Female Reproductive System
This page outlines the basic anatomy and function of the female
reproductive system. Separate pages describe the
male reproductive system and characteristics of the
reproductive system common to both males and
- Anatomy of the female reproductive system:
- The entire external genitalia of the female is called the
vulva. This includes the labia majora, labia minora and clitoris.
- The vagina connects the vulva to the uterus, serving both
as a receptacle for sperm during sexual intercourse and as the passageway for
the infant during birth. The urethra ends in a separate orifice. The
cervix is the neck of the uterus that protrudes into the upper end
of the vagina.
- The walls of the uterus contain a thick layer of smooth
muscle called the myometrium, which serve to expel the fetus during labor.
The inner lining of the uterus, the endometrium, proliferates in preparation
for implantation of the zygote and is then shed during each menstrual cycle.
- Two Fallopian tubes, one on each side, connect the uterus to
the ovaries. Fertilization typically occurs here.
- Closely associated with the end of each Fallopian tube is a
walnut-sized ovary, the female gonad.
- Egg production takes place within the ovaries:
- In the male, all phases of spermatid
production from germ cell to gamete takes place continually over the
entire lifespan. In the female, each phase takes place during specific
periods. About 7 million germ cells, or oogonia, develop in the embryonic
ovary as early as 5 months of gestation. Most of these cells then die,
with about a half a million of them proceeding through the first stage of
meiosis to become primary oocytes before birth.
- After puberty, the primary oocytes then begin to develop
a few at a time, with each contained in a follicle of surrounding
- One or more ovarian follicles rupture at the midpoint of
each menstrual cycle, releasing an egg and surrounding cells into the
- Hormone production in the ovaries occurs primarily within
the developing follicles. The two major steroid hormones produced by the
human ovaries are progresterone and estradiol, a form of estrogen. Production
of these two hormones varies widely over the course of the menstrual cycle:
- The first day of menstruation is usually labeled as the
beginning of the cycle. At this point, rising levels of FSH stimulate
the development of several follicles in the ovaries. These early follicles
in turn begin to produce estrogen. Usually, only one of these follicles will
develop past the early stage.
- Estrogen levels continue to rise as the follicle develops.
Progesterone eventually begin to rise as well. Up to a certain point, the
estrogen being produced exerts negative feedback on both GnRH and gonadotropin
- Around the 14th day of the cycle, the anterior pituitary
abruptly changes its response to the persistently high estrogen levels.
Rather than suppressing gonadotropin release, the estrogen now has a positive
feedback effect. The reasons for this switch are still not clear.
The switch to positive feedback provokes a steep surge in LH, and to a lesser
degree FSH. High LH levels in turn initiates the process of ovulation,
whereby the follicle ruptures and egg is released.
After ovulation, the follicle collapses and the cells within it transform.
This new structure is called the corpus luteum. The luteal cells
produce more progesterone than estrogen, so blood levels of progesterone
rise higher than estrogen levels after ovulation. The corpus luteum
only remains viable for about 14 days, after which both estrogen and
progesterone levels taper off. The declining levels of estrogen remove
the negative feedback on GnRH and FSH production, allowing the cycle to
begin over again.
Female Reproductive Images
Male reproductive system