CARDIOVASCULAR SYSTEM: OVERVIEW & ANATOMY Cathy Proenza

Transcription

1 CV AM CVPR Overview-Anatmy - Prenza CARDIOVASCULAR SYSTEM: OVERVIEW & ANATOMY Cathy Prenza catherine.prenza@ucdenver.edu Recmmended Reading Lilly p 1-12 Other learning resurces: Cardivascular Physilgy Cncepts, Richard E. Klabunde, 2005 ISBN-13: Bard Review Series Physilgy, Linda Cstanz, 5 th ed, 2011 ISBN-13: Learning Objectives 1. Describe the functins f the cardivascular system. 2. Describe the series and parallel arrangement f the circulatry system, and its purpses. 3. Describe the basic anatmy f the heart, including the arrangement and names f the chambers, valves, and majr vessels. 4. Describe the bld flw pathway thrugh the heart. 5. Describe the majr types f bld vessels. 6. Describe the arrangement f the micrcirculatin. 7. Describe the functin f the lymphatic system. I. FUNCTION AND ORGANIZATION OF CARDIOVASCULAR SYSTEM Functins f CV system distributes disslved gases & nutrients. remves metablic waste cntributes t systemic hmestasis by cntrlling temp, O 2 supply, ph, inic cmpsitin, nutrient supply quickly adapts t changes in cnditins and metablic demands Organizatin f the CV system 1) Three parts t cardivascular system: heart, bld, vasculature (including lymphatic system) 2) Heart is a dual pump left side f heart pumps bld t the systemic circulatin right side pumps bld t the pulmnary circulatin right & left heart arranged in series n direct cnnectin between right & left utput f left and right sides f heart must be clsely matched 3) Pulmnary circulatin lw pressure single pathway between heart and lungs 4) Systemic circulatin higher pressure multiple pathways frm heart t different systemic vascular beds. Systemic circulatin is primarily arranged in parallel. This is imprtant because xygenated bld visits nly ne rgan system befre returning t pulmnary circulatin Changes in metablic demand r bld flw in ne rgan d nt significantly affect ther rgans Bld flw t different rgans can be individually varied t match demand. At rest, mst bld directed t brain (~14%), skeletal muscle 1

2 CV AM CVPR Overview-Anatmy - Prenza CV Overview and Anatmy Prenza (~15%), GI system (~21%), and kidney (~22%). During exercise up t 80% t exercising muscle. majr exceptin = hepatic circulatin large fractin f hepatic bld supply is via intestinal circulatin II. FUNCTIONAL ANATOMY OF THE HEART Walls f the heart & membranes 1) Walls have three majr layers: epicardium (uter membrane = cnnective tissue & fat) mycardium (thick muscle layer) = cardiac mycytes endcardium (inner membrane = endthelial cells, as in vessels). 2) Pericardium enclses entire heart fluid-filled membranus sac, nt cnnected t walls f heart Stiff & nn-cmpliant, resists sudden distensin f chambers. Inflammatin = Pericarditis restricts filling f heart. Chambers, vessels & valves 1) 4 chambers Ventricles (left & right) = main pumping chambers. Left ventricle supplies higher pressure systemic circulatin, s is bigger and has thicker walls than right ventricle. Left ventricle des mre wrk, uses mre O 2 than right. Atria (left & right) = small primer chambers, supply the ventricles with bld. Thinner walls than ventricles. 2) 4 vessels Vena cavae (superir vena cava & inferir vena cava) inlet vessel(s) int right atrium Pulmnary Artery utlet vessel frm right ventricle [Arteries g Away frm heart] Pulmnary Vein inlet vessel int left atrium Arta utlet frm left ventricle main bld supply t bdy, size f garden hse ~1 in diameter 3) 4 valves Tricuspid valve between right atrium & right ventricle Pulmnic valve between right ventricle & pulmnary artery Mitral valve between left atrium & left ventricle Artic valve between left ventricle & arta Valves are arranged in 2 sets Atriventricular = Tricuspid & mitral valves between atria & ventricles attached t papillary muscles in ventricles by chrdae tendinaea = tendn-like attachments that prevent valves frm prlapsing int atria during ventricular cntractin. Semilunar valves = Pulmnic & artic valves between ventricles and great arteries Valves = thin flaps ( cusps ) f fibrus tissue cvered by endthelium. Mitral has tw cusps (bicuspid), thers have three One-way, pressure-perated (= passive), Direct frward bld flw, prevent backward flw All 4 valves are lcated in the same hrizntal plane in heart Heart sunds generated by pening and clsing f valves. Defective valves make unusual 2

