Chapter(18(Cardiovascular(system:(The(Heart(• Living&mechanical&pump&• Has&4&pumps:&2&atrial&and&2&ventricular&o Pumps&blood&into&pulmonary&circuit&or&systemic&circuit&§ Pulmonary&• Small,&blood&only&pumped&to&the&lungs&and&back&• Low&pressure&(2-25&mm&Hg)&o Pressurized&the&most&(25&mm)&at&the&ventricle&and&pulmonary&artery&o Pressurized&the&least&(2&mm)&at&the&pulmonary&veins&• Delivers:&o Oxygen-poor&blood&to&lungs&o Oxygen-rich&blood&to&Systemic&Circuit&§ systemic&• large,&blood&is&pumped&throughout&the&entire&body&o have&to&fight&gravity&(ex:&moving&blood&back&to&the&heart&from&the&big&toe&or&ex:&moving&blood&from&the&heart&to&the&brain)&• High&Pressure&(2-120&mm&Hg)&o High&pressure&because&of&the&battle&against&gravity&o Pressurized&the&most&(120&mm)&at&the&aorta&o Pressurized&the&least&(2&mm)&at&the&venae&cavae&• Delivers:&o Oxygen-rich&blood&to&organs&and&tissues&o Oxygen-poor&blood&to&Pulmonary&Circuit&o Blood&moves&down&a&pressure&gradient:&High&pressure&in&the&ventricle&and&artery&to&low&pressure&in&the&vein&• Arteries&carry&blood&away&from&the&heart&• Veins&carry&blood&to&the&heart&Chambers&of&the&heart&• Left&ventricle&is&smaller&than&the&right&because&left&has&thicker&walls&o Left&has&to&create&more&pressure&to&move&blood&throughout&the&whole&body&• Child&can&be&born&with&the&heart&flipped&o Right&ventricle&supports&the&systemic&circuit&and&the&left&ventricle&supports&the&pulmonary&circuit&o Will&only&live&a&few&years&because&the&right&ventricle&is¬&strong&enough&to&sustain&the&systemic&circuit&as&physical&development&occurs&o Can&be&corrected&with&open&heart&surgeries&o Can&be&detected&at&20&week&ultrasound&Valves&• 4&of&them:&pulmonary&(semi-lunar)&valve,&aortic&(semi-lunar)&valve,&tricuspid&valve,&mitral&(bicuspid)&valve&o 2&atrio-ventricular&(AV)&valves:&right=tricuspid,&left=mitral/bicuspid&o 2&semi-lunar&valves&(SL):&right=&pulmonary,&left=&aortic&• direct&blood&flow&through&the&heart&• allows&blood&to&flow&in&one&direction&only&• one&way&valves&• valves&open&and&close&based&on&changes&in&pressure&o pressure&on&one&side&causes&it&to&open&o pressure&on&another&side&causes&it&to&close&o myocardium&creates&the&pressure&that®ulates&the&opening&and&closing&of&the&valves&• blood&in&the&right&atrium&flows&through&the&AV&valve&into&the&right&ventricle,&through&the&pulmonary&valve&• when&atria&relaxes,&pressure&falls&but&is&still&greater&than&the&pressure&in&the&ventricle&at&rest,&ventricle&must&contract&for&pressure&to&be&greater&than&the&atrium&so&the&AV&valve&closes,&SL&valve&isn’t&open&yet,&pressure&has&to&increase&a&lot&for&it&to&open&(about&15-20&mm&Hg)&• at&rest&the&ventricle&has&really&low&pressure&(SL&valve&closed)&• ring&bodies&o solid,&firm,&relatively&hard&o support&the&valves&o similar&to&cartilage&o part&of&a&fibrous&skeleton&o all&of&the&ring&bodies&are&connected&by&connective&tissue&that&separates&the&ventricles&from&the&atria&• valves&are&floppy&o supported&by&the&chordae&tendineae&o papillary&muscles&anchor&down&the&chordae&tendineae&• AV&valve&held&close&by&papillary&muscle&because&of&increase&in&pressure&in&the&ventricle&o