Q. Which of the following is a non-cellular layer in the Graafian follicle?
Solution:
The T.S. of ovary shows the follicles at different stages of maturity. The secondary follicle matures to form Graafian follicle. This is the most mature stage of the follicle. It was discovered by a Dutch scientist Regnier de Graaf.
Follicular cells of primary follicle, divide and redivide (proliferate), to form 6 - 7 layers of cells called Membrana Granulosa (granular cells). A cavity appears inside the follicle, called Antrum/Follicular cavity. The membrana granulosa cells secrete a fluid called Liquour Folliculi which fills the antrum. The antrum is crescent-shaped, but with time it greatly enlarges. The fluid of antrum is liquor folliculi which is rich in hyaluronic acid. As the follicles grow, the theca folliculi become organised into the inner layer of secretory cells, the theca interna, and an outer layer of connective tissue cells containing fibroblast-like cells, the theca externa. The maturing oocytes adhere to the wall of the follicle through a pedicel/stalk, cumulus oophorus, formed by granulosa cells and remains suspended in liquor folliculi. Theca interna is composed of cells having characteristics of steroid secretion like estrogen, rich in blood vessels and theca externa gradually merges with ovarian stroma to release an ovum.
The primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body. The secondary oocyte retains the bulk of the nutrient-rich cytoplasm of the primary oocyte. The tertiary follicle changes into the quaternary follicle or graafian follicle. The secondary oocyte has a new membrane called zona pellucida surrounding it. This thick coat of zona pellucida is composed of glycoproteins and is synthesised by the oocyte. Later, the granulosa cells lying in close vicinity of the ovum and zona pellucida become elongated to form the corona radiata.
Follicular cells of primary follicle, divide and redivide (proliferate), to form 6 - 7 layers of cells called Membrana Granulosa (granular cells). A cavity appears inside the follicle, called Antrum/Follicular cavity. The membrana granulosa cells secrete a fluid called Liquour Folliculi which fills the antrum. The antrum is crescent-shaped, but with time it greatly enlarges. The fluid of antrum is liquor folliculi which is rich in hyaluronic acid. As the follicles grow, the theca folliculi become organised into the inner layer of secretory cells, the theca interna, and an outer layer of connective tissue cells containing fibroblast-like cells, the theca externa. The maturing oocytes adhere to the wall of the follicle through a pedicel/stalk, cumulus oophorus, formed by granulosa cells and remains suspended in liquor folliculi. Theca interna is composed of cells having characteristics of steroid secretion like estrogen, rich in blood vessels and theca externa gradually merges with ovarian stroma to release an ovum.