What is an Ovulated Egg More Technically Referred To?
The more technically accurate term for an ovulated egg is a secondary oocyte. Understanding this requires a brief dive into the process of oogenesis, the creation of female gametes (sex cells).
What is Oogenesis?
Oogenesis is a complex process that begins before a female is even born. During fetal development, oogonia (primordial germ cells) multiply and differentiate into primary oocytes. These primary oocytes begin meiosis, a type of cell division that reduces the chromosome number by half, but they arrest (pause) in prophase I. This means they remain in this stage until puberty.
The Ovulation Process and the Secondary Oocyte
At puberty, under the influence of hormones, some primary oocytes are recruited each month to continue meiosis. This process results in a mature ovum (egg cell), but it happens in two distinct steps:
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Meiosis I: The primary oocyte completes meiosis I, producing two daughter cells of unequal size. One is much larger and contains most of the cytoplasm; this is the secondary oocyte. The other is much smaller and is called a first polar body. This polar body usually doesn't divide further and degenerates.
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Meiosis II: The secondary oocyte begins meiosis II, but it arrests (pauses) in metaphase II. This is the stage at which ovulation occurs. The secondary oocyte is released from the follicle in the ovary and travels down the fallopian tube.
Only if fertilization occurs will the secondary oocyte complete meiosis II, producing a mature ovum (also called an ootid, which then matures into an ovum) and a second polar body. If fertilization doesn't happen, the secondary oocyte degenerates.
So, why is it important to know it's a secondary oocyte?
Using the term "secondary oocyte" reflects the precise stage of development of the egg cell at the time of ovulation. It accurately communicates that it hasn't yet completed meiosis and, therefore, isn't a fully mature ovum. This distinction is crucial in understanding reproductive biology and the processes involved in fertilization.
What about other terms people use?
While "egg" is commonly used and understood, it's a less precise term. Other terms like "mature egg" are often misused, as the egg is not fully mature until after fertilization (if it occurs). Therefore, "secondary oocyte" offers the most accurate scientific description.
How long does the secondary oocyte survive after ovulation?
The secondary oocyte is viable for approximately 12-24 hours after ovulation. If fertilization does not occur within this timeframe, the egg will degenerate.
What happens to the polar bodies?
The polar bodies are small cells that are typically non-functional and eventually degenerate. Their role is to essentially dispose of extra chromosomes during meiosis.
By understanding the difference between an ovum and a secondary oocyte, we gain a much clearer understanding of the intricacies of human reproduction.
