Scanning electron microscopy of hen granulosa cells before and after ovulation.

Using scanning electron microscopy, I examined the granulosa cells of the hen (Gallus domesticus) before and after ovulation. Although the granulosa cells were separated during the final 7-8 days of oocyte maturation, they maintained cell-to-cell contact via cytoplasmic processes. The granulosa cells were cuboidal except at the animal pole (the site of the germinal vesicle) where they were columnar and had surface folds. These morphological characteristics were retained until germinal vesicle breakdown, 1-2 hr before ovulation. At that time the surface of granulosa cells at the animal pole was smoother and their cytoplasmic processes were less numerous and appeared atrophic. Similar changes occurred on the granulosa cells overlying the vegetal pole. About 30 min after ovulation, the granulosa, which remained adherent to its basal lamina, consisted of irregularly shaped columnar cells that lacked surface modifications. These smooth surface cells had rounded apical faces and were generally wider at the apical half. Postovulatory granulosa cells do not transform into luteal cells but undergo fatty degeneration and desquamation during the 4 days after ovulation.