Primary oocyte, light micrograph. A primary oocyte in an antral ovarian follicle shows a large cytoplasm and ovoid nucleus with a dense nucleolus (black). Enclosing the oocyte is a coat of glycoproteins termed the zona pellucida. Granulosa cells surround the oocyte. Gaps and cavities between granulosa cells contain follicular fluid and define the class of follicle as the antral type. Epoxy resin section, toluidine blue stain. Magnification: x400 when width printed at 10cm.