Morphological investigations on follicular atresia in canine ovaries.
Morphologically, canine ovaries show two types of regression pattern in secondary follicles. In type A necrotic changes of the oocytes and the zona pellucida dominate, whereas in type B degeneration, necrobiosis and necrosis of the granulosa prevail. The atretic course of type B regression results in a pseudoantrum and leads, by pseudogrowth, to a structure imitating tertiary follicles. In both type A and type B regression, four consecutive stages of atresia are distinguished by light- and electron microscopy. True teritary follicles display only one regression pattern which resembles type B of secondary follicles. Early, advanced, late, and terminal stages of atresia are again described.
D000818:Animals; D004285:Dogs; D004971:Estrus; D005260:Female; D006107:Granulosa Cells / Q000166:cytology*; D009336:Necrosis; D009865:Oocytes / Q000166:cytology; D009940:Organoids / Q000648:ultrastructure; D010053:Ovary / Q000166:cytology*; D011247:Pregnancy; D013799:Theca Cells / Q000166:cytology*; D015044:Zona Pellucida / Q000648:ultrastructure