How the Lymphatic System Works

LYMPHATIC VESSELS:  These are a system of ducts that collect fluid from the body tissues, deliver it to the filtering lymph nodes and transport it to the heart, where it rejoins the body's main circulatory system.  Lymphatic vessels start as microscopic tubes in the spaces between cells and branch into larger vessels throughout the body.  Like veins, the vessels contain valves that help maintain the flow of lymph back to the heart.

THYMUS:  Located behind the breastbone, the twin lobed thymus gland converts lymphocytes into more specialized T lymphocytes.  Most of this work is completed by puberty after which the thymus begins to shrink.

LYMPH GLANDS (NODES):  Small oval structures that trap invading bacteria and viruses are distributed along the network of lymph vessels and in the clusters around the neck, armpit and groin.  In response to infection lymphocytes in the gland divide and proliferate.  This is why your neck glands swell when you have a throat infection.  Each node has vessels leading in and out of the gland and its own blood supply.

TONSILS:  These oval pads of tissue at the back of the throat protect against infection of the upper respiratory tract.  Tonsils sometimes become infected by the very microorganisms they fight.  Doctors may remove the tonsils, if infections recur and/or resist treatment.

SPLEEN:  This fist sized spongy organ breaks down worn out red blood cells and produces some of the lymphocytes and other infection fighting components of the immune system.

BONE MARROW:  The soft fatty inner part of a bone, the marrow produces all of the body's red blood cells and platelets and most of the white blood cells.