In the natural world, which appears to be a truly hostile place for a human organism, the lymphatic system plays a significant role. It acts as a defensive system against millions of viruses, bacteria, parasitic worms, fungi, and protistans. To provide the necessary defence, the lymphatic system initiates an immune response in the body against pathogens that are about to invade. Other roles of this system include the role of the second circulatory system (the lymphatic system returns fluid from the tissues of the human body, hence regulating the water balance) and the role of the transport system (it moves nutrients that are fat-soluble to the circulatory system – from the digestive system). Structurally, it consists of ducts, nodes, and organs, which transport the lymph, clear water-like fluid (ed. McDowell 2010, p. 225).
How do the specific components of the human lymphatic system (the nodes, the thymus, and malt) help protect the organism from infection? To begin with, a lymph node or a lymph gland is an “encapsulated, organized secondary lymphoid tissue” that acts as a specific trap for dangerous particles that want to enter the immune system. An oval shaped lymph node generates a multitude of antibodies that will seek and attack the dangerous pathogens while in circulation in the lymph. Thus, through the lymph node cells activity (lymphocytes and macrophages functions), dangerous microorganisms and antigens are removed from the system (Williams 2011,ch. 1.19).
Next, the spleen is another organ within the system, which primary function is filtering blood. By the function of erythrocytes, it acts as a reserve for red blood cells, which are released in case of emergency (namely, decreased blood volume, when wounds need to be healed, etc.). In addition, the spleen, through the red pulp area, filters blood and, through the white pulp area, produces active immune response (Handin, Lux, & Stossel 2003, p. 650).
Further, the thymus is a lymphatic system gland located under the breast bone. It helps generate white blood cells. Its role in the protection of the body from the infection is creation of the specific environment where T-lymphocytes, also known as T cells, get developed before they bind to particular invading organisms and destroy them or leave them harmless. Hence, the thymus helps to attack the foreign substance within the immune system.
Finally, MALT (the mucosa-associated lymphoid tissue) performs the role of the diffusion system and is located in different sites of the human body: in gastrointestinal tract (e.g. stomach), lung, thyroid, salivary glands, breast, skin, and eye. Its cells (macrophages, B cells, T cells, and plasma cells) prevent antigens from penetrating further in the body and do not let them pass through the mucosal epithelium. MALT regulates mucosal immunity (Zucca & Bertoni 2004).