Diseases of the Lymphatic System: Definition

00:01 Welcome back to the Advanced Vascular Medicine program.

00:06 This is the last lecture in this series. And we are going to be considering the lymphatic system in this unit.

00:15 First we’ll as always talk about definitions, particularly the various components of the lymphatic system. We’ll talk also something about the diseases: malformations, production of edema and even massive edema known as elephantiasis, which is quite rare and very, very troublesome for patients.

00:37 We’ll also talk somewhat about the function of the lymphatic system.

00:43 So the major function of the lymphatic system is to move fluid in one direction from the tissues to large veins back into the circulatory system.

00:56 The lymphatic system is extensive throughout the body. It drains the body’s interstitial fluid via small lymph vessels or lymph capillaries. And they eventually drain into the thoracic venous system either through the thoracic duct or the right lymphatic duct.

01:20 Now occasionally proteins or cell debris or even bacteria will work their way out into the tissues and then they’re also drained by the lymph system because they cannot re-enter the blood vessel themselves. So the lymph system also is a defence system particularly against bacteria. And we’re going to go over this in much greater detail as we go along.

01:46 The components of the system are numerous. First of all, you have the very small lymph vessels in the tissues that are picking up fluid that leaks out of the capillaries. This becomes progressively larger vessels. Eventually, it connects up with the lymph nodes, which are part of the lymphatic system and in particular the lymph nodes that lie in the neck – the cervical spinal (neck) regions as well as along the face and the jaw.

02:15 Interestingly, most people don’t realize this but the tonsils are actually lymphatic tissue and they also help to control pathogens – that is bacteria – that might be ingested when you’re swallowing.

02:31 So let’s talk about each component of the lymph system.

02:35 It starts out in the tissues with little tiny, thin-walled, valved structures. And again you want valves just like in the veins to keep the fluid moving in one direction – that is back towards the chest and into the venous system so that the fluid is returned to the cardiovascular system.

02:58 There’s an extensive network of these little tiny vessels and, as they progress from the most remote area in the tissues back into the more proximal areas, they get bigger, they get thicker-walled and so forth. And we’re going to show examples of that in a moment.

03:17 But the end capillary ones – the capillary lymphatics that are in intimate contact with the capillaries – are very, very tiny often just a one single cell thick. And they are a major complement to the cardiovascular system.

03:34 Their major roles are two: one is to remove tissue fluid that leaks out of the capillaries and return that fluid to the cardiovascular system. And the other is defence against pathogens – against particularly bacteria. And we’ll talk about both of these functions as we go along here.