Blood, Sweat, and Tears: Human Anatomy

Lymphatic System

What is the lymphatic system?

Perhaps one of the most confusing systems, the lymphatic system is nonetheless very important. The lymphatic system can be confusing because it works in tandem with so many other systems. It first starts out by piggy-backing onto the cardiovascular system, utilizing the system of various vessels to move through the substance known as lymph through the body. Lymph actually starts out as part of the blood; it is the blood plasma that slowly leaks out through the walls of veins and capillaries. This lymph comes out carrying wastes, bacteria, and whatever else it has grabbed on to out of the blood stream. Any typical mixture will include a number of proteins, wastes, leukocytes, and glucose. This lymph then fills the spaces between various muscles, bones, and basically any other empty space in the body. This is another problem when recognizing the lymphatic system - there is no centralized structure. Rather, the system relies on various contractions and movements to propel the lymph through lymphatic vessels and eventually find it's way to one of a couple hundred or so lymph nodes around the body. The lymph nodes grab all the substances that the lymph has been picking up and then send the lymph right back out to eventually make it's way back to the heart and blood stream.  


Lymph is tough to differentiate from blood plasma. Essentially, blood plasma is the background of blood - it is the liquid that encases all the other components. As some of this filters out of the cardiovascular network, it joins a few more components - namely glucose and used leukocytes - and becomes what is known as lymph. A key differentiator between plasma and lymph is their color - plasma tends to be more yellowish whereas lymph is clear. 

Thoracic Duct

This is the largest lymphatic vessel in the body and as such, one of the most important. Running through the center of the body, this duct is where the vast majority of lymph ends up draining to. It relies mostly on the contract of the diaphragm and lungs to push lymph through, and only carries lymph upwards through the body to drain it back into the cardiovascular system. 

Lymph Vessels

This network, though not as developed, is similar to the vascular network of the cardiovascular system. Lymph vessels scoop up lymph when it's been oozed out of the veins or capillaries and send it on to lymph nodes. However, these vessels, instead of being pervasive, are far more sparse than that of the cardiovascular system.

Lymph Nodes

Perhaps off all parts of the lymphatic system, this is the best known. About five to six hundred of these tiny little structures litter the body, functioning almost as train stations for the lymph: lymph comes in, drops off all of it's passengers, or all the wastes it's been carrying from the blood, and is then sent on it's way. These often enlarge when one is sick as they are overloaded with more waste than they can usually handle.