The architecture of the spleen of the Red-eared Slider, Chrysemys scripta elegans (Reptilia, Testudines).

The morphology of the spleen of the Red-eared Slider, Chrysemys scripta elegans, has been described. The outer surface of the spleen is covered by a thin fibromuscular capsule, from which a number of trabeculae extend into the parenchyma. The parenchyma of the spleen shows a definite demarcation into a red and white pulp. The white pulp is composed of two lymphoid compartments: lymphoid tissue surrounds both central arterioles and ellipsoids, forming the periarteriolar and periellipsoidal lymphocyte sheath (PALS and PELS, respectively). The ellipsoids consist of a thick layer of reticular tissue, enclosing a capillary with cuboidal endothelium. In contrast with the PALS, reticular fibers are rarely found in the PELS. Even after severe stimulation with paratyphoid vaccine, germinal centers are not found in the spleen of C.s. elegans. The red pulp of the spleen is composed of a system of venous sinuses and cords.