Thymus Medulla

The medulla of the thymus contains T-lymphocytes and increased numbers of epithelial cells with pale-staining nuclei. The epithelial cells provide structural support to the medulla and negatively select self-reactive T-cells to generate tolerance against self-antigens. A distinguishing feature of the medulla is the presence of Hassall’s corpuscles. They are concentric arrangements of flattened epithelioid cells that are acidophilic. One may occasionally observe keratinization of the structure. The purpose of these structures is currently unknown. Does the number of Hassall’s corpuscles increase or decrease with age?