The female reproductive system consists of the paired ovaries and uterine tubes (or oviducts/fallopian 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 development and function of the reproductive organs and influence other tissues. Beginning at menarche, when the first menses occurs, the reproductive system undergoes monthly changes in structure and function, under the control of neurohormonal mechanisms. Menopause represents 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. (×15; 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 capsule of dense connective tissue, the tunica albuginea, like that of the testis. Most of the ovary consists of the cortex, a region of highly cellular connective tissue stroma containing many ovarian follicles that vary greatly in size after menarche (Figure 22–1). The most internal part of the ovary, the medulla, encompasses loose connective tissue and blood vessels entering the organ through the hilum from the mesenteries suspending the ovary (Figures 22–1 and 22–2). No distinct border delineates 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), a secondary ...