The female reproductive system consists of the following structures, as shown in Figure 1:
- The tunica albuginea is a fibrous layer inside the germinal epithelium.
=The inside of the ovary, or stroma, is divided into two indistinct regions, the outer cortex and the inner medulla. Embedded in the cortex are saclike bodies called ovarian follicles. Each ovarian follicle consists of an immature oocyte (egg) surrounded by one or more layers of cells that nourish the oocyte as it matures. The surrounding cells are called follicular cells, if they make up a single layer, or granulosa cells, if more than one layer is present.
- The uterine tubes (oviducts) transport the secondary oocytes away from the ovary and toward the uterus (the ovaries consist of primary oocytes, which develop into secondary oocytes). The following regions characterize each of the two uterine tubes (one for each ovary):
- The infundibulum is a funnel‐shaped region of the uterine tube that bears fingerlike projections called fimbriae. Pulsating cilia on the fimbriae draw the secondary oocyte into the uterine tube.
- The ampulla is the widest and longest region of the uterine tube. Fertilization of the oocyte by a sperm usually occurs here.
- The isthmus is a narrow region of the uterine tube whose terminus enters the uterus.
The wall of the uterine tube consists of the following three layers:
- The serosa, a serous membrane, lines the outside of the uterine tube.
- The middle muscularis consists of two layers of smooth muscle that generate peristaltic contractions that help propel the oocyte forward.
- The inner mucosa consists of ciliated columnar epithelial cells that help propel the oocyte forward, and secretory cells that lubricate the tube and nourish the oocyte.
- The uterus (womb) is a hollow organ within which fetal development occurs. The uterus is characterized by the following regions:
- The fundus is the upper region where the uterine ducts join the uterus.
- The body is the major, central portion of the uterus.
- The isthmus is the lower, narrow portion of the uterus.
- The cervix is a narrow region at the bottom of the uterus that leads to the vagina. The inside of the cervix, or cervical canal, opens to the uterus above through the internal os and to the vagina below through the external os. Cervical mucus secreted by the mucosa layer of the cervical canal serves to protect against bacteria entering the uterus from the vagina. If an oocyte is available for fertilization, the mucus becomes thin and slightly alkaline. These are attributes that promote the passage of sperm. At other times, the mucus is viscous and impedes the passage of sperm.
The uterus is held in place by the following ligaments:
- Cardinal (lateral cervical) ligaments
The wall of the uterus consists of the following three layers:
- The perimetrium is a serous membrane that lines the outside of the uterus.
- The myometrium consists of several layers of smooth muscle and imparts the bulk of the uterine wall. Contractions of these muscles during childbirth help force the fetus out of the uterus.
- The endometrium is the highly vascularized mucosa that lines the inside of the uterus. If an oocyte has been fertilized by a sperm, the zygote (the fertilized egg) implants on this tissue. The endometrium itself consists of two layers. The stratum functionalis (functional layer) is the innermost layer (facing the uterine lumen) and is shed during menstruation. The outermost stratum basalis (basal layer) is permanent and generates each new stratum functionalis.
- The vagina (birth canal) serves both as the passageway for a newborn infant and as a depository for semen during sexual intercourse. The upper region of the vagina surrounds the protruding cervix, creating a recess called the fornix. The lower region of the vagina opens to the outside at the vaginal orifice. A thin membrane called the hymen may cover the orifice. The vaginal wall consists of the following layers:
- The vulvae (pudendum) make up the external genitalia. The following structures are included:
- The mons pubis is a region of adipose tissue above the vagina that is covered with hair.
- The labia majora are two folds of adipose tissue that border each side of the vagina. Hair and sebaceous and sudoriferous glands are present. Developmentally, the labia majora are analogous to the male scrotum.
- The labia minora are smaller folds of skin that lie inside the labia majora.
- The vestibule is the recess formed by the labia minora. It encloses the vaginal orifice, the urethral opening, and ducts from the greater vestibular glands whose mucus secretions lubricate the vestibule.
- The clitoris is a small mass of erectile and nervous tissue located above the vestibule. Extensions of the labia minora join to form the prepuce of the clitoris, a fold of skin covering the clitoris.
Figure 1. View of the female reproductive system.