PGY 300 1st Edition Exam # 5 Study Guide Lectures: 1 - 7Lecture 1: The Digestive System: Overview4 Basic digestive processes:1) Motility: - Mechanical breakdown- Movement of food through digestive tract- Skeletal m., smooth m.- Voluntary, involuntary2) Secretion:- Chemical breakdown- Release of substance to lubricate food- Exocrine: substances secreted in lumen- Endocrine: substances secreted in interstitial fluid- Paracrine: substances secreted on side of interstitial fluid, but act on side of cells3) Digestion: - Breakdown of food into smaller units to be absorbed4) Absorption: - Transfer of digesting product from GI lumen to blood or lymph across epithelial cellsExcretion: elimination of indigestible material & microorganismsImmune Function: - Physical barrier: GI tract wall; mucus- Chemical barrier: stomach acid & other digestive substances- Extensive gut-association lymphoid tissue (GALT) : recognize & attract invading microorganism- If recognize pathogen or toxin, use protective response: diarrhea or vomitLecture 2: AnatomyThe GI tract:- Oral cavity: mouth, pharynx- Chewing digestion- Small intestine: duodenum, jejunum, ileum- Final digestion - Duodenum & jejunum: most absorption- Large intestine: appendix, cecum, ascending colon, traversing colon, descending colon, sigmoid colon- Indigestible particles; water & salt- Store & concentrates substances into semi-solid feces- Semi-solid feces formed from liquids- Stomach: stores food, regulates speedSphincters: - Upper & lower esophageal sphincters:- Upper sphincter: closes off oral cavity- Lower sphincter: closes off stomach - Pylorus (Pyloric Valve): closes of stomach from small intestine- Ileocecal Valve: closes small intestine from large intestine - Internal & external anal sphincters: regulates excretionAccessory Organs:- Pancreas: secrete digestive enzyme into duodenum- Liver: secretion of bile- Gallbladder: bile stored, released in time of arrival of foodTypes of Epithelial Tissue:- Transporting: cells tightly connected, tight junctions- Prevent exchange from 1 compartment to other- SA increase through microvilli - Stomach, intestine, kidney, exocrine gland- Protective: cells strongly connected by desmosomes- Desmosomes withstand mechanical stress- Skin, lining of mouth, pharynx, esophagus- Secretory: specialized cells; secretory granules or lipid droplets- Lipid droplets: contain substance cells going to release- Exocrine glands: pancreas, liver, salivary glands, stomach Protective Epithelia: ensure cells don’t ruptureTransporting Epithelia: ensures very selective substances to pass b/w cells- Tight junction formed by: Claudin & occluding proteins- 2 functions: 1) prevent passage of molecules and ions through the space b/w cells 2)block movement of integral membrane proteins b/w apical and basolateral surfaces of the cell -> ensures directional movement of substancesSecretory Epithelia: make & release a product- Secretion of endocrine cells (hormones) are released into bloodThe Stomach: SA increased by invaginations called gastric glands- Opening to gastric gland: embedded in secretory cells, secrete substance which makes gastric juices - Lamina Propria: blood, lymph vessels- Submucosa: thick layer of connective tissue w/ more blood, lymph vessels- Submucosal Plexus: embedded in submucosa- Control secretion of cells embedded in gastric gland- Myenteric Plexus: embedded in muscularis externa - Control over contraction of stomach m. layer- Muscularis Externa: - Oblique m.: squeezes stomach in all directions- Circular m.: contract, decreases lumen- Longitudinal m.: contracts it shortens fragments- Serosa: thin layer of connective tissue, hold things togetherThe Small Intestine: SA enhanced by villi & invagination called crypts- Submucosa & mucosa – additional formation to increase SA so proper absorption takes place- Plica: folds submucosa inward - Villi: folding of mucosa - Peyer’s patch: immune sensors, associated w/ specialized epithelium that contains M-cells- M-cells: receptors embedded in membrane Transport luminal antigens & bacteria toward underlying immune cells that activate or inhibit immune response Microvilli extension of single cell & Villi extension of whole mucosa - Both increases SAThe Large Intestine: SA of mucosa & muscularis externa has smooth surface, helps move feces alongLecture 3: GI Motility Function: movement of food from mouth to anus- mechanical mixing of food: break it into smaller particles, mix w/ digestive substancesMuscle types involved in GI Motility:- muscles of mouth, pharynx, upper esophagus (including upper esophageal sphincter), external anal sphincter- skeletal & voluntary m. - muscles of the rest of GI tract are smooth and involuntary m.GI Motility includes process of:1) Ingestion: taking food into the mouth2) Mastication: chewing the food & mixing w/ saliva3) Deglutition: swallowing the food4) Peristalsis & Segmentation: rhythmic wave-like contraction (peristalsis) and mixing contractions (segmentation) move food through GI tract- Peristalsis: directional movement of food- Segmentation: contraction of lumen, use to mix food w/ digestive substances & bring food contact w/ GI wall5) Defecation: discharge of waste materials through anusOropharyngeal stage of swallowing:- Oral phase: ingestion & mastication, skeletal m. pushes food back of oral cavity- Pharyngeal phase: complex reflex involving nerve coordination of skeletal m.- Closes the epiglottis- Opens upper esophageal sphincter - Propels food into esophagusGI Smooth M. Contraction:- GI smooth m. cells are electrically connected through gap junctions- Diff. regions exhibit diff. types of contractions- Tonic contraction: found in sphincters- Phasic contraction: rhythmic, short pd. of contraction & relaxation takes place in area where food is at during the moment, moves it along- Slow wave potential - 3-12 per min- Not all result in contraction Slow waves: waves of partial depolarization that sweep along the digestive tube for a certain distance- # of slow waves in functional GI tract is always constant.- Can only get a certain # of contraction in an area- Force & duration can be changedAcetylcholine: leads to slight depolarization of membrane potential -> when slow waves pass where ACh was before, combined depolarization allows crossing of threshold & action potential -> contractionInterstitial cells of Cajal (ICC) generate slow waves- ICC usually embedded b/w longitudinal & circular muscular layers (small