Is the shrinking of the ovarian follicle a sign of ovulation or atrophy?

If you know some relevant physiological knowledge, you will know that the difference between women and men lies in the reproductive system. Women have their period every month, which is a sign of the maturity of their ovaries. So, do you know if the shrinking follicle means ovulation or atrophy? In fact, generally speaking, the follicles will become smaller during the ovulation period, so if you want to know the specific reason, you need to conduct relevant examinations.

Follicular development begins during the fetal period. When the fetus is born, there are follicles at different early stages of development in the ovaries. When animals enter sexual maturity, batches of follicles will continue to grow in time, one or several of which will mature and be released, and some follicles will also continue to die. Once animals enter old age, follicles no longer develop as ovarian function deteriorates. According to the development status of oocytes and granulosa cells, follicles can be roughly divided into primordial follicles, primary follicles, secondary follicles, tertiary follicles and quaternary follicles. The fourth level follicles are mature follicles, and the rest are growing follicles.

1. Primordial follicles

They are small in size, numerous in number, and located in the superficial layer of the cortex. Their oocytes are surrounded by a layer of flat granulosa cells (cells originating from the ovarian germ cord in the embryonic period). Usually 5 to 6 primordial follicles are clustered together at the junction of the ovarian cortex and medulla, and are rich in blood vessels.

(ii) Growth follicles:

Located deep in the cortex, the oocyte is surrounded by the zona pellucida and corona radiata, and the follicular cavity, cumulus ovary and theca gradually appear. In the primary follicle, the oocyte is surrounded by a layer of cubic granulosa cells. In the secondary follicle, the granulosa cells divide rapidly during this period to form multiple layers of granulosa cells. As the follicle grows, the diameter of the oocyte can increase fourfold, the germinal vesicle (nucleus) also increases, and it enters the reticular phase with very active transcription, and a zona pellucida appears around the egg. In the tertiary follicle, the most obvious feature is the appearance of follicular fluid, which accumulates to form a follicular cavity.

(III) Mature follicles:

The fourth-order follicle is the largest in volume and close to the surface of the ovary. Its follicular cavity is further expanded, large in size and thin in wall, and a cumulus ovary is formed. The follicle migrates to the surface of the ovary and protrudes from the surface. It is also called a Graafian follicle.