Human Anatomy: Please describe the drainage pattern for the lymphatics system and describe its clinical significance.

Question

Please describe the drainage pattern for the lymphatics system and describe its clinical significance.

Answer 1

The lymphatic system may be, in my opinion, the unsung hero of the body. It doesn't normally get a lot of press or space in the textbooks, but its function is certainly no less important than any other system.

Along with the role it plays supporting the immune system, it is also responsible for reclaiming interstitial fluid which is released from the blood vascular system into the tissue space and carrying that back to the heart.

As the lymph fluid is picked up by the lymphatic capillaries, it begins its way through the interspersed lymph nodes. The anatomy of the nodes is such that the lymph is held up for a period of time which allows for more effective inspection and cleansing of any waste products, cellular debris, and pathogens that may have been drawn in from the interstitial space. Harbored within the nodes are the two primary lymphocytes, T-cells and B-cells which can begin the process of an immune response upon detection of pathogenic organisms and potentially cancerous cells.

From the lymphatic capillaries and through the lymph nodes, the lymph then passes into progressively larger lymph vessels known as the lymph ducts. The right side of the head and the upper right quadrant of the trunk are drained by the right lymphatic duct while the larger thoracic duct drains the left side of the body.

Together, the ducts empty their collected lymph fluid into the subclavian veins to return to the blood circulation as the superior vena cava empties back into the right atria.

The lymphatic vessels are similar to the veins of the body in that they contain valves to provide for unidirectional flow and the lymph is moved through the system by muscle contractions similar to the mechanics in moving blood through the veins.

In non-homeostatic conditions, the drainage of lymph may be blocked resulting in the accumulation of fluid such as in lymphedema. Furthermore, this may occur due to excess scar tissue, injuries, or from infectious agents as in lymphatic filariasis.

Answer 2

Lymph must travel through the lymph nodes before it is returned to the bloodstream. The lymph nodes are shaped like the kidneys with a convex surface and a concave surface (also known as the hilum). Lymph enters the lymph nodes at the convex surface and is funneled toward the hilum. This slows the flow of lymph through the lymph node, just like traffic on the highway slows down when lanes are closed. This allows time for lymphocytes (B cells and T cells) and macrophages in the lymph nodes to detect pathogens and clear out bacteria and debris. Sometimes during infection, the lymph nodes become clogged with dying bacteria and immune cells which triggers inflammation. This is most often observed in the cervical lymph nodes (the ones in your neck) and is often referred to as "swollen glands." Keep in mind that this is a misnomer. There are no actual glands in the lymph nodes.