What are the three major regions of the small intestine?

The three major regions of the small intestine are indeed the duodenum, jejunum, and ileum.

The duodenum is the first part of the small intestine and plays a crucial role in the digestion of food. It is where the chyme from the stomach mixes with bile from the liver and digestive juices from the pancreas, allowing for the breakdown of nutrients.

The jejunum follows the duodenum and is responsible for the majority of nutrient absorption. Its lining is highly specialized with villi and microvilli, which increase the surface area and enhance the absorption of carbohydrates, proteins, and fats.

The ileum is the final section of the small intestine, continuing the absorption process and primarily focusing on vitamin B12 and bile salts. Its structure is also adapted for absorption, and it connects to the large intestine at the ileocecal valve.

Each of these sections has distinct functions and anatomical features that are vital for proper digestion and nutrient absorption, making this choice the accurate representation of the regions of the small intestine.