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55 THE FEMALE REPRODUCTIVE SYSTEM

Ervin E. Jones

REPRODUCTIVE FUNCTION IN THE FEMALE HUMAN

Reproductive function in female humans is controlled by hormones that emanate from thehypothalamic-pituitary-gonadal axis (see Chapter 47). The release of a mature ovum from an ovary,known as ovulation, is the dominant event of the menstrual cycle. Whereas ovulation in somemammals is triggered by mating, ovulation in the female human is spontaneous and is regulatedby cyclic functional interactions among signals coming from the hypothalamus, the anterior pituitary,

and the ovaries. Although many aspects of female reproduction are cyclic, maturation and demise(i.e., atresia) of the functional units of the ovaries-the ovarian follicles-are continuous processes thatoccur throughout reproductive life.

The ovaries are not the only female organs that undergo rhythmic changes. Alterations in cervical anduterine function are controlled by changes in the circulating concentrations of ovarian hormones, thatis, the estrogens and progestins. For example, the uterine lining or endometrium thickens under theinfluence of ovarian hormones and deteriorates and sloughs at the end of the cycle when ovarianestrogen and progestin secretion diminishes. Menstruation reflects this periodic shedding of theendometrium. Menstrual cycles are generally repetitive unless they are interrupted by pregnancy or 

terminated by menopause. All the cyclic physiological changes prepare the female reproductive tractfor sperm and ovum transport, fertilization, implantation, and pregnancy.

Female Reproductive Organs Include the Ovaries and Accessory Sex Organs

The ovaries lie on the sides of the pelvic cavity (Fig. 55-1A). A layer of mesothelial cells covers thesurface of the ovary. The ovary itself consists of an inner medulla and an outer zone, or cortex, thatsurrounds the medulla except at the hilar area. The cortex of the ovary in a mature woman contains

developing follicles and corpora lutea in various stages of development (Fig. 55-1B). These elementsare interspersed throughout the stroma, which includes connective tissue, interstitial cells, and bloodvessels. The medulla comprises large blood vessels and other stromal elements.

The female accessory sex organs include the fallopian tubes, the uterus, the vagina, and theexternal genitalia. The fallopian tube provides a pathway for the transport of ova from the ovary tothe uterus. The distal end of the fallopian tube expands as the infundibulum, which ends in multiplefimbriae. The infundibulum is lined with epithelial cells that have cilia that beat toward the uterus. Theactivity of these cilia and the contractions of the wall of the fallopian tube, particularly around the timeof ovulation, facilitate transport of the ovum.

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