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FSH secretion begins to rise in the last few days of the previous menstrual cycle, [3] and is the highest and most important during the first week of the follicular phase [4] (Figure 1). The rise in FSH levels recruits five to seven tertiary-stage ovarian follicles (this stage follicle is also known as a Graafian follicle or antral follicle ...
With the concomitant rise in inhibin B, FSH levels then decline in the late follicular phase. This seems to be critical in selecting only the most advanced follicle to proceed to ovulation. At the end of the luteal phase, there is a slight rise in FSH that seems to be of importance to start the next ovulatory cycle.
During the early and mid-follicular phase, FSH is secreted to promote growth and proliferation of the granulosa cells, which increases GnSAF concentrations. [14] Once the dominant ovarian follicle has been selected at mid-follicular phase, the non-dominant follicles undergo atresia. [15]
A rise in pituitary FSH caused by the disintegration of the corpus luteum at the conclusion of a menstrual cycle precipitates the recruitment of five to seven class 5 follicles to participate in the next cycle. These follicles enter the end of the prior menstrual cycle and transition into the follicular phase of the next one. The selected ...
Estrogen levels peak towards the end of the follicular phase, around 12 and 24 hours. This, by positive feedback, causes a surge in levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This lasts from 24 to 36 hours, and results in the rupture of the ovarian follicles, causing the oocyte to be released from the ovary. [17]
Ovarian follicle activation can be defined as primordial follicles in the ovary moving from a quiescent (inactive) to a growing phase. The primordial follicle in the ovary is what makes up the “pool” of follicles that will be induced to enter growth and developmental changes that change them into pre-ovulatory follicles, ready to be released during ovulation.
The sex steroid production begins with follicle-stimulating hormone (FSH) from the anterior pituitary, stimulating granulosa cells to convert androgens (coming from the thecal cells) to estradiol by aromatase during the follicular phase of the menstrual cycle. [1]
In the early follicular phase, uterine contractions in the non-pregnant woman occur 1–2 times per minute and last 10–15 seconds with a low intensity of usually 30 mmHg or less. This sub-endometrial layer is rich in estrogen and progesterone receptors. [3] The frequency of contractions increases to 3–4 per minute towards ovulation.