Which features maximize absorption in the small intestine, and what is the role of lacteals?

Which features maximize absorption in the small intestine, and what is the role of lacteals?

• A. Plicae circulares and goblet cells; lacteals transport fats into blood capillaries
• B. Villi and microvilli only; lacteals secrete bile
• C. Plicae circulares, villi, and microvilli increase surface area; lacteals absorb dietary fats into lymphatics
• D. Goblet cells increase surface area; lacteals absorb glucose into lymphatics

Answer: (C)

The main idea is that absorption in the small intestine is boosted by a dramatic increase in surface area and by specialized pathways for different nutrients. The circular folds, called plicae circulares, multiply the surface area and slow the passage of chyme so nutrients stay in contact longer. On top of that, villi—finger-like projections—and their even smaller projections, microvilli on enterocytes, together create a vast absorptive surface at both the tissue and cellular levels. Within each villus, there is a lymphatic vessel known as a lacteal. The lacteal’s job is to pick up dietary fats (lipids) and transport them into the lymphatic system rather than directly into blood capillaries. This fat-laden lymph eventually enters the bloodstream via the thoracic duct, after which fats are delivered to tissues. So, the combination of plicae circulares, villi, and microvilli maximizes surface area for absorption, while lacteals specifically absorb fats into the lymphatic system. Goblet cells mainly secrete mucus and don’t increase absorptive surface; lacteals don’t secrete bile; and glucose is absorbed into blood via intestinal capillaries, not lymphatics.

The main idea is that absorption in the small intestine is boosted by a dramatic increase in surface area and by specialized pathways for different nutrients. The circular folds, called plicae circulares, multiply the surface area and slow the passage of chyme so nutrients stay in contact longer. On top of that, villi—finger-like projections—and their even smaller projections, microvilli on enterocytes, together create a vast absorptive surface at both the tissue and cellular levels.

Within each villus, there is a lymphatic vessel known as a lacteal. The lacteal’s job is to pick up dietary fats (lipids) and transport them into the lymphatic system rather than directly into blood capillaries. This fat-laden lymph eventually enters the bloodstream via the thoracic duct, after which fats are delivered to tissues.

So, the combination of plicae circulares, villi, and microvilli maximizes surface area for absorption, while lacteals specifically absorb fats into the lymphatic system. Goblet cells mainly secrete mucus and don’t increase absorptive surface; lacteals don’t secrete bile; and glucose is absorbed into blood via intestinal capillaries, not lymphatics.