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.
They are located strategically to defend against invading bacteria. The tonsils produce lymphocytes. They are located under the epithelial lining of the oral cavity and pharynx. The lingual tonsils are located at the base of the tongue. The single pharyngeal tonsil is located in the posterior wall of the nasal portion of the pharynx above the soft palate and is often referred to as the adenoids.