Why oogenesis is called an discontinuous process?
Dear student,
In humans, oogenesis begins before birth at 5-6th week of gestation. This development carries on till birth, however, only meiosis I takes place. The cells are arrested in prophase I. At birth about 1 million ova are present in the ovary at different stages of follicular development. From birth to puberty, the ova undergo atresia such that by puberty, only about 300,000 ova remain. At puberty, the meiosis is restarted and first meiotic division in completed along with the release of first polar body. The ova is arrested in metaphase II of second meiotic division. The ova that are released into the uterus via ovulation will complete their second meiotic division only after fertilization. This is because when the sperm head comes in contact with the corona radiata, it causes rapid influx of calcium ions which triggers completion of the division with release of second polar body.
Therefore, the meiosis does not take place continuously and is called a discontinuous process.
Regards!
In humans, oogenesis begins before birth at 5-6th week of gestation. This development carries on till birth, however, only meiosis I takes place. The cells are arrested in prophase I. At birth about 1 million ova are present in the ovary at different stages of follicular development. From birth to puberty, the ova undergo atresia such that by puberty, only about 300,000 ova remain. At puberty, the meiosis is restarted and first meiotic division in completed along with the release of first polar body. The ova is arrested in metaphase II of second meiotic division. The ova that are released into the uterus via ovulation will complete their second meiotic division only after fertilization. This is because when the sperm head comes in contact with the corona radiata, it causes rapid influx of calcium ions which triggers completion of the division with release of second polar body.
Therefore, the meiosis does not take place continuously and is called a discontinuous process.
Regards!