Question

How is Theca Externa characterized?

Answer 1

Hint: Theca cells are in charge of synthesising androgens, establishing a vascular system for signal transmission between granulosa cells and oocytes during development, providing nutrients, and providing structure and support to the follicle as it matures.

Complete answer:
A casing or sheath is referred to as theca in Latin. The ovarian follicle's theca cell layer is a connective tissue envelope that surrounds the granulosa cells. Theca interna refers to the innermost layer closest to the granulosa cells, while theca externa refers to the outermost layer. The endocrine cells that produce steroid hormones are found in the theca interna.

The theca externa is a connective tissue layer made up of fibroblast-like cells that produce collagen and other extracellular matrix factors. Theca interna and externa also contain a dense network of blood vessels known as vascular tissue, which transports nutrients, oxygen, and immune cells to the developing follicles. As a result, the theca layer of ovarian follicles is important not only for maintaining the follicle's structure but also for delivering nutrients to the granulosa cells and oocytes that live in a non-vascular environment within the follicle.

Thus, The presence of smooth muscle cells innervated by autonomic nerves distinguishes the theca externa. Even though the theca externa’s physiologic significance is still unknown, there is evidence that it contracts during the ovulation and atresia processes. Ovulation and atresia can both be caused by changes in the contractile activity of the theca externa. However, this has not been rigorously demonstrated. Theca externa is retained by the corpus luteum throughout its life. It's unclear how important this is during luteolysis and luteinization.

Note: In the pre-ovulatory large follicles, theca cells respond to luteinizing hormone (LH) and produce androgens as well as progesterone (Magoffin, 2005; Wickenheisser et al., 2006). Follicle-stimulating hormone (FSH) causes the granulosa cells to produce oestrogen.