the atresia of follicles is due to negative feedback of estrogen on fsh they how early entry of Lh into Antral fluid leads to atresia of follicles
Atresia of follicles, which refers to the degeneration and resorption of ovarian follicles, is a normal physiological process that occurs during the menstrual cycle. It is necessary for the selection of a dominant follicle that will continue to grow and eventually ovulate, while the rest undergo atresia. The interplay of hormones, particularly follicle-stimulating hormone (FSH) and luteinizing hormone (LH), plays a crucial role in this process.
The early entry of LH into the antral fluid (the fluid-filled cavity within the developing follicle) is a significant event in the final stages of follicular development. It is known as the “LH surge,” and it occurs approximately 24 to 36 hours before ovulation. The LH surge is a critical trigger for ovulation and the release of the mature egg from the ovary.
Here’s how the LH surge leads to atresia of non-dominant follicles:
- Follicular Growth and Dominance: During the early follicular phase of the menstrual cycle, multiple small antral follicles begin to grow in response to increasing FSH levels. As these follicles grow, they produce increasing amounts of estrogen.
- Negative Feedback of Estrogen on FSH: As estrogen levels rise, they exert negative feedback on the pituitary gland, which decreases the production and secretion of FSH. This negative feedback mechanism is crucial for selecting a single dominant follicle to continue growing, while the other smaller follicles are inhibited from further development.
- LH Surge: As the dominant follicle continues to grow, it secretes more estrogen, reaching a threshold level. This rising estrogen level eventually switches from exerting negative feedback on the pituitary to exerting positive feedback.
- Positive Feedback on LH Secretion: The increasing estrogen levels now trigger a positive feedback effect on the pituitary gland. This positive feedback leads to a sudden and substantial increase in LH secretion. The rapid surge in LH is known as the LH surge.
- Ovulation and Atresia: The LH surge triggers a cascade of events that result in the rupture of the mature dominant follicle, releasing the mature egg (ovulation). The released egg is then available for potential fertilization. Meanwhile, the smaller non-dominant follicles undergo atresia, which means they degenerate and are absorbed back into the ovary.
In summary, the early entry of LH into the antral fluid (LH surge) is a critical event that leads to the ovulation of the dominant follicle and the subsequent atresia of the non-dominant follicles. The LH surge is the final step in the complex hormonal regulation of the menstrual cycle, ensuring the selection of a single dominant follicle for ovulation and the removal of the remaining follicles through atresia.