Categories: Head and neck | Otolaryngology Adenoids, or pharyngeal tonsils, are folds of lymphatic tissue covered by ciliated epithelium. ... The Palatine tonsils. ... The lingual tonsils are rounded masses of lymphatic tissue that cover the posterior region of the tongue. ... The lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, and lymph vessels that produce and transport lymph fluid from tissues to the circulatory system. ... Structure of the lymph node. ... In mammals including humans, the lymphatic vessels (or lymphatics) are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. ... A lymphocyte is a type of white blood cell involved in the human bodys immune system. ... In anatomy, lymph vessels are thin walled, valved structures that carry lymph away from the tissues, through the lymph nodes and thoracic duct back to the general circulation. ... In human anatomy, the thoracic duct is an important part of the lymphatic system — it is the largest lymphatic vessel in the body. ... The immune system is composed of a complex constellation of cells, organs and tissues, arranged in an elaborate and dynamic communications network and equipped to optimize the response against invasion by pathogenic organisms. ... Grays Anatomy illustration of cells in bone marrow. ... The spleen is a ductless, vertebrate gland that is closely associated with the circulatory system, where it functions in the destruction of old red blood cells in holding a reservoir of blood. ... In human anatomy, the thymus is a ductless gland located in the upper anterior portion of the chest cavity. ... The Palatine tonsils with the soft palate, uvula, and tongue visible. ...