Absorption in the large intestine is characterized by which statement?

Absorption in the large intestine is characterized by which statement?

• A. LI has a smaller surface area and is the last line of absorption
• B. LI contents impede drugs from touching mucosa and getting absorbed
• C. LI actively transports most drugs
• D. LI has higher pH that enhances absorption

Answer: (B)

Absorption in the large intestine is limited because the tissue offers a smaller surface area and the lumen is primarily geared toward water reabsorption, not rapid drug uptake. The presence of luminal contents—feces, mucus, and bacteria—acts as a barrier, reducing how long a dissolved drug stays in contact with the mucosal surface and making it harder for the drug to diffuse across. This is why drugs often show poor and variable absorption from the colon: contact with mucosa is hindered by these contents, so absorption is less efficient. The other statements misstate the situation: the colon isn’t built for active transport of most drugs, its pH isn’t universally higher to boost absorption, and while surface area is smaller, the key point is how luminal contents impede contact with the mucosa.

Absorption in the large intestine is limited because the tissue offers a smaller surface area and the lumen is primarily geared toward water reabsorption, not rapid drug uptake. The presence of luminal contents—feces, mucus, and bacteria—acts as a barrier, reducing how long a dissolved drug stays in contact with the mucosal surface and making it harder for the drug to diffuse across. This is why drugs often show poor and variable absorption from the colon: contact with mucosa is hindered by these contents, so absorption is less efficient. The other statements misstate the situation: the colon isn’t built for active transport of most drugs, its pH isn’t universally higher to boost absorption, and while surface area is smaller, the key point is how luminal contents impede contact with the mucosa.