The female reproductive system consists of the paired ovaries and oviducts (or uterine tubes), the uterus, the vagina, and the external genitalia (Figure 22–1). This system produces the female gametes (oocytes), provides the environment for fertilization, and holds the embryo during its complete development through the fetal stage until birth. As with male gonads, the ovaries produce steroidal sex hormones that control organs of the reproductive system and influence other organs. Beginning at menarche, when the first menses occurs, the reproductive system undergoes monthly changes in structure and function that are controlled by neurohormonal mechanisms. Menopause is a variably timed period during which the cyclic changes become irregular and eventually disappear. In the postmenopausal period the reproductive organs slowly involute. Although the mammary glands do not belong to the genital system, they are included here because they undergo changes directly connected to the functional state of the reproductive organs.
The female reproductive system and overview of ovary.
(a) The diagram shows the internal organs of the female reproductive system, which includes as the principal organs the ovaries, uterine tubes, uterus, and vagina. (b) A lateral sectional view of an ovary shows the ovary and the relationship of its main supporting mesenteries, the mesovarium and the mesosalpinx of the broad ligament. (c) A sectioned ovary, indicating the medulla and cortex, with follicles of several different sizes in the cortex. (X15; H&E)
Ovaries are almond-shaped bodies approximately 3-cm long, 1.5-cm wide, and 1-cm thick. Each ovary is covered by a simple cuboidal epithelium, the surface (or germinal) epithelium, continuous with the mesothelium and overlying a layer of dense connective tissue capsule, the tunica albuginea, like that of the testis. Most of the ovary consists of the cortex, a region with a stroma of highly cellular connective tissue and many ovarian follicles varying greatly in size after menarche (Figure 22–1). The most internal part of the ovary, the medulla, contains loose connective tissue and blood vessels entering the organ through the hilum from mesenteries suspending the ovary (Figures 22–1 and 22–2). There is no distinct border between the ovarian cortex and medulla.
Follicle development and changes within the ovary.
The ovary produces both oocytes and sex hormones. A diagram of a sectioned ovary (a) shows the different stages of follicle maturation, ovulation, and corpus luteum formation and degeneration. All of the stages and structures shown in this diagram actually would appear at different times during the ovarian cycle and do not occur simultaneously. Follicles are arranged here for easy comparisons. The primordial follicles shown are greatly enlarged. The histologic sections identify primordial follicles (b), a primary follicle (c)...