3 CV AM CVPR Overview-Anatmy - Prenza CV Overview and Anatmy Prenza sunds = murmurs. Regurgitatin = minr leakage, Prlapse = majr failure, where valve gets pushed backward. Other anatmical features interventricular septum interatrial septum apex f heart = tip f left ventricle base f heart = psterir surface Cardiac cnductin system Specialized cells initiate the heart beat and crdinate cntractin by cnducting electrical impulses. 1) Sinatrial (SA) nde in wall f right atrium spntaneusly deplarizes t initiate the heart beat intrinsic activity ~100 bpm highly regulated by autnmic nervus system and many humral factrs 2) Impulse spreads thrugh atria via gap junctins between mycytes nt clear whether there is preferential cnductin pathway thrugh atria 3) Atriventricular (AV) nde between atria and ventricles, slws cnductin t allw atrial cntractin t precede ventricular cntractin 4) His-Purkinje system specialized cells that rapidly cnduct deplarizatin t trigger crdinated ventricular cntractin. Crnary Circulatin 1) Crnary bld flw Mst crnary bld flw ccurs during diastle because f cmpressin f micrvasculature during systle. Flw thus depends n heart rate less time fr perfusin at higher heart rates. Heart has high xygen cnsumptin. Supply must clsely match demand r hypxia results (angina). 2) Right & left main crnary arteries arise frm rt f arta Majr crnary arteries curse alng epicardial surface f heart. Smaller branches enter mycardium sme variatin in anatmy between individuals left main crnary artery (shrt ~ 1 cm) bifurcates t left anterir descending (LAD) artery and circumflex artery primary bld supply t left atrium and left ventricle right crnary artery in grve between right atrium and right ventricle primary bld supply t right atrium and right ventricle, as well as psterir part f left ventricle 3

4 CV AM CVPR Overview-Anatmy - Prenza CV Overview and Anatmy 3) Crnary capillaries very dense each mycyte is assciated with several capillaries 4) Crnary veins lcated adjacent t crrespnding crnary arteries drain int crnary sinus, which pens int right atrium near inferir vena cava Prenza III. BLOOD FLOW PATHWAY Dexygenated bld returns frm systemic circulatin via superir & inferir venae cavae, passively enters right atrium (n valve). Right atrium cntracts, increased pressure pushes pen tricuspid valve, bld enters right ventricle. Right ventricle cntracts, pushes pen pulmnic valve, bld enters pulmnary circulatin via pulmnary arteries. Oxygenated bld returning frm lungs enters left atrium via pulmnary veins. Left atrium cntracts, pushes pen mitral valve, bld enters left ventricle. Left ventricle cntracts, pushes pen artic valve, bld enters systemic circulatin via arta. IV.VASCULATURE Vascular system has three parts Arterial system = distributin f xygenated bld and nutrients Micrcirculatin and lymphatic system = diffusin & filtratin system Venus system = cllectin f dexygenated bld and wastes Types f vessels Arta single utlet frm left side f heart diameter ~25 mm (garden hse) dampens pulsatile pressure Arteries thick walled, resist expansin diameter ~ mm, distribute bld t different rgans Arteriles relatively thicker walls (mre vascular smth muscle) 4

5 CV AM CVPR Overview-Anatmy - Prenza CV Overview and Anatmy Prenza diameter ~ m highly innervated by autnmic nerves, circulating hrmnes, and lcal metablites primary site f regulatin f vascular resistance, via changes in diameter Capillaries smallest vessels walls just single layer f epithelial cells, n smth muscle; apprx same size as RBCs, which travel thrugh single-file diameter <10 m; huge ttal surface area primary site f gas & nutrient exchange with interstitial fluid Venules, veins thin walls relative t diameter cmpared t equivalent-sized arteries (but still sme smth muscle), nt much elasticity diameter ~ 20 m 0.5 cm Primary capacitance vessels f the bdy (mst f bld vlume) ne-way valves cmpensate fr lwer pressure in venus system t ensure bld flws nly in the crrect directin Vena cavae superir & inferir diameter ~ mm Anatmy f resistance vessels Arterial walls have three layers: 1) Tunica adventitia uter layer mstly cnnective tissue = cllagen and elastin 2) Tunica media middle layer mstly innervated vascular smth muscle cntrls diameter f vessels, particularly resistance arteries nt present in capillaries 3) Tunica intima inner layer f vessel lined with vascular endthelium: single cntinuus layer f endthelial cells very imprtant in regulatin f bld flw site f athersclertic plaque frmatin. Micrcirculatin Defined as vasculature frm the first-rder arteriles t the venules Capillaries are the site f gas, nutrient, and waste exchange. Bld flw thrugh capillary beds is determined by the pressure gradient, and is highly regulated via cnstrictin/dilatin f arteriles & precapillary sphincters precapillary sphincters = smth muscle bands at junctin f arterile and capillaries Capillaries d nt have a smth muscle layer, nly endthelial cells surrunded by basement membrane Mvement f substances between capillaries and tissue is driven by cncentratin and pressure gradients (mre in hemdynamics lecture) Lymphatic system Lymph is excess interstitial fluid Lymphatic capillaries = blind end capillaries. Less numerus than regular capillaries and much mre prus (regular capillaries have tight junctins between cells, lymphatic capillaries d nt). Lymph flws int lymphatic capillaries in respnse t increased interstitial pressure. 5

6 CV AM CVPR Overview-Anatmy - Prenza CV Overview and Anatmy Prenza Lymph flw within lymphatic capillaries is driven by cntractin f smth muscle in lymph vessels, and cntractin f surrunding skeletal muscle. Lymph vessels have ne-way valves (like veins) s that lymph flw is uni-directinal. Lymph is filtered thrugh lymph ndes (bacteria remved), and rejins the circulatry system in the subclavian veins. Lymph flw ~2-4 L per day (vs ~7000 L bld fld per day) Edema ccurs when interstitial fluid exceeds capacity f lymphatic system 6