A higher magnification view of the wall of the follicle shows the membrana granulosa (HA6 mg) surrounding the antrum (a). The theca folliculi (follicular sheath) surrounds the membrana granulosa. It consists of the vascular theca interna (i), and a poorly defined theca externa (e). Note that some nuclei of the theca externa are wavy in appearance similar to contracted smooth muscle cells.