The female reproductive system is responsible for the continuation of species or the reproductive function. In females, it consists of the reproductive glands such as ovaries and cervix and the tubular structures such as the uterus, the fallopian tubes, and the vagina.
The female reproductive system works in tandem with several other body systems such as the nervous system and the endocrine system for its proper functioning. Multiple body systems and organs should work together in a precise and timely manner to produce a healthy offspring.
Though not critical for life, the health of the reproductive system also affects the health and outlook of a woman. Hence, it is important that we take a look at the functioning and organization of the human reproductive system.
Characteristics of Female Reproductive System
- A female is born with a specific number of oocytes or eggs. This number is predetermined when she herself is in the fetus stage.
- The number of eggs is arrested during the fetal stage. It means a female doesn’t produce new eggs unlike males, who continue to produce new sperms.
- All of the eggs are stored in the ovaries. Some of these eggs mature and are released by the ovaries during the regular menstrual cycle.
- The reproductive system is immature during childhood. It only matures and organs are functional when a child attains puberty.
- Oocytes age along with the woman. The ovaries of a newborn baby girl have nearly one million oocytes. By the time she reaches puberty, only 400,000 to 500,000 oocytes are remaining.
- On average, 500-1000 oocytes are ovulated during a woman’s fertile window.
Functions of a Female Reproductive System
- Releases eggs (ova) during the regular menstrual cycle
- Secretes sex hormones
- Receives the male sperms during coitus
- Protects and nourishes the fertilized egg until it is fully developed
- Delivers fetus through the birth canal
- Provides nourishment to the baby through milk secreted by mammary glands in the breast
- Protection against microbial invasion through the reproductive tract immune cells
Details of Female Reproductive Organs
The female reproductive system is located inside the pelvic cavity. It is categorized into internal organs and external organs. The internal organs include the ovaries, uterus, fallopian tubes, vagina, and uterine tubes. The external organs include the perineum and the vulva. In this specific article, our focus is on the internal organs of the female reproductive system.
The vagina is a muscular canal (approximately 10 cm long) that extends from the external vaginal opening to the cervix of the uterus. The muscular structure allows the vagina to expand and shrink during its normal functioning such as to deliver the baby or to stimulate the penis during sexual intercourse.
The muscular wall of the vagina is layered with mucus, which serves dual functioning of protecting and moistening the canal. The mucosal layer of the vagina is home to a normal population of microorganisms that protect against infections by pathogenic bacteria, yeast, or other organisms that can enter the body through the vaginal canal.
In a healthy woman, the most predominant type of vaginal bacteria is from the genus Lactobacillus. Lactic acid secreted from the bacterial microflora maintains an acidic environment inside the vaginal canal with a pH ranging towards 4. Such acidic conditions make it difficult for pathogens to survive should they enter the canal.
Health and Diseases of the Vagina
A healthy vagina is a self-cleansing organ as the beneficial microbial secretions along with the mucosal discharge prevent infections and undesirable substances. However, washing out the vagina with fluid can disrupt the normal balance of healthy microorganisms and increase the risk of infections.
While it is highly important to maintain personal hygiene, it is suggested that women should not wash out or douche the vaginal area with external fluids.
The vaginal canal is prone to infections, microbial invasions, and sexually transmitted diseases. These diseases can have both internal (hormonal) and external causes, which disrupt the vaginal microflora and result in inflammation and irritation of the vaginal canal.
The Two Ovaries
The ovaries are located inside the pelvic cavity, very close to the uterus. The two ovaries are suspended and supported on each side of the uterus by a broad ligament layer called mesovarium.
The growth and development of female gametes, oocytes, take place inside the ovaries. Each oocyte is surrounded by supporting cells and together they are termed as a follicle. When oocyte matures completely, a luteinizing hormone ( LH ) surge secreted by the pituitary gland stimulates follicle rupture and oocyte is released. This process is termed as Ovulation.
The ovaries are of the size and shape of almonds. The two ovaries take turns to release eggs every month. However, if one ovary is absent or dysfunctional then the functional ovary would release eggs every month.
The ovaries are also endocrine organs and produce hormones that act during the female menstrual cycle and pregnancy. Ovaries secrete estrogen, progesterone, and testosterone hormones with the following primary functions:
- Estrogen directs the development of secondary sex characteristics at puberty. It is also vital for the maturation, functioning, and maintenance of the female reproductive system.
- Progesterone prepares the uterus for pregnancy and the mammary glands for lactation. Progesterone along with Estrogen act on the endometrial layer of the uterus to bring menstrual cycle changes.
- Testosterone is important for the growth of the muscle tissues and to maintain a healthy muscle mass, bone strength, and energy levels in women. It also plays a role in guiding libido or sexual drive in women.
Health and Diseases of the Ovaries
The ovaries of a girl from the fetal stage until puberty are smooth and slightly pink in color, measuring about 3-4 cm long and 1.5 – 2 cm wide. Post-Menarche, the ovarian surface becomes rough and irregular with age as repeated ovulation cycles involve the growth of multiple sacs like follicles that release the mature eggs.
