Quick Facts
An atretic follicle is an ovarian follicle that began to mature but did not become the dominant follicle and has involuted (Dorland, 2011).
Related parts of the anatomy
Structure and/or Key Feature(s)
Most ovarian follicles never complete their maturation and degenerate by a process called atresia during fetal development, early postnatal life, and prior to the onset of puberty. Atresia is mediated by apoptosis of the follicular/granulosa cells.
The oocyte undergoes autolysis and degeneration, and remnants are phagocytosed by macrophages. The zona pellucida is more resistant to autolytic processes that are occurring in the cellular components of the follicle undergoing atresia. It becomes distorted which is a useful diagnostic feature of atresia and is often all that remains of the original follicle until it is slowly broken down.
After puberty, many primary follicles begin to grow at each ovarian cycle. Usually only one will complete maturation in preparation for ovulation. The others fail and become atretic follicles.
Follicles that developed further before failing will give larger, more complex atretic follicles. Often the glassy membrane, which is formed from a much-thickened basement membrane that is between the membrana granulosa and the theca interna, also remains.
In follicles that were near maturity before undergoing atresia, the theca interna cells often enlarge and remain as clusters of radial strands separated by connective tissue. These cords of cells are called interstitial glands and continue to secrete steroid hormones but in humans are probably not active in follicles undergoing atresia after puberty (Mescher, 2013; Ross and Pawlina, 2006).
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Mescher, A. (2013) Junqueira's Basic Histology: Text and Atlas. 13th edn.: McGraw-Hill Education.
Ross, M. H. and Pawlina, W. (2006) Histology: A text and atlas. Lippincott Williams & Wilkins.
