Ovum or Zygote? n or 2n? Source?

[blackmi4]

I'm sure everyone has seen the diagram for oogenesis saying that the secondary ooocyte is arrested in meiosis 2 until fertilization occurs, at which point the secondary oocyte becomes a mature egg (ovum).

But we have also read that a fertilized egg is a zygote (which had better be 2n).

Have you noticed this dilemma?

What I read is that secondary oocyte and ovum are interchangeable terms. I've read that after the LH surge you have ovulation where the ovum comes out of the ovary and the ovum actually contains the secondary oocyte which is fertilized to become a zygote (2n).

However, I haven't found an authoritative source (.edu esque) for this explanation, or any other explanation.

Can you help?

Thank you.

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[labqi]

I don't think they are the same thing. Ovum is term used after fertilization. It's actually the secondary oocyte that is released at ovulation. Upon fertilization I believe it's called a dikaryon until meiosis completes.

 

[dudewheresmymd]

No they are not interchangeable. Secondary oocyte is ( n ) and the ovum is also ( n ). The zygote (2n) is the fusion of the sperm ( n ) and the mature ovum ( n ).

2ndary ooccyte is released into the abdominal cavity and picked up by fallopian tubes. The contact of the sperm is the trigger for meiosis II to complete. Several textbooks however mix this up...so you see this confusion often. Don't worry about it, MCAT won't test this level of detail especially one that is mixed up in textbooks. It is indeed the 2ndary oocyte that is released and not the ovum

You asked for ".edu" credibility for what it's worth:
The secondary oocyte is released from the ovary surrounded by follicle cells forming the corona radiata. Usually the oocyte is drawn into the opening of the fallopian tube by movements of the finger like fimbriae and the ciliary action of the lining of the fallopian tube.
The secondary oocyte finishes the second meiotic division producing an ovum (mature egg cell) and a polar body. The polar body formed during the first meiotic division divides also This results in one ovum and three polar bodies forming from one primary oocyte during meiosis.
http://faculty.ucc.edu/biology-potter/development.htm


http://faculty.stcc.edu/AandP/AP/AP2pages/reprod/oogenesi.htm

The large cell in the picture above is either the product of the first or second meiotic division that lives. If it is the product of the first meiotic division (where the parent cell was the primary oocyte) it is called the secondary oocyte. If it is the product of the second meiotic division (where the parent cell was the secondary oocyte) it is called the ovum. The terms secondary oocyte and ovum are NOT interchangeable-- they are different.

 

[blackmi4]

No they are not interchangeable. Secondary oocyte is ( n ) and the ovum is also ( n ). The zygote (2n) is the fusion of the sperm ( n ) and the mature ovum ( n ).

2ndary ooccyte is released into the abdominal cavity and picked up by fallopian tubes. The contact of the sperm is the trigger for meiosis II to complete. Several textbooks however mix this up...so you see this confusion often. Don't worry about it, MCAT won't test this level of detail especially one that is mixed up in textbooks. It is indeed the 2ndary oocyte that is released and not the ovum

You asked for ".edu" credibility for what it's worth:
The secondary oocyte is released from the ovary surrounded by follicle cells forming the corona radiata. Usually the oocyte is drawn into the opening of the fallopian tube by movements of the finger like fimbriae and the ciliary action of the lining of the fallopian tube.
The secondary oocyte finishes the second meiotic division producing an ovum (mature egg cell) and a polar body. The polar body formed during the first meiotic division divides also This results in one ovum and three polar bodies forming from one primary oocyte during meiosis.
http://faculty.ucc.edu/biology-potter/development.htm


http://faculty.stcc.edu/AandP/AP/AP2pages/reprod/oogenesi.htm

The large cell in the picture above is either the product of the first or second meiotic division that lives. If it is the product of the first meiotic division (where the parent cell was the primary oocyte) it is called the secondary oocyte. If it is the product of the second meiotic division (where the parent cell was the secondary oocyte) it is called the ovum. The terms secondary oocyte and ovum are NOT interchangeable-- they are different.

View attachment 180897

Sorry about replying so late here. Thank you! This helped me out a lot.