Theca externa

The theca externa is the outer layer of the theca folliculi. It is derived from connective tissue, the cells resembling fibroblasts, and contains abundant collagen.^[1] During ovulation, the surge in luteinizing hormone increases cAMP which increases progesterone and PGF2α production. The PGF2α induces the contraction of the smooth muscle cells of the theca externa, increasing intrafollicular pressure. This aids in rupture of the mature oocyte, or immature oocyte at the germinal vesicle stage in the canine, along with plasmin and collagenase degradation of the follicle wall.

• Histology image: 14805loa – Histology Learning System at Boston University
• Anatomy photo: Reproductive/mammal/ovary2/ovary5 - Comparative Organology at University of California, Davis - "Mammal, canine ovary (LM, High)"
• Anatomy photo: Reproductive/mammal/ovary5/ovary6 - Comparative Organology at University of California, Davis - "Mammal, bovine ovary (LM, Medium)"
• UIUC Histology Subject 373 - externa
• Anatomy Atlases – Microscopic Anatomy, plate 13.249
• Slide at trinity.edu Archived 2016-03-03 at the Wayback Machine

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