This is the creation story: In the beginning, you and your partner brought together the sperm and the egg. Since the big bang theory of the universe has yet to be solved, let’s look at the big bang that took place in you. It’s time to go back to Man’s beginnings and look at the fertilization process.
Fertilization process #1: Sperm cells keep swimming
The ejaculation during sex sends millions of sperm cells racing towards an egg cell. Each sperm cell is about 50 μm (0.05 mm) long, and moves at a speed of 35 to 30 μm per second. The end goal is, but of course, the egg cell which is released from the ovary.
The sperm cells can meet the egg cell in the ampulla. The ampulla – the middle portion of the fallopian tube – is the widest part of the fallopian tube. The sperm cells will have to just keep swimming, and travel about 17 cm from the uterine cavity to reach the egg cell in the fallopian tube.
Fertilization process #2: Survival of the fittest
To protect the uterus from attacks from germs, the insides of the vagina is acidic in nature. Since sperm cells are weak against acid, they have to give it their all to fight against the acidic environment.
Sperm cells are protected by the seminal plasma which is alkaline and is created by the seminal vesicle and the prostate. The seminal plasma and the sperm cells make up semen, the jelly-like substance that is ejaculated by men.
This semen allows sperm cells to be able to survive in the vagina. However, most sperm cells don’t make it – about 1% of the original number of sperm cells ejaculated are able to make their way to the cervical canal.
Fertilization process #3: Sperm cells get over obstacles
The sperm cells have finally reached the cervical canal and enter it. However, instead of some form of respite, they are again treated unfavorably in the cervical canal.
The cervical mucus secreted in the cervical canal are tasked with the responsibility of escorting the sperm cells to the uterus, but if antisperm antibodies are present in the fluid, they will attack the sperm cells. Also, since the white blood cells in the uterus attack the sperm cells as foreign objects, this could decrease the number of the sperm cells to around 1000 or less.
What is an antisperm antibody?
An antisperm antibody is a substance that attacks the sperm cells as foreign objects. Should these antibodies be created in the female’s body, they can be the cause of infertility. The reasons why such antibodies are created aren’t yet known, but it’s believed that they are the result of inflammations, allergies or stress.
Fertilization process #4: Sperm cells must choose one of the two tubes
The sperm cells that enter the uterus literally stand at the crossroads of life, and take either a right or left turn into either one of the fallopian tubes. It’s thought that the sperm cells decide which way they go by sensing the smell emanating from follicular fluid. Only several dozens to a few hundreds of sperm cells make it to the ampulla where they can meet an egg cell.
Fertilization process #5: Sperm cells change themselves
The sperm cells don’t have a function of fertilization right after the ejaculation. They gain the function in the process of swimming from the vagina to the ampulla.
Through a process called hyperactivation, the sperm cells also acquire the ability to swim in a zig-zag manner for penetrating the oolemma (membrane) of the egg cell. How the sperm cells change themselves on the way to the egg cell – no matter how science explains it – is really a marvelous process, isn’t it?
Fertilization process #6: Sperm cell meets egg cell
The sperm cells will rush over and crowd around the egg cell in the ampulla. In order to “melt” the membrane of the egg cell, the sperm cell secretes two enzymes: hyaluronidase and acrosin.
The head of the first sperm cell to go through the membrane of the egg cell comes into contact with the plasma membrane of the ovum, and at that very moment, the oolemma of the egg cell changes so that other sperm cells cannot enter any more.
The first sperm cell to reach the egg nucleus fertilizes the egg cell, putting an end to the fertilization process.
Fertilization process shows the miracle of life
It’s indeed a tale depicting the “survival of the fittest”. The sperm cell overcomes the odds to become fertilized – herein lies the saying that fertilization process illustrates the miracle of human life. The creation story has come to an end, but this is only the mere beginning. There is still more to come – pregnancy and life postpartum.