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Digestive System
Consists of digestive tract and accessory organs Digestive Tract : Mouth, Esophagus, Stomach, small intestine, large intestine, rectum Accessory Organs: Salivary Glands, pancreas, and biliary system Digestive System is characterized by: Motility Digestion Secretion Secretion Absorption TERM 2
Histology of the Digestive Tract
DEFINITION 2
- Serosa/Adventia 2. Muscularis Externa (longitudinal and circular) 3. Muscularis Mucosae (longitudinal and circular) 4. Mucosa 5. Mucosal Folds 6. Stratified Squamous Epithelium
- Exocrine Glands TERM 3
pH in the Digestive System
DEFINITION 3 Saliva pH = 7 Stomach = 1.5 Small Intestine = 8 TERM 4
Saliva (1500 mL/24 Hours)
DEFINITION 4 Salivary secretion regulated by Medulla Oblongota Saliva is important for speech articulation and dental health. Water : 95% Electr: Na+, K+, Cl-,HCO3- Wastes: Urea, Uric Acid Enzymes: Salivary Amylase (ptyalin) Mucus Antimicrobial Agents: IgA, Lysozyme, Growth Factor TERM 5
Salivary Amylase
DEFINITION 5 Amylase is an enzyme that breaks starch down into sugar. Salivary Amylase starts the process of polysacharide digestion. Breaks Starch into maltose (carb.) Salivary Amylase is inactivated in the stomach by the low Ph.
Swallowing (coordinated reflex)
- Swallowing Center inhibits respiratory center. 2. Uvula elevated to prevent food from entering nasal passages. 3.Position of tongue prevents food from reentering the motuh. 4. Epiglottis is pressed over closed glottis to prevent food entering airways. Tongue prevents backflow. TERM 7
Peristalsis
DEFINITION 7 Peristalsis is a radially symmetrical contraction of muscles which propagates in a wave down the muscular tube. TERM 8
Esophagus
DEFINITION 8 25cm Long 1/3 Skeletal Muscle 1/3 Smooth and Skeletal Muscle 1/3 Smooth Muscle Passes through the lower esophageal sphincter. TERM 9
Stomach
DEFINITION 9 Store food Initiate Protein Digestion Kill bacteria Moves food to small intestine TERM 10
Gastric Gland Secretion (1500mL/ Day)
DEFINITION 10 Goblet Cells - mucus Parietal Cells - HCl (ACh, gastrin, histamine - stimuli) Chief Cells - Pepsinogen (ACh, gastrin, histamine - stimuli) Argentaffin Cells - Serotonin, Histamine - stimulus for parietal and chief cells. G Cells - Gastrin (stimulus for parietal and chief cells) D Cells - Somatostatin Inhibitor
Bile + Gallbladder
Bile Bile Salts Bile pigments Phospholipids cholesterol inorganic ions Gallbladder Store Bile Concentrate Bile TERM 17
Enterohepatic
DEFINITION 17 Enterohepatic circulation refers to the circulation of biliary acids from the liver, where they are produced and secreted in the bile, to the small intestine, where it aids in digestion of fats and other substances, back to the liver. 1.Liver 7. Portal Circulation 2.Gall Bladder 8. Liver (5%) 3. Common Bile Duct 4. Sphincter of Oddi 5.Duodenum 6. .Illeum TERM 18
Pancreas + Pancreatic Enzymes
DEFINITION 18 Endocrine Functions: Produce and release insulin and glucagons into the blood. Exocrine Functions: Produce and release pancreatic enzymes into small intestine. Pancreatic Enzymes Exocrine Cells ----> Pancreatic Enzymes Duct Cells - -----> Bicarbonate TERM 19
Pancreatic Enzymes Activation
DEFINITION 19 Trypsinogen Enterokinase (crucial) Trypsin Chemotrypsinogen Chemotrypsin Procraboxypeptidase Carboxypeptidase TERM 20
Energy Balance
DEFINITION 20 Energy balance consists of energy input and of energy output. Under Normal physiological conditions energy delivery to the body must equal energy output.
Energy Output + Energy Conversion to Heat
Energy Output = External Work (skeletal muscles) + Internal Work (activities to sustain life) Energy Conversion to Heat 50% of food energy transferred to ATP 25% of food energy during ATP expenditure converted to heat therefore 75% of food energy is converted to heat. Heat is used to maintain body temp. TERM 22
Pancreatic Enzymes of Small Intestine
(1000mL / Day)
DEFINITION 22 Proteins Chemotrypsin Elastase Carboxypeptidase Amylase -- --> Polysaccharide Lipase ----> Fat Ribonuclease ------> Nucleic Acids Deoxyribonuclease -----> Nucleic Acids TERM 23
Small Intestine
DEFINITION 23 Extends from Pyloric Sphincter Plica Villi -columnar epithelium -microvilli -goblet cells - Subepithelial Blood vessels - Central Lacteal Intestinal Crypts TERM 24
Small Intestine
DEFINITION 24 Contraction Peristalsis Segmentation Digestion Absorption TERM 25
Bile Salts
DEFINITION 25 Bile acids are steroid acids found predominantly in the bile of mammals. An increase in bile flow is exhibited with an increased secretion of bile acids. The main function of bile acid is to facilitate the formation of micelles, which promotes processing of dietary fat.
