Final answer:
Villi, along with even smaller structures on them called microvilli, are the hairlike projections in the small intestine responsible for nutrient absorption.
Step-by-step explanation:
The hairlike tubes in the small intestine responsible for the absorption of nutrients are called villi. The surface of each villus contains even smaller projections known as microvilli, which further maximise nutrient absorption. These structures are lined with epithelial cells that facilitate the uptake of nutrients from the digested food, allowing them to enter the bloodstream and be transported to various parts of the body. The highly folded surface of the small intestine increases the efficiency of nutrient absorption, similar to how a large, folded towel has more surface area to absorb water compared to an unfolded one.