Female Reproductive System: Anatomy and Function
Female Reproductive System
Ovarian Development and Function
The female reproductive system begins to form and function in utero at 20 days of gestation. Its activity is cyclical and lasts for many years.
Ovaries
The ovaries are almond-shaped organs that are initially pink but eventually shrivel and darken. Inside, there are many primary follicles, which, after a process, become Graafian follicles.
Fallopian Tubes
The fallopian tubes are two canals that connect to the uterus. They are broader at the ovarian end and narrower at the uterine end. The tubes have cilia (short hairs) inside that aid in the movement of the egg or zygote.
Fertilization occurs in the upper third of the tube if an egg is fertile. If a zygote forms, it travels through the fallopian tube, taking about five days to reach the uterus for implantation and embryonic development.
Uterus
The uterus is a highly muscular, pear-shaped organ where the embryo develops. It sits in front of the rectum and behind the bladder. It has three layers:
- Endometrium: The inner layer that nourishes the embryo in the first days of gestation or is shed during menstruation.
- Myometrium: The middle, muscular layer.
- Perimetrium: The outer layer.
Cervix
The cervix is the lower part of the uterus. Samples are taken from this area to determine if there are fibroids in the uterus; this is called a Pap test and is essentially mandatory.
The Graafian Follicle
The Graafian follicle is a structure that matures on average every 28 days. It contains fluid and an egg and ruptures in the middle of the menstrual cycle. The follicle progresses through these stages: primary follicle, secondary follicle, tertiary follicle, and finally, the Graafian follicle.
Menstrual Cycle Hormones
The menstrual cycle is regulated by hormones, primarily LH (luteinizing hormone) and FSH (follicle-stimulating hormone).
External Genitalia
The external genitalia of women include:
- Mons Pubis: A soft tissue (mainly adipose tissue) located in front of the pubic symphysis, forming a small hill. Pubic hair appears on the skin covering this area during puberty.
- Labia: Folds of skin around the external opening of the vagina. The labia majora are pigmented and have hair, while the labia minora are located inside the majora.
- Interlabial Space: The ovoid space bounded by the labia. It contains the vestibule, urinary meatus (exit hole of the urethra), and the external orifice of the vagina (introitus).
- Clitoris: A small erectile body situated in front of the labia, involved in female sexual stimulation.
Internal Genitalia
Ovaries
There are two ovaries located within the pelvic cavity in front of the rectum. In cross-section, two areas are distinguishable:
- Medulla: The central, reddish area, consisting of a large number of blood vessels and fibrous tissue.
- Cortex: The peripheral zone containing oocytes within primordial follicles.
Oviducts or Fallopian Tubes
There are two oviducts or fallopian tubes, each closely related to one of the ovaries. Structurally, each is a muscular tube about 10 cm long, whose mucosa presents a series of longitudinal folds that aid in the progression of oocyte II.
Uterus
The uterus is a hollow, thick-walled, pear-shaped muscular organ, measuring 6-7 cm long and 4 cm wide. It is located in the pelvis behind the bladder, in front of the rectum, and above the vagina. Histologically, it has three layers:
- Perimetrium: The outer layer, also independent of the peritoneum, covers only up to the cervix.
- Myometrium: The middle layer, the thickest, composed of smooth muscle. It contains most of the vessels supplying the uterus and contracts during childbirth, allowing the expulsion of the fetus.
- Endometrium: The inner layer, also called the uterine lining. It is a highly specialized tissue that undergoes cyclic changes and is partly shed during menstruation. It serves as a receptacle for the product of conception and houses the fetus until birth. Therefore, it is the organ of gestation.