part of start stage end stage thymus epithelium thymic epithelium Epithelium within the thymus where lymphocytes mature. Cells of the thymic epithelium have cytoplasm that appear devoid of most membrane bound organelles but contain bundles of cytoplasmic filaments, and frequent desmosomes occur between these epithelial cells. There are also secretory epithelial cells that contain a heterogeneous population of electron-dense, cytoplasmic granules and a well developed Golgi complex. Epithelial cysts are present after 3 weeks. zebrafish_anatomy ZFA:0005779 Ceri 2014-03-11T03:25:06Z larval:protruding-mouth adult