Q.Differentiate between a primary follicle and a mature (Graafian) follicle of the ovary.

[!TLDR]

A primary follicle is an early, small follicle with a primary oocyte surrounded by a single/few cuboidal cell layer(s) and no antrum; a Graafian follicle is the large, fully mature, antrum-filled follicle ready for ovulation.

[!ANSWER]

Primary follicle = early stage, oocyte with a cuboidal cell layer, no antrum; Graafian follicle = mature stage, large fluid-filled antrum, cumulus oophorus, corona radiata, theca layers, ready to rupture at ovulation.

A primary follicle represents an early stage of follicular growth, in which the primary oocyte is surrounded by a single layer (or, as it grows, a few layers) of cuboidal follicular cells, with no fluid-filled cavity yet present. A Graafian (mature) follicle, by contrast, is the end stage of follicular development: it is much larger, contains a large fluid-filled antrum, and the oocyte is held eccentrically within a mound of cells (cumulus oophorus) surrounded immediately by the corona radiata, with an outer theca interna and theca externa; only the Graafian follicle actually ruptures at ovulation to release the oocyte.

[!ANSWER]

Primary follicle = early stage, oocyte with a cuboidal cell layer, no antrum; Graafian follicle = mature stage, large fluid-filled antrum, cumulus oophorus, corona radiata, theca layers, ready to rupture at ovulation.

Contrast the two stages on three features: presence/absence of an antrum, size, and the specific structures (cumulus oophorus, corona radiata, theca layers) present only in the mature follicle.

Treating 'primary follicle' and 'Graafian follicle' as interchangeable names for the same stage -- they are, in fact, an early and a fully mature stage of the same overall developmental sequence, separated by the secondary follicle stage.