1. Human alimentary canal Section II Structures and functions in living organisms

2. Syllabus recognise the structures of the human alimentary canal and describe in outline the functions of the mouth, oesophagus, stomach, small intestine, large intestine, and pancreas recognise the structures of the human alimentary canal and describe in outline the functions of the mouth, oesophagus, stomach, small intestine, large intestine, and pancreas understand the processes of ingestion, digestion, absorption, assimilation and egestion understand the processes of ingestion, digestion, absorption, assimilation and egestion explain how and why food is moved through the gut by peristalsis explain how and why food is moved through the gut by peristalsis

3. Syllabus understand the role of digestive enzymes to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases understand the role of digestive enzymes to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases recall that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids recall that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids explain how the structure of a villus helps absorption of the products of digestion in the small intestine explain how the structure of a villus helps absorption of the products of digestion in the small intestine

4. Terminology Ingestion Ingestion Taking food into the alimentary canal Taking food into the alimentary canal Digestion Digestion The chemical and physical process where large molecules are broken down to small molecule, so that the body can use them to build and nourish cells, and to provide energy. The chemical and physical process where large molecules are broken down to small molecule, so that the body can use them to build and nourish cells, and to provide energy. Chemical digestion involves a chemical change from one sort of molecule to another. Chemical digestion involves a chemical change from one sort of molecule to another. Mechanical digestion involves the teeth and churning movements of the alimentary canal. Mechanical digestion involves the teeth and churning movements of the alimentary canal.

5. Terminology Absorption Absorption The uptake of a substance into the cells of an organism’s body. The uptake of a substance into the cells of an organism’s body. Assimilation Assimilation The incorporation of absorbed food into various parts of the body The incorporation of absorbed food into various parts of the body Egestion Egestion The removal of indigestible food from the body The removal of indigestible food from the body

6. The Human Digestive System

8. Structures Alimentary canal is a muscular tube, running from mouth to anus Alimentary canal is a muscular tube, running from mouth to anus Oral cavity Oral cavity Mouth Mouth Teeth Teeth tongue tongue Oesophagus Oesophagus Stomach Stomach

9. Structures Liver Liver Bile duct Bile duct Pancreas Pancreas Small intestine Small intestine Duodenum Duodenum ileum ileum Large intestine Large intestine Colon Colon Rectum Rectum Anus Anus

10. Functions Mouth Mouth Ingestion of food here Ingestion of food here Bolus formed here. Bolus is a ball of food formed after chewing. Bolus formed here. Bolus is a ball of food formed after chewing. Physical digestion Physical digestion Tongue and teeth use to masticate the food Tongue and teeth use to masticate the food Mastication = mechanical grinding action of teeth Mastication = mechanical grinding action of teeth Chemical digestion Chemical digestion Saliva released contains salivary amylase which breaks down carbohydrates Saliva released contains salivary amylase which breaks down carbohydrates

11. Functions of the digestive system Oesophagus Oesophagus Carry the food from mouth to stomach Carry the food from mouth to stomach Peristalsis – rhythmic waves of contraction by smooth muscles in the wall of the canal that move the food Peristalsis – rhythmic waves of contraction by smooth muscles in the wall of the canal that move the food

13. Functions Stomach Stomach Physical digestion Physical digestion Churning of the stomach helps break down the food Churning of the stomach helps break down the food Chemical digestion Chemical digestion Hydrochloric acid released Hydrochloric acid released Protease breaks down proteins Protease breaks down proteins

15. Accessory Digestive Organs

16. Functions Liver Liver Bile duct = bile (yellowish-green watery liquid) Bile duct = bile (yellowish-green watery liquid) used in mechanical digestion of lipids used in mechanical digestion of lipids Large fat droplets broken down, increasing the surface area = emulsification Large fat droplets broken down, increasing the surface area = emulsification contains NO enzymes contains NO enzymes

17. Functions Liver Liver Functions of: Functions of: maintenance of a constant glucose level in bloodstream maintenance of a constant glucose level in bloodstream detoxification of drugs & alcohol detoxification of drugs & alcohol production of bile (acts as emulsifier – begins fat breakdown production of bile (acts as emulsifier – begins fat breakdown destruction old RBC & converts haemoglobin to bilirubin destruction old RBC & converts haemoglobin to bilirubin regulation of cholesterol & other fats regulation of cholesterol & other fats Hepatic portal system: drains blood from digestive tract Hepatic portal system: drains blood from digestive tract Metabolic functions: storage, synthesis, chemical processing Metabolic functions: storage, synthesis, chemical processing

