Splanchnic Circulation – Digestion and Absorption

00:01 The last aspect is now that you’ve reabsorbed these particular molecules, whether it be a water, whether it be ions, whether it be things like fats, proteins, carbohydrates, where do they go? Most of this is going to be picked up in the hepatic circulation, but to talk about the hepatic circulation, we need to diagram out a little bit where the blood flow goes.

00:26 So from the heart, you would have places like the celiac artery that delivers blood flow to places like the spleen, the stomach, and the liver.

00:37 The superior mesenteric artery delivers blood flow to the pancreas and parts of the small intestine, and then the inferior mesenteric artery delivers to some of the intestines as well as the colon.

00:50 But it’s interesting that all of these molecules are also linked to the liver via the hepatic circulation.

00:57 So, you are actually passing through multiple capillary beds as you go from the celiac artery through the stomach, and then it goes back to the liver.

01:08 Why is this so important for digestion and absorption? Is once you absorb something through say some place like the small intestine, what you’ve absorbed is going to travel back to the liver.

01:21 If you’ve absorbed water form the colon, that’s also going to travel back to the liver via the portal circulation.

01:30 Individual components of the circulation involve different amounts of blood flow to it.

01:37 The majority of the blood flow goes to the mucosal layer and less of the blood flow goes to the muscular layer.

01:45 The other item to consider especially in the small intestine is that there are differences in the amount of blood flow based upon the villi and microvilli in those regions.

01:57 So if we have a microvilli over here, you can see that there is a change in the partial pressure of oxygen as you move towards the tip of the microvilli.

02:08 And that’s because of less and less circulation as you move towards those microvilli.

02:14 Why this becomes important, is that there are already low amounts of oxygen in the microvilli themselves and what can happen is these can become ischemic if there’s a pronounced vasoconstriction for prolonged periods of time.

02:28 And that can then change intestinal barrier properties and cause problems with allowing certain bacteria across the GI wall, making it a little bit leakier.