Digestion. Digestive System (Blank) Digestive System (Labeled)
Chapter 17 Digestive System system.pdfChapter 17 Digestive System Functions of Digestive System •...
Transcript of Chapter 17 Digestive System system.pdfChapter 17 Digestive System Functions of Digestive System •...
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Chapter 17 Digestive System
Functions of Digestive System • ingestion • mechanical digestion • chemical digestion • propulsion • absorption • defecation
Consists of the alimentary canal and accessory organs
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Alimentary Canal
About 8 meters long
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Movements of the Tube • mixing movements • segmentation • peristalsis
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Mouth
• ingestion • mechanical digestion (mastication) • prepares food for chemical digestion
• Parts • Cheeks • Lips • Tongue • Palate
• uvula
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Tongue
• Taste • Moves food • Forms bolus
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Palate
• roof of oral cavity • uvula
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Primary Teeth
• 8 incisors • 4 cuspids • 8 molars
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Secondary Teeth
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Salivary Glands
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Secretions of Salivary Glands
• Major salivary glands • Parotid glands • Submandibular glands • Sublingual glands
• Saliva • Moistens food particles • Helps bind the food particles together to form bolus • Begins chemical digestions of carbohydrates (salivary amylase) • Helps clean the mouth
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Pharynx
Connects nasal and oral cavities with the larynx and esophagus 3 parts • Nasopharynx • Oropharynx • Layrngopharynx
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Swallowing Mechanism
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Esophagus
Straight, collapsible tube about 25 cm long Carries food from pharynx to stomach Lower esophageal sphincter (cardiac sphincter) - controls the opening to the stomach
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Stomach
J-shaped, pouchlike organ 25-30 cm long 3 regions • Cardiac region • Fundic region • Body • Pyloric region
Wall contain three layers of muscle
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Lining of Stomach
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Gastric Secretions
• pepsinogen • from chief cells • inactive form of pepsin
• pepsin • from pepsinogen in presence of HCl • protein splitting enzyme
• hydrochloric acid • from parietal cells • needed to convert pepsinogen to pepsin
• mucus • from goblet cells and mucous glands • protective to stomach wall
• intrinsic factor • from parietal cells • required for vitamin B12 absorption
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Gastric Absorption
• some water • certain salts • certain lipid-soluble drugs • alcohol
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Mixing and Emptying Actions
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Pancreas
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Pancreatic Juice
• pancreatic amylase – splits glycogen into disaccharides • pancreatic lipase – breaks down triglycerides • trypsin, chymotrypsin, and carboxypeptidase – digest proteins • nucleases – digest nucleic acids • bicarbonate ions – make pancreatic juice alkaline
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Regulation of Pancreatic Secretions
• acidic chyme stimulates release of secretin • secretin stimulate release of pancreatic juice
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Liver Largest internal organ
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Liver Functions
• produces glycogen from glucose • breaks down glycogen into glucose • converts noncarbohydrates to glucose • oxidizes fatty acids • synthesizes lipoproteins, phospholipids, and cholesterol • converts carbohydrates and proteins into fats • deaminates amino acids • forms urea • synthesizes plasma proteins • converts some amino acids to other amino acids • stores glycogen, vitamins A,D, B12, iron, and blood • phagocytosis of worn out RBCs and foreign substances • removes toxins from blood • produces and secretes bile
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Composition of Bile
• water • bile salts
• emulsification of fats • absorption of fatty acids, cholesterol, and fat-soluble vitamins
• bile pigments • cholesterol • electrolytes
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Gallbladder Stores bile until it is released into the small intestine
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Regulation of Bile Release
• fatty chyme entering duodenum stimulate gallbladder to release bile
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Three Parts of Small Intestine Tubular organ 5.5 - 6.0 m long
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Intestinal Villus
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Wall of Small Intestine
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Secretions of Small Intestine
• peptidase – breaks down peptides into amino acids • sucrase, maltase, lactase – break down disaccharides into monosaccharides • lipase – breaks down fats into fatty acids and glycerol • enterokinase – converts trypsinogen to trypsin • somatostatin – hormone that inhibits acid secretion by stomach • cholecystokinin – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, stimulates gallbladder to release bile • secretin – stimulates pancreas to release bicarbonate ions in pancreatic juice
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Absorption in the Small Intestine
• monosaccharides and amino acids
• through facilitated diffusion and active transport • absorbed into blood
• electrolytes and water • through diffusion, osmosis, and active transport • absorbed into blood
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Absorption in the Small Intestine
• fatty acids and glycerol • several steps • absorbed into lymph and blood
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Movements of the Small Intestine
• mixing movements • peristalsis – pushing movements • segmentation – ringlike contractions • overdistended wall triggers peristaltic rush resulting in diarrhea
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Large Intestine
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Functions of Large Intestine • little or no digestive function • absorbs water and electrolytes • secretes mucus • houses intestinal flora
• Absorbs vitamins K, B12, thiamine and riboflavin produced by the bacteria
• forms feces • carries out defecation
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Movements of Large Intestine
• slower and less frequent than those of small intestine • mixing movements • peristalsis • mass movements usually follow meals
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Feces
• water • electrolytes • mucus • bacteria • bile pigments altered by bacteria provide color • smell produced by bacterial compounds
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Life-Span Changes
• teeth become sensitive • gums recede • teeth may loosen or fall out • heartburn more frequent • constipation more frequent • nutrient absorption decreases • accessory organs age but the effects are less noticeable
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Clinical Application
Hepatitis • inflammation of the liver • most commonly caused by viral infection • can be caused by reactions to drug, alcoholism or autoimmunity
Signs and Symptoms • headache • low fever • fatigue • vomiting • rash • foamy urine • pale feces • jaundice • pain
Hepatitis A – not washing hands or eating raw shellfish Hepatitis B – chronic; serum Hepatitis C – serum Hepatitis D – very severe; only produces symptoms if infected with B; serum Hepatitis E, F, G – more rare
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Clinical Application
Ulcers • Sores in the lining of stomach • most commonly caused by helicobacter pylorus • can be caused by reactions to drug and certain foods
Signs and Symptoms • pain • Blood in feces
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Clinical Application
Gastric Reflux Disorder • recurrent heartburn • Can cause the lining of the esophagus to wear away • Treat with acid reducers and/or surgery
Signs and Symptoms • pain