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C. Chace Tydell, DVM 25-1 Veterinarian/surgeon for more than 15 years Immunology researcher for 10 years UCI Caltech Scientific publications Taught Developmental Biology at Caltech 25-2 Your name Your career goals One disease about which you would like to know more Does someone in your family have a health problem? Diabetes? Heart attack? Stroke? A disease or disorder that you have heard about? Lupus? Leprosy? Hepatitis? 25-3 Chapter 25 Lecture Outline Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 25-4 -osis = condition or process -itis = inflammation eg- gastritis, colitis, hepatitis -ostomy = a surgically created opening for waste products to move out of the body eg- cyanosis, cirrhosis, leukocytosis colostomy, ileostomy, ostomy -scopy = to view, to have a look colonoscopy, gastroscopy, endoscopy 25-5 Mechanical digestion physical breakdown of food into smaller particles teeth and churning action of stomach and intestines Chemical digestion series of hydrolysis reactions that break macromolecules into their monomers enzymes from saliva, stomach, pancreas and intestines results polysaccharides into monosaccharides proteins into amino acids fats into glycerol and fatty acids 25-6 Ingestion Digestion breakdown of molecules Absorption intake of food uptake nutrients into blood/lymph Defecation elimination of undigested material 25-7 Motility Secretion muscular contractions that break up food, mix it with enzymes and move it along digestive enzymes and hormones Membrane transport absorption of nutrients 25-8 Digestive tract (GI tract) 30 foot long tube extending from mouth to anus Accessory organs teeth, tongue, liver, gallbladder, pancreas, salivary glands 25-9 Mucosa Submucosa Muscularis externa epithelium lamina propria muscularis mucosae inner circular layer outer longitudinal layer Adventitia or Serosa areolar tissue or mesothelium 25-10 25-11 Able to function independently of CNS Composed of two nerve networks submucosal plexus controls glandular secretion of mucosa contractions of muscularis mucosae myenteric plexus controls peristalsis contractions of muscularis externa Peristalsis is alternate waves of longitudinal and circular muscular contraction that pushes food along the alimentary canal. 25-12 25-13 Serous membrane that lines the peritoneal cavity of the abdomen and covers the mesenteries and viscera Of the GI tract, only duodenum, pancreas and parts of large intestine are retroperitoneal Dorsal mesentery suspends GI tract and forms serosa (visceral peritoneum) of stomach and intestines Ventral mesentery forms lesser and greater omentum lacy layer of connective tissue that contains lymph nodes, lymphatic vessels, blood vessels 25-14 Lesser - attaches stomach to liver Greater - covers small intestines like an apron 25-15 Mesentery of small intestines holds many blood vessels Mesocolon anchors colon to posterior body wall 25-16 Neural control short myenteric reflexes (swallowing) long vagovagal reflexes (parasympathetic stimulation of digestive motility and secretion) Hormones messengers diffuse into bloodstream, distant targets Paracrine secretions messengers diffuse to nearby target cells 25-17 25-18 Cheeks and lips Tongue is sensitive, muscular manipulator of food keep food between teeth for chewing; essential for speech and suckling in infants vestibule - space between teeth and cheeks lips: cutaneous area versus red area (vermilion) papillae and taste buds on dorsal surface lingual glands secrete saliva, tonsils in root Hard and soft palate allow breathing and chewing at same time palatoglossal and palatopharyngeal arches 25-19 Baby teeth (20) by 2 years; Adult (32) between 6 and 25 Occlusal surfaces and cusp numbers differ 25-20 25-21 Periodontal ligament is modified periosteum Cementum and dentin are living tissue Enamel is noncellular secretion formed during development Root canal leads into pulp cavity anchors into alveolus nerves and blood vessels Gingiva or gums 25-22 Breaks food into smaller pieces to be swallowed surface area exposed to digestive enzymes Contact of food with sensory receptors triggers chewing reflex tongue, buccinator and orbicularis oris manipulate food masseter and temporalis elevate the teeth to crush food medial and lateral pterygoids swing teeth in side-toside grinding action of molars 25-23 Functions of saliva moisten begin starch and fat digestion cleanse teeth inhibit bacteria bind food together into bolus 25-24 Functions of saliva moisten, begin starch and fat digestion, cleanse teeth, inhibit bacteria, bind food together