d. Ovaries (2) (see figure 1-4).
Figure 1-4. Human ovary.
(1) Functions. The ovaries are for oogenesis-the production of eggs
(female sex cells) and for hormone production (estrogen and progesterone).
(2) Location and gross anatomy. The ovaries are about the size and shape
of almonds. They lie against the lateral walls of the pelvis, one on each side. They are
enclosed and held in place by the broad ligament. There are compact like tissues on
the ovaries, which are called ovarian follicles. The follicles are tiny sac-like structures
that consist of an immature egg surrounded by one or more layers of follicle cells. As
the developing egg begins to ripen or mature, follicle enlarges and develops a fluid filled
central region. When the egg is matured, it is called a graafian follicle, and is ready to
be ejected from the ovary.
Process of egg production--oogenesis (see figure 1-5).
(a) The total supply of eggs that a female can release has been
determined by the time she is born. The eggs are referred to as "oogonia" in the
developing fetus. At the time the female is born, oogonia have divided into primary
oocytes, which contain 46 chromosomes and are surrounded by a layer of follicle cells.
(b) Primary oocytes remain in the state of suspended animation
through childhood until the female reaches puberty (ages 10 to 14 years). At puberty,
the anterior pituitary gland secretes follicle-stimulating hormone (FSH), which stimulates
a small number of primary follicles to mature each month.