Final answer:
The small organs associated with lymphatic vessels are lymph nodes, which are critical for immune responses and positioned throughout the lymphatic system. Lymph nodes contain immune cells and act as filters that lymph passes through, aiding in the activation and coordination of the immune system.
Step-by-step explanation:
Small organs that are intimately associated with lymphatic vessels are known as lymph nodes. These bean-shaped organs are vital for the immune system's function. Lymph nodes act as major staging areas for the development of critical immune responses. They are positioned throughout the lymphatic system at intervals along the lymphatic vessels.
Within the lymph nodes, you can find lymphoid follicles containing rapidly dividing B cells surrounded by a layer of T cells and other accessory cells. As lymph flows through the node, it encounters these immune cells and additionally passes through the medullary sinuses, which collect the lymph before it exits the node through efferent lymphatic vessels.
While the spleen and Peyer's patches are also important components of the lymphatic system, they are not as directly associated with lymphatic vessels as lymph nodes are. The spleen functions as a filter for blood, targeting blood-borne pathogens, whereas Peyer's patches are areas of aggregated lymphoid tissue found in the small intestine that also help in immune response.