Andrew Huberman

And then you have your adaptive immune system, which recognizes the specific surface of foreign invaders and generates antibodies to essentially bind that specific surface and its properties and neutralize that foreign invader.

So innate immune system and adaptive immune system.

Within your lymph nodes, you basically have a confluence of a lot of different immune cell types, evaluating what's coming through in the lymph fluid, which reflects, of course, what's in the blood, because remember,

The blood supply is giving oxygen and nutrients and other things to your cells.

A lot of the fluid that's put out into the interstitial space, remember about 16 or 17 of the 20 liters per day will be drawn back up into the blood supply.

But then some significant portion, that three to four liters of fluid that ends up in the lymphatic system is going to reflect what's in the global circulation system.

And these lymph nodes are a place where what's in the lymphatic system can be evaluated to determine whether or not you've got something in your body that you shouldn't

or that you would like to eradicate.

So the lymphatic system, which we've mostly been talking about up until this point as a drainage system, has a second purpose, right?

It's a multitasker.

It also serves an immune system role to evaluate what's in the lymph and therefore in the blood and therefore in the entire body.

Now, while we have lymph nodes in our jaw, behind our ears, in the back of our head, in the occipital area, lower back part of our head, we also have them behind our knees, in our groin, in our elbow region.

We have collections of lymph nodes distributed essentially across the entire body, okay?

You're not gonna see them continuously across the body, but every area needs to be surveilled, right?

And so you have these checkpoints everywhere along the lymph system.

where viruses, bacteria, other foreign invaders can be evaluated and combated by your immune system.

Now, does that mean that if you have, for instance, sore lymph nodes in your left armpit, that you necessarily have something wrong with your left arm?

No, not necessarily because of the way the lymphatic drainage occurs.

However, many people who have a sore lymph node in their armpit will kind of rub it.

And that makes perfect sense.