PHYSIOLOGY OF HUMAN DIGESTION

1. absorption: passage of digested products from the intestinal lumen through mucosal cells and into the bloodstream or lacteals

2. chemical digestion: enzymatic breakdown of food

3. chyme: soupy liquid created when food is mixed with
digestive juices

4. defecation: elimination of undigested substances from the
body in the form of feces

5. ingestion: taking food into the GI tract through the mouth

6. mastication: chewing

7. mechanical digestion: chewing, mixing, and segmentation
that prepares food for chemical digestion

8. peristalsis: muscular contractions and relaxations that propel
food through the GI tract

9. propulsion: voluntary process of swallowing and the
involuntary process of peristalsis that moves food through the
digestive tract

10. segmentation: alternating contractions and relaxations of
non-adjacent segments of the intestine that move food
forward and backward, breaking it apart and mixing it with
digestive juices

1. PHYSIOLOGY OF DIGESTION By- Deepanshu K umar Yadav B.Sc B.Ed CBZ V TH Semester

2. Th e digestive s y ste m i s f o rme d of Alimentary canal Digestive glands

3.  Mucosa     S ub mucosa C ircular m uscle layer Longitudinal m uscle layer S erosa Structure of A limentary canal

4. Mastication (Chewing) Mechanical breakdown of large food particles into smaller ones in the mouth. Increase exposed surface area to enzymes and help swallowing . Forming bolus.

5. Salivary Secretion Saliva is secreted primarily by three pairs of glands: the parotid glands: 20% the submandibular: 75%. the sublingual glands: 5%. many small buccal glands in mouth cavity.

6. Salivary Secretion Saliva (Water- 99.5%) (Solids-0.5%) 800- 1500 ml/day with proteins & electrolytes pH→ 6- 7.0 ( 8.0 during active secretion) Hypotonic ( Na + & Cl - less , K + & HCO 3 more than plasma Contains IgA, lysozyme, l a c t o f erri n , mucin prolin rich proteins

7. Functions of Saliva     Cooling hot foods. Neutralizing acid. Lysozyme attacks the walls of bacteria. Antibodies (immune globulin IgA) destroy oral pathogenic bacteria.

8. Digestive Functions Of Saliva Saliva has 3 digestive enzymes, namely salivary amylase, maltase and lingual lipase. Salivary Amylase – it is a carbohydrate – digestive enzyme. It acts on cooked or boiled starch and converts into dextrin and maltose. Optimum pH, necessary for the activation of salivary amylase is 6. salivary amylase cannot act on cellulose. Maltase – It is present only in traces in human saliva and it converts maltose into glucose. Lingual Lipase – lingual lipase is a lipid digesting (lipolytic) enzyme. It is secreted from serous glands situated on the posterior aspect of the tongue. It digests milk fats. It hydrolyses triglycerides into fatty acids and diacylglycerol.

9. Swallowing (Deglutition) Propelling of food from mouth to stomach through pharynx and oseophagus .

10. Stomach

11. Stomach is divided anatomically Fundus Body Antrum Pylorus

12. Secretory function of stomach Gastric gland

13. Functions of HCl Killing bacteria Dissolve food into chyme Activate pepsinogen Iron & calcium absorption Stimulate secretin hormone & bile flow

14. Acid secretion 1 2

15. Digestive Function Pepsin – it is secreted as inactive pepsinogen. Pepsinogen is converted Into pepsin by HCL. Optimum pH, for activation of pepsinogen pH 1.0-2.0 . Action of Pepsin – it converts proteins into proteoses, peptones, and polypeptides, pepsin also causes curdling and digestion of milk (Casein). Gastric Lipase – it is a weak lipolytic enzyme when compared to pancreatic lipase. It is active only when the pH, is between 4 and 5 and becomes inactive at pH, below 2.5.

16. Pancreas

17. Pancreatic secretion The pancreas is involved in blood sugar control and metabolism within the body. Volume → 1500 ml / day pH → 8-8.3, Alkaline ( HCO 3 ) α alpha cells secrete glucagon (increase glucose in blood) β beta cells secrete insulin (decrease glucose in blood) δ delta cells secrete somatostatin (regulates/stops α and β cells) γ (gamma) cells , secrete pancreatic polypeptide.

