Ovarian Follices

The correct answer is E.


Explanation:

Follicles in different stages of maturation have different appearances. The most primitive follicles, primordial follicles (choice D), are inactive reserve follicles that contain primary oocytes (arrested in prophase of first meiotic division) surrounded by a single layer of flattened follicular cells.

Primary follicles (choice C), the next stage, are slightly larger and contain a central oocyte surrounded by one or several cuboidal follicular cells. When several small spaces in the follicular mass fuse to form the antrum (follicular cavity), the follicle is termed a secondary follicle (choice E). The secondary follicles continue to enlarge, and develop a more complex structure that includes cumulus oophorus, corona radiata, theca interna, theca externa, and zona pellucida.

The Graafian follicle (choice B) is the mature form of the follicle, which extends through the entire cortex and bulges out at the ovarian surface. After it ruptures and releases the ovum, the corpus luteum (choice A)develops as the cells of the follicle and the theca interna cells enlarge, become epithelioid, and secrete estrogen.

The granulosa lutein cells contain yellow pigment and secrete progesterone. If pregnancy does not occur, the corpus luteum eventually degenerates; if pregnancy occurs, it is maintained throughout the pregnancy.

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