BIOLOGY Volume 3 - A Guide to General Biology - 2004

21. REPRODUCTION

21.7. Human Reproductive Systems

21.7.2. Female Reproductive System

The Anatomy of the FEMALE Reproductive System is illustrated in Fig. 21.34. Its main components and their Functions are described below. Note that, unlike in males, the URINARY AND REPRODUCTIVE systems in females have separate external orifices.

Class="center">

Fig. 21.34. A. Schematic diagram of the female reproductive system. The Uterus and Vagina are shown in section. The external genitalia, urethral opening, and anus are depicted as viewed from above with the labia parted. B. Anterior view of the FEMALE REPRODUCTIVE Organs. Organs belonging to the Urinary System are highlighted in grey. Together, the two systems are frequently referred to as the Urogenital System.

1. Ovaries. The paired ovaries are the female Gonads, i.e., the sites where female Gametes, known as ova, are produced. Almond-shaped, the ovaries measure 3–5 cm in length and 2–3 cm in width. They secrete the Female Sex Hormones oestrogen and progesterone. Typically, a woman produces one egg per month throughout her reproductive years. The outermost layer of the Ovary consists of germinal epithelium Cells from which gametes develop. The outer cortex contains developing follicles, while the central region, or stroma, contains Connective Tissue, Blood Vessels, and mature follicles.

2. Fallopian tubes, or oviducts. These tubes are about 12 cm long and serve to transport eggs from the ovaries to the uterus. The funnel-shaped free ends of the tubes, positioned close to the ovaries, feature fringe-like projections called fimbriae. During ovulation, these move even closer to the ovaries. The beating of cilia covering the fimbriae creates a current that catches the egg (more precisely, the secondary oocyte) upon its release from the ovary. Ciliary action along the inner lining of the Fallopian tube, combined with peristaltic contractions of its smooth Muscle, propels the oocyte toward the uterus. Fertilization, if it occurs, takes place within the tube.

3. Uterus. The uterus is a pear-shaped organ, roughly 7.5 cm long and 5 cm wide, located behind the Urinary Bladder. If fertilization occurs, the embryo implants in the uterine wall and develops there until birth. During Pregnancy, the uterus expands dramatically. The outer muscular layer of the uterine wall, the myometrium, consists of smooth muscle that undergoes powerful contractions during childbirth. The inner layer, the endometrium, contains numerous glands and blood vessels.

4. Cervix. This is a narrow canal leading from the vagina into the uterus. The uterine entrance is normally blocked by a mucous plug.

5. Vagina. This is a muscular tube, 8–10 cm in length, whose walls contain elastic tissue. It stretches during childbirth to allow the passage of the baby, as well as during sexual intercourse to accommodate the Penis. The Clitoris is a small Structure homologous to the male penis and capable of erection.