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Dormant, small, only one layer of flat granulosa cells: Primordial follicles are about 0.03–0.05 mm in diameter. Primary: Mitotic cells, cuboidal granulosa cells: Almost 0.1 mm in diameter Secondary: Presence of theca cells, multiple layers of granulosa cells: The follicle is now 0.2 mm in diameter Early tertiary
Sawyer et al. hypothesized that in sheep most of the granulosa cells develop from cells of the mesothelium (i.e., epithelial cells from the presumptive surface epithelium of the ovary). [5] In 2013, it was proposed that both granulosa cells and the ovarian surface epithelial cells are instead derived from a precursor cell called gonadal-ridge ...
The immature ova originate from cells from the dorsal endoderm of the yolk sac. Once they have reached the gonadal ridge they are called oogonia. Development proceeds and the oogonia become fully surrounded by a layer of connective tissue cells (pre-granulosa cells). In this way, the rudiments of the ovarian follicles are formed.
Calcitonin-producing parafollicular cells are also found along the basement membrane of the thyroid follicle, interspersed between follicular cells; and in spaces between the spherical follicles. Parafollicular cells can be distinguished from follicular cells based on their lighter staining cytoplasm using H&E.
Germinal centers are initiated in the B cell follicle of the lymph node. Following activation of naive B cells in the lymph node follicles, the B cells migrate to the interfollicular areas so that they can interact with T cells. When the B and T cells interact, the antigen-specific T cell receptors bind the antigen + MHC presented by the B cells.
Theca cells are a group of endocrine cells in the ovary made up of connective tissue surrounding the follicle. They have many diverse functions, including promoting folliculogenesis and recruitment of a single follicle during ovulation. [2] Theca cells and granulosa cells together form the stroma of the ovary.
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.
A follicle is a small, spherical or vase-like group of cells enclosing a cavity in which some other structure grows or other material is contained. Thyroid follicles make up the thyroid gland. Follicles are best known as the sockets from which hairs grow in humans and other mammals, but the bristles of annelid worms also grow from such sockets. [1]