Although many afferent lymphatic vessels carry lymph to a lymph node, there is only one efferent lymphatic vessel carrying lymph away from the node (Applegate, 2000, 289). Because there are more afferent vessels than efferent vessels, lymph flows slowly through the sinuses of the node, allowing time for the cleansing process to take place. It is important that lymph flow slowly through the lymph nodes because they are the only structures in the body that filter the lymph, which is their primary function. As the lymph passes through the sinuses of the lymph node, damaged cells, cellular debris, infectious agents, and cancer cells are trapped by the fibrous mesh in the node and removed from the lymph before it is returned to the blood.
In the node, lymphocytes react against the bacteria, viruses, and cancerous cells and destroy them (Applegate, 2000, 290). Macrophages in the node engulf the destroyed pathogens, damaged cells, and cellular debris. The slow filtration of the lymph through the nodes gives time for all these cleansing processes to take place so that nothing toxic or infectious, or dangerous to the body gets through and into the bloodstream, where it would be spread rapidly throughout the body. For instance, cancer can be spread through the lymphatic system if cells from a tumor get into the lymph and are carried to other parts of the body to metastasize (289). Slow passage of lymph through the nodes helps to restrict this, but if large numbers of cancer cells enter the lymph, the nodes cannot filter them all out and some get through into the bloodstream to spread the cancer to other parts of the body.
If lymph passed quickly through the lymph nodes, the filtering process and cleansing of lymph would be ineffective, and infectious agents, cancer cells, cellular debris, and damaged cells would pass through the nodes and into the bloodstream. This would mean the rapid spread of infections because infectious...