Relationship between lymphatic and cardiovascular systems

In this post I will describe the flow between blood vessels and lymphatic vessels, and back. This flow is sort of cyclical as from the end part of capillaries some part of blood get into so-called tissue space. This is the space between (or outside) cells, and the liquid portion of it is called interstitial fluid.

 

Many proteins in the blood are too large to squeeze between the cell that make the blood vessels, so they stay within the cardiovascular system. But many other proteins are really small, so they can get out, and they need to have an extra way to get back to the bloodstream. And that's where the lymphatic system comes very handy.

 

Lymphatic vessels pick up these small proteins from interstitial fluid, and return them back into blood vessels through so-called subclavian vein. Once inside the lymphatic vessels, the fluid is called the lymph. This first picture shows nicely how the fluid flows from blood vessels into tissue space, and then into the lymphatic vessel.

 

 

In the body, there is a number of bacteria, gases, microbes, and metabolic waste, which needs to be drained out of the system. For that purpose, the lymph is full of white blood cells, which fight those substances. They need to be discharged or destroyed, so by the time when the lymph enter the bloodstream, it's clean and purified.

 

The composition of lymph and interstitial fluid are very similar, the main difference is their location. Plus in lymph, there is large number of lymphocytes and macrophages, which are the structures that fight foreign substances like toxins, microbes, and cancer cells.

 

Because the lymphatic system doesn't have a special pump (like the heart is for the cardiovascular system), there is a joint effort of lungs, muscular contrations, and valves inside of them, which support the movement of lymph in one direction, and stop it going the opposite direction. This second picture is another flow diagram showing the flow of lymph and blood, and the interraction between them.