The female reproductive system is one of the most important parts of the body for continuing offspring. For pregnancy to occur, a woman needs a mature egg so it is ready to be fertilized. However, did you know that the process of forming egg cells does not happen instantly? This process is known as oogenesis. Oogenesis is a complex process involving various stages to produce egg cells that are ready for fertilization. 

In this article, you will find out in depth what oogenesis is, how this process takes place, as well as the important stages you need to know. Come on, read the full explanation below!

What is Oogenesis?

Oogenesis is the process of formation and maturation of egg cells (ovum) in women which takes place in the ovaries (ovaries). This process starts when the baby girl is still in the womb, to be precise at the age of 8-20 weeks. At this stage, the embryonic ovary has approximately 600 thousand oogonium cells. Oogonium, or egg mother cells, reproduce through mitosis until the number reaches more than 7 million primary oocytes.

Primary oocytes are immature egg cells that will later develop and mature in the outer layer of the ovary. However, the number of primary oocytes will continue to decrease over time until the fetus is born. Of the more than 7 million primary oocytes, only about 1–2 million remain when the baby girl is born. These egg cells will then stop developing temporarily until they enter puberty.

At puberty, the oogonium or egg mother cells become active again following the menstrual cycle. Of the approximately 2 million primary oocytes that exist, only about 400 are able to survive and develop into mature follicles. A mature follicle is a small sac with cell walls that contains a single egg cell inside. This egg cell will be released during the fertile or reproductive period.

This oogenesis process is very important in the female reproductive cycle, because only mature egg cells can be fertilized by sperm to produce pregnancy. Thus, understanding oogenesis not only provides insight into basic biology, but is also important in the context of reproductive health and fertility.

Tahapan Oogenesis

Oogenesis is a complex and important process in the female body that produces mature egg cells ready to be fertilized. These mature egg cells play a crucial role in embryo development. The following are the stages in the oogenesis process:

1. Division and Doubling Phase

The oogenesis process begins with important stages involving cell division through mitosis and meiosis. Mitosis is the process in which one parent cell divides into two genetically identical daughter cells. In contrast, meiosis is cell division that produces four daughter cells, each with half the number of chromosomes of the parent cell. 

This process begins with the oogonium, the egg's mother cell, which undergoes mitosis to form the primary oocyte. This primary oocyte then undergoes the first meiotic division, which produces two cells: a secondary oocyte and a smaller polar body. This secondary oocyte will enter the second stage of meiosis, but this process will only be completed if fertilization occurs.

Division and maturation of primary oocytes into secondary oocytes usually begins at puberty, which generally occurs around the age of 12 years. At this stage, the woman's body begins to produce hormones that stimulate the oogenesis process, thus allowing the menstrual cycle to occur and readiness for fertilization.

Thus, oogenesis is a complex and ordered process, which ensures that the resulting egg cells are ready for fertilization and embryo development. This process is not only important for reproduction, but also shows the beauty and complexity of biological mechanisms in the human body. 

2. Development Phase

In contrast to the spermatogenesis process, the oogenesis process is characterized by the division of the first egg cell which experiences uneven cytoplasm distribution. This causes the formation of one oocyte (immature egg cell) with an abundant amount of cytoplasm, while the other oocyte has almost no cytoplasm. This imbalance plays an important role in preparing the dominant oocyte to develop further into a mature egg cell, which is ready for the fertilization process.

In this context, oocytes that receive more cytoplasm have an advantage in terms of nutrition and cellular organelles, allowing them to support early embryonic development in the event of fertilization. In contrast, oocytes that lack cytoplasm usually degenerate and do not play a further role in the reproductive process.

This uneven distribution of cytoplasm is not a coincidence, but rather a biological mechanism designed to ensure that only the best oocytes can develop into mature egg cells. This process also reflects nature's efficiency and selectivity in preparing the most optimal egg cells for reproductive success.

Thus, the developmental phases in oogenesis exhibit different complexities and uniqueness from spermatogenesis, emphasizing the importance of cytoplasmic distribution in determining the quality and developmental potential of the oocyte.

3. Maturation Phase

After passing through the growth phase, oogenesis enters the maturation phase where the primary oocyte undergoes the first meiotic division. In this phase, the larger primary oocyte will form a secondary oocyte and the first polar body. This division is asymmetrical, so the secondary oocyte has more cytoplasm than the first polar body.

The secondary oocyte then undergoes a second egg cell division which produces the ootid. This process also produces two second polar bodies from the fission of the first polar body. At this stage, ovulation or cell maturity occurs when the secondary oocyte has reached the stage of development into an ootid. The ootid is the final stage of oocyte development before it becomes an egg cell that is ready to be fertilized.

During a woman's lifetime, it is estimated that she can produce about 400 mature eggs. This is a very small number compared to the number of oocytes present at birth, which reaches millions. However, only eggs that are mature and ovulated have the potential to be fertilized.

After fertilization by sperm, the ootid will go through the final stage of maturation and turn into an egg cell which is ready to develop into a zygote. This process involves combining genetic material from sperm and egg cells, which then initiates cell division to form an embryo.

