State one way the ileum is adapted for absorption.

State one way the ileum is adapted for absorption.

• A. Long length
• B. Microvilli
• C. Capillary network
• D. Villi

Answer: (D)

Absorption is maximized by increasing surface area. The ileum uses villi—finger-like projections lining the intestinal wall—to massively raise the area available for nutrients to cross into the body. Each villus contains a rich capillary network and a lacteal, so absorbed sugars and amino acids quickly enter the bloodstream and fats enter the lymphatic system. Tiny microvilli on the surface of the absorptive cells also add surface area, but the defining adaptation of the ileum is the presence of villi. Longer length would help, but it doesn’t as clearly reflect how absorption is structurally enhanced, and the capillary network is a feature inside the villi rather than a separate adaptation.

Absorption is maximized by increasing surface area. The ileum uses villi—finger-like projections lining the intestinal wall—to massively raise the area available for nutrients to cross into the body. Each villus contains a rich capillary network and a lacteal, so absorbed sugars and amino acids quickly enter the bloodstream and fats enter the lymphatic system. Tiny microvilli on the surface of the absorptive cells also add surface area, but the defining adaptation of the ileum is the presence of villi. Longer length would help, but it doesn’t as clearly reflect how absorption is structurally enhanced, and the capillary network is a feature inside the villi rather than a separate adaptation.