Lectures

Venous Drainage – Portal System

by James Pickering, PhD
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    00:01 This lecture is going to look at the portal venous system. The portal venous system is really important and there is a few of them throughout the body, but the portal system in general is where a capillary bed runs into another capillary bed before it returns to the systemic circulation and passes through the heart. So, for example we are used to blood passing via the arteries to a capillary bed, say a muscle and then into the venules and the veins which take it back to the heart, it can then be sent to the lungs for gases exchange to occur and then return and be distributed again. But this portal system allows blood that’s passed through a capillary bed to then pass to another capillary bed before returning to the heart and the portal venous system is a real good example of this.

    00:53 Venous drainage from the GI tract and the accessory organs travels to the liver, the second capillary bed via the hepatic portal vein and then via hepatic veins does it then drain into the systemic system and towards the heart. We also have some anastomoses between the portal system and the systemic system and this occurs normally during pathological situations which means blood can’t pass through the liver and it is actually directed via small blood vessels in the systemic circulation. So the portal venous system receives poorly oxygenated blood, it is nutrient rich blood because it is passed through the GI tract but the oxygen has been used up by those tissues to actually absorb the nutrients and blood from the gastrointestinal tract within the abdomen and pancreas and gall bladder and spleen passes to the liver. It is carried to the capillary beds of the liver and then subsequently it is returned to the systemic circulation.

    01:59 So, let’s have a look for the arterial supply we did foregut, midgut and hindgut and we can keep these similar principles. So here we can just concentrate with organs such as the stomach and the liver. So if we look at the organs of in the foregut, remember we have the oesophagus, the stomach, spleen, pancreas, duodenum and we have the gall bladder and we can see that we have a whole series, look at the stomach here, we can have a whole series of veins draining this region and they drain into one of several blood vessels, but ultimately they end up going to the hepatic portal vein. So, if for example the oesophagus may well drain in to the left gastric vein which then passes into the hepatic portal vein here. We can see the stomach with its left and right gastric veins draining directly perhaps in the hepatic portal vein; the left gastro-omental may well drain into the splenic vein which then passes back to the hepatic portal vein. The right gastro-omental vein that may or pass through the superior mesenteric vein which we can see running lining this direction, but ultimately passing into the hepatic portal vein. So there is considerable variation and this detail on the side of the screen is really just an indication of the most likely route, but ultimately this blood passes back to the hepatic portal vein. We can see some other examples for the gall bladder, be the cystic vein which drains directly into the hepatic portal vein. Similar occurs for the midgut and the hindgut; if you are familiar with the arterial supply then the venous drainage will be that much similar, very similar to it, so the ileum and the jejunum would drain via ileal and jejunal veins. These will drain into the superior mesenteric veins; they will drain into the superior mesenteric vein here. The caecum and appendix, ileocolic vein and that can drain into the superior mesenteric alongside the right colic and the middle colic veins, all draining into the superior mesenteric vein.

    04:13 Here we have a slight discrepancy, a slight alteration from the normal plan you would suggest and that is where superior rectal veins here and the sigmoid veins, descending part of the colon draining via the left colic vein, these actually pass into the inferior mesenteric vein. Now the inferior mesenteric vein actually runs up towards the splenic vein in a significant number of people. The inferior mesenteric vein runs up into the splenic vein and the splenic vein then, as we have suggested before, unites with the superior mesenteric vein and here we have the formation of the hepatic portal vein and if you remember this occurs posterior to the neck of the pancreas. We can see a number


    About the Lecture

    The lecture Venous Drainage – Portal System by James Pickering, PhD is from the course Abdomen.


    Included Quiz Questions

    1. Posterior
    2. Anterior
    3. Superior
    4. Inferior
    1. Inferior mesenteric
    2. Superior mesenteric
    3. Splenic
    4. Sigmoidal
    1. Splenic and superior mesenteric vein.
    2. Right gastric and splenic vein.
    3. Splenic and inferior mesenteric vein.
    4. Superior mesenteric and inferior mesenteric vein.
    5. Cystic and splenic vein.
    1. Left gastric vein.
    2. Right gastric.
    3. Cystic.
    4. Superior mesenteric.
    5. Right gastro-omental vein.

    Author of lecture Venous Drainage – Portal System

     James Pickering, PhD

    James Pickering, PhD


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