Graafiansfollikel

A Graafian follicle, also known as a mature ovarian follicle, is a pre-ovulatory stage of a developing ovum within the ovary. It is characterized by a large, fluid-filled cavity called the antrum, which surrounds the oocyte. The Graafian follicle is the largest and most developed of the ovarian follicles, typically reaching a diameter of about 10-20 millimeters before ovulation. Internally, it contains the oocyte, which is surrounded by several layers of cells. The outermost layer is the theca, which is further divided into the theca interna and theca externa. Inside the theca interna is the granulosa layer, which secretes estrogen. The oocyte itself is enclosed by the zona pellucida and the corona radiata. The formation and maturation of a Graafian follicle are regulated by hormonal signals, primarily follicle-stimulating hormone (FSH) and luteinizing hormone (LH), during the menstrual cycle. As the follicle matures, the concentration of estrogen it produces increases, which eventually triggers a surge in LH. This LH surge is the direct stimulus for ovulation, the process by which the mature oocyte is released from the ovary. After ovulation, the remnants of the Graafian follicle transform into the corpus luteum, which has a different hormonal function.