EXSC%223:%Week%of%11/7/16%%Lecture%11/7%notes%Intestines'• Major'function:'absorb'water'from'indigestible'food'and'eliminate'them'from'the'body'• It'includes'from'the'ileocecal'valve'to'the'anus'• Has'3'features'not'found'elsewhere'o Teniae'coli:'3'bands'of'smooth'muscle'o Haustra:'pocket-like'sacs'o Epiploic'appendages:'fat-filled'pouches'that'hang'from'the'surface'• Vitamin'K'produced'and'absorbed'in'the'large'intestine'• Vitamin'B12'produced'with'bacteria'and'absorbed'in'the'large'intestine'• Rectum'is'controlled'by'rectal'valves'• Anal'canal'o 3'cm'long'o 2'sphincters'§ internal'anal'sphincter:'smooth'muscle'§ external'anal'sphincter:'skeletal'muscle'• microscopic'anatomy'o mucosa:'simple'columnar'epithelium'(except'anal'canal)'o no'villi,'no'digestive'enzymes'secreted'o anal'canal'mucosa:'stratified'squamous'epithelium'• hemorrhoidal'veins'o inflammation'of'them='hemorrhoids'o Valsalva'maneuver'§ moderately'forceful'attempted'exhalation'against'a'closed'airway,'usually'done'by'closing'one's'mouth'§ Leads'to'an'increase'pressure'and'tensing'of'abs,'chest'etc.'§ Raises'blood'pressure'§ Raises'pressure'on'the'hemorroidal'veins'• Bacterial'flora'o From'GI'tract'and'anus'o Ferment'indigestible'CHO'§ Releasing'inrritating'acids'and'gases'(500'mL'per'day)'§ Dimethyl'sulfide'§ Important'function'• B'complex'and'K'vitamin'synthesis'• Vitamin'K'regulation'to'synthesize'clotting'proteins'• Movement'o Muscle'contractions'are'infrequent'and'short'lived'o Eating'stimulates'peristalsis'in'the'large'intestine'to'move'o Food'moves'in'waves'o Haustial'contractions:'slow,'30'minute'cycles'o Gastrointestinal'reflux'o Fiber'adds'bulk'and'increases'movement'Liver'• Stores'glucose'• Packages'cholesterol'and'fat'for'the'body'• Most'cholesterol'in'the'body'is'produced'here'• Produces'bile'• Detoxifies'blood'o Breaks'down'hormones'and'drugs'• Very'large'organ'• Made'of'lobules'o Made'of'hepatocytes'§ Large'smooth'ER'o Hexagonal'structures'o Central'vein'in'the'middle'of'the'hexagon'• Receives'25%'of'the'body’s'blood'flow'per'minute'• Can'donate'part'of'your'liver'and'it'will'grow'again'o Connective'tissue'replaces'the'missing'tissue'before'the'hepatocytes'reform'• portal'triad'(located'at'the'lobules)'o portal'arteriole'§ carries'in'fresh'oxygenated'blood'o portal'venule'§ branch'of'the'portal'vein'§ takes'materials'from'the'small'intestine'into'the'liver'o bile'duct'§ carries'bile'• stellate'macrophages'(Kupffer'cells)'o line'of'defense'o absorb'harmful'things'o alert'the'immune'system'gall'bladder'• stores'bile'• bilirubin'o breaks'down'heme'from'blood'o yellow'in'color'o jaundice:'disease'where'skin'and'eyes'look'yellow'§ too'much'bilirubin'in'the'blood'§ indication'of'liver'failure'or'complications'• signaled'to'secrete'bile'when'fatty'contents'enter'the'duodenum'pancreas'• secretes'enzymes'into'the'duodenum'o bicarbonate'• pancreatic'juice''o Contains''§ Proteases'(digest'proteins)'§ Amylase'(digest'starch)'§ Lipases'(digest'fats)'§ Nucleases'(digest'nucleic'acids)'o Role:'chemically'digests'our'food''Lecture%11/9%notes'Enteric'nervous'system'• Submucosal'nerve'plexus'and'myenteric'nerve'plexus'• Independently'functioning'system'from'the'central'nervous'system'• Pacemaker'cells:'neurons'that'can'fire'by'themselves'o Responsible'for'peristalsis'• Autonomous:'operates'on'its'own'• Receives'input'from'the'autonomic'nervous'system'• Chemical'signaling'molecules'o Hormones'o Paracrines'o Secreted'by'organs'in'the'alimentary'canal'• Short'reflex'o Internal'stimuli'(GI'tract)'triggers'chemoreceptors,'osmoreceptors,'or'mechanoreceptors'o They'trigger'the'local'(intrinsic)'nerve'plexus'o This'triggers'effectors'(smooth'muscle,'glands)'to'do'their'job'''o This'causes'the'response'(change'in'contractile'or'secretory'activity)'• Long'reflex'(2'possible'pathways)'1. External'stimuli'a. External'stimuli'triggers'the'central'nervous'system'b. CNS'triggers'the'local'(intrinsic)'nerve'plexus'c. This'triggers'effectors'(smooth'muscle,'glands)'to'do'their'job'''d. This'causes'the'response'(change'in'contractile'or'secretory'activity)'2. Internal'stimuli'a. Internal'stimuli'(GI'tract)'triggers'chemoreceptors,'osmoreceptors,'or'mechanoreceptors'b. They'trigger'the'central'nervous'system'c. CNS'triggers'the'local'(intrinsic)'nerve'plexus'd. This'triggers'effectors'(smooth'muscle,'glands)'to'do'their'job'''e. This'causes'the'response'(change'in'contractile'or'secretory'activity)'Swallowing'• Buccal'phase'o Upper'esophageal'sphincter'is'contracted'o Tongue'is'against'the'hard'palate'o Food'is'forced'into'the'oropharynx'• Pharyngeal-esophageal'phase'o Uvula'and'larynx'rise'to'prevent'food'from'respiratory'passageways'o Tongue'blocks'off'the'mouth'o Upper'esophageal'sphincter'relaxes'o Food'enters'the'esophagus'• Constrictor'muscles'of'the'pharynx'contract'and'the'upper'esophageal'sphincter'closes'after'food'enters'• Peristalsis'moves'the'food'through'the'esophagus'to'the'stomach'• Cardiac'sphincter'opens'and'food'goes'into'the'stomach'Food'movement'• Propulsion'o Peristaltic'waves'pressurize'contents'of'the'stomach'to'move'them'to'the'pyloric'valve'• Grinding'o Most'vigorous'peristalsis'and'mixing'near'the'pylorus'• Retropulsion'o Small'amount'of'chyme'goes'into'the'small'intestine'Regulation'of'defecation'• Feces'move'into'the'rectum'and'activate'stretch'receptors,'signal'transmitted'to'the'spinal'cord'• Spinal'reflex'is'initiated'and'stimulates'contraction'of'rectum'and'sigmoid'colon,'internal'anal'sphincter'relaxes'•