A nutrient in the small intestine is absorbed into the bloodstream. In doing so, it moves from being dissolved in the chyme present in the small intestine to being dissolved in the plasma of the blood. How many times did the nutrient pass through epithelial tissue when moving from the intestine to the blood?

• A. 0
• B. 1
• C. 2
• D. 3

Answer: (C)

Verified step by step guidance

1. Understand the structure of the small intestine: The small intestine is lined with epithelial cells that form the mucosal layer. These cells are responsible for the absorption of nutrients.
2. Identify the process of absorption: Nutrients in the chyme must pass through the epithelial cells of the intestinal lining to enter the bloodstream. This involves crossing the cell membrane twice: once to enter the epithelial cell and once to exit into the bloodstream.
3. First passage through epithelial tissue: The nutrient first crosses the apical membrane of the epithelial cell, moving from the lumen of the intestine into the cell itself.
4. Second passage through epithelial tissue: The nutrient then crosses the basolateral membrane of the epithelial cell, moving from the cell into the interstitial fluid and subsequently into the capillaries of the bloodstream.
5. Conclude the number of passages: Since the nutrient crosses two membranes (apical and basolateral) of the epithelial cells, it passes through epithelial tissue twice during absorption from the intestine to the blood.