08.01 Vessels & Fluid

In this lesson, we are going to take a look at the lymphatic system.

So to get started in the first thing we need to take a look at all the functions of the lymphatic system. The lymphatic system is part of the immune system, and its purpose really here is to produce the mature T lymphocytes & B lymphocytes, and plasma cells. Even though the cells don't originate in the lymphatic system this is where they are actually stored and mature so that they're ready for use. The other thing is that the lymphatic system also houses macrophages, which go to the sites of infection and they actually destroy any sort of pathogen. So they essentially clean all the fluid out. The other thing in lymphatic system does is that it returns fluids and proteins and back to the blood through lymphatic circulation which we're getting to get into.

When we talk about the lymph system the first thing you need to know is that the lymph system is a complementary system to the circulatory system. And just like the cardiovascular system, there are different sizes of vessels that have different purposes. So starting at the smallest size, we have these things called lymph capillaries. They're similar to size of a blood capillaries but they don't have a continuous system. They essentially have these dead end sacs, that are very porous and allow for any of that fluid that gets lost outside of the cardiovascular system to get pulled into the lymphatic system to get put back into circulation. Now the lymph capillaries are in close proximity to the blood capillaries and they're all intermingled.

Once the fluid is put back into the lymph system starting at these lymph capillaries, the fluid then migrates through these tubes called lymph collecting vessels. And they're formed essentially by the fusion of capillaries and they’re similar to veins even though they have thinner walls and they contain valves. And valves are one of the most important functions of these vessels. The lymph system doesn't have a heart or a pump to continue to propel the lymph fluid through the system, so there has to be a way for it to move. This happens by a couple of ways. The first one is at these valves, and they are very important. The valves open for fluid to pass through them, and then they close to keep the fluid from going backward. The other thing is that skeletal muscle around all of the lymph vessels squeezes the lymph vessels and propels the fluid forward to the system. At different areas there are these interconnecting lymph nodes, which help to filter out all of the lymph fluid from different types of pathogens and allows the immune system to do its job.

At some point, just like the cardiovascular system, this lymphatic system has to get the fluid back to its starting point. So as lymph fluid comes from the vessels that has to go back up to the circulatory system and essentially is going to end by emptying the lymph fluid into a vein. But it has to make its way up first. So from the lower extremities these lymph vessels dump the lymph fluid into these lymphatic ducts. From the lower extremities, they enter into a lymphatic duct called the cisterna chyli and that's at about the space of L2. It's going to receive that lymph from the lower extremities and then it splits into the right and left lymphatic ducts. The right lymphatic duct drains from the right upper side, and then the left lymphatic duct drains from the left side and both of the legs.

As this fluid moves through the lymphatic system, it's going to enter back into the cardiovascular system at the subclavian veins. On the right side it's going to enter into the right subclavian vein and for the left side is going to enter into the left subclavian vein. Because this is a low pressure system at this area, it allows for easy transport of this fluid to go from the lymphatic system back into the cardiovascular system where it mixes with blood and it can transport all of the nutrients that it needs to.

Now let's take a second to talk about lymphatic fluid. The lymphatic fluid is nearly identical to plasma, but it has less protein. During the transport of the lymphatic fluid, what happens is blood plasma is filtered through this fluid exchange and this happens at the level of the high-pressure capillary arterioles. Because of this high pressure system, this tissue fluid gets filtered, and as it leaks out and then re enters back into the lymph system as lymph fluid and it'll enter at the level of lymph capillaries. Then is transported through those collecting vessels to the lymphatic ducts, and then it re-enters the cardiovascular system through that subclavian vein.
Okay so let's recap.

We were talking about the lymphatic system, remember that its main purpose is to return the blood back to the circulatory system and it houses those mature T & B lymphocytes so that it helps with the immunity.

The lymph capillaries are the first stage of returning that lymph fluid back into the circulatory system, and then it travels to those lymphatic ducts.

The cisterna chyli is the main area that receives lymph from the legs and then it split into the right and left lymphatic ducts.

Valves and skeletal muscle contraction are the main source of propelling that lymph fluid back up to the level of the heart.

And lastly lymph fluid is the fluid that's being transported back into the circulatory system. It contains far less Protein than blood plasma, but it also serves to filter out that fluid at the same time.
And that's it for our lesson on lymphatic vessels and fluid. Make sure you check out all the resources attached to this lesson. Now, go out and be your best selves today, and as always, happy nursing!