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Blood vessels Lymph vessels Nerves Smooth muscle Connective tissue lymphocytes Plasma cells Eosinophiles Villous epithelium Undifferentiated Goblet Mitoses.

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Presentation on theme: "Blood vessels Lymph vessels Nerves Smooth muscle Connective tissue lymphocytes Plasma cells Eosinophiles Villous epithelium Undifferentiated Goblet Mitoses."— Presentation transcript:

1 Blood vessels Lymph vessels Nerves Smooth muscle Connective tissue lymphocytes Plasma cells Eosinophiles Villous epithelium Undifferentiated Goblet Mitoses Endocrine cells Crypt epithelium Crypt lumen Muscularis mucosa Absorp- tive cells Goblet cells Endocrine cells Cell Loss

2 Crypts of Lieberkuhn: Small and Large Intestine -Contain Primarily Epithelial Cells, Mucus Goblet Cells, and Endocrine Cells. -Water Secretion - VIP Activates Water Secretion by Elevating cAMP and Cl - conductance. -Cell Growth and Differentiation: Cell Turnover at the Tip of a Villus is High (3-6 day Cycle). Secretions of the Small Intestine (2000 ml/day)

3 Crypt Secretion H2OH2O 2 Cl - Na + K+K+ PDte cAMP ? Ca 2+ Cl - Na + ATP ADP + Pi 3 Na + 2 K + Key Players: cAMP Activated Cl - Channel Na + / K + / Cl - Co-transport Na-K ATPase VIP – neurotransmitter Histamine also can activate

4 Daily Secretions into the Alimentary Canal Saliva 1200 7.0-7.4 Gastric secretion 20001.0-3.5 Pancreatic secretion12008.0-8.3 Bile 700 7.8 Intestinal Secretions 20007.4-7.8 Brunner’s gland secretion 50 (?)8.0-8.9 Large intestinal secretion 607.5-7.8 Total 7210 Daily Volume (ml) pH

5 Blood vessels Lymph vessels Nerves Smooth muscle Connective tissue lymphocytes Plasma cells Eosinophiles Villous epithelium Undifferentiated Goblet Mitoses Endocrine cells Crypt epithelium Crypt lumen Muscularis mucosa Absorp- tive cells Goblet cells Endocrine cells Cell Loss

6 Sugar Absorption  -Amylase Lactose Sucrose Starch Glycogen 30% 70% Glucose Galactose Na + Fructose Glucose Na +  -Limit Dextrins Oligosaccharides Lactase Glucose Carrier Fructose Carrier (Xylose) Glucose Carrier Gluco- amylase Sucrase  -Dex trinase LUMEN Brush Border

7 Absorption of Nutrients: Carbohydrates -Glucose and Galactose - Sodium Co- transporter Across Luminal Membranes -Fructose - Facilitated Transport (Na + Independent) -Xylose: Pentose; Uses the Fructose Carrier not Na + Dependent. ABSORPTION

8 Capillary Amino Acids Amino Acids Small Peptides Carrier Peptidases Carrier Mediated Intracellular Peptidases ? Free Amino Acids Neutral Basic Acidic Large Peptides Small Peptides Pepsin, Pancreatic Protease Protein A.A

9 Emulsion: TG. MG. FFA. B.S. Micelles MG. FFA. B.S. Large oil droplet (TG) MG. FFA Intestinal epithelial cell Microvilli Lipase Co-Lipase Lipid Digestion and Absorption

10 Triglyceride Monoglyceride Pancreatic lipase Free fatty acids Glycerol Lacteal Capillary Micelle Liver Ileum Conjugated bile salts Monoglyceride acylation pathway Phosphatidic acid pathway Protein (Apo B) Cholesterol Chylomicron Phospholipids FABP

11 Nutrient Digestion and Absorption -Only Monomers and small digestion products can be absorbed. For amino acids and carbohydrates, most absorption is Na + dependent - Lipids are digested before absorption, then re-synthesized in epithelia cells before packaging and secretion into lymph Glycerol and Monoglycerides diffuse into the blood. Complex fats are packaging into chylomicrons and secreted to the lymph. Lymphatic flow increased 10X during absorption of a high fat meal.

12 Blood vessels Lymph vessels Nerves Smooth muscle Connective tissue lymphocytes Plasma cells Eosinophiles Villous epithelium Undifferentiated Goblet Mitoses Endocrine cells Crypt epithelium Crypt lumen Muscularis mucosa Absorp- tive cells Goblet cells Endocrine cells Cell Loss

13 Relations Between Salt /Water Secretion and Absorption Net Fluid and NaCl Villus Epithelia Absorption Net Fluid and NaClCrypt Epithelia Secretion

14 Crypt Secretion H2OH2O 2 Cl - Na + K+K+ PDte cAMP Cl - Na + ATP ADP + Pi 3 Na + 2 K + Key Player: cAMP Activated Cl - Channel CFTR VIP – neurotransmitter Histamine also can activate formation of cAMP

15 Absorption of Na + Concentration in Chyme: Na + Conc. K + Conc. Volume Duodenum Ileum Colon (Prox) 140 mEq/L 125 mEq/L 40 mEq/L 5 mEq/L 23 mEq/L 80 mEq/L 5 Liters 1 Liter 200 mL

16 Na + is Absorbed Along the Entire Intestine -Na + Diffuses Down its Electrochemical Gradient into Epithelial Cells -Luminal Membrane: Co-transport with Nutrients, Diffusion Through Na + Channels and Na + /H + Exchange -Transported Across the Basolateral Membrane by the Na-K ATPase. -Cl- Moves to the Blood to Maintain Electroneutrality. Absorption of Na +

17 25-OH-D 3 1,25-(OH) 2 -D 3 Liver Kidney Intestine RNA Ca 2+ Na + Plasma Ca 2+ Ca 2+ ATPase CaBP Parathyroid Hormone Vitamin D 3

18 Vitamins Fat Soluble – absorbed all along the intestine via normal fat absorptive pathways. (D, K, A) Water Soluble: Specific Transport Most all along the intestine. Several Ileal Specific- Vitamin: B12 also Ileal Specific: Bile Salts. Vitamins and Ileal Transport

19 -90-95% of Water (re)absorption in the Small Intestine -1-2 L/day is Absorbed in the Colon. -A Normal Colon Can Reabsorb a Maximum of About 4.5 liters per day. Mechanism of H 2 O Absorption- –Where salt goes, so too does water. Absorption of Water

20 The Causes of Diarrhea Delineate into 3 Categories Motility Based: Limiting Time for Absorption Bacterial Infiltration Malabsorption; Maldigestion: Osmotic -Lactase Deficiency -Ileal Resection: Biles Salts also stimulate secretion. -Celiac Disease (Sprue; Gluten Sensitive) – Xylose Test Secretory: Initiated by Effectors which Alter cAMP Levels in Enterocytes; Bile Salts Pathophysiology of Diarrhea


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