part of part of theca cell ZFA:0009229 A specialized stromal cell that forms the theca layer outside the basal lamina lining the ovarian follicle, appearing during the secondary follicle stage. BTO:0002850 Theca cells are specialized stromal cells found within the ovaries, more specifically in the follicles that house and nurture the developing ovum. They exist in two forms: theca interna cells and theca externa cells, both playing significant roles in ovarian function and the reproductive system as a whole. Found in all mammalian species, these cells allow intricate processes like ovulation and hormonal control to function seamlessly. Theca interna cells are highly vascularized and specialized to produce androgens, specifically androstenedione, a precursor to estradiol. When the follicle-stimulating hormone (FSH) stimulates granulosa cells to produce aromatase, this enzyme then converts the androgens into estrogens. Consequently, the hormonal interaction between theca interna cells and granulosa cells supports the production of estrogen necessary for the reproductive cycle. Theca externa cells, on the other hand, are mechanically supportive cells. They form an outer protective layer around the follicle. While they do not directly influence hormone production, they play an essential role in structural integrity and act in concert with the granulosa and theca interna cells during the rupture of the mature ovarian follicle, releasing the egg for potential fertilization. Simultaneously, these cells participate in the formation of the corpus luteum, which secretes progesterone to prepare the uterus for potential implantation. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) https://cellxgene.cziscience.com/cellguide/CL_0000503 stromal cell of ovary follicular cell of ovary Homo sapiens theca cell layer