The lymphatic system defends the body from foreign invasion of disease causing agents such as viruses, bacteria, or fungi. The lymphatic system consists mainly of the spleen, bone marrow, thymus gland, lymph nodes, tonsils, appendix, and a few other organs. The lymphatic system and the cardiovascular system are closely related structures that are joined by a capillary system. The Lymphatic System is important to the body's defense mechanisms. It filters out organisms that cause disease, produces certain white blood cells and generates antibodies. It is also important for the distribution of fluids and nutrients in the body, because it drains excess fluids and protein so that tissues do not swell up. "Lymph" is a transparent body fluid that contains white blood cells called "lymphocytes," along with proteins and fats. Lymph seeps outside the blood vessels in spaces of body tissues and is stored in the "lymphatic" system to flow back into the bloodstream. Through the flow of blood in and out of arteries, and into the veins, and through the lymph nodes and into the lymph, the body is able to eliminate the products of cellular breakdown and bacterial invasion. Two very large areas are of significance in this system - the right lymphatic duct which drains lymph fluid from the upper right quarter of the body above the diaphragm and down the midline, and the thoracic duct, a structure roughly sixteen inches long located in the mediastinum of the pleural cavity which drains the rest of the body. It is through the actions of this system including the spleen, the thymus, lymph nodes and lymph ducts that our body is able to fight infection and to ward off invasion from foreign invaders. Lymph plays an important role in the immune system and in absorbing fats from the intestines. The lymphatic vessels are present wherever there are blood vessels and transport excess fluid to the end vessels without the assistance of any "pumping" action. There are more than 100 tiny, oval structures (called lymph nodes). These are mainly in the neck, groin and armpits, but are scattered all along the lymph vessels. They act as barriers to infection by filtering out and destroying toxins and germs. The largest body of lymphoid tissue in the human body is the spleen.
Tonsils and Adenoids
When people refer to swollen glands in the neck, they are usually referring to swollen lymph nodes. Common areas where lymph nodes can be easily felt, especially if they are enlarged, are: the groin (inguinal), armpits (axilla), above the clavicle (supraclavicular), in the neck (cervical), and the back of the head just above hairline (occipital).
The tonsils are patches of lymph tissue at the upper rear part of the throat. They help to destroy foreign substances that are breathed in or swallowed. The adenoids are similar patches at the rear of the nasal cavity in the nose.
The thymus gland in the front of the chest is large during childhood, but shrinks away during adulthood. It helps certain white cells of the immune system to develop and play their part in the body's defenses.
The spleen is just behind the stomach on the left side. It makes and stores various kinds of white cells, especially the phagocytes that "eat" germs. It also makes and stores red cells for the blood, and generally cleans and filters blood.
Tonsils and Adenoids