How do sperm cell and egg meet

Sperm Meets Egg: Weeks 1 to 3 of Pregnancy | Parents

how do sperm cell and egg meet

All about what it takes to get an egg fertilized, aka what it takes to get pregnant. 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. Hundreds of millions of sperm vie for a single egg cell. The sperm cells are streamlined in design for this purpose: a long tail to help them move, lots of. If your egg meets up with a healthy sperm on its way to the womb, the process . the genetic material in the sperm and egg combine to create a new cell that will.

Sperm Health: How Long Sperm Live & Details of the Journey -

This is why all mitochondria in humans are of maternal origin. Still, a considerable amount of RNA from the sperm is delivered to the resulting embryo and likely influences embryo development and the phenotype of the offspring.

Their membranes dissolve, leaving no barriers between the male and female chromosomes. During this dissolution, a mitotic spindle forms between them.

Biological Steps to Becoming Pregnant | SexInfo Online

The spindle captures the chromosomes before they disperse in the egg cytoplasm. Upon subsequently undergoing mitosis which includes pulling of chromatids towards centrioles in anaphase the cell gathers genetic material from the male and female together.

how do sperm cell and egg meet

Thus, the first mitosis of the union of sperm and oocyte is the actual fusion of their chromosomes. The egg can now be called a fertilised embryo and would normally be at this stage 1 day after ovulation. This doubling of genetic material and halving continues over the next 2 days until the embryo is around 8 cells. 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.

This lowers vaginal pH to as low as 3.

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However, this environment can also be toxic to sperm, though the semen a basic fluid can buffer the vaginal acidity to preserve sperm cells. Only about 1 in 1 million sperm that are ejaculated into the vagina will reach the site of fertilization.

Estrogen also relaxes the cervix, causes cervical mucus to become watery and more alkaline, and stimulates uterine contractions — all of which help sperm penetrate and navigate the female reproductive system. 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.

Human fertilization

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. As the sperm approach the egg, they bind to the zona pellucida in a process known as sperm binding.

how do sperm cell and egg meet

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.