Capillaries – Blood vessels and blood circulation

00:00 Let’s talk a little bit about the capillaries because, of course, that’s where the oxygen and nutrient and waste product exchange is going on.

00:09 So the capillaries are the main exchange blood vessels. Their structure is that they emerge from the arterials. They are very small in diameter and very numerous and very thin-walled.

00:25 And they allow exchange of nutrients both to the cells and also removing waste products from the cells. This exchange of oxygen, carbon dioxide, nutrients and waste products occurs by osmosis, a process of diffusion from a higher level to a lower level.

00:47 So, for example, in the blood oxygen is at a very high level and in the cells at a lower level. So oxygen diffuses across the capillary membrane and is taken up by the cells. There can be a limit in terms of the amount of blood that is delivered to the periphery when there is contraction of the arterioles and, as we talked about before, the arterioles are the main resistance vessels. When they contract, they limit the blood supply going into a particular tissue. When they relax, they increase the blood supply going into a specific tissue.

01:26 Let’s move on then and talk about the veins.