CIE IGCSE Biology: 复习笔记：7.1.14 Adaptations of the Small Intestine: Extended

• The ileum is adapted for absorption as it is very long and has a highly folded surface with millions of villi (tiny, finger like projections)
• These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently

Adaptations of the small intestine

• Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
• Wall of villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport
• Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
• Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph