Reticular cells are quite abundant. Their cytoplasm is eosinophilic, and their large, ovoid and light nuclei may contain one or two nucleoli. The cells are branched, and their slender processes are connected with the processes of other reticular cells to form a cellular reticulum (or cellular network). This cellular network (reticular fibres are scant in the thymus) provides support for other cells of the thymus.
Reticular cells sheathe the cortical capillaries; they form an epitheloid layer which delimits the cortical tissue from the connective tissue and secrete substances (hormones and other factors) important for thymic function. Thereby they create and maintain the microenvironment necessary for the development of T-lymphocytes in the cortex. Their functions thus go beyond those of “typical” reticular cells and, to reflect this, they are also referred to as thymic epitheliocytes.