Thymus medulla (rat, young adult)

Electron microscopy. Epithelioreticular cells of the medulla (1) close to each other. The electron-light cytoplasm contains many small vesicles (1, Golgi area) as well as cross-sections of vacuoles (2) with small finger-like cytoplasmic extrusions in the lumen. Electron-dense lysosomal structures (3) are also present. (4) keratin filaments