The small intestine is adapted for efficient absorption of nutrients through several mechanisms: it has a large surface area due to numerous villi and microvilli that increase absorption area; the epithelial membrane is thin to facilitate diffusion; and a concentration gradient is maintained by transporting digested substances away from the villus via blood and lymphatic capillaries, allowing for continual absorption. Nutrients like glucose, amino acids, and water are absorbed directly into the bloodstream, while fatty acids and glycerol enter the lymphatic system to be recombined and absorbed.

1. Mouth EsophagusStomachSmall intestine

2. Absorption of nutrients in the small intestines 6.4 pg 102 What is Absorption? http://www.yenching.edu.hk/biology/absorption.swf

4. Lined with vili

5. Microvilli on villi

6. 1 cell thick epitheliumMany capillaries to carry substance away quickly Each villus is a lacteal or lymphatic capillary surrounded by blood capillaries. This continuous transport of digested food substances away from the villus maintains the concentration gradient for absorption.

7. Increased intestinal surface area 1 cell thick epithelium

8. Q. How is Concentration gradient maintained at the site of the intestinal villus? A concentration gradient is maintained at the villus by the continual transport of digested food substances away from the villus.

9. How does absorption take place? Legend Glucose amino acids fatty acid & glycerol fat molecule

10. Glucose & amino acids diffuses into blood capillaries of villi Glucose & amino acids also enters via active transport Glycerol & fatty acid diffuse into the epithelium, then combines back when they enter lacteal Water & mineral salts also absorbed. How does absorption take place?