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Why does most chemical digestion take place in the small intestine?

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Diagram of the human digestive system viewed from the front, showing and labeling organs including the mouth, teeth, tongue, salivary glands, pharynx, esophagus, liver, stomach, gallbladder, pancreas, large intestine, small intestine, appendix, rectum, and anus. — digestion The human digestive system as seen from the front.

Most chemical digestion occurs in the small intestine because it is the primary site where food is thoroughly mixed with a comprehensive array of digestive enzymes and secretions.12

While digestion begins in the mouth and continues in the stomach, the small intestine receives critical contributions from accessory organs that facilitate the breakdown of complex molecules:31

Pancreatic and Liver Secretions: The pancreas delivers enzymes capable of digesting proteins, fats, and carbohydrates into the duodenum. The liver and gallbladder provide bile, which aids in fat digestion.542
Intestinal Enzymes: The intestinal wall itself secretes a variety of enzymes, such as disaccharidases and peptidases, which further hydrolyze nutrients into simpler forms like monosaccharides and amino acids.65
Surface Area: The structure of the small intestine—featuring plicae circulares, villi, and a brush border of microvilli—provides an enormous surface area that maximizes contact between enzymes and food particles, ensuring efficient chemical breakdown and subsequent absorption.62