Liver and hepatic portal vein sim

What the sim shows

After a meal, glucose and amino acids absorbed in the small intestine enter its capillaries, which join into the hepatic portal vein. A portal vein carries blood from one capillary network to another: this one runs from the gut to the liver, so the liver deals with the absorbed food before the rest of the body gets it. The hepatic artery brings oxygenated blood from the heart, and the hepatic vein carries blood away to the heart. The liver keeps the blood's glucose steady: when there is an excess it converts it into glycogen and stores it, and in a fast it breaks glycogen down and releases glucose. Excess amino acids cannot be stored, so the liver deaminates them: the amino group is removed and becomes ammonia, which is quickly converted into the much less toxic urea; the rest of the molecule is used for energy or stored. The urea leaves in the hepatic vein and the kidneys excrete it. The model (illustrative, in realistic ranges): blood flows through the liver at 1.5 dm³/min (1.1 from the portal vein, 0.4 from the artery); a meal is absorbed over about two hours; above 5 mmol/dm³ the liver takes in 30% of the excess glucose, and below it releases up to 0.6 mmol/min from glycogen; above 2.5 mmol/dm³ it deaminates 50% of the excess amino acids, and each amino acid's nitrogen makes half a urea; the body's other tissues take up glucose too. Time moves only when you press Wait 30 minutes. Model limits: one well-mixed liver; no hormones are shown, though in the body insulin and glucagon switch the storing and releasing on and off (a later topic); the meal sizes and rates are typical values, not one person's measurements.

• Blood vessels: oxygenated bright red, deoxygenated dark red
• Blood analyser: glucose, amino acids and urea in a sample
• Molecules (a diagram key): glucose orange, amino acids violet, urea green

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