for fertilization to occur sperm must enter the vagina this usually happens through
sexual intercourse sperm use their tails to swim through the layers of cervical mucus that guard
the entrance to the uterus during ovulation this barrier becomes thinner and changes its acidity
creating a friendlier environment for the sperm on the other side after releasing the egg at
about day 14 of the period the egg arrives at a specific portion of the tube called the angular
isms junction it rests for another 30 hours fertilization occurs in this portion of the tube
once the sperm has entered the uterus contractions propel the sperm upward into the fallopian tubes
to meet the waiting egg sperm must travel from the vagina to the fallopian tubes a tough journey that
few sperm survive this process may be nature's way of allowing only the healthiest sperm to fertilize
the egg to provide the best chances of having a healthy baby the first sperm enter the tubes a
few minutes after ejaculation but however, the first sperm are not likely to fertilize the egg
modal sperm can survive in the female reproductive tract for up to five days the magic happens in the
fallopian tubes the fallopian tube pushes the egg towards the uterus cilia pushed the sperm
towards the egg also the surrounding cells of the egg produce a chemical that attracts sperm
the sperm first burrowed through the cells of the corona Radiata
then upon contact with the zona pellucida the sperm bind to the receptors in the zona pellucida
then the enzyme-filled cap of the sperm called the acrosome releases its stored digestive enzymes
finally the sperm must fuse with the egg plasma membrane
this event causes the egg membrane to change and prevent other sperm from attaching to it
now attached the sperm's nucleus where the chromosomes are stored
enters the egg cell looking for the egg's nucleus
egg combines genetic material with the sperm to create a full set of chromosomal DNA
with 23 pairs of chromosomes that contain a unique copy of half the genes of the parent source
this is the blueprint for a whole new unique person that instantly determines gender hair
color eye color and many other characteristics the combined sperm and egg is called a zygote
it is the earliest developmental stage it divides rapidly in the days following fertilization
the zygote then travels down the fallopian tube to the uterus
after fertilization the zygote continues to divide and morph into a blastocyst ball of 16 cells
approximately five to six days after fertilization it is smaller than the tip of a ballpoint pen only
20 percent to 30 percent of fertilized eggs will reach the blastocyst stage embryos that survive
this stage of development have a high implantation potential once transferred into the uterine cavity
the blastocyst hatches out of its shell and attaches itself to the uterus
then it attaches deeper into the uterine lining beginning implantation
for the next nine months, she or he is growing and maturing until ready for birth
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