370
UNIT 3
Organ Systems
Figure 19-13A
Overview of the Placenta
Figure 19-13B
Fetal Portion of the Placenta
Figure 19-14A
Umbilical Cord
Vagina
Figure 19-14B
Vagina
Mammary Glands
Figure 19-15A
Overview of the Mammary Gland
Figure 19-15B
Inactive (Resting) Mammary Gland
Figure 19-15C
Active (During Pregnancy) Mammary Gland
Figure 19-16A
Nipple, Mammary Gland
Figure 19-16B
Clinical Correlation: Adenocarcinoma of the Breast (Breast Cancer)
Synopsis 19-1
Clinical and Pathological Terms for the Female Reproductive System
Introduction and Key Concepts for the
Female Reproductive System
The
female reproductive system
comprises the
ovaries
,
oviducts
,
uterus
,
vagina
,
external genitalia
, and
mammary glands
.
The
external genitalia
(
vulva
) includes the
labia
minora
,
labia
majora
,
mons
pubis
,
clitoris
, and
vestibule
. Female secondary
sex characteristics appear at puberty, along with the monthly
menstrual cycle. This cycle of changes in the reproductive sys-
tem is infl
uenced by interactions among the hypothalamus,
pituitary gland, ovaries, and uterus; related events occur peri-
odically during each menstrual cycle (Fig. 19-8). The menstrual
cycle is infl
uenced by hormones including
follicle-stimulating
hormone (FSH)
,
luteinizing hormone (LH)
,
estrogen
, and
progesterone
. These hormones cause changes in the female
reproductive organs and their functions, promote development
of follicles and oocytes, and produce an ideal environment
for fertilization, implantation, and fetal growth. The female
reproductive system plays an important role in the
production
and
regulation
of female hormones (estrogen and progester-
one) and in the development and maintenance of female sex
characteristics.
Ovaries
The
ovaries
are paired, almond-shaped structures located in
the upper part of the pelvic cavity. Their size and position vary
depending on the age and reproductive state of the individual.
The ovaries are suspended by the
mesovarium
of the broad liga-
ment and are attached to the uterus by the ligament of the ovary
(Fig. 19-1). Each ovary has a
cortex
and
medulla
. The
cortex
contains numerous
developing follicles
in various stages as
well as
postovulatory structures
, a
corpus luteum
, and several
corpora albicans
. Each developing follicle contains an
oocyte
.
The
medulla
is composed of loose connective tissue and blood
vessels, nerve ± bers, and lymphatic vessels (Fig. 19-3A).
1.
Primordial follicles
:
In the earliest stage of follicular
development,
primordial follicles
rest at the periphery of the
cortex. Each primordial follicle consists of a
primary oocyte
surrounded by a single layer of squamous supporting cells
called
follicular cells
(Fig. 19-4A,B). The
oocyte
is small
(about 20–30
μ
m) and is in prophase (
dictyotene
) of meiosis
I. The nucleus of the oocyte has a pale appearance and
contains decondensed chromatin.
2.
Primary follicles
:
At puberty, the primordial follicles begin
to grow, the oocyte increases its size, and the supporting
follicle cells also increase in size and become cuboidal
cells. These follicle cells are now called
granulosa cells
.
When the oocyte of the
primary follicle
is surrounded
by a single layer of granulosa cells, the follicle is called a
unilaminar primary follicle
. As the oocyte increases in size,
the granulosa cells build up more layers, and the follicle is
called a
multilaminar primary follicle
(Fig. 19-5A,B). The
zona pellucida
, a
gel-like layer between the oocyte and the
granulosa cells, ±
rst appears in the multilaminar primary
follicle (Fig. 19-5B).
3.
Secondary follicles
:
As granulosa cells continue to prolifer-
ate, the follicle size increases, and spaces ±
lled with follicular
fl uid (
liquor folliculi
) develop among the cells. These spaces
merge to become a single large space called the
antrum
. The
stromal cells that cover the follicle develop into a layer called
the
theca folliculi
. The theca folliculi is well developed in the
secondary
follicle
, and it includes the
theca interna
and
theca
externa
(Fig. 19-6A).
4.
GraaF
an
(
preovulatory
)
follicle
:
In its ±
nal stage, the
follicle reaches a maximum size of up to 25 mm (2.5 cm).
This follicle has a large antrum ±
lled with liquor folliculi.
It has reached its mature stage and is ready to release the
oocyte (
ovulation
). The oocyte has reached its maximum
size, and is embedded in a mound of granulosa cells that
protrude into the antrum (Fig. 19-6B). The granulosa cells
that are in immediate contact with the oocyte are called the
corona radiata
and remain with the oocyte at ovulation.
The
graa±
an follicle
bulges from the surface of the ovary. In
response to a sharp increase in the level of LH (
LH surge
),
the oocyte resumes meiotic division, becomes arrested as a
secondary oocyte
, and ovulation then occurs.
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