Absorption

1. Absorption 20/4/09 Prepared by Miss Izzati Apr 09

2. Previously…

3. GROUP ACTIVITY You are provided with: • Organs Cards (O) • Physical Digestion Cards (P) • Chemical Digestion Cards (C) • Mahjong Paper with body outline. • Markers (to draw arrows).

4. Instructions • Label all the organs in the digestive system. Use all the Organs (O) cards . • Label all the physical digestion processes that you have learnt. Stick the Physical Digestion (P) cards near the correct body part where the process occurs. • Label all the chemical digestion processes that you have learnt. Stick the Chemical Digestion (C) cards near the correct body part where the process occurs. • Fastest group wins!

5. Example Starch  maltose amylase (P) chewing (O) oesophagus

6. INGESTION Food is taken into body Carbohydrates, proteins and fats are broken down into soluble glucose, amino acids, fatty acids and glycerol. DIGESTION Glucose, amino acids, fatty acids and glycerol are absorbed into body cells ABSORPTION Absorbed nutrients are transported and utilized by the body ASSIMILATION Removal of undigested food e.g. dietary fibre EGESTION

7. lumen http://www.colorado.edu/intphys/Class/IPHY3430-200/image/villi.jpg ABSORPTION Monosaccharides (glucose, fructose and galactose), amino acids, fatty acids, glycerol and water are absorbed in the small intestine. The absorbed nutrients passes from the lumen of the small intestine into the bloodstream.

8. How to ensure that nutrients are quickly absorbed?

9. Adaptations of the Small Intestine • Large surface area: volume ratio 1.1 The inner walls of the small intestine have numerous folds http://www.path.cam.ac.uk/Normal/AR_Alimentary/SI_Small_intestine/N_AR_SI_08small.jpg

10. Adaptations of the Small Intestine • Large surface area: volume ratio 1.2 Folded inner walls are lined with numerous minute finger-like projections called villi http://www.technion.ac.il/~mdcourse/274203/slides/Digestive%20tract/17-Intestinal%20villi%20Jejunum-A.jpg

11. Adaptations of the Small Intestine • Large surface area: volume ratio 1.3 The epithelial cells of the villi have numerous microvilli.

13. Adaptations of the Small Intestine • The villi wall (epithelial cell layer) is only one cell thick. http://www.biog1105-1106.org/demos/105/unit6/media/villus.structure.jpg http://www.siumed.edu/~dking2/erg/images/GI020b.jpg

14. Adaptations of the Small Intestine Digested food enters villus lumen • Presence of numerous capillaries to carry away the absorbed nutrients. epithelial cell layer Lacteal/lymphatic capillary blood capillaries

15. Adaptations of the Small Intestine Lymphatic capillaries (lacteals): transport fats Blood capillaries: transport monosaccharides and amino acids. The continual removal of nutrients maintains a concentration gradient for diffusion. liver

16. http://blog.lib.umn.edu/trite001/pstl1082anatomy/SmallIntestine.jpghttp://blog.lib.umn.edu/trite001/pstl1082anatomy/SmallIntestine.jpg Adaptations of the Small Intestine • Small intestine is long to provide sufficient time for absorption. The small intestine is about 6m long!

17. glucose glycerol How are the nutrients absorbed? Fatty Acids amino acids Recall what you have learnt in the topic Movement of Substances! (Diffusion, osmosis, active transport….)

18. What type of movement occurs through the epithelium in these situations? • High concentration of glucose and amino acids in the lumen of the small intestine. • Low concentration of glucose and amino acids in the lumen of the small intestine. • High concentration of fatty acids and glycerol in the lumen of the small intestine • High water potential in the lumen of the small intestine. • High concentration of minerals salts in the lumen of the small intestine.

19. How does absorption take place in the villi?

20. SUMMARY • Movement into villi: • Glucose and amino acids absorbed by diffusion or active transport into blood capillaries of the villi. • Glycerol and fatty acids diffuse into the epithelium  combine to form minute fat globules which enter lacteals. • Water and mineral salts are also absorbed by the small intestine. • Adaptations of the small intestine: • Large SA: Vol.  folds, villi and microvilli. • Villi epithelial wall is one cell thick  rapid diffusion. • Blood capillaries and lacteals maintain concentration gradient. • Long  allows sufficient time for absorption

21. Egestion • In the colon, water and mineral salts are absorbed from the undigested food material. • Bacterial Activity • Presence of dietary fibre/roughage helps in peristalsis. • Unabsorbed matter is stored temporarily in the rectum. • Faeces is discharged through the anus. http://z.about.com/d/coloncancer/1/0/1/3/LargeIntestine.300x300.jpg colon rectum anus

22. INGESTION Food is taken into body Carbohydrates, proteins and fats are broken down into soluble glucose, amino acids, fatty acids and glycerol. DIGESTION Glucose, amino acids, fatty acids and glycerol are absorbed into body cells ABSORPTION Absorbed nutrients are transported and utilized by the body ASSIMILATION Removal of undigested matter e.g. dietary fibre EGESTION

23. QUICK CHECK • Which one of the following features of the small intestine does not help in its function of absorption? • The constant production of mucus • The folding of its inner surface • One cell thick villi wall • Presence of villi and microvilli.

24. I II III QUICK CHECK • Which of the following statements correctly describe the labelled diagram?

25. I II III QUICK CHECK • Which of the following statements correctly describe the functions of II and III?

26. QUICK CHECK • How are glucose and amino acids absorbed into the blood capillaries of the villi? • Diffusion only. • Diffusion and active transport • Active transport only • Osmosis and diffusion.

27. QUICK CHECK • How are water and mineral salts absorbed into the blood capillaries of the villi? • Active transport only. • Diffusion and active transport • Osmosis and active transport • Osmosis and diffusion.