The Body’s Highways

The Story

When Stina’s LDL kept climbing, the workup centered on her liverA large organ that produces bile, detoxifies blood, and stores nutrients. — and at first that seemed an odd place to look for a blood-vessel problem. The reason is anatomical: the blood vessels of the body are organized into specific circuits, and one of them deliberately routes nutrient-rich blood from the gut through the liver before it reaches the rest of the body. To understand her lipidsOrganic molecules including fats, oils, and steroids., you have to follow the highways.

Blood travels in organized routes rather than a single loop. The pulmonary circuitThe circulation of blood between the heart and the lungs, where blood is oxygenated. carries oxygen-poor blood from the right heart to the lungs and back; the systemic circuitThe part of the circulatory system that carries oxygenated blood from the heart to the body and retu carries oxygen-rich blood from the left heart out to the body and back. Nested inside the systemic circuit are special routes: the coronary circulation, which feeds the heart muscle itself, and the hepatic portal system, which collects blood draining the digestive organs and delivers it to the liver before returning it to the heart. That portal detour is why the liver gets first pass at everything absorbed from the gut — and why it sits at the center of cholesterolA lipid molecule that is a key component of cell membranes and a precursor for bile acids and steroi handling. Mapping these routes sets up the next pages: it explains why Stina’s lipid story is a liver story, and it locates exactly where atherosclerotic plaque does its damage along the arterial highways.

From Stina’s chart: Stina’s cholesterol story is really a liver story — and the reason the liver is central is written into the body’s circulatory routes, especially the hepatic portal system.