Nutrition in Humans (part 2): Absorption & Assimilation

1. Absorption in the Absorption in the 1 1small and small and 2 2large intestines intestines large

2. Small intestine Small intestine Absorption of Absorption of simple sugars simple sugars a.a a.a. . f.a f.a. and glycerol . and glycerol in in villi villi of of jejunum ? ? 1. 1. 2. 2. 3. 3. jejunum and and ileum ileum

3. Structure of the small intestine Structure of the small intestine

4. (lacteal) microvilli

5. Adaptations of small intestine Adaptations of small intestine to absorption to absorption Numerous transverse folds and furrows (↑ (↑ s.a s.a.) .) 2. 2. Numerous Numerous villi villi (minute finger like (minute finger like projections) projecting into the intestinal projections) projecting into the intestinal cavity + cavity + microvilli microvilli; ↑ ; ↑ s.a 3. 3. Rich network of blood and Rich network of blood and lymphatic vessels vessels to continually transport away to continually transport away 1) sugars and 1) sugars and a.a a.a. (by blood capillaries) . (by blood capillaries) 2) 2) f.a.(by f.a.(by lacteals lacteals) ) → → continual transport maintains continual transport maintains diffusion gradient for absorption of diffusion gradient for absorption of digested food digested food 1. 1. Numerous transverse folds and furrows s.a. . lymphatic

7. Large intestine Large intestine functions to: functions to: absorb absorb water from undigested food material from undigested food material helps remove bacteria helps remove bacteria periodically during periodically during egestion ? ? water and and mineral salts mineral salts 1. 1. 2. 2. egestion

9. Assimiliation Assimiliation

10. Path of absorbed food substances and the Path of absorbed food substances and the blood vessels associated with the liver blood vessels associated with the liver insulin excess glucose glycogen (requires insulin; produced by pancreas)

11. Deamination Deamination of of a.a a.a. . ammonia (toxic to cells) carbon residue glucose urea (non toxic, excreted in urine) glycogen (stored in liver and muscles)

12. Fats Fats assimiliation assimiliation ? ? Brought to liver to be converted to Brought to liver to be converted to forms that can be forms that can be oxidised ? ? Used to build protoplasm (e.g. in cell Used to build protoplasm (e.g. in cell mbs mbs) ) ? ? Excess fats stored in Excess fats stored in adipose tissues tissues (fat storage and insulating (fat storage and insulating tissues) tissues) ? ? Used only when there is inadequate Used only when there is inadequate supply of glucose (during fasting) supply of glucose (during fasting) oxidised or stored or stored adipose

13. Functions of the liver: Functions of the liver: bile Production of Production of bile (stored in gall bladder) (stored in gall bladder) Regulates blood glucose Regulates blood glucose concentration concentration - - conversion of excess glucose to conversion of excess glucose to insoluble glycogen by the hormone insoluble glycogen by the hormone insulin insulin - - conversion of glycogen to glucose conversion of glycogen to glucose when required by the hormone when required by the hormone glucagon glucagon / /adrenaline adrenaline (during fight flight situations) flight situations) 1. 1. 2. 2. (during fight- -

14. Functions of the liver: Functions of the liver: 3. 3. Iron storage Iron storage - - worn out worn out RBCs - - haemoglobin haemoglobin brought to liver to be brought to liver to be broken down, releasing iron which is broken down, releasing iron which is stored in the liver stored in the liver 4. 4. Protein synthesis Protein synthesis - - liver synthesizes proteins found in liver synthesizes proteins found in plasma e.g. albumins, globulins and plasma e.g. albumins, globulins and fibrinogen using fibrinogen using a.a a.a. digested in diet 5. 5. Deamination Deamination of of a.a a.a (refer to previous slides) slides) RBCs destroyed in spleen destroyed in spleen . digested in diet (refer to previous

15. Functions of the liver: Functions of the liver: Detoxification (process of converting Detoxification (process of converting harmful substances into harmless ones) harmful substances into harmless ones) 6. 6. alcohol alcohol dehydrogenase dehydrogenase alcohol alcohol acetaldehyde acetaldehyde - - acetaldehyde can be broken down further acetaldehyde can be broken down further to compounds used in respiration to compounds used in respiration Note Note Excessive alcohol consumption causes: Excessive alcohol consumption causes: - - Increased risk of Increased risk of gastric ulcers gastric ulcers (as alcohol stimulates acid secretion in the stomach) stimulates acid secretion in the stomach) - - cirrhosis cirrhosis of the liver of the liver → → bleeding in liver → → liver failure liver failure → → death (prolonged alcohol death (prolonged alcohol consumption) consumption) (as alcohol bleeding in liver

16. Use of Use of Mneumonics Mneumonics D D2 2RIP RIP2 2 D D etoxification etoxification D D eamination eamination of R R egulation egulation of blood glucose concentration of blood glucose concentration I I ron ron storage storage P P rotein rotein synthesis synthesis P P roduction roduction of bile of bile of a.a a.a. .

17. Summary Summary

18. Ingestion