Fertilization and Implantation

Introduction

Fertilization and implantation are when the human embryo is developed by a series of complex and remarkable events. The implantation and fertilization refer to the fusion of male as well as female gametes. The semen is inseminated in the female vagina during copulation during this process. 

Fertilization to Implantation

Fertilization is the process where the male and female gametes unite together into the fallopian tube leading to the formation of a zygote. The process called capacitation takes place when ejaculated semen comes into contact with the female genital tract. The acrosomal membrane breaks, and the sperm undergoes chemical processes, which enables it to penetrate and fertilize the egg. 

In this process, the secondary oocyte is released from the mature Graafian follicle and enters the fallopian tube. The fertilization of the zygote occurs after 24 hours; it is released from the ovary. Even though several forms, the outside surround one egg, it gets fertilized, and during the sperm enters the secondary oocyte and completes the remaining process.

After this step, if the secondary oocyte is known as the egg then both the sperm and egg show their vitality to a limited amount. And the sperms only remain alive for 48 to 72 hours in the female reproductive system, whereas the egg fertilized can be without releasing it.

• Sperm Capacitation 

Sperm Capacitation is the physiological maturation of the sperms, which helps them to penetrate the egg.

The sperm, after reaching the ovary in the ampullary-isthmic junction, comes in contact with the zona-pellucida layer of the ovum and blocks the entry of the additional sperms; thus, only one sperm fertilizes the ovum.

• Acrosomal reaction

In this process, the plasma membrane of the secondary size gets fused with the contents of the egg so that it can enter. The plasma membrane of the sperm binds to the secondary side, making a difference and which prevents polyspermy; calcium ions are very important in acrosomal reaction. It is one of the essential functions that help in keeping the temperature, magnesium and pH concentration. 

• Cortical reactions

After the plasma membrane fusion, the outside shows the cortical reaction, and these are found on the plasma membrane of the inside, which is used with the plasma membrane and produces enzymes to prevent polyspermy. Then they are shown as sperm or a single sperm entering the secondary side after being in contact with it, and then there is karyogamy.

• Karyogamy

It is a process in which the male and female gametes fuse together hair the meals acrosome from the sperm gets attached, and the also called as male pronucleus which then gets in contact with the female pronuclei and forms the zygote. Here the egg is already fertilized.

Implantation

From the moment of fertilization until the eighth week of pregnancy, the developing human is called an embryo. First, it divides into two cells; then, they each divide again to give four cells. The process of cell division is repeated many times until a solid ball of cells called a morula is produced after about three days. As the cells in the morula continue to divide, they begin to move towards the outer edges of the ball until it becomes a hollow ball of cells called the blastocyst at about five days after fertilization.

After all these processes, it takes about 6 or 12 days for the fertilized eggs to travel to the uterus and get attached to the uterus wall. This process is also known as implantation hair; the eggs are pushed back towards the uterus with the help of cilia. The egg mass attached to the uterus becomes available for pregnancy; after that, the egg starts dividing itself and forms many structures.

In nature, about 50% of all fertilized eggs are lost before a woman misses their measurement in the use of in vitro fertilization, or IVF begins developing but not in the blastocyst stage. In the first stage, they start dividing themselves so that they can divide themselves between making the placenta. Three or four blastocyst cells develop into the inner cell mass, which — over the next few weeks — will form into the recognizable structures of a human embryo, with a head, beating heart, and tiny limbs. Some of these cells also develop into the fetal membranes that form a fluid-filled protective ‘bag’ around the embryo.

The remaining 100 or so blastocyst cells form a structure called the trophoblast, which will provide the baby’s contribution to the placenta. The first stage of development of the placenta is when the trophoblast cells burrow into the endometrium.

Difference between Fertilization and Implantation

The fusion of male and female gametes informs the zygote, whereas implantation is the method of blastocyst attaching to the uterus wall; moreover, fertilization is a process that occurs after the implantation. It takes about 24 hours of evolution, whereas implantation occurs just after 8 to 10 days of fertilization.

Conclusion

Fertilization and implantation are very different from each other. The first process to occur is fertilization and then implantation. There are many steps included while performing these processes. After fertilization, cell division starts to form the developing embryo in stages, including the morula (solid ball of cells) and then the blastocyst (hollow ball of cells). 

Implantation of the embryo takes place in the endometrium (lining) of the uterus.