When&open,&CT&and&papillary&muscles&are&relaxed&• SL&valve&consist&of&3&cups&o No&CT&or&papillary&muscles&o Separates&ventricle&and&artery&(Always&pressure&in&the&artery)&o When&pressure&in&ventricle&is&lower&than&in&aorta,&SL&closed&o Pressure&in&ventricle&>&aorta,&SL&valve&opens&• Pathology&of&valves&o Incompetent(valve((leaky)&§ Called&Regurgitation&§ Doesn’t&close&properly&§ Allows&blood&to&flow&the&wrong&direction&• Some&blood&will&flow&from&ventricle&to&atrium&or&aorta&to&ventricle&§ Blood&works&harder&§ Can&be&caused&just&from&wear&and&tear&o Stenosis((narrowing)&§ Doesn’t&open&as&wide&as&a&normal&valve&§ Can&be&caused&by&bacterial&infection,&bacteria&in&blood&sits&on&the&valves&so&they&don’t&open&properly&o Read&up&on&these&disorders&through&AHA&link&in&ppt.&o If¬&treated,&results&in&heart&failure=death&Pericardial&layers&of&the&heart&• Serous&membrane,&like&a&balloon,&hollow&structure&with&layers&of&epithelium&• Wraps&around&the&heart&• 2&layers&o visceral&§ adjacent&to&the&heart&o parietal&§ opposite&side&• made&of&connective&tissue&and&epithelium&• has&a&hollow&cavity&filled&with&fluid&o fluid=lubricant&o lubricant&reduces&friction&from&the&heart&constantly&increasing&and&decreasing&in&size&with&contracting&and&relaxing&• decreases&friction&between&two&lauers&of&pericardium&• pericarditis=inflammation&of&pericardium&o stops&production&of&this&lubricant&o no&lube=pain&o symptoms&like&a&heart&attack&o treated&easily&with&antibiotics&• fibrous&pericardium&o outside&of&pericardium&o extra&layer&of&connective&tissue&Coronary&arteries&• coronary&artery&disease&o plaque&buildup&in&the&coronary&arteries&o plaque&narrows&the&blood&vessels,&restricting&blood&flow&and&oxygen&that&reaches&the&myocardium&o results&in&heart&attack&o treatment:&coronary&artery&bypass&graft&(CABG)&§ take&a&vein&out&of&the&leg&and&attach&it&to&the&heart&to&bypass&the&blockage&o alternative&treatments:&balloon&angioplasty&and&coronary&stents&Cardiac&muscle&• primary&tissue&in&the&heart&• specialized&striated&muscle&o contractile&proteins&arranged&in&the&same&way&as&skeletal&muscles&(striations)&• made&of&cardiomyocytes&o very&small,&they&string&together&end&to&end&o form&organized&bundles&• don’t&run&in¶llel&lines,&just&wrap&around&the&organ&• disorganized&• ventricles&don’t&have&a&conventional&shape&• muscle&thicker&in&left&ventricle&(looks&like&a&circle),&right&ventricle&is&thinner&(looks&like&a&crescent)&o left&is&3x&thicker&• there&are&NO&neuromuscular&junctions,&communication&by&junctions&between&&• conduction&propagated&by&gap&junctions&o allows&adjacent&cells&to&communicate&without&neurotransmitters&o myocytes&contract&as&a&unit&because&of&gap&junctions&o has&a&long&refractory&period&§ absolute&refractory&period&§ long&time&after&being&stimulated&before&another&stimulus&can&stimulate&it&to&contract&again&• desmosomes&o keep&cells&close&together&o helps&relieve&stress&• intercalated&discs&o stain&darkly&because&lots&of&protein&o 2&cell&junctions&found&here:&desmosomes&and&gap&junctions&• automaticity:&self-regulated&contraction&• aerobic:&dependent&on&oxygen&to&produce&ATP&o
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