Final answer:
The correct order of the small intestine sections from anterior to posterior is a) Duodenum, jejunum, ileum, with the duodenum as the first section for chemical digestion, followed by the jejunum for nutrient absorption, and ending with the ileum, which joins the large intestine.
Step-by-step explanation:
The sections of the small intestine are arranged in the following order from anterior to posterior: duodenum, jejunum, and ileum. Therefore, the correct answer to the question is a) Duodenum, jejunum, ileum. The duodenum is the first segment that initiates chemical digestion and is located just beyond the stomach. Next, the jejunum, which is the site of most nutrient absorption, follows the duodenum. Lastly, the ileum is the final and longest segment of the small intestine, leading to the large intestine.
The jejunum, measuring about 0.9 meters (3 feet) in length, connects the duodenum to the ileum, and there is no clear boundary between the jejunum and ileum. The ileum is about 1.8 meters (6 feet) long and features developed mucosal folds for efficient absorption, joining the cecum at the ileocecal sphincter. These three parts of the small intestine play a vital role in digestion and nutrient absorption due to their structural adaptation, including a highly wrinkled mucosa with villi and microvilli.