Lesson 5 of 7 / Nutrition in humans
From the intestine to the liver
What happens to glucose after it enters the blood?
In this lesson: Trace absorbed nutrients through the hepatic portal vein and explain assimilation.
About 5 min
The key ideaThe hepatic portal vein carries nutrient-rich blood from the small intestine to the liver. The liver processes nutrients before blood carries them onwards.
Hepatic means related to the liver. A portal vessel carries blood between two capillary networks; here it connects the intestine to the liver.
Explore the idea
Follow absorbed glucose to the liver
The hepatic portal vein delivers nutrient-rich blood to the liver. Converting absorbed glucose into glycogen is assimilation and storage.
Original flow diagram. Hormonal regulation is studied in homeostasis. Absorbed fat follows mainly the lacteal and lymph route, not this immediate portal route.
Explanation
After glucose and amino acids cross the villus epithelium, they enter the blood capillaries. Blood leaving the small intestine is collected into vessels that lead to the hepatic portal vein. This vein takes the blood to the liver, where absorbed substances can be processed.
After a carbohydrate-containing meal, the blood arriving from the intestine can be rich in glucose. Liver cells can remove some glucose and convert it to glycogen for storage. When needed, the liver can break glycogen down to glucose and release glucose into the blood.
Nutrients are also carried to other body cells. Glucose can be used in respiration, and amino acids can be assembled into cell proteins. These uses belong to assimilation, which follows absorption. Glucose does not remain permanently inside the blood just because it was absorbed there.
The route depends on the nutrient. Absorbed fat enters lacteals mainly through the lymphatic system and reaches the bloodstream by that route. Do not draw every fat digestion product travelling straight from a villus into the hepatic portal vein.
Step by step
- 1
Start at the absorption surface
Small nutrients cross the villus epithelium; glucose and amino acids enter blood capillaries.
- 2
Name the vessel and destination
The hepatic portal vein carries blood from the small intestine to the liver.
- 3
State the use
For example, glucose is stored as glycogen or released for use in respiration; amino acids can build proteins.
Worked example
After a carbohydrate-rich meal
Glucose concentration rises in blood leaving the small intestine. Name the vessel taking it to the liver and describe one way the liver can store it.
One way to explain it
The hepatic portal vein takes the glucose-rich blood to the liver. Liver cells convert glucose into glycogen for storage. Glycogen can later be broken down to glucose when needed.
Why this answer works
- Give the precise vessel name.
- Use the correct direction: intestine to liver.
- Distinguish glucose from its storage molecule glycogen.
Is this true? "The hepatic portal vein carries bile from the liver to the intestine."
It carries blood from the intestine to the liver. Bile travels towards the intestine through bile ducts, which are not blood vessels.