2)medulla ---epithelial reticular cell medullary epithelial cell: secret thymosin thymic corpuscle epithelial cell thymic corpuscle /spherical or ovoid, 30-50um in D /concentrically-arranged epithelial reticular cells /peripheral cell: inmature near centra: mature /center cell: keratinased-eosinophilic, hyalinised with invading of macrophage, eosinophil and LC /function unknown thymocyte, macrophage2) medulla: ---epithelial reticular cell medullary epithelial cell: secret thymosin thymic corpuscle epithelial cell * thymic corpuscle: /spherical or ovoid, 30-50um in D /concentrically-arranged epithelial reticular cells /peripheral cell: inmature /near centra: mature /center cell: keratinased-eosinophilic, hyalinised, with invading of macrophage, eosinophil and LC /function: unknown ---thymocyte, macrophage