What is oogenesis? Explain with the help of a diagram.
Hint: Oogenesis is the process involving the formation and maturation of an oocyte, or egg cell. It is a stage of gametogenesis, and the female gamete produced is known as an ovum. This process takes place in the primary reproductive organ, the ovary, and occurs in a non-continuous manner.
Complete answer:
Gametogenesis:Gametogenesis is the process by which gametes are formed. It consists of:
Spermatogenesis
Oogenesis
Oogenesis:Oogenesis is the process through which an oocyte, or egg cell, is created and developed. As part of gametogenesis, it results in the formation of the female gamete, known as the ovum. This process occurs in the female reproductive organ, the ovary.
The ovary, a primary sex organ in females, is where the gamete (ovum) is produced. The transformation of a primordial germ cell into an ovum is called oogenesis. This is a non-continuous process and involves the following stages:
Multiplication Phase – Mitosis takes place, leading primordial germ cells to develop into oogonia.
Growth Phase – Oogonia mature into primary oocytes.
Maturation Phase – Meiosis occurs; the primary oocyte generates the first polar body and a secondary oocyte.
Following sperm entry, the secondary oocyte creates the second polar body and an ovum.
Throughout this process, the oocytes are encased by a layer of granulosa cells, forming a structure called the follicle. Eventually, the tertiary follicle encasing the secondary oocyte transforms into a Graafian follicle, which ruptures to release the secondary oocyte in a process called ovulation.
The secondary oocyte then forms a haploid ovum and a haploid second polar body.
Note:
The ovaries develop only one egg within a follicle during each 28-day cycle. This means a female can produce up to 13 mature eggs in a year. The structure of the ovum includes primary, secondary, and tertiary layers in addition to the plasma membrane.