Q17. Explain the process of oogenesis with a labelled schematic representation.

Answer:

❖ The process of formation of a mature haploid female gamete from the diploid oogonium is called oogenesis.
❖ Oogenesis is initiated during the embryonic development stage, couple million of oogonia are formed within each foetal ovary.
❖ Oogonia undergo meiosis and enters prophase-I, and get temporarily arrested at the stage called primary oocytes.
❖ Each primary oocyte then gets surrounded by a layer of granulosa cells and then called the primary follicle.
❖ The primary follicles get surrounded by more layers of granulosa cells and a new theca and called secondary follicles.
❖ The secondary follicle soon transforms into a tertiary follicle which is characterised by a fluid filled cavity called antrum.
❖ The primary oocyte within the tertiary follicle undergoes first meiotic division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body.
❖ Secondary oocyte undergoes second meiotic division to produce a haploid ovum (n) with a second polar body.

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