Adder by Wildlife Wanderer on Flickr.
Today we talked about the anatomy of the lymphatic vessels of the lower limb, and the mechanisms by which lymph is transferred from lower limb tissues back to the abdomen, thorax and circulatory system. We used examples of elephantiasis (and the filariasis worm), peripheral oedema, exercise recovery (after running or cycling racing) and snakebite.
As we’re midway through year 2 and students are close to having covered all of the human anatomy in the medical curriculum we were all aware of the purposes of the lymphatic system and some of the fine structure, but there was no harm in reviewing some of the smaller anatomical details to help understand the relations between structure and function here. For example, lymphatic vessels begin as small, open ended vessels into which fluid from a tissue can pass. This fluid is most likely to have come from the plasma of the capillary bed that perfuses the tissue, and not all of the fluid is collected on the venous side. Normally the fluid is returned to the systemic circulation by the lymphatic system but your foot is a long way away from your heart, so how does this work? The lymphatic system is a collection of vessels that drain into larger and larger vessels, but the flow is only in one direction, there is no pump attached directly to them, and the pressure within these vessels is very, very low.
Lymphatic capillaries (This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license).
