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(Human ovary) Locate the tunica albuginea. You may have mesothelium (germinal epithelium) covering it in your specimen. Also locate the cortex and medulla. Within the cortex, identify the primary oocytes in follicles. Note that the medulla is composed primarily of connective tissue and blood vessels. Identify primordial, primary, and secondary follicles. |
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Primary Ovarian Follicle - As soon as the primordial follicle grows a bit and the epithelium becomes cuboidal or stratified cuboidal it becomes a Primary Follicle. The epithelium is called follicular epithelium and later in the follicle's development it will be called the granulosum layer. Texts vary in where they decide to change the name so either name will be accepted as correct at all stages. |
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Identify the theca interna. In maturing follicles locate the antrum, cumulus oophorus, oocyte, granulosa cell layer, and zona pellucida. (That part of the cumulus oophorus that leaves the follicle with the oocyte during ovulation is called the corona radiata. (Many of your atlases have applied this label when they should have used "cumulus oophorus.") |
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Remember that any of these stages can begin to degenerate and become an atretic follicle. The appearance of an atretic follicle will depend on how mature the follicle was when it began to undergo atresia. How far the follicle is into the process of atresia also plays a role: young and old atretic follicles look VERY different. [See your text books and atlases, especially Ross, Romrell, and Kaye (3rd. ed.), p. 716.] What is a pyknotic nucleus? What is a zona pelucida remnant? What is a glassy membrane? This is a young atretic follicle being formed by the breakdown (death) of a large secondary follicle. Compare with healthy secondary follicle above. |
