Liberal Arts Blog — Missing Links II: The Hepatic Portal Circulation
Liberal Arts Blog — Wednesday is the Joy of Science, Engineering, and Technology Day
Today’s Topic — Missing Links II: The Hepatic Portal Circulation
There are two circulations, right? The pulmonary and the systemic? The pulmonary pumps the de-oxygenated blood from the right ventricle to the lungs to get the oxygen and that blood returns to the left to be pumped by the left ventricle to the rest of the body so all the cells can get the oxygen and get rid of the carbon dioxide, right? Well, that was my mental model until I wondered: how do the nutrients enter the bloodstream? Cells need more than oxygen. How do these nutrients get into the bloodstream? The missing link in this case is the “hepatic portal circulation.” Experts — please chime in. Correct, elaborate, elucidate.
FROM THE SMALL INTESTINE TO THE LIVER TO THE VENA CAVA
1. The portal system takes nutrient-rich blood from the gastrointestinal system (principally the small intestine) to the venous system via the liver.
2. The liver gets 25% of its flow from the hepatic artery but 75% of its flow from the portal circulation.
3. The blood the liver gets is partly oxygenated.
THE VILLAE OF THE SMALL INTESTINE AND THE HEPATOCYTES
1. In the stomach and small intestine, hydrochloric acid and pepsin break up the stuff you ingest into pieces small enough to be absorbed through the villae into capillaries. For example, they break up proteins into amino acids.
2. The liver and cells can process these components into larger units — eg. proteins that we need.
3. No portal circulation, no life.
LEAVING THIS THIRD OF THE CIRCULATORY SYSTEM OUT IS COSTLY
1. Without this third, the student can’t possibly make sense of the big picture.
2. Organ systems are usually taught as isolated systems.
3. Deep understanding only comes when you see how they relate to each other.
NB: This failure is emblematic of science curricula generally. And for that matter humanities and social science curricula as well.
Heart and Circulatory System (for Teens) — Nemours KidsHealth
What is a portal system? What is the purpose of the hepatic portal? | Socratic
YOUR TURN
Please share the coolest thing you learned this week related to science, engineering, or technology. Or, even better, the coolest or most important thing you learned in your life related to science and engineering.
This is your chance to make someone else’s day. Or to cement in your mind something that you might otherwise forget. Or to think more deeply about something dear to your heart. Continuity is key to depth of thought.
