Usually only one follicle develops at a
time - the follicle can be seen in the photograph taken by Patrick Steptoe and
through the laparoscope. It can be seen as a bright 'bulging' structure
outlined by the circle in the graphic on the RIGHT.
The ovaries are the female gonad (where the eggs are formed), are oval
structures about 3.5 x 2 x 1.5 cm in size, lie alongside the uterus attached by
ovarian ligaments. They often appear pitted and scarred as a result of repeated
ovulations which usually take place from the onset of menstruation until the
menopause. It is interesting to note that the human is the only animal to
suffer from the menopause.
Usually only one follicle develops at a
time - the follicle can be seen in the photograph taken by Patrick Steptoe and
through the laparoscope. It can be seen as a bright 'bulging' structure
outlined by the circle in the graphic on the RIGHT.
The follicles are formed in the fetus during the fourth month of gestation. The primordial follicles (below left) are only 30 micrometers in diameter (0.03 mm). About 7 million are formed during gestation and by the time of birth the number has already fallen to about 2 million. By the time the menopause is reached the number has fallen below 1 thousand.
A number of the primordial follicles (pf on the LEFT) are recruited at each cycle but usual only one or two develop to maturity - the dominant follicle suppressing the development of the remainder.
The ovaries produce mature eggs (oocytes) which are released during ovulation. The hormone oestrogen is released into the blood stream in increasing quantities as the follicles grow. Once ovulation has taken place the collapsed follicle (becomes the corpus luteum) also produces the hormone progesterone which stimulates the development of the uterine lining - the endometrium.