The female reproductive system is made up of several organs, including the ovary. Each female human being has two ovaries that have an oval shape, are approximately four centimeters, and are located on either side of the womb against the pelvis wall in a region referred to as the ovarian fossa. Ligaments linked to the womb hold them in place, ensuring that the ovaries are not directly linked to the other organs of the female reproductive tract. 1 The main functions of the ovary include the production of oocytes for fertilization and the production of oestrogen and progesterone, the female reproductive hormones. It is highly organized and made up of germ cells and somatic cells. 2 The germ cells include oocytes referred to as the eggs, while the somatic cells are the thecal cells, stromal cells, and granulosa cells. The ovary is made up of three major histological features. The surface comprises a simple cuboidal epithelium covering the dense connective tissue capsule. 3 A connective tissue stroma forms the cortex with several ovarian follicles, containing oocytes surrounded by follicular cells. The medulla is a loose connective tissue with a comprehensive neurovascular network that goes through the hilum of the ovary.
How the Ovary Works
The interactions between the cells control the formation of oocyte-containing follicles and the corpus luteum. The corpus luteum is the endocrine structure that is created during ovulation and is critical in maintaining a pregnancy. 4 The ovaries work under the regulation of gonadotrophin-releasing hormone released by the nerve cells in the hypothalamus. The GnRH transfers information to the anterior pituitary gland to stimulate the production of luteinizing hormone and follicle-stimulating hormone. The hormones are transported to the bloodstream to regulate the menstrual cycle. Low-frequency gonadotrophin-releasing hormone (GnRH) pulses cause a slight increase in the follicle-stimulating hormone levels at the beginning of the menstrual cycle, stimulating follicle growth. 5 On the other hand, high-frequency GnRH pulses stimulate a luteinizing hormone surge just before midcycle. The ovary ensures that the fertilizable oocytes are released on time and that the luteal cell function is well maintained in pregnancy.
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The ovaries release the oocytes during mid-cycle. Only one ovary releases an oocyte in every menstrual cycle, with the ovaries taking alternate turns in releasing them. Girls have all the eggs they will ever have in their life from when they are born. Approximately two million eggs are stored in the ovary of a female when they are born, but reduce such that only about 400,000 eggs are present in the ovaries by the time they are adolescents. 6 Only about 400 to 500 eggs reach maturity age and are released from the ovary monthly during ovulation and subsequently be fertilized in the fallopian tube of the female reproductive system. 7 The oocytes are usually held in a single layer of cells referred to as the follicle, whose primary function is to support the egg. Over time the eggs begin the maturity stage that ensures that an egg is released in every menstrual cycle.
Maturation of the oocytes leads to a division of cells in the follicle, enlarging the follicle. The majority of the follicles lose their functioning ability during maturation which sometimes takes more than one month. Still, one of them dominates each menstrual cycle and releases an egg at ovulation. The hormone oestrogen is produced during the development of follicles. After ovulation, the empty follicle left releases progesterone in more significant amounts and progesterone in smaller quantities. These hormones are helpful in lining the uterus in anticipation of fertilization taking place. Failure of the released egg to get fertilized during a menstrual cycle, the corpus luteum breaks down, subsequently halting the secretion of oestrogen and progesterone. 8 Lack of fertilization and the absence of hormones make the womb’s lining start falling away and gets out of the body through menstruation. After menstruation, another cycle begins.
After some years, a woman undergoes menopause. Menopause is the ending of a female’s reproductive years, after which they do not experience a menstrual flow since oestrogen and progesterone are no longer produced. 9 Menopause is stimulated by the depletion of all the follicles in the body that contain oocytes. Most women experience menopause at around the age of 50.
Clinical Disorders Related to the Ovary
Disruption of the finely organized network of the ovary can lead to several clinical syndromes such as premature ovarian failure, polycystic ovarian syndrome, amenorrhea, ovulation defects, poor oocyte quality, and cancer. 10 The medical conditions have a high probability of reducing a woman’s fertility as fertility is dependent on the highly complex endocrine events that involve multiple organs, including the ovary.
Premature ovarian failure or premature ovarian insufficiency is menopause for women below the age of forty, while polycystic ovarian syndrome (PCOS) is characterized by hormonal dysfunction and numerous ovarian cysts. PCOS is the most prevalent ovarian disorder, and it affects 5 to 10 percent of reproductive-age females. 11 A polycystic ovary causes the follicles to mature to a certain age, after which the growth stops making it impossible to release an egg.
Ovarian cancer arises from germ cells or epithelial components. Over 90% of ovarian tumors are caused by epithelium and are known as ovarian adenocarcinomas. 12 Most germ cell cancers are known as teratomas made up of cells from all three germ cell layers and are usually benign.
Amenorrhea is when a woman ceases to receive her menstrual periods during her reproductive years. It can be caused by hypothalamic amenorrhea, which may be caused by having a lean build, psychological stress, or abnormal levels of regular exercise. 13 Fertility can be restored by reducing the rate of training, weight gain, and psychological interventions such as therapy.
In conclusion, the ovary is a critical organ in the reproductive system whose disruption affects the fertility of women and the normal functioning of the body due to the sensitivity of the hormones they produce.
Bibliography
“ Ovaries | You and Your Hormones from The Society for Endocrinology”. 2018. Yourhormones.Info . https://www.yourhormones.info/glands/ovaries/.
Richards, Joanne S., and Stephanie A. Pangas. 2010. “The Ovary: Basic Biology and Clinical Implications”. Journal of Clinical Investigation 120 (4): 963-972. doi:10.1172/jci41350.
Thompson, Louisa. 2020. “The Ovaries”. https://teachmeanatomy.info/pelvis/female-reproductive-tract/ovaries/.
1 1. “Ovaries | You and Your Hormones from The Society for Endocrinology”. 2018. Yourhormones.Info . https://www.yourhormones.info/glands/ovaries/.
2 2. Richards, Joanne S., and Stephanie A. Pangas. 2010. “The Ovary: Basic Biology and Clinical Implications”. Journal of Clinical Investigation 120 (4): 963-972. doi:10.1172/jci41350., 1.
3 3. Thompson, Louisa. 2020. “The Ovaries”. https://teachmeanatomy.info/pelvis/female-reproductive-tract/ovaries/.
4 4. “Ovaries | You and Your Hormones from The Society for Endocrinology”. 2018. Yourhormones.Info . https://www.yourhormones.info/glands/ovaries/.
5 5. Richards, Joanne S., and Stephanie A. Pangas. 2010. “The Ovary: Basic Biology and Clinical Implications”. Journal of Clinical Investigation 120 (4): 963-972. doi:10.1172/jci41350., 1.
6 6. “Ovaries | You and Your Hormones from The Society for Endocrinology”. 2018. Yourhormones.Info . https://www.yourhormones.info/glands/ovaries/.
7 7. Ibid.
8 8. Ibid.
9 9. Ibid.
10 10. Richards, Joanne S., and Stephanie A. Pangas. 2010. “The Ovary: Basic Biology and Clinical Implications”. Journal of Clinical Investigation 120 (4): 963-972. doi:10.1172/jci41350., 1.
11 11. Ibid., 1.
12 12. Ibid., 1.
13 13. “Ovaries | You and Your Hormones from The Society for Endocrinology”. 2018. Yourhormones.Info . https://www.yourhormones.info/glands/ovaries/.
