Light micrograph of a whole spleen stained to show its connective tissue framework, comprised mostly of collagen type III, otherwise known as reticular fibres or reticulin. Originating from the splenic capsule, trabeculae extend into the spleen lymphoid tissue and branch into the red pulp as a network of reticular fibres supporting the rich vascular supply. This architecture is the basis for the spleen to function in part as a filter for the blood essential for immune surveillance in response to antigenic challenges from pathogens, toxins and other blood-borne antigens. Paraffin section, reticulin stain. Magnification: x 4.5 when width printed at 10cm.