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How does blood carry nutrients absorbed from the digestive tract?

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Blood plasma — blood Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).

Blood serves as the essential transport medium for nutrients absorbed from the gastrointestinal tract to the rest of the body. These nutrients, including precursors of carbohydrates, proteins, and fats, as well as minerals, salts, and vitamins, enter the bloodstream and are carried through the plasma.12

The transport process involves several mechanisms:
* Direct Transport: Many substances, such as glucose, are transported in simple solution within the plasma.1
* Carrier Proteins: Certain nutrients require specific binding proteins to form temporary unions, allowing them to be conveyed through the plasma. For example, alpha and beta globulins transport lipids, while other proteins are dedicated to carrying iron and copper.12
* Portal Circulation: Blood from the digestive organs flows through the portal vein to the liver. Within the liver, nutrients can be added to the blood, removed for storage, or processed before entering general circulation.3