Human Digestive S ystem

1. Human Digestive System

2. Objectives Describe the structure of the inner wall of the small intestine and explain it’s role in terms of increased surface area for absorption of nutrients. Explain the role of a lacteal and blood capillaries in the transport and absorption of nutrients. Describe the functions of the colon, rectum and anus in relation to absorption of water and mineral salts, temporary storage and egestion of faeces.

3. Small Intestine • What happens to the digested food? • Digested food products, • mineral salts and waterare • absorbed throughout the small • intestine especially in the ileum.

4. Video Time! As you watch the video clip, observe the inner walls of the small intestine .

5. Inner wall of small intestine Folds Villi – minute finger like projections

6. Inner wall of small intestine Microvilli Fold Villi – minute finger like projections

7. Inner wall of small intestine Why is there a need for numerous folds, villi and microvilli? To increase surface area for absorption of digested food substances – Increasing the absorption rate of water and digested food products

8. What is the epithelium one cell thick? Epithelium Sugars, amino acids, are absorbed by diffusion into the blood capillaries Blood capillaries transport sugars and amino acids away from the small intestine. One cell thick Faster diffusion of the digested food products Blood capillaries Lacteal Glycerol and fatty acids diffuse into the epithelium – form fat globules – enter the lacteals Lacteal transport fats away from the small intestine. Villi

9. Would the absorption of nutrients be affected if digested food substances cannot be transported away by the blood capillaries? Explain your answer. Yes. To a certain extent

10. The continual transport of digested food substances maintains a concentration gradient for the absorption of digested food substances by diffusion Lower concentration of digested food substances in the lumen of the small intestine, glucose and amino acids are absorbed by active transport Mineral salts enter the blood capillaries by active transport

11. Activity time! I need a doctor!

12. I need a doctor! Work in pairs/trios. You have3 minutes You are a doctor that specializes on the ileum. As the doctor of a patient who is overweight and has the intentions to lose weight, what procedures can be done to help the patient lose weight? Explain your answer.

13. Large intestine Colon • Absorb water and mineral salts from undigested food materials Rectum • Temporarily stores the faeces • When the rectum contracts, faeces is expelled through the anus Anus – Egestion/defaecation of faeces

14. Let’s Review Describe the structure of the inner wall of the small intestine and explain it’s role in terms of increased surface area for absorption of nutrients. Explain the role of a lacteal and blood capillaries in the transport and absorption of nutrients. Describe the functions of the colon, rectum and anus in relation to absorption of water and mineral salts, temporary storage and egestion of faeces.

15. Write 3 key things that you learn today What am I still unsure about?