The primary role of the small intestine is the digestion and absorption of nutrients from food. It is a long, coiled tube where most enzymatic breakdown of food occurs, facilitated by various digestive enzymes. The surface of the small intestine is lined with villi and microvilli, which significantly increase its surface area, allowing for efficient nutrient absorption into the bloodstream. The small intestine also plays a role in the absorption of water and electrolytes, helping to maintain the body's fluid balance.