<P> The spleen develops from mesenchymal cells between layers of the dorsal mesentery of the stomach . The thymus arises as an outgrowth of the third pharyngeal pouch . </P> <P> The lymphatic system has multiple interrelated functions: </P> <Ul> <Li> It is responsible for the removal of interstitial fluid from tissues </Li> <Li> It absorbs and transports fatty acids and fats as chyle from the digestive system </Li> <Li> It transports white blood cells to and from the lymph nodes into the bones </Li> <Li> The lymph transports antigen - presenting cells, such as dendritic cells, to the lymph nodes where an immune response is stimulated . </Li> </Ul> <Li> It is responsible for the removal of interstitial fluid from tissues </Li>

One of the following is not a secondary lymphoid tissue