Human fertilization - Wikipedia
Something magical is about to happen! Watch as the ovulation process occurs, and then millions of sperm swim upstream on a quest to fertilize. However, for a pregnancy to develop it must first meet sperm from the male whilst it is still held in the The sperm then begin their long journey towards the egg. If the egg is not fertilized during that time, the egg disintegrates (breaks down) and menstruation (your period) begins 2 weeks later. 2. Fertilization: Sperm meets.
If the egg is not fertilized during that time, the egg disintegrates breaks down and menstruation your period begins 2 weeks later.
Sperm Meets Egg: Weeks 1 to 3 of Pregnancy
Sperm meets egg The mature egg is fertilized when it is joined with a sperm cell. Sperm is contained in the semen which travels up the vagina, through the cervix and uterus and into the fallopian tubes. If an egg is less than 24 hours old, it can be fertilized by a sperm.The difficult journey of the sperm - Signs
Fertilization sometimes but rarely happens when semen has been ejaculated outside but near the entrance of the vagina. The fertilized egg attaches to the lining of the uterus and pregnancy begins.
Most eggs are fertilized by sperm while still in the fallopian tube.
Sperm Meets Egg: Weeks 1 to 3 of Pregnancy | Parents
The fertilized egg then travels down the fallopian tube into the uterus. This can take days. When the egg reaches the uterus, it may attach itself to the uterine lining the endometrium and pregnancy will begin. Relaxing the cervix allows sperm to pass from the vagina into the uterus and reduces a potential physical barrier. Cervical mucus may prevent sperm from passing into the uterus, but during ovulation when the egg is released from the ovaries, the mucus gets thinner and lower in pH.
These changes make the mucus a great transport medium for the sperm, and help the sperm continue traveling.
As we can see, the progress of sperm is really influenced by where in the menstrual cycle the female is. The closer to ovulation, the easier it is for sperm to pass.
The vagina and uterus are very susceptible to infection, so the body has to balance on a fine line between protecting these areas and allowing sperm to come through. Diagram showing the female reproductive tract. The path of the sperm is highlighted via a blue arrow. As the sperm approach the egg, they bind to the zona pellucida in a process known as sperm binding.
How Pregnancy Happens
This triggers the acrosome reaction, in which the enzymes of the acrosome are freed. When the sperm cell finally reaches the egg cell, the plasma membranes of the two cells fuse together and the sperm releases its genetic material into the egg.
Fusion also triggers the cortical reaction. When the sperm and egg fuse it triggers a release of calcium ions, which cause the cortical granules inside the egg to fuse with the plasma membrane. As they fuse, these granules release their contents outside of the cell, toward the remains of the zona pellucida. The enzymes of the cortical granules further digest the zona pellucida, making it unable to bind more sperm, while other molecules found in the granules create a new protective layer around the fertilized egg.
This doubling of genetic material and halving continues over the next 2 days until the embryo is around 8 cells.
Egg meets sperm (article) | Embryology | Khan Academy
At 8 cells the embryo continues to keep dividing to make more cells, but now the cells become very tightly bound and start to communicate with each other. Around day 4 to 6 after fertilisation the blastocyst stage of the embryo begins.
Fluid starts to fill inside the embryo making a small cavity. The outer cells begin to form a wall and the inner cells form a ball - this will become the future baby.
Implantation All this time the embryo has been rolling down the Fallopian tube, but at the blastocyst stage the embryo enters the womb.
Over the next few days it will hatch out of its shell and begin to bury into the wall of the womb.