How Many Polar Bodies Are Formed During Oogenesis In Humans?

oogenesis

Three polar bodies.

Polar bodies are small cytoplasmic exclusion bodies that form to enclose excess DNA that takes form at the time of oocyte meiosis following the process of sperm fertilization. There are about 2-3 polar bodies that are derived from the oocyte found in the zygote. This number is based on whether the first polar body (formed during meiosis I), divides at the time of meiosis II. Such an exclusion body comprises excess DNA which is derived from the reductive division (2nd and 3rd polar bodies are formed from meiosis II at the time of fertilization). Such polar bodies do not contribute to the future genetic complement of the zygote, foetus or embryo.

Polar Bodies

First one is produced when a mature primary oocyte transforms into a secondary oocyte. The first polar body divides again to produce two more polar bodies. When the secondary oocyte transforms into an ovum (mature), a polar body is generated. Hence, three polar bodies are produced during oogenesis.

Oogenesis is the process of the formation of female gametes. It is a type of gametogenesis taking place in the female reproductive system. Here, the female gamete or ova are formed. This female gamete comes to be known as the ovum. Oogenesis involves three stages – pre-natal stage, antral stage, and Pre-Ovulatory Stage. 

Once fertilization occurs, meiosis-II is said to be completed. This gives away the third polar body. In the event that fertilization does not take place, oocytes degenerate 24 hours post ovulation while it is still arrested in the meiosis-II cell division. 

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