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Ovary: secondary follicles
A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x
![Primary oocyte <p>A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x </p>](https://digitalhistology.org/wp-content/uploads/2018/03/O.R.F.OV_.08.P01.png)
Primary oocyte
A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x
![Zona pellucida <p>A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x </p>](https://digitalhistology.org/wp-content/uploads/2018/03/O.R.F.OV_.08.P02.png)
Zona pellucida
A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x
![Stratum granulosum <p>A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x </p>](https://digitalhistology.org/wp-content/uploads/2018/03/O.R.F.OV_.08.P03.png)
Stratum granulosum
A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x
![Antral spaces <p>A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x </p>](https://digitalhistology.org/wp-content/uploads/2018/03/O.R.F.OV_.08.P05.png)
Antral spaces
A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x
![Basement membrane <p>A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x </p>](https://digitalhistology.org/wp-content/uploads/2018/03/O.R.F.OV_.08.P04.png)
Basement membrane
A secondary follicle forms as antral fluid accumulates in spaces among the proliferating follicle (granulosal) cells. The multiple antral spaces coalesce into a single, fluid-filled antrum. Granulosal cells surrounding the antrum are now called the stratum granulosum. The (non-human) follicle on the left is an earlier secondary follicle than the one on the right. 100x, 200x
![Theca interna > <p>The theca differentiates into a double layer surrounding the follicle. The theca interna is a highly vascularized layer of steroid-secreting cells located immediately external to the basement membrane; this layer synthesizes and secretes androgens in response to LH stimulation. Theca externa surrounds the interna and serves as a reserve-cell source for the interna.</p>](https://digitalhistology.org/wp-content/uploads/2018/03/O.R.F.OV_.08.P06.png)
Theca interna >
The theca differentiates into a double layer surrounding the follicle. The theca interna is a highly vascularized layer of steroid-secreting cells located immediately external to the basement membrane; this layer synthesizes and secretes androgens in response to LH stimulation. Theca externa surrounds the interna and serves as a reserve-cell source for the interna.
![Theca externa <p>The theca differentiates into a double layer surrounding the follicle. The theca interna is a highly vascularized layer of steroid-secreting cells located immediately external to the basement membrane; this layer synthesizes and secretes androgens in response to LH stimulation. Theca externa surrounds the interna and serves as a reserve-cell source for the interna.</p>](https://digitalhistology.org/wp-content/uploads/2018/03/O.R.F.OV_.08.P07.png)
Theca externa
The theca differentiates into a double layer surrounding the follicle. The theca interna is a highly vascularized layer of steroid-secreting cells located immediately external to the basement membrane; this layer synthesizes and secretes androgens in response to LH stimulation. Theca externa surrounds the interna and serves as a reserve-cell source for the interna.