Final answer:
The small intestine is divided into the duodenum for chemical digestion, the jejunum for nutrient absorption, and the ileum for continuing absorption. It features villi and microvilli which increase its surface area, aiding in its primary functions of digestion and absorption.
Step-by-step explanation:
Small Intestine: Duodenum, Jejunum, and Ileum
The small intestine is a critical organ for digestion and nutrient absorption, extending to about 7 meters in adults. It consists of three parts: the duodenum, jejunum, and ileum. The duodenum, the shortest section, is where chyme from the stomach is further digested chemically. The jejunum, approximately 0.9 meters long, is predominantly involved in nutrient absorption. The jejunum and the following section, ileum, contain villi and microvilli which are structural adaptations that significantly increase the mucosal surface area, heightening the efficiency of absorption.
While the jejunum is known for being 'empty' at death, hence its name derived from Latin, its role in life is substantial. The ileum also plays a role in the absorption process, including B12 and bile acids crucial for digestion. These regions do not have clear demarcations but work together seamlessly to process and absorb nutrients before transferring the remaining chyme to the large intestine. Together, the intricate morphology of the small intestine exemplifies its hefty task in digestive systems, facilitated by the increased surface area and digestive movements including segmentation and migrating motility complexes.