I have been sitting here in front of my computer thinking of something to write about cells. Somehow, after writing about the egg cell and the sperm cell, I cannot think of anything else to talk about. Of course there is still so much more to discover about cells. I have not even talked about the energy-generating centers in cells yet – meaning the mitochondria and chloroplasts. However, I don’t feel like starting their stories today. Not just yet anyway. So what cell story should I tell today?
Okay, here’s one – do you know that egg cells can start the first stages of development even without the sperm cells? Yes they can!
The first stage of development after fertilization is what is called as cleavage. This simply involves the rapid cell division of the fertilized egg. Experiments have shown than even a pin-prick can trigger this initial stage. However, after dividing several times, the egg cell will stop dividing and will not proceed to the next stage of development which is called gastrulation.
So later stages of development need the combined information coming from both the egg cell and sperm cell but the initial stage of development does not need the information from the sperm cell. Isn’t this amazing?
Showing posts with label sperm cell. Show all posts
Showing posts with label sperm cell. Show all posts
Saturday, December 27, 2008
Friday, December 26, 2008
sperm cell
source of photo: http://aycu31.webshots.com/image/44110/2002564320883082356_rs.jpg
Since I talked about the egg cell yesterday, I thought I might as well talk about the sperm cell today.
If you look at the picture, you will notice the big difference between the size of the sperm and the egg. What is shown in the picture is only a small segment of the egg cell. A sperm cell is only about 25 micrometers or less in diameter while the egg cell is about 200 micrometers or even more in some animals.
A sperm cell contains only the nucleus which occupies the "head" part of the sperm, plus several mitochondria in the "neck" part. The rest of the sperm consists of the flagellum.
According to http://hypertextbook.com/facts/2000/EugeneKogan.shtml, the average speed of a sperm is "1–4 millimeters per minute".
Subscribe to:
Posts (Atom)