18. Liver - Assimilation Defined as the incorporation of absorbed food into various parts of the body Defined as the incorporation of absorbed food into various parts of the body The hepatic portal vein delivers the sugars and amino acids to the liver. The hepatic portal vein delivers the sugars and amino acids to the liver. The liver ensures the right nutrients are sent to the right cells so that various bodily functions can occur The liver ensures the right nutrients are sent to the right cells so that various bodily functions can occur eg. Amino acids are made into new proteins for growth & repair OR glucose which is used for respiration eg. Amino acids are made into new proteins for growth & repair OR glucose which is used for respiration

19. Pancreas: exocrine functions Pancreas: exocrine functions Produces pancreatic juice Produces pancreatic juice contains digestive enzymes: contains digestive enzymes: Amylase Amylase Protease Protease lipase lipase Secretes sodium bicarbonate to neutralize the stomach acids Secretes sodium bicarbonate to neutralize the stomach acids Gallbladder: stores bile Gallbladder: stores bile Accessory Organs: Aid Digestion and Absorption

20. Functions Small Intestine Small Intestine Functions: Functions: Digestion: Digestion: neutralize acid from stomach, neutralize acid from stomach, add digestive enzymes and bile, add digestive enzymes and bile, break proteins, carbohydrates and lipids to absorbable materials break proteins, carbohydrates and lipids to absorbable materials Absorption: 95% of food absorbed here Absorption: 95% of food absorbed here

21. Small Intestine Very long ~5 metres (adult), more time for the food to be absorbed Very long ~5 metres (adult), more time for the food to be absorbed Highly folded, increases the surface area for absorption Highly folded, increases the surface area for absorption Hepatic portal vein carries the amino acids and sugars to the liver, where they are sorted and redirected to be used by the body or if in excess stored. Hepatic portal vein carries the amino acids and sugars to the liver, where they are sorted and redirected to be used by the body or if in excess stored. Excess sugar stored as GLYCOGEN Excess sugar stored as GLYCOGEN Excess amino acids deaminated (broken down) to GLYCOGEN and UREA Excess amino acids deaminated (broken down) to GLYCOGEN and UREA

22. Small Intestine Two parts Two parts Duodenum Duodenum Food is mixed with Food is mixed with Bile Bile Pancreatic juice Pancreatic juice Ileum Ileum Food is mixed with Food is mixed with Intestinal juice Intestinal juice Maltase Maltase Protease (peptides to amino acids) Protease (peptides to amino acids) Where absorption occurs Where absorption occurs Inner surface folded and covered in villi Inner surface folded and covered in villi

23. Structure of the small intestine

24. Villus Function Function Increase the surface area that can absorb food Increase the surface area that can absorb food Structure Structure Capillary network Capillary network Blood Blood - to collect the sugars and amino acids Lacteal (lymph vessels) Lacteal (lymph vessels) - collect the fatty acids and glycerol One cell thick One cell thick Goblet cells Goblet cells Produce mucus which Produce mucus which protect lining of gut protect lining of gut

25. Absorption of Proteins and Carbohydrates

26. Absorption of Fats

27. Major enzymes of digestive system Carbohydrates Carbohydrates Amylase Amylase Mouth & duodenum Mouth & duodenum Substrate = starch Substrate = starch Product = maltose Product = maltose Proteins Proteins Protease Protease Stomach (pepsin) & duodenum (trypsin) Stomach (pepsin) & duodenum (trypsin) Substrate = proteins & polypeptides Substrate = proteins & polypeptides Product = polypeptides (Stomach) & amino acids Product = polypeptides (Stomach) & amino acids Lipids Lipids Lipase Lipase Duodenum & ileum Duodenum & ileum Substrate = emulsified fats Substrate = emulsified fats Product= fatty acids and glycerol Product= fatty acids and glycerol

29. Functions Large Intestine Large Intestine Functions: absorbs nutrients and water, and eliminates waste Functions: absorbs nutrients and water, and eliminates waste Substances found in large intestine = mostly water, dead bacterial cells, cellulose fibers, other indigestible materials, lubricated by mucus Substances found in large intestine = mostly water, dead bacterial cells, cellulose fibers, other indigestible materials, lubricated by mucus Anus Anus Where egestion of waste occurs Where egestion of waste occurs