The reproductive role of the female is far more complex than that of a male. Not only must she produce gametes, but her body must prepare to nurture a developing embryo for a period of approximately nine months. Ovaries, the female gonads, are the primary reproductive organs of a female, and like the male testes, ovaries serve a dual purpose: They produce the female gametes (ova) and sex hormones, the estrogens * and progesterone (pro-ges′tĕ-rōn). The accessory ducts (uterine tubes, uterus, and vagina) transport or otherwise serve the needs of the reproductive cells and a developing fetus. As illustrated in Figure 27.11, the ovaries and duct system, collectively known as the internal genitalia, are mostly located in the pelvic cavity. The female’s accessory ducts, from the vicinity of the ovary to the body exterior, are the uterine tubes, the uterus, and the vagina. The external sex organs of females are referred to as the external genitalia.
The paired ovaries flank the uterus on each side. Shaped like an almond and about twice as large, each ovary is held in place in the fork of the iliac blood vessels within the peritoneal cavity by several ligaments. The ovarian ligament anchors the ovary medially to the uterus; the suspensory ligament anchors it laterally to the pelvic wall; and the mesovarium (mez″o-va′re-um) suspends it in between. The suspensory ligament and the mesovarium are part of the broad ligament, a peritoneal fold that “tents” over the uterus and supports the uterine tubes, uterus, and vagina. The ovarian ligaments are enclosed by the broad ligament. The ovaries are served by the ovarian arteries, branches of the abdominal aorta, and by the ovarian branch of the uterine arteries. The ovarian blood vessels reach the ovaries by traveling through the suspensory ligaments and mesovaria. Like each testis, each ovary is surrounded externally by a fibrous tunica albuginea which is in turn covered externally by a layer of cuboidal epithelial cells called the germinal epithelium, actually a continuation of the peritoneum. The ovary has an outer cortex, which houses the forming gametes, and an inner medullary region, containing the largest blood vessels and nerves, but the relative extent of each region is poorly defined.
Embedded in the highly vascular connective tissue of the ovary cortex are many tiny saclike structures called ovarian follicles. Each follicle consists of an immature egg, called an oocyte (o′o-sīt; oo= egg), encased by one or more layers of very different cells. The surrounding cells are called follicle cells if a single layer is present, and granulosa cells when more than one layer is present. Follicles at different stages of maturation are distinguished by their structure. In a primordial follicle, one layer of squamouslike follicle cells surrounds the oocyte. A primary follicle has two or more layers of cuboidal or columnar-type granulosa cells enclosing the oocyte; it becomes a secondary follicle when fluid-filled spaces appear between the granulosa cells and then coalesce to form a central fluid-filled cavity called an antrum. At the mature vesicular follicle, or Graafian follicle (graf′e-an), stage, the follicle bulges from the surface of the ovary. The oocyte of the vesicular follicle “sits” on a stalk of granulosa cells at one side of the antrum. Each month in adult women, one of the ripening follicles ejects its oocyte from the ovary, an event called ovulation. After ovulation, the ruptured follicle is transformed into a very different looking glandular structure called the corpus luteum (lu′te-um; plural: corpora lutea), which eventually degenerates. As a rule, most of these structures can be seen within the same ovary. In older women, the surfaces of the ovaries are scarred and pitted, revealing that many oocytes have been released.
The Female Duct System
The Uterine Tubes
The uterine tubes...