Anatomy and Physiology: The Unity of Form and Function

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1 Chapter 25 Anatomy and Physiology: The Unity of Form and Function Second Edition Kenneth S. Saladin (c) The McGraw-Hill Companies, Inc.

3 Structures and Location A. Location from mouth through thoracic and abdominal cavities B. Structures - 1. Alimentary Canal organs: food tube wherever food passes through: Mouth, Pharynx, Esophagus, Stomach, Small and Large Intestines 2. Accessory Organs: Produce enzymes Salivary glands, liver, gall bladder, pancreas

4 Functions 1. Ingestion tasting or taking in food 2. Mastication chewing/salivating food in mouth 3. Deglutition - swallowing 4. Digestion breaking food into smaller pieces (mechanical) or chemically changing into smaller molecules (chemical) 5. Absorption movement of digested food from the alimentary canal to the blood 6. Defecation elimination of feces (waste products) from alimentary canal

5 Four Layers of Alimentary Canal A. Mucosa simple columnar epithelial Inner layer protects the other layers from acids/bases, bacteria, viruses, etc B. Submucosa loose connective Next layer connects epithelium to muscle C. Muscular smooth muscle Next layer towards peritoneal cavity helps move food through alimentary canal D. Serosa areolar loose connective Visceral Peritoneum covers the organs of the GI tract Parietal Pertoneum - Lines the peritoneal cavity

9 Mechanical Digestion A. Mixing motions rhythmic contractions of smooth muscle mixes food with digestive enzymes B. Propelling motions Peristalsis alternate smooth muscle contraction and relaxation slowly squeeze food and waste through alimentary canal

12 Oral Cavity A. Lips/Cheeks skin covered striated muscle holds food in mouth B. Palate roof of mouth (hard: palatine bone and maxilla, soft striated muscle and uvula) C. Tongue striated muscle with taste buds (gustatory senses)- tasting and manipulating food during mastication D. Teeth 32 adult/permanent teeth Location sockets of maxillary and mandibular processes Structure regions: upper (crown), middle (neck), lower (periodontal) Layers: inner (pulp), middle (dentine), outer (enamel) Function mastication of food

17 Salivary Glands Location outside oral cavity near ear, mandible, and tongue Structure serous cells secrete amylase, mucous cells line and produce mucous Function saliva cleans, moistens, and begins starch digestion

21 Pharynx A. Location between mouth and esophagus B. Structure - striated muscular tube lined with stratified epithelial and mucous glands C. Function swallowing bolus (food and saliva from mouth) reflex action

22 Esophagus A. Location within mediastinum penetrating diaphragm at the esophageal hiatus B. Structure inch tube of striated/smooth muscle (collapsible tube) C. Function propel bolus from pharynx to stomach

26 Stomach A. Location inferior to diaphragm left hypochondriac region B. Structure 1. Four regions: cardiac(upper end), fundus, body, and pyloric (lower end) 2. Ruggae collapsible folds allowing for expansion and contraction

28 Gastric Glands a. Mucus cells secrete alkaline mucous prevent self digestion by gastric juices b. Chief cells secrete pepsinogen (precursor to pepsin) c. Parietal cells secrete hydrochloric acid which changes pepsinogen to pepsin d. Entereoendocrine cells secrete various hormones (endocrine function) like gastrin

31 Stomach Functions 1. Receive and mechanically mix bolus with gastric juices 2. Initiate protein digestion 3. Propel Chyme (bolus + gastric juices) to small intestine

35 Small Intestines A. Location Lower 2/3 of abdominal cavity B. Structure 20 feet of convoluted (twisted) smooth muscular tube lined with simple columnar epithelial 1. Three regions Dudoenum, jejunum, ileum 2. Villi- mucosal finger-like projection for nutrient absorption contain lacteals (absoroption of lipids (lymph capillaries) blood capillaries absorption of other nutrients into hepatic portal system 3. Crypts of Lieberkuhn intestinal glands secrete intestinal juices (water and mucous) 4. Brush Border cells produce mucosa-bound digestive enzymes (disaccharidases, aminopeptidases, carboxypeptidase, dipeptidase, and nucleotidases)

