Andrew Huberman

The lymphatic vessels have a very important property, which is that they are one-way vessels, okay?

Fluid can only pass one direction through them.

And that unidirectionality of the vessels is oh so important when thinking about how to encourage lymphatic drainage and lymphatic flow.

And when I say lymphatic flow, what I really mean is the passage of fluid from the interstitial extracellular space into these lymphatic vessels

sometimes people will call them lymphatic ducts, but that's actually a technical term related to something else, but into these lymphatic vessels, then through these vessels and back into the venous blood supply where all sorts of good things happen and we'll talk about it in a bit.

So they're one-way vessels.

And if you think about the lymph that accumulates and then goes into the vessels in say your feet,

If it's a one-way vessel, you know that vessel is going to be directed towards the heart, right?

The fluid will be able to go towards the heart, right?

Because eventually that's where this stuff needs to go.

It needs to dump back into the venous blood supply, get oxygenated and so forth.

And the waste has to be disposed.

And we have this thing called gravity, which is pulling down, right?

And it's pulling down.

It's a force that's literally pulling down, and you've got these one-way vessels trying to pass the lymph, which is fluid, but it's kind of a slightly viscous fluid up toward the heart.

You also have lymphatic vessels in your hands, in your arms, and gravity's, of course, pulling down on the fluid within them as well, and your brain, et cetera.

Now, here's a critical feature of the lymphatic system that is different from the cardiovascular system.

which is there's no pump.

In the cardiovascular system, you have a pump, you have a heart that can generate a lot of force to move that liquid out through the arteries and back through the veins, and you've got a lot of mechanical force coming from that heart.

The lymphatic system doesn't have that at all.