The corpus luteum (HA7) is a large structure, only part of which is in this low magnification image. It has remnants of the antrum (a), which is filled with clotted blood. The antrum is surrounded by granulosa lutein (gl) cells, which are large polyhedral cells that are pale staining. These were the membrana granulosa cells of the follicle. The darkly stained paralutein (pl) cells, which were the thecal cells, surround the entire structure. Note the large blood vessels that supply this endocrine structure.