Chapter 17 Digestive System. Alimentary Canal. Movements of the Tube

Transcription

1 Chapter 17 Digestive System Functions of Digestive System ingestion mechanical digestion chemical digestion propulsion absorption defecation Consists of the alimentary canal and accessory organs 1 Alimentary Canal About 8 meters long 2 Movements of the Tube mixing movements segmentation peristalsis 3 1

2 Mouth ingestion mechanical digestion (mastication) prepares food for chemical digestion Parts Cheeks Lips Tongue Palate uvula 4 Tongue Taste Moves food Forms bolus 5 Palate roof of oral cavity uvula 6 2

3 Primary Teeth 8 incisors 4 cuspids 8 molars 7 Secondary Teeth 8 Salivary Glands 9 3

4 Secretions of Salivary 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 Major salivary glands Parotid glands Submandibular glands Sublingual glands 10 Pharynx Connects nasal and oral cavities with the larynx and esophagus 3 parts Nasopharynx Oropharynx Layrngopharynx 11 Swallowing Mechanism 12 4

5 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 13 Stomach J-shaped, pouchlike organ cm long 3 regions Cardiac region Fundic region Body Pyloric region Wall contain three layers of muscle 14 Lining of Stomach 15 5

6 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 B 12 absorption 16 Gastric Absorption some water certain salts certain lipid-soluble drugs alcohol 17 Mixing and Emptying Actions 18 6

7 Pancreas 19 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 20 Regulation of Pancreatic Secretions acidic chyme stimulates release of secretin secretin stimulate release of pancreatic juice 21 7

8 Liver Largest internal organ 22 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, B 12, iron, and blood phagocytosis of worn out RBCs and foreign substances removes toxins from blood produces and secretes bile 23 Composition of Bile water bile salts emulsification of fats absorption of fatty acids, cholesterol, and fatsoluble vitamins bile pigments cholesterol electrolytes 24 8

9 Gallbladder Stores bile until it is released into the small intestine 25 Regulation of Bile Release fatty chyme entering duodenum stimulate gallbladder to release bile 26 Three Parts of Small Intestine Tubular organ m long 27 9

10 Intestinal Villus 28 Wall of Small Intestine 29 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 30 10

11 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 31 Absorption in the Small Intestine fatty acids and glycerol several steps absorbed into lymph and blood 32 Movements of the Small Intestine mixing movements peristalsis pushing movements segmentation ringlike contractions overdistended wall triggers peristaltic rush resulting in diarrhea 33 11

12 Large Intestine 34 Functions of Large Intestine little or no digestive function absorbs water and electrolytes secretes mucus houses intestinal flora Absorbs vitamins K, B 12, thiamine and riboflavin produced by the bacteria forms feces carries out defecation 35 Movements of Large Intestine slower and less frequent than those of small intestine mixing movements peristalsis mass movements usually follow meals 36 12

13 Feces water electrolytes mucus bacteria bile pigments altered by bacteria provide color smell produced by bacterial compounds 37 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 38 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 39 13

14 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 40 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 41 14