The fertilized ootid will develop into a mature egg cell only if it encounters sperm that successfully penetrates the egg cell membrane. This is a crucial step in reproduction, determining the success of fertilization and embryo development. Ultimately, this process is the basis for the formation of new life, starting from oogenesis until reaching the stage of fertilization and embryonic development.

What if the Egg Doesn't Develop?

Meanwhile, undeveloped egg cells will shed from the uterine wall to become menstrual blood. Naturally, the oogenesis process can change, depending on factors in the body that influence the menstrual cycle. The oogenesis process occurs due to the contribution and influence of follicle stimulating hormone (FSH hormone) and luteinizing hormone. The FSH hormone is able to stimulate the follicles in the ovaries before the release of egg cells during the oogenesis process.

Undeveloped egg cells are a common phenomenon in a woman's menstrual cycle. With each menstrual cycle, several follicles in the ovaries will begin to develop, but only one usually reaches full maturity and is ready for ovulation. Follicles that do not reach this stage will experience atresia, which means they will shrink and eventually be reabsorbed by the body. This process is part of the body's natural mechanism to ensure that only the healthiest and most ready eggs are released during ovulation.

Factors such as stress, diet, physical activity, and overall health condition can affect the menstrual cycle and, in turn, egg development. Hormonal imbalances can also cause disturbances in the oogenesis process, which can result in egg cells not developing. For example, FSH hormone levels that are too low can inhibit follicle development, while inadequate luteinizing hormone levels can interfere with the ovulation process.

Monitoring and managing hormonal health is an important step in ensuring a healthy menstrual cycle and optimal reproductive function. For women who experience problems with the menstrual cycle or fertility, consultation with an obstetrician and gynecologist can provide insight and the right solution. Hormonal examination and ovarian ultrasound can help identify the cause of eggs not developing and determine the necessary treatment steps.

Watch the video "Understanding the Concept of Oogenesis”

Hormones that Influence the Oogenesis Process

The oogenesis process occurs due to the presence of influencing hormones, namely Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). Follicle Stimulating Hormone (FSH) plays a role in stimulating the growth of follicles in the ovaries before egg cells are released for the oogenesis process. Apart from the FSH hormone, there is the LH hormone which is useful for triggering ovulation.

Hormones that influence the oogenesis process are not only limited to FSH and LH. Gonadotropin-Releasing Hormone (GnRH) produced by the hypothalamus also has an important role in regulating the release of FSH and LH from the pituitary gland. GnRH is released in a specific pulse pattern, which in turn regulates the menstrual cycle and ensures that oogenesis occurs properly.

In addition, the hormones Estrogen and Progesterone produced by the ovaries also play a role in preparing the endometrium for possible implantation of a fertilized egg. Estrogen helps in endometrial proliferation, while Progesterone helps in thickening and maintaining the endometrial lining.

Overall, the complex coordination between the various hormones that influence the oogenesis process ensures that the female reproductive cycle runs smoothly. An in-depth understanding of the interactions of these hormones is critical to the fields of reproductive medicine and women's health.

How to Maintain Egg Cell Quality

After understanding the process of oogenesis or egg cell formation, it is important to know how to maintain the quality of egg cells. This is essential to increase the chances of pregnancy. Here are several ways to maintain the quality of egg cells.

• Avoid Excessive Stress-Inducing Activities

Stress can affect the quality of egg cells. Hormones such as cortisol and prolactin produced during stress can interfere with or stop ovulation, thereby inhibiting egg production. To deal with stress, you can do activities such as yoga, meditation, exercise, or bathe in warm water.

• Consume Nutritional food

Eating healthy foods can improve overall health, including egg quality and fertility. Increase your consumption of vegetables, whole grains and fruit. Avoid foods that contain trans fats, processed meats and excessive sugar.

• Take care Healthy lifestyles

To improve the quality of egg cells, change your lifestyle to be healthier. Do regular exercise, get enough rest, stop smoking, and reduce excessive alcohol consumption.

• Maintain Ideal Body Weight

Having an ideal body weight is important for every woman. Being overweight can influence fertility and reduce the quality of egg cells. Apart from that, being overweight can also disrupt hormonal balance and ovulation.

• Consume Supplements

If needed, you can consume supplements such as folic acid, antioxidant vitamins A and E to improve the quality of egg cells. Make sure you maintain a healthy lifestyle and consume nutritious food to improve the quality of egg cells.

By understanding oogenesis, it is important to adopt a healthy lifestyle to maintain the health of the body and reproductive organs. A balanced diet, regular exercise and avoiding stress are simple steps that can support the oogenesis process and improve overall well-being.

References:

https://www.klikdokter.com/info-sehat/reproduksi/proses-oogenesis

https://hellosehat.com/wanita/proses-oogenesis/

https://www.halodoc.com/artikel/wajib-tahu-ini-perbedaan-spermatogenesis-dan-oogenesis

https://bocahindonesia.com/oogenesis-pembentukan-sel-telur/#Hormon_yang_memengaruhi_proses_oogenesis