The egg cell or Ovum (plural form: Ova) is the female productive cell, which differs in many aspects from the male productive cell, the Spermatozoon. These cells carry the burden of reproduction in anisogamous organisms (organisms that reproduce sexually) and are called gametes or sex cells. Gametes are haploid cells, which means that they only have one chromosome each, and during fertilization, they fuse to form another anisogamous organism. This type of production happens of gametes each, the male and female sex cells. The female body in these organisms produces a large and non-motile gamete (the egg cell), and the male organisms produce a smaller and motile gamete, the sperm.
The egg formation process is called Oogenesis. The number of eggs present in a female's body is all she will ever have, and their production begins even before her birth. The eggs are produced in the ovary long before a female's birth. During the second to fifth months of pregnancy, the egg-forming cells or oogonia undergo mitosis and increase dramatically to around seven million. Then they start decreasing in a process named atresia till birth, and at the time of birth, the female ovary contains approximately two million eggs. A primary oocyte is produced during mitosis, starting its first cell division and entering meiosis. Still, then the process is arrested, and it remains inactive inside a follicle (which is the cellular covering around the egg) until puberty. The arrest is maintained by a chemical messenger called Cyclic adenosine monophosphate (cAMP), produced by the oocyte and the surrounding follicle.
When puberty hits, the number of eggs decreases even more, going down about 40000, and only about 400 of them ovulate during the female's lifetime. Out of these 400 eggs, the remaining ones will persist on their primary arrest. The oocyte resumes its meiosis. The meiosis happens by certain hormonal stimulations. In every menstrual cycle, the pituitary gland produces FSH and LH hormones. The FSH hormone (Follicle Stimulating Hormone) stimulates the follicle to cause them to produce estrogen, and the LH hormone (Luteinising Hormone) makes them produce androgens. The follicle enlarges under these considerable hormonal influences, and the egg inside continues meiosis. During the meiosis, a secondary oocyte and a polar body form. This body does not play a known function and will break down the release.
During ovulation, the mature follicle bursts open and releases the secondary oocyte. The secondary oocyte goes through another process of meiosis, which again is arrested and only activated when fused and fertilized with a sperm. After the secondary oocyte is released, it travels through the fallopian tube. If it is fertilized by sperm while traveling through the fallopian tube, it will form another mature egg, but if not, it will pass through the uterus and soon be eliminated.
The egg structure:
the egg consists of three main parts:
1. The nucleus, bears the genetic data of the cell in the form of chromosomes.
2. Mitochondria and Cytoplasm of the cell, the mitochondria are the primary energy source for the cell, and the cytoplasm is where every component of the cell is.
3. Zona Pellucida, or the egg wall. It is the hard layer that surrounds the egg and helps the sperm enter it before fertilization.
4. Corona Radiata is another layer that surrounds the Zona Pellucida or the egg wall. It contains a few layers of the follicle, and its main task is to nurture the egg cell with essential proteins it needs to maintain.
In contrast to the egg formation process, the primary part of the spermatozoid production process does not begin until puberty. While an embryo is forming, the primordial germ cells migrate to the testes (the male reproductive organ). The germ cells are located in the seminiferous tubules, and as the result of mitotic divisions, they turn to spermatogonial stem cells. During puberty, the male sex hormone (testosterone) causes the original copies of the stem cells to duplicate. Half of these cells turn to produce haploid spermatids; these cells are not original and cannot move. They will turn to future mature sperms in about 72 days, while the other half remain stem cells to ensure a constant source to produce more sperm.
The spermatids continue to mature in the testicles and then move to the epididymis by muscular contractions, where they will continue their development. The epididymis is a tube on the posterior of the testes that stores sperms. In this stage, they have heads and tails. The head contains all the genetic data which originates from original stem cells, and the tail helps the sperms to travel through to the egg.
The sperms stay in the epididymis until ejaculation and when they are ready to leave the body and fertilize the egg.
The whole process of sperm formation happens because of the FSH hormone (Follicle Stimulating Hormone) and the LH hormone (Luteinising Hormone). The LH hormone causes the Leydig cells in the testes to produce testosterone. The FSH hormone stimulates the Sertoli cells (the cells in the seminiferous tubules), so the spermatids develop into mature sperms. Besides, by this stimulation, the estrogen is made by testosterone, which plays a crucial part in sperm maturation.
The Sperm Structure:
The sperm consists of three major parts:
1. The head, or the nucleus, contains all the genetic data of the cell. Besides holding the cell's DNA, it has certain enzymes that help the sperm penetrate through the egg’s cell membrane.
2. The middle part contains mitochondria. The mitochondria provide the chemical energy the cell needs to maintain. The sperm uses this chemical energy storage to maintain its motility.
3. The tail, which helps the sperm to push forward and swim.
Infertility Causes and Treatment
The common causes of infertility in men happen with the inability of sperm to fertilize the egg. These can include:
· Low sperm count, one of the most common causes of infertility in men, happens when the number of sperm is lower than the average amount.
· Low sperm motility, when the sperms lack a certain amount of mobility to reach the egg.
· Abnormal shape of the sperm, which makes it unable to fertilize the egg.
The common causes of infertility in women might be:
· Ovulation disorders, such as PCOS, premature ovarian failure, Hyperprolactinemia, or poor egg quality.
· Problems in the uterus or fallopian tubes.
All of the above problems can be treated by surgery or taking medication. More severe cases in women might need assistance in conceiving, with methods such as:
· Intrauterine insemination (IUI), or placing the sperm directly inside the uterus.
· In vitro fertilization (IVF), fertilizing the egg with sperm in the lab, and harvesting it inside the uterus.
· Intracytoplasmic sperm injection (ICSI), similar to IVF, except that the specialized doctor injects the sperm directly into the harvested egg inside the uterus.
· Third-party ART, which means using egg donors, sperm donors, and donor embryos to enhance the chance of pregnancy.
Infertility treatment in Iran
IUI, IVF, ICSI, along with the possibility to use a broad range of egg, sperm, and embryo donors, and making use of high-quality technology, have made Iran one of the best destinations to do infertility treatments.
Performing IVF treatment in Iran, along with the IUI and ICSI treatments in Iran, are one of the most popular treatment plans that patients around the globe make use of, which is the result of highly qualified doctors with extensive experience in infertility treatments. The emotional and financial strains of infertility treatments are not something to neglect, and for minimizing them, you can always consult our health providers in Iran and count on us to determine the most suitable infertility treatment for you.