Physiology question regarding meiosis/oogenesis.

[qweewq11]

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I have a question regarding oogenesis that I can't seem to find a clear answer to anywhere. Perhaps someone here can help.

My understanding is that fertilization = union of male and female gametes = union of sperm and ovum.

However, the thing that is released during ovulation is the secondary oocyte, which is frozen in metaphase of meiosis II. Thus, it isn't an ovum, but rather, a secondary oocyte that is waiting to become an ovum (and a polar body). The trigger for the secondary oocyte to finish meiosis II (and thus become an ovum and polar body) is when a sperm penetrates the secondary oocyte. But isn't that fertilization?

Here is an explanation I found on the web:
If the oocyte is fertilized by a sperm cell, it finishes Meiosis II, again keeping most of the cytoplasm while the other cell becomes a polar body. These polar bodies eventually break down. This allows the egg to keep most of the cytoplasm to use as a source of nutrients for the developing embryo. The final result then, assuming fertilization occurs, is one egg cell and two polar bodies.

So see: first it says that "if the oocyte is FERTILIZED by a sperm cell, it finishes meiosis II." But I thought fertilization was the union of the sperm and ovum? If the secondary oocyte is getting fertilized, what's the point of the ovum? Perhaps I am unclear about the meaning of fertilization...

Thanks in advance!

 

[fava]

i think this is just a case of textbook writers and profs being loose with terminology. in this case, what is referred to as the "ovum" is the same thing as the oocyte in metaphase of meiosis II.

 

[qweewq11]

btt

 

[DALABROKA]

I think that your trouble is in the definition of fertilization. Fertilization is a dynamic PROCESS that begins with the penetration of the secondary oocyte by the sperm. The sperm penetrates the secondary oocyte and triggers meiosis II. After the second polar body and secondary oocyte have completed meiosis II, the ovum has been formed. At this point, the ovum has two pronuclei, one haploid nuclei from the mother and one from the father. The fertilization PROCESS ends when these two pronuclei fuse and the zygote is formed.

Ovum specifically refers to "the haploid and FULLY MATURED female gamete."

DALA

 

[Zeusers]

After the female primary oocyte completes its first reductive division it is now haploid. The ovum by definition is the haploid unfertilized egg. It can either be called the ovum, as in your understanding, or the secondary oocyte......that should probably clear up your confusion.


University of MIAMI 07'!