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Membrane digestion & absorption
This document summarizes membrane digestion and absorption in the small intestine. It discusses how enzymes digest substrates in the mucus, glycocalyx, and on enterocyte membranes. Key points include the large surface area and efficiency of membrane digestion, as well as its close connection to absorption. Absorption involves both passive diffusion and active transport across enterocyte membranes and within microvilli. The major nutrients - proteins, carbohydrates, fats, vitamins and minerals - are absorbed primarily in the duodenum and jejunum through these membrane transport processes.
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Membrane digestion & absorption
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- 2. Membrane digestion Goes insuccession in three zones: In mucus In glycocalyx On the apical membrane of enterocytes Was discovered by prof. Ugolev A.M.
- 3. Ugolev experiment Amylase+ starch Amylase+ starch +intestine piece Amylase+ starch +boiledintestine piece 48-52 h 48-52 h3-4 h
- 4. muscels Nervous fibres Blood vessels epithelium lymphaticcapillaries villae
- 5. Sponsored Medical Lecture Notes– All Subjects USMLE Exam (America) – Practice
- 6. Substrates depolymerization I thecavity & on the surface of the intestines
- 7. Membrane with adsorbed enzymes МФ– memnbrane enzymes ПФ – pancreatic enzymes КЦФ – active centers of enzyme РЦФ – regulatory centers of enzymes ТСМ – membrane transport syst
- 8. Brush boarder region microvilli– Up to 3000 on one enterocyte – increase the square up to 30 times 0,01-0,02 10-6 m Membrane enzymes Enzymes active centers 1-2мкм
- 9. Enteral medium • Thinwater film above the glycocalics which isn’t mixed up • Its content is homeostated water film Enteral cavity blood
- 10. Characteristic properties of membranedigestion 1. Large catalytic surface 2. Highly effective 3. Sterile 4. Closely connected with absorption
- 11. Enzymes • Secreted byenterocytes • Fixed on the apical membrane of the enterocyte • On enterocyte destruction get into glycocalyx, mucus & enteric juice • Break down olygo- & dimers to form monomers
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- 14. absorption • Это сложныйфизиологический процесс проникновения различных веществ через биологическую мембрану в кровь и лимфу • В результате организм получает питательные вещества, воду, соли, витамины и лекарственные вещества
- 15. Methods of studying absorptionin the intestines
- 16. Acute methods Lymphatic vesselsstudying vividiffusion v. portae печень solution
- 17. Chronic methods Isolated loopof small intestine Thiry’s mehod Thiry-Vella method
- 19. 1.Polyfistule method intestine skin fistuli 2.London’s angiostomy -Fistula of vena cava
- 20. macrovilli Macrovilli & criptare structural & functional component of intestine
- 21. muscels Nervous fibres Blood vessels epithelium lymphaticcapillaries villae
- 22. Macrovilli contents • arteriola •Capillary net • venula • Lymphatic capillary • Muscle fibres • Nervous ending • Enterocytes with brush boarder • Surface of absorption is about 200 m2
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- 24. Types of transport passive: •filtration • osmosis • diffusion Goes along the gradients created by macrovilli contraction 15-20 ml of fluid is absorbed per 1 minute Active • Primary active (sodium-potassium pump) • Secondary active (glucose & amino acids transport)
- 25. enterocyte Renewed very quickly Non-differentiatedcylindrical cells rise up from cripts to the top of the villi in 24-36 hours
- 26. Blood supply ofsmall intestine • Upper mesenterical artery • Coeliac artery • Lower mesenterical artery Small intestines get 10-15% of Q (MBF) 400 ml/min During digestion blood supply increases by 30-130% 750 ml/min 5% submucous 20% muscle layer 75% mucous
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- 28. Via cells •Protein-carrier •Energy requering activepassive Viacells •diffusion •convection Via cell gaps •diffusion •convection
- 29. Water transport Goes viagaps between the enterocytes along the gradients: • Hydrostatic • Osmotic (created additionally by sodium absorption) • Dissolved in water substances are absorbed
- 30. Water can besecreted from blood into the intestinal cavity 1. Active secretion of anions 2. Decrease of active absorption 3. High osmotic pressure in the intestinal cavity 4. Increased hydrostatic pressure in the serose layer 5. Increased permeability of intracellular gaps for ions
- 31. Dehydroxyle derivatives ofbile acids & laxatives increase permeability of intracellular junctions. Magnesium sulphate increases osmotic pressure in the intestinal cavity Hydrostatic pressure “leaking” junction
- 32. Bacterial toxins (Cholera toxin, coletoxin) Hormones (prostaglandies, secretin,VIP) C-AMP Calcium concentration in the enterocytes changes, Chlorine permeability increases Chlorine gets into the cavity, sodium follows along the electrical gradient , water follows along the osmotic gradient
- 33. Proteins • 70-90 gper day with food 60 г белка с пищеварителными соками ( ферменты и энтероциты). • В полости 30% расщепляется до нейтральных и основных АК – 70% до олигопептидов • Ологипептиды расщепляются до АК в щеточной кайме (10%) и в цитоплазме
- 34. Digestion & absorptionof proteins
- 35. Amino acids absorption •Goes in duodenum (50-60%) & jejunum (30%) by means of secondary active sodium dependent transport • Protein-carriers are selective for: Neutral АA Двухосновных АA Dicarbonic АA Glycin
- 36. Carbohydrates Daily dose 250-280g: • 60% vegetable starch • 30% saccharase • 10% lactose, glucose, fructose, glycogen Enzymes: • In the cavity – alpha-amylaze • On the villi – olygosacharidazes: lactatdehydrogenaze (lactase), glycosidase
- 37. Lactase deficit • InEurope – 15% of population • In Africa – 80% of population • In Muslim states of India – 15% of population • In Hindu states of India– 80% of population Lactose increases osmotic pressure in the cavity & can cause dyarhea
- 38. Transport of carbohydrates monomers Monomers: •Glucose • Galactose • Fructose Absorbed by means of secondary active sodium dependent transport in duodenum (30%) & jejunum (50-60%)
- 39. Scheme of secondaryactive transport ATP К+ Na+ Na+ glucose Apical membrane Basilar membrane
- 40. Fats • 60-100 gof fat per day 90% of them are thryglcerides 5-7 g are excreted with faeces • Emulsified in duodenum (fat drop in stomach is 100 nm in diameter, I the intestines – 5 nm) • Absorbed in the form of fine emulsions or micells with bile acids 95% in duodenum
- 41. Lipids absorption lipid Bile acidblood chilomicrone TG lipoproteins lymph
- 42. Relative volumes ofabsorption Duodenum 30 сm jejunum 120 сm ileum 130 сm 95% 50% 30% 30% 50-60% fats Amino acids glucose
- 43. Large intestine Absorption iscompleted here & faeces are formed: • 400 g of chyme per day enters from small intestine • 150-200 g of faeces is formed – 70-80% of water; 20-30% of dry matter (cellulose, non- organic substances; fats) • The number of microorganisms is exceptionally great— up to tens of milliards per kg of contents.