Andrew Huberman

they have walls of those tubes that can resist a lot of pressure.

And that's important because we need to put a lot of pressure to be able to pump blood far out into the body, out to your fingertips, your toes and everything in between.

Okay.

Oxygenated blood is going to travel out through those arteries.

And then eventually as those arteries approach the tissues that they need to oxygenate, and by the way, the blood is delivering not just oxygen, but also glucose, blood sugar, hormones, different proteins, amino acids, all the stuff that your tissues need, not just oxygen.

But then those arteries are going to transition into smaller diameter tubes that we call the arterioles.

And then eventually, as those arterioles approach the tissues, they need to deliver all that stuff, all those goodies within the blood.

those arterioles are going to transition and start branching into what are called capillaries.

Most of you have probably heard of capillaries.

Capillaries have a very, very thin wall, just one cell thick, which allows things within the blood like oxygen, amino acids, and other things that the cells in the tissues of your body need to actually get out into those tissues.

So most of us think about the blood system as pumping stuff out there, but we probably haven't thought about how the stuff that needs to get to our cells actually gets out of the blood and into those cells.

And I just explained how, by having a very thin walled set of capillaries carrying that oxygenated amino acid containing glucose containing blood, those nutrients and that oxygen can actually get out of the vasculature, out of those capillaries and into the cells that need them.

Okay.

At a future date, I'll talk about the actual mechanics of how that's done.

But for right now, I think that's sufficient.

Now, once that stuff arrives in the tissue, and here when I say tissue, it could be brain tissue, it could be muscle tissue, it could be liver tissue.

Once that stuff gets out into the cells, the cells are going to use it.

They're going to use the oxygen, they're going to use the glucose, they're going to use the amino acids, they're going to use the hormones.

And as a consequence, they are going to create some waste products.

There's going to be carbon dioxide that's created.