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luteum begins to secrete progesterone with a small amount of estrogen.  Progesterone will decrease the amount of LH in the blood.   The corpus luteum will continue to secrete progesterone for at least the next two weeks, when you will either get your period or become pregnant. 

 

Cervical fluid   Within an hour to a day later, the egg-white cervical fluid you noticed during ovulation will dry up.  Your cervical fluid might feel sticky or even nonexistent at this time.  Usually this will progress to a lotion-like cervical fluid within about a week's time. 

 

Ovulation spotting  You may notice spotting the day of or the day after ovulation occurs.   This happens when a bit of blood, released from the burst follicle, makes its way through your tubes, your uterus, and out of your cervix.  Not everyone notices or has this symptom. 

 

Breast tenderness  After ovulation occurs, the hormonal changes in your body can make your breasts tender and sore.  You might also get sore nipples at this time.  Many often think that breast changes are a sign of pregnancy, but they are normal during any cycle.  However, an increase in tenderness can indicate pregnancy, as can tenderness when you normally don't have any.

 

Increased libido  Your body's natural tendency when not pregnant is to become pregnant - even when you don't want to be!  You will most likely notice an increased desire for sex in the time leading up to and during ovulation.

 

What are the chances I'll get pregnant?  If you have sex anywhere from 5 days prior to or 1 day after ovulation, you have a chance of getting pregnant!  The highest chance exists the day prior to and the day of ovulation.  Once sex has occurred, approximately 100 million to 300 million sperm are injected into your vagina.  Your cervix, located at the end of your vagina, is usually closed tightly, but if you have sex during ovulation, your cervix will be open to allow the easy passage of sperm into your uterus.  The sperm cells use a liquid called semen to get into your uterus, and then they use the fluid within your uterus to move around.  Of that large number, only 3,000,000 sperm cells actually make it through your cervix and into your uterus!  Since only one tube holds the egg, many of these sperm will swim up the wrong tube and never find an egg to fertilize.  The ones that do choose the right tube will encounter roadblocks as they search for the egg.  Many get pushed back by the constant motion of the fallopian tubes.  Others get tangled in the cilia of the tubes.  Still others get attacked by white blood cells searching for "intruders."  It is estimated that only 500 sperm actually reach the egg!  This is one way to make sure that only the strongest and healthiest sperm reach the egg.

 

Sperm have been known to live for up to 5 days, which is why you can get pregnant by having sex 5 days before ovulation!  The time that fertility is at its highest is the day before ovulation; that way the sperm are waiting in place before the egg is ovulated.  The egg only lives for 24 hours, so any sex that occurs more than 24 hours after ovulation has occurred should not result in pregnancy. 

What is happening in my body?  Last week ended with an egg being expelled out of an ovary and into the abdominal cavity. The egg might have been lost in your abdomen if not for the actions of the fallopian tubes. There are two fallopian tubes, each branching off of the uterus and opening onto an ovary.  The part of the tube closest to the ovary has finger-like projections called fimbriae that move over the surface of the ovary in a constant, wave-like motion.  This motion will sweep the newly ovulated egg up and into the fallopian tube. Once the egg is in the tube, more finger-like projections, called cilia, continue to brush the egg towards the uterus. 

 

The follicle that ruptured to expel the egg remains on the ovary.  Almost immediately, the hormone LH (leutinizing hormone) begins to change the burst follicle into a yellow-colored piece of tissue called the "corpus luteum" (literally meaning "yellow body").  The corpus  

What is happening with my baby?  Once the egg has been swept into the fallopian tube (assuming there are sperm present from sex a few days prior to or the day of ovulation) the egg will be covered with sperm.  The egg is surrounded by a protective layer called the “zona pellucida,” which houses little receptors (think of them as wall outlets).  The sperm that cover the egg ar searching for a receptor to plug into.

 

Once the sperm find and begin plugging into receptors on the egg, the front of their heads release a chemical, called acrosome, that breaks down the zona pellucida so that each sperm can drill a hole to get to the egg. After they have made it through the zona pellucida, which takes about 20 minutes, they finally encounter the actual egg cell, known as the oocyte.  The sperm cell that does this the fastest is able to bind to the oocyte. When this happens, the zona pellucida hardens and locks any competing sperm cells in place so that only one sperm is able to fertilize the egg.  The sperm cell that made it into the oocyte releases its DNA into the egg. Fertilization has just occurred!

 

DNA Combine  When the sperm cell enters the egg, the new creation they form is called a zygote, and it is the first of many steps your baby will make on the road to birth.  Within 12 hours from fertilization, the DNA from both the sperm and the egg join together and form a unique combination of DNA that your baby will have in every cell of his or her body for the rest of its life!  This DNA will determine, based on the genes that were passed on by you and your partner, whether your baby is a boy or girl, whether she or he has brown eyes or blue, brown hair or blond, is tall or short, and whether he or she likes to read or prefers sports.  Everything your child will be is mapped out in this one instant.  Pretty amazing!

 

Cell Division   Now that the two cells have become one, one cell must become two.  The zygote undergoes something called mitosis, also known as cleavage.  Within a few hours of the DNA fusing together, the DNA will make a clone of itself.  The two copies of DNA will be pulled to opposite ends of the cell, and the cell will split down the center, resulting in two separate cells with the same DNA in each one.  (Note:  To view this in action, click on “How Cells Dvide” in the video box below, and pay close attention to the left side of the screen.)  After the first cell division takes place, a chemical is secreted from the zygote called Early Pregnancy Factor (EPF).  Without EPF, your body might mistake the zygote for a foreign body (like bacteria or a virus) and attack it.  With EPF, your baby can continue to develop safely.  Approximately every 20 hours, each cell will split again leading to 4 cells, then 8 cells, then 16 cells.  When they have split into 16 cells, the zygote is called a morula, which is Italian for mulberry.  Using the fluids within your reproductive system, the morula begins to float toward the end of the fallopian tube headed for the uterus.  The cells of the morula rely on the nutrients stored in the egg for nourishment.  

 

Cell Differentiation   When the 16- to 32-cell morula enters the uterus, distinct changes start to occur.  In the fallopian tube, the cells of the morula were clumped together in a cluster.  Now, however, the cells cling to the outer ring of the cell membrane, leaving a hollow, fluid-filled space in the center of the morula.  When the cells make this transition, the morula becomes known as a blastocyst.  It is at this point that the cells within the blastocyst start to do different jobs - known as differentiation.  Some cells clump together on one side.  These cells will become the baby, and the remaining cells in the outer ring, called the trophoblast, will become the placenta, the amniotic sac, and the umbilical cord.   

Human Egg

Human Sperm

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Two-cell zygote
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Fertilization Sequence

Sperm Cells Covering Egg

Sperm Cell Entering Egg

Of Note This Week

Emergency Contraception

Wondering what it is and what it does?  Click here to find out!

Videos of Interest:

Month One:  via Discovery Health

How Cells Divide:  via Nova Online

Passing On Your DNA:  via Nova Online

The Egg's Journey:  via Nova Online

The Sperm's Journey:  via Nova Online

The First Two Weeks:  via Nova Online

 

Fertilization

(Week 1)