18. Pancreatic Digestive Enzymes

19. Liver & Biliary system

20. Functions of the liver Liver acts as a chemical factory, an excretory system, an exocrine and an endocrine gland 1 . Vascular Functions for Storage and Filtration of Blood: store 200-400 ml. of blood Kupffer cells(remove 90% of bacteria in the portal venous blood (the colon bacilli)

21. 2 . Metabolic Functions : Carbohydrate metabolism : ( glucostat" ) Glycogenesis- glycogenolysis- gluconeogenesis- Cori cycle ( formation of glycogen from lactic acid) Lipid metabolism: oxidation of fatty acids - Formation of lipoproteins - lipogenesis Protein metabolism : Deamination of amino acids - Formation of urea , plasma proteins, most of coagulation factors & non-essential amino acids Storage of vitamins : Such as vitamin A, D, E, K and B 12 . & iron Detoxification or excretion of drugs, hormones and other substances

22. 3 . Secretory and excretory functions: Formation of bile : Bile is required for the digestion and absorption of fats ( bile salts) and for the excretion of water-insoluble substances such as cholesterol and bilirubin Secretion is continuous through all the day & is stored in gall bladder

23. Composition of bile 500-1500 ml/day Fresh bile is alkaline Becomes acidic during storage in gall bladder to prevent precipitation of calcium

24. Bile S alts • • Primary bile acids : cholic acid and chenodeoxycholic acid . • Secondary bile acids : In the colon, bacteria convert cholic acid to deoxycholic acid and chenodeoxycholic acid to lithocholic acid . Sodium and potassium salts of bile a cids conjugated to glycine or taurine ( glycocholic & taurocholic acids) The bile acids are synthesized from cholesterol.

25. 1 . Digestion of fat a . A ctivation of pancreatic lipase E mulsification of fat preparatory to its digestion and absorption by detergent action reduce surface → tension between fat globules hydrotropic action Function of bile salts

26. 2 . Absorption of fat & fat soluble vitamins - form micelles , micelles are bile acid-lipid water-soluble complexes that play an important role in keeping lipids in solution and transporting them to the brush border of the intestinal epithelial cells, where they are absorbed.

27. The Gallbladder Functions of the Gallbladder: Storage of Bile Concentration of B ile removal of sodium by the gallbladder mucosa through an active transport mechanism, which passively draws chloride, bicarbonate and water. Prevention of marked rise in the Intrabiliary pressure Secretion of white bile Acidification of Bile : ( absorption of bicarbonate)

28. Control of Gallbladder Emptying = Cholagogues Cholecytokinin (CCK) major stimulus for gallbladder contraction and sphincter of Oddi relaxation . Vagal stimulation cephalic stage of digestion and vago-vagal reflex during the gastric phase of digestion

29. PARTS The small intestine is divided into three structural parts: (I)The duodenum (II)The jejunum (III)The ileum

30. The duodenum is a short structure ranging from 20 cm to 25 cm in length, and shaped like a "C". The jejunum is the midsection of the small intestine, connecting the duodenum to the ileum. It is about 2.5 m long . The ileum is the final section of the small intestine. It is about 3 m long, and contains villi similar to the jejunum.

31. FUNCTIONS Digestion The small intestine is where most chemical digestion takes place. Many of the digestive enzymes that act in the small intestine are secreted by the pancreas and liver and enter the small intestine via the pancreatic duct. Digestion of proteins & carbohydrate

32. MCQ QUESTION

33. 1. Chymosin is also known as ______. Lipase Amylase Trypsin Rennin

34. Answer : (d)Rennin

35. 2. Pancreatic juice is stimulated by the release of Secretin Cholecystokinin Enterokinase Both (a) and (b)

36. Answer : (D) Both (a) and (b) Secretin & Cholecystokinin

37. 3. Enterokinase helps in the conversion of Lactose to Sucrose Trypsinogen into trypsin Pepsinogen into pepsin Proteins into Polypeptide

38. Answer : (b) Trypsinogen into trypsin

39. 4. In humans, lacteals are found in ______. Ileum Oesophagus Ear Rennin

40. Answer : (a) Ileum

41. 5 . ______ is a characteristic feature of epithelial cells of the intestine. Glottis Pilus Bolus Microvilli

42. Answer : (d) Microvilli

43. Thank Y ou