Final answer:
Microvilli are the processes that increase nutrient absorption on the apical ends of intestinal cells, supported internally by actin filaments. They are vital in expanding the surface area for substance exchange and finishing the digestion of some nutrients.
Step-by-step explanation:
The long processes that facilitate absorption of nutrients on the apical ends of intestinal cells are called microvilli. These microvilli have an internal skeleton formed by actin filaments, not microtubules or intermediate filaments.
Microvilli are cylindrical extensions of the plasma membrane that greatly expand the surface area of the plasma membrane, enhancing the absorption of nutrients.
The difference between villi and microvilli is significant in understanding this process. Villi are larger folds on the surface of the small intestine, whereas microvilli are microscopic projections on the cells themselves.
The presence of enzymes on the microvilli's membranes allows them to finish digesting carbohydrates and proteins, contributing to efficient nutrient absorption.