Ovarian Follicular Development

The ovary has mainly two functions. firstly, the ovary produces hormones that drive the female reproductive system. the second one is it controls the development and the selection of mature oocytes for fertilization. This process known as ovarian folliculogenesis begins while the female is in-utero. and in simple language One of the pair of female glands in which the eggs form and the female hormones estrogen and progesterone are made. these hormones play an important role in female traits, such as breast development, body shape, and body hair.  

• The Role of the ovary- The role of ovary, ovaries are in small size, oval-shaped glands locate on either side of your uterus. They produce and store your eggs (also called an ovum) and make the hormones that control your menstrual cycle and pregnancy. during ovulation time, one of your releases an egg. if sperm are also fertilized then the egg can become pregnant.
• Importance of the ovary – Your ovary plays the main role in menstruation and Conception. They produce eggs for fertilization and they will make the hormones estrogen and progesterone. . An ovary releases an egg around the middle of your menstrual cycle (around day 14 of a 28-day cycle) in a process called ovulation.

Ovarian Follicular Development

Ovarian follicular development beings start when the female fetus is in her uterus. during the fifth stage of the pregnancy, a female fetus’s ovary contains about 500 to 1300 primordial germs cells. The primordial germ cell undergoes mitosis, and in the twentieth week of pregnancy, the female fetus has approximately 6 to 7 million germ cells. once the mitosis cell is complete, the germ cells are in the meiosis stage and arrest in the meiotic prophase1, forming germ cell cysts.

Stages of Follicle Development in the ovary

Follicular development is divided into three stages

• Activation of primordial follicles
• The primary to secondary follicle transition 
• The development of secondary follicles to the pericentral stage.

Primordial Follicle Formation

In humans, the primordial follicles are formed in the fetal ovaries between the sixth and ninth months of gestation. At this time, it is believed that all viable female germ cells have committed to meiosis. As a result, by the end of gestation, there is no further production of new oocytes.

How is a primordial follicle formed-The formation of primordial follicles occurs when germ cell nests break apart and individual oocytes become surrounded by pregranulosa cells.

Primary Follicle Development

When the primordial follicle is stimulated, it becomes a primary follicle. The oocyte enlarges, and the follicular cells divide. A follicle that has two layers of follicular cells is called a primary follicle. These cells continue to hypertrophy and proliferate to form many layers surrounding the oocyte. There are some hormones that develop the primary follicle development GnRHstimulates (causes) the pituitary gland to produce follicle-stimulating hormones (FSH) the hormone responsible for the starting follicle (egg) development and causing the level of estrogen (the primary female hormone) to rise. 

Pre-antral Follicle 

Pre-antral follicles are those follicles that are primordial, primary, or secondary, whereas antral follicles are either tertiary or ovulatory also called graafian follicles. Primordial follicles can be defined as nongrowing, with all other types being committed to growth, differentiation, and ovulation or to atresia.

Pre-antral follicle development- Pre-antral follicular development can be divided into three stages: activation of primordial follicles, the primary to secondary follicle transition, and the development of secondary follicles to the preantral stage.

Antral follicle development

Antral follicles begin producing increasing levels of progestins, estrogens, and androgens. The mural granulosa cells and the adjacent theca cells surrounding. antral follicles are formed when the formation of the antrum also requires the movement of granulosa cells relative to each other to allow the fluid to accumulate. this presumably involves the remodeling of cell-cell junctions and species with small follicles may involve the death of centrally located granulosa cells.

Folliculogenesis

folliculogenesis is the process in which a recruited primordial follicle grows and develops into the grows and develops griffin follicle with the potential the ovulate its egg into the oviduct at mid-cycle to be fertilized or to die by atresia.

In women, this process long takes approximately 1 year for primordial follicle growth and development to the ovulatory stage. Folliculogenesis, growth is achieved by the cell proliferation and formation of follicular fluid, Only a few follicles in the human ovary survive and complete the cytodifferentiation process, with 99.9% dying by a programmed cell death mechanism called apoptosis.

