23. Characteristics and disorders of splanchnic blood flow

Last updated on May 24, 2019 at 18:23

Physiological splanchnic circulation

The GI-tract, liver, pancreas and spleen all together receive about 1.3-1.4 L/min which is 27% of the blood flow. Of this value, 300-350 mL goes to the hepatic artery alone.

The gastrointestinal motility and the secretion and absorption are all highly dependent on the organs involved receiving enough blood.

In response to food intake will the blood supply of these organs be increased. This increase is mediated by the hormones cholecystokinin (CCK), secretin and vasoactive intestinal peptide (VIP), along with kinins like bradykinin and kallidin.

Disorders of splanchnic circulation

When there is an impairment of the gastrointestinal circulation, the cells on the tip of the villi will be the first to be affected. This is because of the countercurrent blood flow inside the villi. The apical part of the villi is mainly responsible for absorption, so in the cause of circulation impairment, the absorption is the first function to deteriorate.

Blood Flow Through The Colon Countercurrent1305247179921
The countercurrent blood flow of the villi. Because the vein and artery are so close to each other will some of the oxygen and nutrients from the artery diffuse into the vein, which means that the blood in the tip of the villi contains the least oxygen and nutrients.

While absorption is impaired first, secretion and motility will be maintained as normal for a while. Later the motility will be impaired as well, potentially causing subileus.

In the case of ischemia of the pancreas will pancreatic proteolytic enzymes be released. A peptide called myocardial depressing factor (MDF) will also be released by the pancreas, which causes decreases the myocardial contractility.

In addition to the 350 mL of minute blood from the hepatic artery will the liver also receive 1000 mL from the portal vein. Therefore around 30% of cardiac output flows through the hepatic veins. Therefore, many disorders of the liver easily can impair the filling of the heart, and how a congested heart always gives symptoms in the liver.

It’s important to keep in mind that if there is any need for redistribution of the circulation will blood always be directed from the splanchnic areas to the areas that need more blood, like the brain, muscles or skin.

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24. Pulmonary circulation, pulmonary hypertension

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