Atlas of plant and animal histology

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Virtual microscopy


Image: ovary of a rabbit. Hematoxylin and eosin staining.

Oocyte: it is the female gamete. It is a large cell covered by a pink-stained coat known as zona pellucida.

Primordial follicles: they are the small and abundant follicles found at the periphery of the ovary. Primordial follicles consist of an oocyte surrounded by a single layer of somatic cells. Primordial follicles are generated during the embryonary and perinatal periods, and a few of them enter the maturation process that happens in each menstrual cycle.

Primary follicles: they are activated follicles that started the maturation process. Primary follicles increase the size with many somatic cells organized in two layers: the inner granulosa layer and the outer theca layer. They still lack inner acellular cavity.

Secondary follicles:they are activated follicles in a later maturation stage. They show well-developed granulosa and theca somatic layers. Secondary follicles develops a cell-free fluid-filled cavity known as antrum.

Graffian follicle: it is the last developmental stage of follicles before ovulation. The Graffian follicle is the largest follicle of the ovary, with an enormous antrum. The oocyte is displaced to the edge of the antrum and surrounded by a layer of granule cells called cumulus oophorus.

Granulosa layer: it is the inner layer of somatic cells that form the follicle.

Theca layer: it is the outer layer of somatic cells of the follicle. Theca cells are flattened.

Antrum: it is the cell-free cavity of the secondary and Graffian follicles. It is formed and during follicle maturation and increases is size as development goes on.

Tunica albuginea: it is a layer of connective tissue that covers the ovary.

Hilum: it is a region of the ovary through which blood vessels enter the organ.