Lymphatic and Immune Systems
The lymphatic system is responsible for removing foreign substances from the body. This body system includes the immune system and has organs and tissues that help fight infections. Communicable diseases can develop often if this system is not healthy. The main organs of the lymphatic and immune systems include the following:
lymphatic vessels
lymph nodes
tonsils
the spleen
the thymus
white blood cells
Lymphatic Vessels and Lymph Nodes
The lymphatic vessels are similar to blood vessels, but they do not carry blood. Instead, they carry fluid that builds up in tissues of the body. This fluid comes from the body’s millions of tiny capillaries. Each time the heart beats, it creates blood pressure in capillaries. This pressure pushes fluid out of the capillaries and into tissues. The fluid becomes lymph when it enters the lymphatic capillaries and flows into other lymphatic vessels (Figure 2.19). Lymphatic vessels collect and transport lymph to the chest. There, lymph rejoins the blood.
Lymph is filtered by lymph nodes before it reenters the blood. Inside the lymph nodes, lymph contacts white blood cells. These cells remove bacteria and viruses from the fluid. They can also grow and reproduce to fight infections. In some infections, lymph nodes become swollen because of the buildup of extra white blood cells. For this reason, swollen lymph nodes are a sign that the body is fighting an infection.
Tonsils are lymphatic tissues that guard the throat from infection. They are located on the sides and top of the back of the throat. The tonsils also contain white blood cells. When the throat is infected, tonsils enlarge and become red. Swollen tonsils are a sign that your body is fighting a throat infection.
