Where does the majority of chemical digestion occur and nutrients begin to be absorbed?

Where does the majority of chemical digestion occur and nutrients begin to be absorbed?

• A. Duodenum
• B. Stomach
• C. Esophagus
• D. Large intestine

Answer: (A)

Digestion and nutrient uptake begin in the duodenum, the first section of the small intestine, where chyme from the stomach mixes with pancreatic enzymes and bile. This combination provides the enzymes needed to break down carbohydrates, proteins, and fats, and the brush-border enzymes lining the intestinal wall complete much of the chemical digestion. As digestion proceeds, nutrients start to be absorbed right away, with monosaccharides, amino acids, and other digested units taken up by the intestinal cells and into the bloodstream, continuing further along the small intestine where absorption is most extensive. The stomach does contribute to digestion, especially of proteins with pepsin, but the majority of chemical digestion and the initial phase of nutrient absorption occur in the duodenum. The esophagus mainly serves as a conduit with no chemical digestion, and the large intestine focuses on absorbing water and electrolytes rather than digesting and extracting nutrients.

Digestion and nutrient uptake begin in the duodenum, the first section of the small intestine, where chyme from the stomach mixes with pancreatic enzymes and bile. This combination provides the enzymes needed to break down carbohydrates, proteins, and fats, and the brush-border enzymes lining the intestinal wall complete much of the chemical digestion. As digestion proceeds, nutrients start to be absorbed right away, with monosaccharides, amino acids, and other digested units taken up by the intestinal cells and into the bloodstream, continuing further along the small intestine where absorption is most extensive. The stomach does contribute to digestion, especially of proteins with pepsin, but the majority of chemical digestion and the initial phase of nutrient absorption occur in the duodenum. The esophagus mainly serves as a conduit with no chemical digestion, and the large intestine focuses on absorbing water and electrolytes rather than digesting and extracting nutrients.