The primary source for estrogen is the ovaries. At puberty, estrogen stimulates enlargement of various accessory organs, which include the vagina, uterus, fallopian tubes, and external structures. Estrogen is also responsible for the development and maintenance

Figure 1-61.-The female reproductive system. style="mso-spacerun: yes">

of female secondary sexual characteristics. See section titled "Endocrine System" for listing of secondary female sexual characteristics.

The ovaries are also the primary source of progesterone (in a nonpregnant female). This hormone promotes changes that occur in the uterus during the female reproductive cycle. In addition, progesterone stimulates the enlargement of mammary glands and ducts, and increases fat deposits in female breasts during puberty.