Thursday, April 28, 2011

Miracle of Conception and Weeks One to Three of Pregnancy

I never fully appreciated the beauty and awesomeness of the creation of a human being until now. I am just in awe learning about it all! God is just so amazing and beautiful and I love Him so much and I love my baby so much already too! I figured I would share some of the most fascinating things I've been learning week by week, but since I am already 7 weeks (today!), I will need to combine the first few weeks into a two or three posts so I can catch up!

*    *    *

It's simply awe-inspiring how God sets the conditions of the body to be perfect for fertilization. It is like a puzzle that fits perfectly together - and if any piece is missing then a pregnancy will not occur.

Man's Role in Conception

The man's testes produce about 1,500 sperm per second and each sperm has a lifespan of about 72 days. The testes send their immature sperm to the epididymis, where they spend time maturing while they pass slowly along for many days The epididymis is a coiled tube that lies behind the testes. The sperm need to be mature enough before they are forcefully expelled in ejaculation. 

We'll revisit the man's role a little further on...

Photo Credit: Shands Health Care

Woman's Role in Conception

Week One

Week One with the first day of the woman's last menstrual period where she bleds for 5 to 7 days. You will will a little later on exactly what it is she is bled and why. However, this week is included as part of the pregnancy because it includes an important part of the cycle and sets the stage for ovulation and subsequently, fertilization, a.k.a. conception.

Week Two

When her menstrual period ends there is a hormone that is released into the bloodstream by the pituitary gland, which lies behind her eyes in her brain. This hormone is called follicle stimulating hormone or FSH. We will come back to this hormone shortly.

Each ovary, which is housed at the end of the fallopian tubes, release only one egg (only occasionally more than one) in alternate menstrual cycles - so ovulation only takes place through one ovary at a time every month. There are around 20 eggs that are selected to mature within a fluid-filled bubble called a follicle. This is where FSH comes into play. The follicle stimulating hormone which was secreted from behind the woman's eyes, moves through the bloodstream and reach the fallopian tubes and begins acting on the eggs to enlarge them. One egg typically becomes the "dominant" follicle and matures fully and eventually ovulates, while the other follicles shrivel and the eggs within them die. 

Before full maturation, however, within the follicle the egg grows on one side and is surrounded by cells called granulosa cells, which produce estrogen and feed the egg nutrients. These cells also stimulate the lining of the uterus, called the endometrium, as well as the breast tissues. When the level of the hormone estrogen rise in your bloodstream, it triggers a message in the hypothalamus, which is the "control center" of your brain and tells it that the follicle which contains the egg is mature and ready to ovulate. The hypothalamus then tells the pituitary gland (behind your eyes, remember?) to release a burst of a luteinizing hormone that triggers the release of the egg about 36 hours later. The follicle, which has at this point grown to about the size of a quarter, bursts and releases the egg. This is ovulation and typically occurs around the 14th day of the menstrual cycle (one week after your period). 

The egg carries chromosomes that carry genetic information and which are at the perfect stage for further development. Also, the egg is capable of of allowing only one sperm to enter it while blocking out all the others. When ready, the egg is swept into the fallopian tubes by "wandlike" projections called fimbria and is helped along into the uterus by hairlike strands called cilia. The remaining cells from the ruptured follicle form a swelling in the ovary called the corpus luteum and it begins to produce the hormone progesterone. Progesterone begins to make the cells receptive to pregnancy and produces nutrients needed to support a developing embryo and thickens the lining in the uterus. The lining becomes perfectly primed for new life and the granules of mucus are ready to provide nutrients for a newly fertilized egg. 

Now, if at 3 weeks or so the egg is not fertilized then this is where everything begins to wither away and the blood-filled lining begins to disintegrate and eventually becomes the woman's menstrual period around week 4 of the menstrual cycle.

Continuation of Man's Role in Conception

The statistical probability of the man's sperm meeting the woman's egg is minute. On average a man ejaculates around 100 to 300 million sperm, yet only 100,000 make their way through the cervix and only twenty sperm survive to make the journey up the fallopian tubes in order to fertilize the egg!

When the sperm are mature enough for ejaculation, they are forcefully sent up through the epididymis to the vas deferens, and these tubes then contract during orgasm and the sperm are sent out of the scrotum, past the seminal vesicles and the prostate gland, and finally into the urethra - which is the tube that travels from the bladder to the penis. During ejaculation, the opening to the bladder is shut off and the sperm are transported to the penis and ready for their journey into the vagina. And the journey for the sperm only begins here...

The sperm go through an amazing obstacle course to reach the egg that is ready to be fertilized. They navigate a considerable distance through the very hostile and acidic environment of the vagina, up through the narrow opening of the cervix and into the uterus - the fastest ones making it within about 5 to 10 minutes. Within the next 72 hours more cohorts of sperm continue to make their way from the cervix to the uterus. Only around 20 actually make their way up the fallopian tube with the help of muscular contractions from the uterus. 

Week Three: Conception!

The journey makes them hyperactive and they are fully charged to fertilize. When they get close to the egg, they shed their cap, called the acrosome, and the one chosen by God fuses with the egg and penetrates the oocycte, which is the inner most part of the egg, and begins fertilization. 

Within 24 hours of the sperm entering and fusing together with the egg, the newly formed single cell - now called a zygote - forms a thick wall around it to prevent other sperm from entering. It then begins to divide into further cells, called blastomeres, while it travels down the fallopian tube to the uterus - a journey that takes about 60 hours. Within this time the zygote is made up of about 50-60 cells and is now called a blastocyst.

There are two distinct cell types already: an outer layer made up of trophoblast cells that develop into the placenta, and an inner cell mass that eventually forms the fetus. Two or three days later (one week after fertilization, a.k.a. one week ACTUALLY pregnant!) the blastocyst embeds itself into the lining of the uterus (which remember is primed for new life with all the nutrients!!). It has now subdivided into about 100 cells and produces the hormone called human chorionic gonadotropin, or HCG. This hormone then tells the corpus luteum to carry on producing progesterone, because if it fails to do so the lining of the uterus would wither away to become a period, or in this case, a miscarriage and you probably have never known you were ever pregnant.

How Your Body is Feeling

Some women are so in tune with their body that they actually know they are pregnant before their period is even due. Most however do not notice anything at all. I sure didn't have a clue! So, during week three there are no real outward signs of pregnancy that one would typically notice.

Week Three of Pregnancy. Photo Credit:

No comments:

Post a Comment