1022
U N I T 1 1
Genitourinary and Reproductive Function
lipoproteins. They produce an increase in high-density
lipoproteins (HDLs), a slight reduction in low-density
lipoproteins (LDLs), and a reduction in cholesterol lev-
els. Estrogens also increase plasma triglyceride levels, and
they enhance the coagulability of blood by increasing the
circulating levels of plasminogen and factors II, VII, IX,
and X. Estrogens, which have a chemical structure similar
to adrenal cortical hormones, can also cause sodium and
water retention by the kidney. Most women retain sodium
and water and gain weight just before menstruation. The
actions of estrogens are summarized in Table 40-1.
Although the ovaries are the major source of estrogen,
the biosynthesis of estrogens that occurs in adipose tis-
sue may be a significant source of the hormone. There
is evidence that a certain minimum body weight and fat
content are necessary for menarche to occur and for the
Primordial
follicle
Hilum
Corpus
albicans
Germinal
epithelium
Stroma
Ovulation
Primary
follicle
Preantral
follicle
Preovulatory
follicle
Atretic
follicle
Antral
follicle
Early corpus
luteum
Mature corpus
luteum
Theca externa
Theca interna
Granulosa cells
Oocyte
Antrium
A
B
FIGURE 40-7.
(A)
Cross-section of preovulatory follicle.
(B)
Schematic diagram of an ovary, showing
the sequence of events in the origin, growth, and rupture of an ovarian follicle and the formation and
retrogression of a corpus luteum.The atretic follicles are those that show signs of degeneration and
death.
TABLE 40-1
Actions of Estrogens
General Function
Specific Actions
Growth and development
Reproductive organs
Stimulate development of vagina, uterus, and fallopian tubes in utero and of secondary sex
characteristics during puberty
Skeleton
Accelerate growth of long bones and closure of epiphyses at puberty
Reproductive processes
Ovulation
Promote growth of ovarian follicles
Fertilization
Alter the cervical secretions to favor survival and transport of sperm
Promote motility of sperm within the fallopian tubes by decreasing mucus viscosity
Implantation
Promote development of endometrial lining in the event of pregnancy
Vagina
Proliferate and cornify vaginal mucosa
Cervix
Increase mucus consistency
Breasts
Stimulate stromal development and ductal growth
General metabolic effects
Bone resorption
Decrease rate of bone resorption
Plasma proteins
Increase production of thyroid and other binding globulins
Lipoproteins
Increase high-density and slightly decrease low-density lipoproteins
