Human fertilization - Wikipedia
Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube. The result of this union is the production of a zygote cell, or fertilized egg, plasma membrane, the sperm head disconnects from its flagellum and the egg travels down the Fallopian tube to reach the uterus. Fertilization: Sperm meets egg. The mature egg is fertilized when it is joined with a sperm cell. This usually happens after a penis* has ejaculated semen inside. Conception is the moment when egg and sperm meet. . During fertilisation, the genetic material in the sperm and egg combine to create a new cell that will.
When Sperm Meets Egg
Upon fusion with the egg, NOS is released into the egg, whereby the NO produced activates calcium release red spray. Calcium activates NOS already present in the egg, releasing more NO, which releases more calcium, and so on.
In recent years, researchers have learned that nitric oxide NO is much more than an air pollutant. Indeed, a Nobel prize went to the three scientists who found it was a potent signaling molecule in the human body. This versatile gas regulates blood pressure by keeping the arteries open, serves as an important neurotransmitter in the brain and, when produced by white blood cells, battles invading bacteria and parasites.
Now, scientists find NO has yet another purpose: Since the turn of the century, one of the standing puzzles about how fertilization takes place involved the moment when a sperm enters an egg. For many years, reseachers knew that shortly thereafter, internal calcium ion stores in the egg opened, releasing calcium into the cytoplasm.
Thus activated, the egg would start dividing and growing into an embryo. But how the sperm triggered this calcium release had remained a mystery.
Fertility Basics - Complete Fertility Centre Southampton
David Epel and his colleagues from Stanford University may have found the answer, studying the gametes--eggs and sperm--of sea urchins. Epel and the lead author of the study, graduate student Richard C.
Kuo, report the findings in the August 10th issue of Nature. They have long been popular models in early development studies because, unlike humans, their fertilization takes place in the open sea where it is easy to observe. To date, sea urchins have helped solve several important questions about human fertilization, including how an egg becomes activated.
This time, the scientists found that both sperm and eggs contain an enzyme that can produce NO from precursor molecules: A just-ejaculated sperm cell has to spend a couple of hours going through biochemical changes, picking up tail-thrashing speed as it makes its way into the uterus and fallopian tubes to find its target.
The biggest key to successful fertilization is timing.
Sperm Meets Egg: Weeks 1 to 3 of Pregnancy | Parents
Sperm must reach their destination — your egg which is slowly making its way down the fallopian tube from your ovary — within the right time frame. If they get there too early, they risk dying before the egg shows up. Too late, and the egg will be gone and they'll have missed their shot, so to speak.
They also need to pick their destination carefully: An egg is usually only present in one of your two fallopian tubes in any given month.
Pick the wrong tube, and the sperm end up hanging out partying together with no guest of honor in sight. Battle to the finish.
- Sperm Meets Egg: Weeks 1 to 3 of Pregnancy
- Egg meets sperm
- Human fertilization
Even the sperm who reach the egg still have their work cut out for them. The race is on to be the first one to plow through the hard outer layer of the egg.
And there's plenty of competition. Hundreds of sperm will surround the egg during the frantic battle to the finish, all trying to penetrate the egg's membrane to reach the cytoplasm, where the sperm will then release its own genetic contribution.
May the best sperm win! As soon as one lucky sperm cell succeeds in penetrating the egg, the egg immediately undergoes a chemical reaction that prevents other sperm cells from penetrating as well.