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An antral or secondary follicle, also known as Graafian follicle and tertiary follicle, is an ovarian follicle during a certain latter stage of folliculogenesis. Definitions differ in where the shift into an antral follicle occurs in the staging of folliculogenesis, with some stating that it occurs when entering the secondary stage, [ 1 ] and ...
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).
In addition, follicles that have formed an antrum are called antral follicles or Graafian follicles. Definitions differ in where this shift occurs in the staging given above, with some stating that it occurs when entering the secondary stage, [ 2 ] and others stating that it occurs when entering the tertiary stage.
The labels in the folliculogenesis diagram (Folliclesinovary.jpg) are incorrect - they have been reversed. The arrow is pointing in the wrong direction "Corpus albicans" should be "Primary follicle" "Mature corpus luteum" should be "Secondary follicle" "Corpus luteum" should be "Graafian follicle" or "Mature vesicular follicle" etc.
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.
As the follicle matures, the area between the follicle and the ovarian surface begins to thin and weaken under the influence of the luteinizing hormone and local cytokines. At ovulation the stigma ruptures and the secondary oocyte is released along with surrounding granulosa cells, from the region of the cumulus oophorus, and follicular fluid.
The follicular antrum is the portion of an ovarian follicle filled with follicular fluid. Appearance of the follicular antrum during follicular maturation is the first sign that a follicle has reached the next stage of maturation. It has changed from a primary follicle to a secondary follicle.
The cumulus-oocyte complex contains layers of tightly packed cumulus cells surrounding the oocyte in the Graafian follicle. The oocyte is arrested in Meiosis II at the stage of metaphase II and is considered a secondary oocyte. Before ovulation, the cumulus complex goes through a structural change known as cumulus expansion. The granulosa cells ...