Where are carbohydrates, amino acids, and water soluble vitamins first received after entering the portal vein?

• A. Muscles
• B. Heart
• C. Liver
• D. Small Intestine

Answer: (C)

Nutrients absorbed from the gut are carried to the liver first via the hepatic portal circulation. After digestion, carbohydrates are broken down to monosaccharides and amino acids, and water-soluble vitamins enter the blood; all of these travel via the portal vein to the liver. The liver’s hepatocytes take up these nutrients for immediate use, storage, or processing before they enter the general circulation. This is why the liver is the first organ to encounter these absorbed nutrients. The small intestine is where absorption occurs, not where these nutrients are first received after entering the portal vein, and the heart and muscles receive nutrients later through systemic circulation after the liver processes them.