Which region of the small intestine primarily digests chemical substances?

• A. Pylorus
• B. Ileum
• C. Jejunum
• D. Duodenum

Answer: (D)

Chemical digestion is driven by enzymes that break down carbohydrates, proteins, and fats. The duodenum is the first segment of the small intestine and is where chyme from the stomach mixes with pancreatic juice and bile. This is where most chemical digestion occurs, thanks to pancreatic enzymes (amylase for carbohydrates, lipase for fats, proteases for proteins) and the action of bile, along with brush-border enzymes that finish the job on the intestinal lining. The jejunum mainly handles nutrient absorption, the ileum absorbs bile acids and vitamin B12, and the pylorus is a stomach region that gates passage into the small intestine. So the duodenum is the region where chemical digestion is primarily carried out.