Lymph nodules are scattered throughout loose connective tissue, especially beneath moist epithelial membranes such as those that line the upper respiratory tract, intestine, and urinary tract. Lymph nodules appear to be strategically distributed to defend the body against disease organisms that penetrate the lining of passageways that communicate with the outside of the body. A lymph nodule consists mainly of large numbers of lymphocytes enmeshed within reticular fibres. Lymph nodules do not have vessels bringing lymph to them. The periphery of the nodule is not sharply defined.
Some lymph nodules develop germinal centres, central areas filled with immature lymphocytes.
Here new lymphocytes proliferate from stem cells that originate in the bone marrow. Most lymphatic nodules are small and solitary. However, Some are found in large clusters. These large masses of lymph nodules are known as Peyer's patches. Tonsils are also aggregates of lymph nodules.