Which sections compose the small intestine?

The small intestine is composed of three distinct sections: the duodenum, jejunum, and ileum. The duodenum is the first segment, where most of the chemical digestion occurs thanks to enzymes from the pancreas and bile from the liver. Following the duodenum is the jejunum, which is primarily responsible for the absorption of nutrients. Finally, the ileum is the last section of the small intestine, which further absorbs nutrients and bile salts before the remaining material passes into the large intestine.

Understanding the composition of the small intestine is essential in pathophysiology, as different diseases or disorders can affect specific sections, leading to varied symptoms and treatment approaches. For instance, conditions such as Crohn's disease often impact areas within the ileum, while lactose intolerance may involve issues that start in the duodenum.

The other choices contain structures that are not part of the small intestine. For example, the colon and cecum are components of the large intestine, while the sigmoid colon specifically refers to another part of the large intestine.