
 Each lobe, separated from the others by connective tissue
and adipose tissue. Also it contains excretory lactiferous
duct, which emerge in the nipple.
 The inactive glands (before puberty) are small, consist of
ducts and do not exhibit any developed alveoli.
 The active glands (during pregnancy) are consist of ducts
and numerous developed alveoli. All alveoli become
surrounded by myoepithelial cells.
 the mammary glands undergo intense growth during
pregnancy as a result of the action of hormones, estrogen,
progesterone, prolactin, and human placental lactogen.
 After menopause, the mammary glands is characterized by
a reduction in size and the atrophy of their secretory
portions. Atrophic changes also in the connective tissue.
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