Ovarian Follicular Theca Layer Or Theca Cell

Theca is a Latin word for a casing, outer covering, or sheath. The theca of the ovarian follicle is an envelope of connective tissue surrounding the granulosa cells. It is comprised of the theca interna and theca externa. The theca interna contains theca endocrine cells; the externa is a fibrous, connective tissue layer derived from fibroblastlike cells. The theca interna/externa also contains vascular tissue, immune cells, and matrix factors. Thus, the theca layer of ovarian follicles is critical not only for maintaining the structural integrity of the follicle but also for delivering nutrients to the avascular granulosa cell layer, cumulus cells, and oocyte and for producing key endocrine regulatory factors, such as androgens (testosterone and dihydrotestosterone), and growth-regulatory factors, such as bone morphogenic proteins (BMPs) and transforming growth factor-β.