Lymphoreticular System

The lymphoreticular system consists of the spleen, lymphnodes, lymphatic vessels, thymus, and bone marrow. The functions of these systems include immune defense, transport of fats throughout the body, and collection and transport of interstitial fluid (the fluid bathing the cells) back to the circulatory system.

During necropsy, one of the most obvious signs of infection or disease is enlarged or discolored lymphnodes. Lymphnodes are located throughout the body and in general should be rounded, smooth, and uniform in color. When an infection is present however, the lymphnodes nearest the infection will often swell and may become inflamed turning red, purple, or dark in color. Lymphnodes are also great for detective work! If you are looking at an animal with multiple lesions, tumors, or massive infection, the lymphnodes can act as a breadcrumb trail to tell you where the problem started. This is because as the disease process progresses it will often have progressed further in lymphnodes near where the problem started. Sampling all lymphnodes near and far from a lesion can help the pathologist localize the origination of a disease process. Be sure to bisect the lymphnode to examine the cross sectional surface for color and texture.

Detailed annotated images of the lymphoreticular system in a California Sea Lion are shown below.  CLICK on an image to see an enlarged view.