Andrew Huberman· PhD
Now, some of the waste product and the water, so carbon dioxide and water, et cetera, will be taken back up by the blood supply. How does that happen? Well, there are capillaries that are referred to as "venous capillaries." Okay. So we talked about the arterial system, which delivers oxygenated blood. There's also another system called the "venous system," which takes deoxygenated blood back up to be oxygenated by the lungs, and it does that, of course, in concert with the heart. So, we have the arterial system that delivers oxygenated blood. There are rare exceptions of arteries that deliver non-oxygenated blood to tissues such as the lungs, but let's just set that aside for now. We've got this arterial system that delivers oxygenated blood, and then now, we have the venous system. So, we have these little venous capillaries that are also just one cell wall thick, and the water, the carbon dioxide, the ammonia, the waste products are going to get reabsorbed there.