38 Functions of Small Intestines 1. Completion of most chemical digestion with enzymes from brush border, pancrease, and gall bladder/liver 2. Most absorption of nutrients into blood. 3. Transportation of feces to colon 4. Most nutrient absorption occurs from small intestine into hepatic portal veins which are then transported to liver for detoxification prior to entering systemic circulation) 5. Propulsion of chyme and feces by peristalsis

39 Large Intestines A. Location frames small intestines on three sides and part of the fourth side B. Structure 4-5 feet U-shaped muscular bag 1. Mucosa simple columnar epithelial (no villi, secretory cells, nor enzymes) 2. Regions a. cecum first section blind pouch at the proximal end (near appendix) right inguinal region b. colon ascending, transverse, descending, and sigmoid frame the small intestines c. rectum 1-2 inch stratified squamous epithelium lined tube with sphincter muscles (anus for defecation)

43 Functions of Large Intestines 1. Electrolyte and water absorption by active transport, osmosis 2. Vitamins K and B (12, thiamin, riboflavin) synthesis by bacterial flora 3. Fecal storage - feces undigested material (fiber) with water, electrolytes, bacteria, and some mucous

44 Liver A. Location - inferior to diaphragm right hypochondriac region B. Structure highly vascularized hepatocytes in liver lobules (functional unit of liver)

47 Functions of the Liver detoxification destroys old erythrocytes protein metabolism lipid metabolism carbohydrate metabolism secretion of bile

50 Gall Bladder A. Location Inferior to liver (between liver lobes) B. Structure Thin walled green muscular bag C. Function Stores bile for secretion into duodenum when fat is present

52 Pancreas A. Location next to duodenum B. Structure Acinar cells secrete pancreatic juices C. Function Secrete pancreatic juices 1. Bicarbonate ions (alkaline) neutralized acidic chyme 2. Digestive enzymes: amylases, lipases, peptidases, and nucleases a. peptidases: trypsin, chymotrypsin, and carboxypeptidases,

56 Chemical Digestion A. Carbohydrate Digestion 1. Starch amylase (salivary and pancreatic in mouth and small intestines) 2. Disaccharides disaccharidases (sucrase, maltase, lactase - from small intestines in small intestines) B. Protein Digestion 1. Proteins Pepsin (stomach) Breaks down large globular proteins into large polypeptide chains 2. Large Polypeptides Trypsin, chymotrypsin, and carboxypeptidase (in small intestsines) Breaks down large polypeptides into small polypeptides and peptides 3. Small Polypeptides Aminopeptidase, carboxypeptidase, and dipeptidases (in small intestines) Break down small polypeptides and peptides into amino acids

62 Chemical Digestion C. Lipid Digestion 1. Fat globules Bile breaks larger pieces of fat into smaller fat globules (emulsification not chemical) 2. Fat droplets Lipase breaks triglycerides into fatty acids and glycerol (small intestines) D. Nucleic acid Digestion 1. DNA and RNA - Convert into nucleotides (small intestines) 2. Nucleotides - monomers of Nucleic acids

66 Autonomic Control of Digestive System Sympathetic - slows visceral motility Parasympathetic Vagus nerve increases visceral motility

67 Digestive Disorders Peptic ulcers Ulcers in stomach (largely caused by Helobacter pylori) Appendicitis Inflammation of appendix Diverticulitis Inflammation of diveticuli Diverticulosis Production of diverticuli (outpouching of colon can become polyps develop into tumors) Anorexia nervosa disorder in which person eats very little and exercises excessively Bulimia disorder in which person binges on food and then forces vomiting immediately afterward

68 The End.

Two main groups Alimentary canal continuous coiled hollow tube Accessory digestive organs

Digestion Breakdown of ingested food Absorption of nutrients into the blood Metabolism Production of cellular energy (ATP) Constructive and degradative cellular activities Two main groups Alimentary canal