Ovaries are prone to develop benign fluid-filled or semi-solid sacs, called cysts during the menstrual cycle. This is fairly normal and the cysts usually faint away after a couple of days. In some cases, these sacs may keep growing, or turn into painful and malignant cysts, or ovarian tumors, or may lead to ovarian cancer.
Another condition is Polycystic ovarian syndrome PCOS, where multiple follicles form during the menstrual cycle. However, the ovary is unable to release the egg, resulting in several cysts that do not recede but only grow with time. Often ovarian health conditions pose symptoms such as abdominal cramps, anxiety, and irregular menstrual cycle.
The Fallopian Tubes
The fallopian tubes are also known as oviducts or the uterine tubes is the channel for the oocyte from the ovary to the uterus. The fallopian tubes are not directly connected to the ovary. However, the closest end of each of the tubes to the ovary has finger-like projections known as fimbria.
After ovulation, the fimbriae on either of the tubes help to move the released oocyte further into the uterine tube. The beating of the cilia (tiny hairs) that line the outside and lumen of the length of the uterine tube pushes oocyte towards the uterus.
If the oocyte is successfully fertilized, the resulting zygote will begin to divide into two cells, then four, and so on, as it makes its way through the uterine tube and into the uterus. There, it will implant and continue to grow. If the egg is not fertilized, it will simply degrade—either in the uterine tube or in the uterus, where it may be shed with the next menstrual period.
Health and Diseases of Fallopian Tube
The fallopian tubes are fairly narrow in structure and do not carry any specific protection system against the antigens. Any infection or inflammation can lead to obstruction, damage, and may eventually lead to infertility in women.
An ectopic or tubal pregnancy is declared if a fertilized egg is unable to move down to the uterus and ends up implanting itself in the fallopian tube. Such an unusual pregnancy need to be terminated as it poses a life threat to the mother through hemorrhage and damage to the fallopian tubes.
The uterus is a muscular pouch-like structure with a shape and size as that of an upside-down pear. Its average size is approximately 5 cm wide by 7 cm long (approximately 2 in by 3 in) when a female is not pregnant. It has the following functions:
- Receive and release the unfertilized egg during the regular menstrual cycle.
- Receive and nourish the fertilized egg or zygote through the uterine tubes. It implants the zygote into the endometrium and derives nourishment from the blood vessels that develop exclusively to support the growth of embryo during 9 months of pregnancy.
- Guide the sexual response by directing blood flow to the pelvis and to the external genitalia, including the ovaries, vagina, labia, and clitoris.
- Allow the passage of sperm from the vaginal canal to the fallopian tubes.
The uterus has three sections. The upper portion of the uterus above the opening of the fallopian tubes is called the fundus. The middle section or the main body of the uterus is called the corpus. The lowermost portion just above the cervix is called the isthmus or lower uterine segment. The uterine walls contain three distinct layers:
- The endometrium that lines the uterine cavity. The thickness and structure of the endometrium vary with hormonal stimulation during the menstrual cycle.
- Myometrium, the middle layer which is the thickest layer consisting of smooth muscle fibers. These fibers run into several directions and allow for uterine contractions during the regular menstrual cycle to discharge the wasted endometrial layer as menstrual blood and also during labor to help deliver the baby.
- Serosa, the outermost lining.
Health and Diseases of the Uterus
The uterus gets exposed to antigens via the vaginal canal. Should microbes reach the uterine region, they can lead to infections and inflammation. Additionally, hormonal changes and disturbances in the menstrual cycle also pose the danger of uterine fibroids, malignant or harmful tumors, and uterine lesions such as endometriosis.
The cervix is the lowermost and narrow tubular structure of the uterus. It connects the uterus with the vagina and also acts as a channel for the passage of reproductive system fluids and the baby.
During labor, the contractions of the uterus dilate the cervix up to 10 cm in diameter to allow the baby to pass through. During orgasm, the cervix convulses and the external os dilates.
The cervix contains small secretory glands that produce mucus, which is thick, sticky, and creamy most of the time. The mucosal secretions become clearer, wetter, thinner, and stringy, and also increase in quantity during the ovulation phase under the influence of estrogen hormone. This mucosal environment facilitates the passage and survival of sperm through the reproductive tract.
During pregnancy, the cervix becomes plugged with very thick mucus to protect the growing fetus from infection and any other external materials.
Health and Diseases of the Cervix
There is a structural difference in the alignment of epithelial cells between different portions of the cervix. The cervix lining that enters into the vaginal canal is called the ectocervix and it has a vertical alignment of the epithelial cells. The inner lining of the cervical canal is called the endocervix and it has a horizontal (stratified) alignment of the epithelial cells.
The region where the ectocervix and the endocervix meet is is the transformation zone. It is characterized by the transformation of epithelial cells from vertical to horizontal alignment. This transformation zone is the most frequent location for cervical dysplasia and malignant transformation such as cervical cancer.