The Menstrual Cycle
Graafian follicle
The ovum develops from oogonia present in the cortex of ovary. These oogonia are surrounded by cells that form stroma. These stromal cells form Graafian follicle. The stages in the formation of Graafian follicle are as follows.
Table of Contents
1. Follicular cells: Some of the cells of stroma becomes flattened and surround oocyte and ultimately give rise to ovarian follicle and hence they are called follicular cells.
2. Primordial follicle: The flattened follicular cells become columnar. The follicle up to this stage is called primordial follicle.
3. Zona pellucida (zona—belt, pellucida—transparent): It is a transparent belt present between follicular cells and oocyte.
Read And Learn More: General Histology Question And Answers
Functions of the zona pellucida:
- It protects the oocyte.
- It prevents sticking to the endometrium.
- It prevents entry of micromolecules into oocytes.
- It prevents entry of more than one sperm into the oocyte.
4. Membrana granuloma: Follicular cells proliferate and enclose granules. These are called granular cells. They form a structure having many layers of cells. Such structure is called membrana granulosa.
5.Antrum (cavity): The cavity appears within the membrana granulosa. The cavity of the follicle increases rapidly in size. This results into thinness of wall of the follicle. The oocyte now lies eccentrically in the follicle.
6. Cumulus oophoricus: (cumulus—accumulation of cells, oophoricus—surrounding ovum). The follicular cells surrounding oocyte are called cumulus oophoricus.
7. Discus proligerus (discus—flat plate, proligerus—producing offspring): The cells attached to the wall of follicle are given the name discus proligerus.
8. Theca interna (theca—cover): The cells surrounding the membrane granulosa become condensed and form theca interna. They secrete estrogen hormone and the cells are called thecal glands.
9. Theca externa: The fibrous tissue surrounding the follicle get thickened and are called theca externa.
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