What is an Ovulated Egg More Technically Referred To As?
The more technically accurate term for an ovulated egg is a secondary oocyte. Understanding this requires a brief look at 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 (diploid germ cells) undergo mitosis, creating millions of primary oocytes. These primary oocytes begin meiosis I (the first division of meiosis), but arrest in prophase I until puberty. At puberty, under the influence of hormones, a primary oocyte completes meiosis I, resulting in two very unequal daughter cells:
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A secondary oocyte: This is the larger cell, containing most of the cytoplasm and organelles. It's what is released during ovulation and is the cell that can be fertilized. Importantly, it is haploid, meaning it contains only half the number of chromosomes as a somatic (body) cell. However, it is arrested in metaphase II of meiosis II until fertilization.
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A first polar body: This is a much smaller cell containing very little cytoplasm. It may or may not undergo meiosis II, eventually degenerating.
So, Why Not Just Call it an Egg?
While "egg" is a commonly used and understood term, it's not technically precise in the context of reproductive biology. The term "egg" can refer to the ovum, which is the final product of meiosis after fertilization. The secondary oocyte is a crucial intermediate stage. Only after fertilization does the secondary oocyte complete meiosis II, forming a mature ovum (or egg) and a second polar body.
What Happens After Ovulation?
After ovulation, the secondary oocyte is released from the ovary and travels down the fallopian tube. If it encounters sperm, fertilization can occur. Fertilization triggers the completion of meiosis II, transforming the secondary oocyte into a mature ovum. The resulting zygote (fertilized egg) then begins the process of cell division and development.
What is the difference between an oocyte and an ovum?
This is a frequently asked question that clarifies the terminology. The oocyte is the immature egg cell undergoing meiosis. The ovum is the mature egg cell that is capable of being fertilized and is the haploid product of the complete meiotic process. The ovulated egg is technically the secondary oocyte, awaiting the completion of meiosis II.
What if the secondary oocyte is not fertilized?
If the secondary oocyte isn't fertilized within approximately 24 hours of ovulation, it degenerates, and menstruation occurs.
In summary, while "egg" is commonly used, the technically correct term for an ovulated egg is a secondary oocyte, a crucial stage in the complex process of female reproduction. Using precise terminology is important for accurate communication within the field of reproductive biology.
