The small intestine is adapted for absorption through several specialized structural features that maximize surface area and facilitate efficient nutrient uptake.
Key Adaptations for Absorption
- The small intestine is very long, providing a large overall surface area for absorption.
- Its inner surface is highly folded with millions of tiny finger-like projections called villi.
- Each villus is covered with microvilli, further increasing the surface area at a microscopic level.
- The walls of the villi are only one cell thick, minimizing the diffusion distance for nutrients.
- Each villus contains a rich network of blood capillaries to rapidly transport absorbed glucose and amino acids into the bloodstream.
- A central lacteal in each villus transports absorbed fatty acids and glycerol into the lymphatic system.
- The villi also have efficient blood supply and lymph vessels to maintain concentration gradients for rapid absorption.
- Secretion of digestive enzymes within the small intestine helps break down food molecules to smaller absorbable units.
Together, these features enormously increase the surface area—by folds, villi, and microvilli—and reduce absorption distance, enabling the small intestine to absorb nutrients quickly and efficiently.
