six stages in the course of folliculogenesis were observed , determined by ( 1 ) the formation of follicular and thecal cellular layers and a collagen-filled space between them , ( 2 ) the development of microvilli of oocytal and follicular origin , ( 3 ) the differentiation of the vitelline envelope and the pore channels , ( 4 ) pinocytotic activity of the oocytes , and ( 5 ) rapid growth of the oocyte and its envelopes during vitellogenesis .
C0007634
cellular
C0026049
microvilli