Recently I have been appalled at what people do and do not know about sex, about birth control, about pregnancy.

One of our fine members here, Altenweg (Alty for short), gave me an idea to start a thread about sex ed. As a labor and delivery nurse, I thought it might be a good idea to take her advice to heart and help all people who really are not sure how this all works.

Please go ahead and ask away!!!

snowalps

but it takes just one to fertilize, and infact after one has made contact with the egg, the others do not make any contact with it, there is a kind of shield that prevents others from reaching the egg..just one does the job.

spyderglass

That is why we needed this thread, J_9 is an expert, and Alty should be one-

aaj2008

I did not say the egg itself...I said the outer layer...

spyderglass

The outer layer of the egg is the egg.

snowalps

then its the egg..

aaj2008

An egg cell is 150 microns in size, and is colourless and semi-transparent. It is the shape of a sphere and its outer part is surrounded by a soft yet tough membrane. Within the structure of the egg there are extra nutrients like fat, sugar and proteins. This reserve of nutrients will ensure that the egg cell is nourished on its journey and, if fertilization occurs, will take care of its needs until it reaches the uterus.....

Wondergirl

Here ya go (from Wikipedia) --

Penetration
Fertilization starts with a man and a woman initiating sexual intercourse. The man inserts the penis into the womans vagina, penetrating her vaginally. When the man experiences orgasm, semen containing millions of sperm are ejaculated from the penis and deposited in the vagina. Propelled through the female reproductive tract by flagellation, some of these sperm may reach the cell membrane of the oocyte, and a single sperm may penetrate the membrane. To reach the oocyte, the sperm must pass through the corona radiata and the zona pellucida; two layers covering and protecting the oocyte from fertilization by more than one sperm.

Corona radiata
The sperm passes through the corona radiata, a layer of follicle cells on the outside of the secondary oocyte.

Acrosome reaction
The acrosome reaction must occur to mobilise enzymes within the head of the spermatozoon to degrade the zona pellucida.

Zona pellucida
The sperm then reaches the zona pellucida, which is an extra-cellular matrix of glyco-proteins. A special complementary molecule on the surface of the sperm head then binds to a ZP3 glyco-protein in the zona pellucida. This binding triggers the acrosome to burst, releasing enzymes that help the sperm get through the zona pellucida.

Some sperm cells consume their acrosome prematurely on the surface of the egg cell, facilitating for surrounding, having on average 50% genome similarity, to penetrate the egg cell.[1] It may be regarded as a mechanism of kin selection.

Cortical reaction
When the sperm penetrates the zona pellucida, the cortical reaction occurs: cortical granules inside the secondary oocyte fuses with the plasma membrane of the cell, causing enzymes inside these granules to be expelled by exocytosis to the zona pellucida. This in turn causes the glyco-proteins in the zona pellucida to cross-link with each other, making the whole matrix hard and impermeable to sperm. This prevents fertilization of an egg by more than one sperm.

spyderglass

Thank you wondergirl, I hate going back and forth

Mrcuddlesworth

Is it true that mastubation is healthy for the males body??

DoulaLC

Yes, many are trying to be the first in as they surround the egg, but once that soft, yet tough membrane is penetrated by just one, a reaction takes place that causes that membrane to harder to all other sperm trying to get in.

In actuality there are very few (given the number that started the journey) who even get to the egg. Many are misshapen, are too weak, or have no sense of direction (and certainly won't just follow the others because that would be conceding that they don't know where they are going in the first place). Given that, along with several other steps along the way....secretion of necessay enzymes, penetration, acceptance by the egg, available proteins, etc., having any of those functions fail, will cause the egg not to be fertilized. When you think about all that has to be in place for it to happen, from both the male and the female side, it is no wonder it can take quite a bit of time for conception to occur.

Even more simple.....Think of it as a pie eating contest....all the members are trying to be first to finish as quickly as possible and win the prize. They aren't helping each other, just focusing on the job at hand, and they will vary in what they bring to the table and how they tackle the job. There can be only one winner who finishes first. Once that one finishes, the others stop the race....