BIOL 320 1st EditionLecture 17Outline of Last Lecture I. Oxygen/Carbon Dioxide ExchangeII. Oxygen-Hemoglobin Dissociation CurveIII. Factors Influencing Hemoglobin SaturationIV. Neural ControlV. Depth and Rate of BreathingVI. HyperventilationVII. HypoventilationVIII. Gas ImbalanceIX. Developmental AspectsI. Digestive SystemII. Digestive ProcessIII. Regulation of DigestionIV. PeritoneumV. Histology of the GI TractVI. Oral CavityVII. TongueOutline of Current Lecture X. Salivary GlandsXI. TeethXII. Pharynx/EsophagusXIII. Digestive Processes: Mouth – EsophagusXIV. StomachXV. Stomach MucosaXVI. Gastric Secretion RegulationXVII. Regulation of HCl SecretionXVIII. Gastric MotilityXIX. Gastric EmptyingXX. Small IntestineXXI. Liver LobulesXXII. Accessories to Small IntestineXXIII. BileXXIV. Role of the PancreasXXV. Pancreatic RegulationXXVI. Digestion: Small IntestineXXVII. Motility: Small IntestineXXVIII. Large IntestineXXIX. Large Intestine: Microscopic AnatomyXXX. Motility & DefecationXXXI. CancerXXXII. Malabsorption of NutrientsXXXIII. UlcersXXXIV. Developmental ConsiderationsCurrent LectureSalivary Glands- Extrinsic glands: activated when you smell, taste, or thinking about foodo -Parotid (have ducts that open into mouth)o -Submandibular (have ducts that open into mouth)o -Sublingual (has 10-12 ducts that open under tongue…gleeking)- Intrinsic glands: in oral mucosa…all about keeping mouth moisto -Buccual glands in oral mucosa; keep mouth moist- Saliva components1. 97-99.5% water2. Electrolytes3. Proteins (lysosyme, defensins, IgA)4. Salivary amylase5. Metabolic waste- Function: to produce and secrete saliva- Saliva:1. Cleanses the mouth2. Moistens and dissolves food3. Aids in bolus formation4. Contains enzymes to break down starch- Regulation:o -Extrinsic salivary gland secrete saliva in response to...1. Ingested food2. The thought of foodo -Strong sympathetic stimulation inhibits salivationTeeth (usually you have 32)- -Function: mechanical digestion (mastication - chewing)- -Incisors: cutting- -Canines: tearing and piercing- -Premolars & Molars: grinding and crushingPharynx: food goes from oral cavity to oropharynx to laryngopharynx- -Epithelial lining: stratified squamous with mucous glands- -Muscular layers: skeletal muscleEsophagus- -Pathway: pierces diaphragm, connects to stomach- -Layers: standard four described before (adventia instead of serosa)- -Mucosa: stratified squamous ET- -Typically flattened, opens with food passage- -Mucous secreted as bolus moves through- -Muscularis changes from upper skeletal to smooth, lower this is why swallowing is voluntary and thenyou have no controlDigestive Processes: Mouth-Esophagus- Ingestion- Mechanical digestion: Begins in the mouth = Chewing- Chemical digestion: salivary amylase begins starch breakdown- Propulsion- Deglutition: Swallowingo Coordinated activity of: tongue, soft palate, pharynx, esophagus and 22 muscle groupso Buccal phase: bolus forced into oropharynxo Pharyngeal-esophageal phase: air passages closed off controlled by medulla and ponsStomach- Regionso Cardiac: surrounds the cardiac orifice, where esophagus connects at cardiac sphinctero Fundus and bodyo Pyloric: surrounds pylorus and pyloric sphincter, where duodenum leaves stomach- Innervationo S-ANS and P-ANS- Layers: standard four- Muscularis externa: three layers, longitudinal, circular and oblique allows further mechanical digestion- Extra:o Tissue layers specialized for stomach functiono Simple columnar epitheliumo Goblet cells: mucus secretiono Penetrated by gastric pits which terminate in gastric glandso Fundus & body: produce gastric juice comprising mucus (neck cell secretion), hydrochloric acid (parietal cell secretion), & pepsin (chief cell secretion)Stomach Mucosa- Epithelial lining: simple columnar with goblet cells- Protective properties1. Mucous layer traps bicarbonate to protect stomach against acid.2. Epithelial cells connected by tight junctions.3. Gastric glands impermeable to gastric juice.- Gastric pits: extend deep into mucosao -Contain: gastric glandso -That secrete: gastric juiceo -Which allows: chemical digestiono -Enteroendocrine cells: histamine & gastrin…etco -Neck cells: mucouso -Parietal cells: HCl & intrinsic factor (allows uptake of vitamin B12)o -Chief cells: pepsinogen- Pepsinogen activation: converted to pepsin by HCl - Chyme: result of chemical and mechanical digestionGastric Secretion Regulation- The cephalic phase is the reflex phase… occurs prior to ingestion; works through the vagus nerve of P-ANSo Note the two excitatory stimuli and the two inhibitory stimuli- The gastric phase occurs with food in the stomach; works through the vagus nerve and by gastrin releaseo Note the excitatory stimuli, know the end resulto Note the inhibitory stimuli, know the end result- The intestinal phase occurs when stomach begins to empty; works through gastrin releaseo Inhibition- Distension of duodenum; inhibits local reflexes & vagus n.; closes pyloric sphincter; inhibit gastric secretionRegulation of HCl Secretion- Stimulated by: ligand-binding (ACh, histamines, and gastrin stimulate parietal cells via 2nd-messenger system)- If one ligand binds to parietal cells: low HCl- If three ligands bind to parietal cells: high HCl- Antihistamines: bind histamine receptors, decrease HCl release- Function of HCl: pH 1.5-3.5 denatures proteins, activates pepsin, & kills bacteriaGastric Motility- -Rate of peristaltic waves: 3times/min (pacemaker cells)- -Most vigorous peristalsis & mixing: pylorus- -Chyme movement: small amounts…~3ml at a timeGastric Emptying:- -As peristalsis forces chyme into the duodenum: stimulates neural enterogastric reflex & hormonal enterogastro mechanism- -Resulting inhibition: gastric secretion & duodenal filling- -Carb rich chyme: goes quicker- -Fat rich chyme: travels slower, causing it to remain in the stomach longerSmall Intestine:- -Proximal opening: pyloric sphincter- -Distal opening: ileocecal valve (at large intestine)- -Subdivisions:o --Duodenum: proximal 1st foot…bile & pancreatic duct open hereo --Jejunum: middle 8 fto --Ileum: distal 12 ft- -Suspended by: mesentery- -Covered by: greater omentumSmall Intestine Histology- Surface area increased by modifications1. Plicae circulares (deep circular folds of mucosa & submucosa)=> slow chyme via spiralling thru)2. Villi (fingerlike extensions of