When men ejaculate, they release millions of sperm. Only one of these swimmers will make it through a woman’s cervical canal, uterus and fallopian tube to reach an egg.
To do so, it has to pass a sperm test: movement (motility), shape (morphology) and a few other factors. Then comes the hard part.
How long does it take for sperm to reach the egg?
During unprotected sex, millions of sperm cells are set free with the sole purpose of finding an egg to fertilize. They do this by swimming up the vaginal walls through the fallopian tubes and entering the uterus. Once inside the reproductive tract, sperm have a lifespan of several days.
As sperm swim towards the egg, they encounter many obstacles including the thick fluid in the vagina and cervix that slows their advancement. This is called cervical secretions and varies in consistency throughout the female cycle, but it becomes much more viscous around ovulation. There are also numerous cavities in the uterus and Fallopian tube that sperm can get trapped in.
Once sperm reach the egg, it’s a race against time. The egg has a limited life span of only 24 hours after being released from an ovarian follicle. It will then be captured in the end of one of the Fallopian tubes by a surrounding layer of cells known as cumulus oophorus.
Millions of sperm swim up toward the egg, but only one out of every 200 will manage to break through the cumulus oophorus and penetrate the egg’s outer membrane. Once the sperm gets inside the egg, a series of complex chemical reactions take place over 16 hours that results in the sperm’s nucleus combining with the egg’s female pronucleus to create a fertilized egg, or blastocyst. This is when pregnancy officially starts.
How many sperm do you need to fertilize an egg?
There’s no exact number of sperm it takes to fertilize an egg. On average, each time a man ejaculates, around 100 million sperm are released. However, it only takes one of these sperms to fertilize an egg and create a baby. This means that millions of sperm don’t make it to the egg, which is why semen analysis and sperm count are so important.
In order to fertilize an egg, a sperm must penetrate the wall of cells that surrounds the egg. This is a very difficult task and only healthy sperm can do it. To do so, the sperm must be able to break down the cell membrane and use enzymes to reach the egg. It’s like throwing hundreds of thousands of darts at a bull’s eye – only the healthiest sperms will hit the target and fertilize the egg.
In addition to sperm count, the shape and structure of the sperm is also important for fertility. A normal sperm is oval in shape and has a long tail to help it swim faster and find an egg. The egg also sends out chemicals that encourage sperm to swim in the “fast lane,” while slowing down sperm that is swimming too fast. This is called cryptic female choice and is thought to be the way nature helps the best sperms reach the egg and fertilize it.
How long does it take for sperm to fertilize an egg?
Men’s bodies produce millions of sperm every day and each one has just the single purpose of swimming towards an egg cell and penetrating it. But despite this, only a tiny fraction of sperm are actually fertilized. This is because the process of fertilization takes a lot longer than you might think.
First, an egg has to mature in the ovaries. Hormones control this and once an egg is ready, it will leave the ovary, move through the Fallopian tube towards the uterus, and wait for a sperm cell to reach it. However, this is no easy task. Egg cells have a very short life expectancy once they’re outside the ovaries and even if you have unprotected sex in your fertile window, it could take up to six days for an egg to become fertilized by sperm.
The moment a sperm reaches an egg, it will begin a frantic battle for survival. Hundreds of sperm will circle the egg and attempt to penetrate its membrane, but only one will succeed. The lucky sperm will inject its nucleus into the egg cytoplasm and fertilize it.
However, this is far from the end of the story. A fertilized egg will then need to grow and attach itself to the uterine wall, which can take up to ten days. This is known as implantation and is the beginning of pregnancy.
How do sperm fertilize an egg?
As men and women go through sexual intercourse, sperm make their way from the testicle, through the epididymis, vas deferens, and urethra to reach the female reproductive tract. After ejaculation, they enter the vagina through the cervix. They then swim through the fallopian tubes and reach the egg, which is held by tiny finger-like structures called fimbriae in the uterus. If the sperm are lucky, they will penetrate the egg and fertilize it. When the sperm and egg fuse, they share their genetic material, creating a fertilized egg known as a zygote.
The fertilized egg then implants in the uterus wall, which takes about six days to occur after fertilization. Once implantation occurs, the body gives off hormones to help the egg grow and develop into your baby.
A woman’s menstrual cycle causes a few eggs to mature each month. These eggs are ready for fertilization by the time she ovulates, which happens about halfway through her menstrual cycle. The hormones that control the ovulation process also prepare the uterus for pregnancy by thickening and moistening the lining of the uterus. During ovulation, the ovary releases one mature egg to meet up with a sperm cell. Fertilization usually happens through sexual intercourse, but it can happen spontaneously as well. Only a very small percentage of the sperm cells that are ejaculated ever make it to the egg, and even fewer are able to fertilize it.