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An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries.It secretes hormones that influence stages of the menstrual cycle.In humans, women have approximately 200,000 to 300,000 follicles at the time of puberty, [1] [2] each with the potential to release an egg cell (ovum) at ovulation for fertilization. [3]
Over time, many studies have been conducted with the aim to optimize the characteristics of ovarian tissue culture systems and to better support the three main phases: 1) activation of primordial follicles; 2) isolation and culture of growing preantral follicles; 3) removal from the follicle environment and maturation of oocyte cumulus complexes.
Figure 2. Follicular phase diagram of hormones and their origins. Follicle-stimulating hormone (FSH) is secreted by the anterior pituitary gland (Figure 2). 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).
Ovulation occurs about midway through the menstrual cycle, after the follicular phase, and is followed by the luteal phase.Note that ovulation is characterized by a sharp spike in levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), resulting from the peak of estrogen levels during the follicular phase.
In a reference group representing all women, the 95% prediction interval of the LMP-to-ovulation is 8.2 to 20.5 days. [31] The average time to birth has been estimated to be 268 days (38 weeks and two days) from ovulation, with a standard deviation of 10 days or coefficient of variation of 3.7%. [33]
The ovary is generally thought of as an egg bank from which the woman draws during her reproductive life. The human ovary contains a population of primordial follicles.At 18–22 weeks post-conception, the female ovary contains its peak number of follicles (about 300,000 in the average case, but individual peak populations range from 35,000 to 2.5 million [3]). p The size of the initial ...
Oocytes are immature eggs and are surrounded by granulosa cells and internal and external theca cells. [3] Oocytes are then able to mature within the follicle through meiosis. In humans with ovaries, this process occurs continuously, as they are born with a finite number of follicles (between 500,000-1,000,000 follicles), and about 99% of ...
Many studies show that cumulus expansion is critical for the maturation of the oocyte because the cumulus complex is the oocyte's direct communication with the developing follicle environment. It also plays a significant role in fertilization, though the mechanisms are not entirely known and are species specific.