▶️ Answer/Explanation
The part labelled $X$ is the lacteal, which is a central lymphatic vessel located inside each villus of the small intestine. While the surrounding blood capillaries are responsible for absorbing water-soluble nutrients like glucose and amino acids, the lacteal specializes in the transport of lipid-soluble molecules. Specifically, products of fat digestion, such as fatty acids and glycerol, are reassembled into chylomicroons and absorbed into the lacteal. This makes row $D$ the correct identification of both the structure’s name and its physiological role in the digestive system.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
A villus is a finger-like projection in the small intestine designed to maximize absorption. Label A points to the epithelium, the single layer of cells that facilitates rapid diffusion. Label B indicates the general internal space or goblet cells, while Label D represents the network of blood capillaries that absorb glucose and amino acids. Label C identifies the lacteal, which is the central lymphatic vessel responsible for absorbing fatty acids and glycerol. Because fats are too large to enter the narrow capillaries directly, they are transported via the lymphatic system. Thus, the central vessel marked C is the correct identification for the lacteal.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
The primary role of the small intestine is the absorption of nutrients into the bloodstream. To make this process efficient, the inner lining is covered in tiny, finger-like projections called villi, which themselves are covered in even smaller microvilli. These structures significantly expand the total surface area available for diffusion and active transport. By increasing the area of the plasma membrane, more nutrient molecules can be absorbed simultaneously. This ensures that the body maximizes the uptake of glucose, amino acids, and fatty acids from digested food.
✅ Answer: (B)
✅ Answer: (B)