Growth Factor Control of Folliculogenesis 

Early folliculogenesis involves the breakdown of germ cell nests into primordial follicles and the subsequent transition of follicles to the primary and secondary stages. Different transforming growth factor beta (TGF-β) superfamily ligands regulate each of these developmental processes. Which hormone is primarily responsible for folliculogenesis? Follicular-stimulating hormone (FSH) and Luteinizing hormone (LH) are two major gonadotropins that promote follicle development and oocyte maturation (Williams & Erickson, 2000).

Alteration in Ovulation 

Luteinizing hormone stimulates egg release (ovulation), which usually occurs 32 to 36 hours after the surge begins. The estrogen level peaks during the surge, and the progesterone level starts to increase. During the luteal phase, luteinizing hormone and follicle-stimulating hormone levels decrease.

Alteration in the Steroid Hormones 

Steroid hormones act on the cells by passing through the cell membrane, when entering the nucleus and binding to the DNA, and gene transcription and protein production. Steroid hormones are classified into two categories that are estrogens, progestogens, glucocorticoids, and mineralocorticoids. Steroid hormones are produced by the maturing follicle. As the follicles in the ovary grow, they produce increasing amounts of oestradiol and inhibin. In turn, these hormones act on the hypothalamus and pituitary gland to reduce the release of the gonadotrophin-releasing hormone and follicle-stimulating hormone. 

Clinical Aspects

• How many Ovarian Follicles are normal?

In normal cases there are between 8 and 15 ovarian follicles is an acceptable amount of follicles. during the egg retrieval, every follicle will not appear necessarily contain a quality egg. your doctor will aspirate the follicles with an ultrasound-guided needle.

• Is an Ovarian Follicle the same as of Cyst?

Your ovarian cyst normally grows cyst-like a structure called a follicle each month. Follicles produce the main hormones called estrogen and progesterone. they have released in an egg when you ovulate  If a normal monthly follicle keeps growing, it’s known as a functional cyst.

• Can an Ovarian follicle cause Pain?

Most follicular cysts don’t cause any symptoms. some times the follicular cyst becomes large or ruptures, and sometimes you feel pain in your lower abdomen. because of the pressure and bloating in your lower abdomen.

Roles of Hormones

Under the stimulus of pituitary LH, the theca cells produce androgens that reach the granulosa cells, and in these, under the control of pituitary FSH, that can activate aromatase, they are aromatized to estrogens (mainly estradiol). These estrogens are released into the systemic circulation and follicular fluid.  

The pituitary gland produces follicle-stimulating hormone (FSH), the hormone responsible for starting follicle (egg) development and causing the level of estrogen (the primary female hormone) to rise.

FAQs on Ovarian Follicle

Question 1: What are the stages of folliculogenesis?

Answer:

Folliculogenesis is divided into three stages; Follicle recruitment selection and ovulation and there are two phases; the initial gonadotropin-independent phase and the later gonadotrophin-dependent phase. 

Question 2: What are the 2 main roles of the female ovaries? 

Answer:

There are the main roles of the ovary in females, the ovaries are the main reproductive function in the body. they produce oocytes which are called eggs, for fertilization and they produce the reproductive hormones which are estrogen, and progesterone, which helpful in reproduction. 

Question 3: What roles are play ovaries after menopause?

Answer:

The hormones level decrease after menopause, your ovaries continue producing testosterone for up to 20 years. testosterone is a hormone that plays an important part in stimulating sexual desire and sexual pleasure.

Question 4: How do you fix ovulation problems?

Answer:

Fertility drugs are the main treatment for women who are infertile due to ovulation disorders. Fertility drugs generally work like natural hormones — follicle-stimulating hormone (FSH) and luteinizing hormone (LH) — to trigger ovulation.

Question 5: What are the 5 steroid hormones?

Answer:

There are five major classes of steroid hormones: testosterone (androgen), estradiol (estrogen), progesterone (progestin), cortisol/corticosterone (glucocorticoid), and aldosterone (mineralocorticoids).

Question 6: How long does folliculogenesis last?

Answer:

Folliculogenesis lasts for approximately 375 days. It coincides with thirteen menstrual cycles. The process begins continuously, meaning that at any time the ovary contains follicles in all stages of development, and ends when a mature oocyte departs from the preovulatory follicle in a process called ovulation.