Which organ is primarily responsible for digestion and absorption of nutrients?

The small intestine is primarily responsible for digestion and absorption of nutrients due to its specialized structure and function. It has a large surface area, thanks to the presence of villi and microvilli, which significantly enhances its ability to absorb nutrients. The small intestine is where the majority of chemical digestion occurs, facilitated by enzymes from the pancreas and bile from the liver. Carbohydrates, proteins, and fats are broken down into their basic units—simple sugars, amino acids, and fatty acids—before being absorbed into the bloodstream through the walls of the small intestine. This process is critical for providing the body with the nutrients it needs for energy, growth, and repair.

In contrast, while the stomach plays a role in the initial digestion of food through acidic secretion and enzyme action, its primary function is to break down food into a semi-liquid form called chyme. The liver is essential for producing bile, which helps emulsify fats, but it does not perform digestion itself. The large intestine, on the other hand, primarily focuses on the absorption of water and electrolytes and the formation of waste products, rather than nutrient absorption. Hence, the small intestine holds the key role in the digestive process.