into bolus Hypotonic solution of 99.5% water and solutes salivary amylase, begins starch digestion lingual lipase, digests fat activated by stomach acid mucus, aids in swallowing lysozyme, enzyme kills bacteria immunoglobulin A, inhibits bacterial growth electrolytes = Na+, K+, Cl-, phosphate and bicarbonate pH of 6.8 to 7.0 25-25 Small intrinsic glands found under mucous membrane of mouth, lips, cheeks and tongue - secrete at constant rate 3 pairs extrinsic glands connected to oral cavity by ducts parotid submandibular sublingual 25-26 Compound tubuloacinar glands (see pg 177) Mucous cells secrete mucus Serous cells secrete thin fluid rich in amylase Mixed acinus has both 25-27 Total of 1 to 1.5 L of saliva per day Cells filter water from blood and add other substances Food stimulates receptors that signal salivatory nuclei in medulla and pons parasympathetic stimulation salivary glands produce thin saliva, rich in enzymes sympathetic stimulation produce less abundant, thicker saliva, with more mucus Higher brain centers stimulate salivatory nuclei so sight, smell and thought of food cause salivation 25-28 25-29 Skeletal muscle deep layer – longitudinal orientation superficial layer – circular orientation superior, middle and inferior pharyngeal constrictors 25-30 Straight muscular tube 25-30 cm long Extends from pharynx to cardiac stomach passing through esophageal hiatus in diaphragm nonkeratinized stratified squamous epithelium esophageal glands in submucosa skeletal muscle in upper part and smooth in bottom inferior pharyngeal constrictor excludes air from it Lower esophageal sphincter closes orifice to reflux 25-31 25-32 25-33 Series of muscular contractions coordinated by centers in the brain Buccal phase tongue collects food and pushes it back into oropharynx Pharyngeal-esophageal phase soft palate rises and blocks nasopharynx infrahyoid muscles lift larynx; epiglottis folded back pharyngeal constrictors push bolus down esophagus liquids in 2 seconds -- food bolus may take 8 seconds lower esophageal sphincter relaxes 25-34 25-35 Mechanically breaks up food, liquifies food and begins chemical digestion of protein and fat resulting soupy mixture is called chyme Does not absorb significant amount of nutrients absorbs aspirin and some lipid-soluble drugs 25-36 Muscular sac (internal volume from 50ml to 4L) J - shaped organ with lesser and greater curvatures regional differences cardiac region just inside cardiac orifice fundus - domed portion superior to esophageal opening body - main portion of organ pyloric region - narrow inferior end antrum and pyloric canal Pylorus - opening to duodenum thick ring of smooth muscle forms a sphincter 25-37 Cardia Fundus Body Pylorus Notice: bulge of fundus, narrowing of pyloric region, thickness of pyloric sphincter and greater and lesser curvatures 25-38 Innervation by parasympathetic fibers from vagus sympathetic fibers from celiac plexus All blood from stomach enters hepatic portal circulation and is filtered through liver before returning to heart 25-39 25-40 Mucosa simple columnar glandular epithelium lamina propria is filled with tubular glands (gastric pits) Muscularis externa has 3 layers outer longitudinal, middle circular and inner oblique layers 25-41 25-42 Mucous cells Regenerative cells secrete HCl acid and intrinsic factor Chief cells divide rapidly to produce new cells that migrate to surface Parietal cells secrete mucus secrete pepsinogen chymosin and lipase in infancy Enteroendocrine cells G cells Make gastrin Others secrete hormones and paracrine messengers 25-43 25-44 Parietal cells contain carbonic anhydrase (CAH) CO2 + H2O H2CO3 HCO3- + H+ H+ is pumped into stomach lumen by H+K+ATPase HCO3- in blood causes alkaline tide (blood pH ) 2 to 3 L of gastric juice/day (H2O, HCl and pepsin) 25-45 Activates pepsin and lingual lipase Breaks up connective tissues and plant cell walls Converts ingested ferric ions (Fe3+) to ferrous ions (Fe2+) liquefies food to form chyme absorbed and used for hemoglobin synthesis Destroys ingested bacteria and pathogens 25-46 Intrinsic factor Pepsin - protein digestion essential for B12 absorption by small intestine RBC production (lack causes pernicious anemia) secreted as pepsinogen (inactive) HCl converts it to pepsin (active) Gastric lipase and chymosin lipase digests butterfat of milk in infant chymosin curdles milk by coagulating proteins 25-47 25-48 Many produced by enteroendocrine cells hormones enter blood distant cells paracrine secretions neighboring cells Gut-brain peptides signaling molecules produced in digestive tract and CNS 25-49