Where does most chemical digestion and absorption of food take place?

The correct answer is the small intestine because it is specifically structured to maximize chemical digestion and nutrient absorption. The small intestine consists of three main parts: the duodenum, jejunum, and ileum.

In the duodenum, digestive enzymes from the pancreas and bile from the liver mix with the partially digested food (chyme) from the stomach, breaking down carbohydrates, proteins, and fats into their smaller components. As the chyme moves through the jejunum and ileum, the absorptive surfaces, lined with tiny structures called villi and microvilli, significantly increase the surface area for absorption.

This anatomy allows for the efficient uptake of essential nutrients, such as amino acids, simple sugars, fatty acids, vitamins, and minerals, into the bloodstream. The small intestine is also where most water absorption occurs, making it vital for maintaining hydration and nutrient balance in the body. While the stomach does perform some digestion and the large intestine is critical for water absorption and fiber processing, neither is primarily responsible for the majority of digestion and nutrient absorption as the small intestine is. The spleen, on the other hand, is involved in immune response and recycling of iron from red blood cells but does not play a direct role in digestion.