Final answer:
The small intestine is named for its smaller diameter and is specialized for digestion and nutrient absorption, while the large intestine has a larger diameter, absorbs water and salts, forms feces, and houses beneficial bacterial flora. The small intestine's structure includes circular folds, villi, and microvilli, while the large intestine's wall is characterized by a higher population of goblet cells aiding in fecal movement.
Step-by-step explanation:
The small intestine is significantly longer than the large intestine but is referred to as "small" due to its smaller diameter. The small intestine is where most chemical digestion and nutrient absorption occur, thanks to specialized structures like circular folds, villi, and microvilli, which increase its surface area to enhance these processes. The large intestine, comparatively, has a more robust diameter and is responsible for absorbing water and salts from food waste, with the help of a large number of intestinal glands and goblet cells, before it gets eliminated from the body.
The small intestine is composed of three main parts: the duodenum, jejunum, and ileum, and utilizes segmentation and migrating motility complexes to move chyme and optimize absorption. The large intestine consists of the cecum, colon, and rectum, and is crucial for compressing the remaining food waste into feces. The mucosa of the large intestine largely lacks the enzyme-secreting cells and the extensive degree of surface area enhancement seen in the small intestine, but is abundant in mucus-secreting goblet cells, aiding in the movement of feces and protecting the intestinal lining.
Overall, the small intestine's adaptation for an increased absorptive capacity contrasts with the large intestine's role in water absorption and fecal formation. The presence of bacterial flora within the large intestine also plays a beneficial role in synthesizing certain vitamins and facilitating digestion.