Ovary Structure And Stage Of Differentiation

Over the course of a female fetus's whole life, the ovaries are an essential organ.

Structure Of The Ovary

 The germinal epithelium is another name for the surface cuboidal epithelium. Follicles in the outer cortex are developing. Tunica albuginea is the name for the cortex's outermost layer.

The vascularity of the ovaries is located in the inner medulla. The Hilum is the region where arteries and nerves enter the ovaries.The connection point between the ovaries and the mesovarium is called the hilum. There are also hilus cells in it.

Hilus cells bear resemblance to the testicular Leydig cells. They possess the ability or propensity to generate steroids. For example, tumors that produce testosterone are called Hilus cell tumors.

Also Read: Mechanism Of Sex Steroid Hormones 

Fetal Ovary 

The fetal ovary's development:
1. Indifferent Gonad Stage: This stage is experienced by all fetuses, male or female.
2. Stage of Differentiation: The testes in the male fetus and the ovaries in the female fetus will begin to develop.
3. Stage of Oogonial Multiplication and Oocyte Production: The oocyte formation stage is unique to the female foetus.
4. Follicle Creation Stage

Also Read: Neuroendocrinology Of Female Reproduction And Steroid Hormones

Indifferent Gonad Stage

Gonadal ridge in the posterior body wall is where gonads develop. This stage lasts 7–10 days and happens during week 5 of gestation. Primordial germ cells are ectodermal in origin and descended from epiblast cells. At the conclusion of the third week of fertilization, they are found in the area where the early embryo's developing yolk sac is located. After that, they move to the gonadal ridge.The time of this migration is between four and six weeks of gestation. As the cells migrate, they have also begun to proliferate.

10,000 primordial germ cells and a small number of somatic cells (derived from coelomic epithelium, mesenchyme, and mesonephric tissue) are found in the gonadal ridge at the end of the migration. The migration is crucial; without it, the gonads won't develop normally, which will result in gonadal dysgenesis.

Also Read: Puerperium: Understanding the Postpartum Period

Stage Of Differentiation

In a male fetus, there will be 46xy primordial germ cells. The SRY gene is present. Other somatic genes, such as FGF-9 and SOX-9, are upregulated. As a result, the gonads mature into the testes. The indifferent gonad develops into a male embryo at this point in gestation, which is 6–9 weeks.

Primordial germ cells in a female fetus are 46xx. SRY is not a gene. Upregulated somatic genes include wnt-4 and RSPO-1. It was believed that gonads would develop into ovaries if the SRY gene was absent, making ovarian development a passive process. That is untrue, though. It is significant that other somatic genes are upregulated. The somatic genes (FGF-9 and SOX-9) necessary for the development of the testes are not upregulated as much as they should be, and the opposite is also true. The ovaries develop from indifferent gonads. This occurs between weeks 8 and 10 of pregnancy.

The internal female genitalia are produced by the paramesonephric duct.  The mesonephros and the gonadal ridge are medial. The main oocytes are located inside and are encircled by follicular cells. Follicle cells enclose the main oocyte as part of the process of oocyte development and differentiation. The ovary's cuboidal epithelium is derived from coelomic epithelium.

Also Read: Comprehensive Insights on Covid in Pregnancy

Oogonial Multiplication And Oocyte Formation

Oogonia are first recognized in the ninth week of life. Primordial germ cells began the process of multiplication during migration and divided by mitosis, giving rise to numerous oogonia. At about 11–12 weeks, they start the first meiosis division. But the multiplication is not finished.

During the first meiotic division, during the diplotene stage, the primary oocyte that is produced is arrested. The granulosa cells around the oocyte produce a variety of inhibitory substances that trigger this arrest.  All of this occurs during the course of the pregnancy and is finished at birth.

The first and second stages involve the deployment of oogonia and primary oocytes. The primary oocyte is halted in prophase during the third stage. The female fetus experiences this development during its intrauterine life. Throughout the reproductive lifespan, the primary oocyte will mature more. One meiosis finishes right before ovulation.

The first polar body is discharged and the primary oocyte develops into the secondary oocyte. After that, the metaphase of the secondary oocyte is stopped, and it is eventually finished when the sperm enters the egg. At the moment of fertilization, the second meiotic division is finished.

The release of the second polar body and the formation of a mature oocyte are the following stages. The entire process of meiosis is finished within a woman's reproductive lifetime.

Also Read: From HPO Axis To Ovulation

Hope you found this blog helpful for your Basic Sciences OBS-GYN preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.