A network of lymphatic vessels connects the widely dispersed organs. The vessels carry lymph, a colorless fluid that leaks from the bloodstream, collects between our cells, and then seeps into the small lymphatic capillaries, whose walls allow fluid in but prevent it from escaping again. Lymph, like blood, transports the cells of the immune system, as well as foreign substances that find their way into body tissues.
The network of vessels begin in a multitude of thin walled capillaries that branch throughout the tissues. Like small tributaries that feed into major waterways, these tiny tubes drain into larger and larger vessels. From the top of the scalp, they run down through the neck; from the hands and feet, they flow up through the limbs to the torso. In the lower part of the neck, the biggest vessels pour their contents into two large lymphatic channels. These channels, in turn, ultimately converge with veins that lead into the heart.
Unlike the blood circulatory system, the lymphatic system has no pump to keep its vital fluid in continual motion. Instead, body movements and muscle contractions squeeze the vessels, propelling lymph along its course.
Amazing isn’t it?