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Section of vesicular ovarian follicle of a cat. X 50. Membrana granulosa labeled at upper left. In the development of the urinary and reproductive organs, the oogonia become invaginated in the gonadal ridge. The embryological origin of granulosa cells remains controversial.
The larger ovarian follicles consist of an external fibrovascular coat, connected with the surrounding stroma of the ovary by a network of blood vessels, and an internal coat, which consists of several layers of nucleated cells, called the membrana granulosa.
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 ...
This remaining follicle, called the dominant follicle, will grow quickly and dramatically—up to 20 mm in diameter—to become the preovulatory follicle. Note: Many sources misrepresent the pace of follicle growth, some even suggesting that it takes only fourteen days for a primordial follicle to become preovulatory.
The anterior pituitary complex and hypophyseal portal system, where FSH and LH are released. Theca cells are responsible for synthesizing androgens, providing signal transduction between granulosa cells and oocytes during development by the establishment of a vascular system, providing nutrients, and providing structure and support to the follicle as it matures.
As a follicle grows in size and the antrum develops, more layers of cumulus oophorus cells accumulate around the oocyte to aid in the acrosome reaction and sperm penetration into the oocyte. The proximity between the cumulus oophorus cells and the oocyte favors bidirectional communication, which is vital for oocyte development.
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.
[citation needed] It is formed by follicle cells adhering to the oocyte before it leaves the ovarian follicle, and originates from the squamous granulosa cells present at the primordial stage of follicular development.