What are the parts of the small intestine?

The small intestine is comprised of three specific sections: the duodenum, jejunum, and ileum. This configuration is crucial for proper digestion and nutrient absorption. The duodenum is the first part of the small intestine and is primarily responsible for the initial phase of digestion, where food mixes with digestive juices from the pancreas and bile from the liver. Following this, the jejunum takes over as the main site for nutrient absorption, owing to its extensive surface area and rich blood supply. Finally, the ileum, which is the longest segment, continues the absorption process and also plays a key role in the absorption of vitamin B12 and bile salts.

The option that identifies these three specific components accurately captures the anatomy of the small intestine, which is essential knowledge for understanding gastrointestinal function and veterinary pharmacology. The other choices mix elements from various parts of the digestive system that do not belong to the small intestine, such as the cecum and colon, highlighting the importance of distinguishing between different sections to accurately understand their functions.