Ch 17 Heart Lecture PDF

Cardiovascular System - Heart Chapter 17, Human Anatomy (LibreTexts) "Human Heart Photo" by Patrick J. Lynch via OpenStax is licensed under CC BY 4.0)  17.1 Introduction Heart – the central, pumping organ of cardiovascular system – heart, blood ve...

Cardiovascular System - Heart Chapter 17, Human Anatomy (LibreTexts) "Human Heart Photo" by Patrick J. Lynch via OpenStax is licensed under CC BY 4.0)  17.1 Introduction Heart – the central, pumping organ of cardiovascular system – heart, blood vessels, blood Heart – “double pump” Systemic circuit & pulmonary circuit (& coronary circuit) "Dual System of Human Circulation" by OpenStax is licensed under CC BY 3.0  17.2 Heart Anatomy ~75 contractions/min → 108,000 contractions/day! ~70 mL/contraction → 5.25 L/min → 14,000 L/day (3,698 gallons)! Heart – mediastinum, pericardium (= pericardial sac), pericardial cavity Base – great veins (superior & inferior vena cavae), great arteries (aorta & pulmonary trunk) Apex – off center, towards left (cardiac notch in left lung) "Heart Position in Thorax" by OpenStax is licensed under CC BY 3.0  Shape & Size of Heart Pine-cone shaped, fist-sized (250-300 g/9-11 oz , 300-500 g/11-12 oz ) Four chambers – 2 atria & 2 ventricles (receiving & pumping) Pulmonary circuit – blood picks up O2 & delivers CO2 (deoxygenated blood → oxygenated blood) Systemic circuit – blood delivers O2 & picks up CO2 (oxygenated blood → deoxygenated blood)  Blood Circulation Right ventricle → pulmonary trunk → L & R pulmonary arteries → L & R lungs → pulmonary capillaries (gas exchange, diffusion) → pulmonary veins → left atrium → left ventricle → aorta → systemic circuit (gas exchange, diffusion) → veins → superior & inferior vena cavae → right atrium → right ventricle "Dual System of Human Circulation" by OpenStax is licensed under CC BY 3.0  Membranes, Surface Features, & Layers Pericardium (= Pericardial sac) – 2-layered sac; fibrous pericardium (dense irregular CT) & serous pericardium (mesothelium & areolar CT) Serous pericardium – 2 layers with pericardial cavity: parietal pericardium & visceral pericardium (= epicardium) Serous pericardium mesothelium – serous fluid (pericardial cavity) "Heart Wall" by Julie Jenks is licensed under CC BY 4.0 / A derivative from the original work  Membranes, Surface Features, & Layers Atria & ventricles Atria – auricles (extensions) Coronary sulcus Anterior & posterior interventricular sulci Heart wall layers: Epicardium (= Visceral pericardium) (mesothelium, SS ET) Myocardium (cardiac muscle) Endocardium (endothelium, SS ET) "Surface Anatomy of the Heart" by OpenStax is licensed under CC BY 3.0  Membranes, Surface Features, & Layers Heart wall layers: Myocardium cardiac musculature – built on cardiac skeleton (dense CT) in swirling figure 8 patterns (efficient contraction) Left ventricle – thicker walled (systemic circuit); right ventricle – thinner walled (pulmonary circuit) "Heart Musculature" by OpenStax is licensed under CC BY 3.0 "Ventricular Muscle Thickness" by OpenStax is licensed under CC BY 3.0  Internal Structures of the Heart Septa – divide the atria & ventricles Interatrial septum – fossa ovalis (foramen ovale) Interventricular septum Atrioventricular septum – atrioventricular valves & semilunar valves "Internal Anatomy of the Heart" by OpenStax is licensed under CC BY 3.0  Cardiac Skeleton Cardiac skeleton – dense irreg CT Reinforces atrioventricular septum, attachment for values, & insulating boundary for heart’s electrical conducting system “Cardiac Skeleton" by Julie Jenks is a derivative from the original work of Daniel Donnelly and is licensed under CC BY 4.0  Heart Chambers Right atrium: Receives blood from inferior & superior vena cavae & coronary sinus Pectinate muscles – atrium & auricle; spread electrical signals Tricuspid valve (= R atrioventricular valve) Right ventricle : Tricuspid valves anchored by chordae tendineae to papillary muscles Trabeculae carneae – muscular ridges Moderator band – spreads electrical signals Pulmonary semilunar valve "Chordae Tendineae and Papillary Muscles" by OpenStax is licensed under CC BY 3.0 / A derivative from the original work  Heart Chambers Left atrium: Receives blood from pulmonary veins Pectinate muscles – auricle only; spread electrical signals Bicuspid valve (= Mitral valve, = L atrioventricular valve) Left ventricle : Bicuspid valves anchored by chordae tendineae to papillary muscles Trabeculae carneae – muscular ridges Thicker walled vs R ventricle Aortic semilunar valve  Cardiac Cycle Systole – chamber contraction Diastole – chamber relaxation Cardiac cycle – time period between beginning of ventricular relaxation & end of ventricular contraction (one heart beat): Atria & ventricles relaxed (cardiac diastole) → blood enters atria, passively enters ventricles → atrial systole → ventricles fill → ventricular systole (& atrial diastole) → blood ejected from ventricles → ventricular diastole (& cardiac diastole)  Heart Valves Structure & Function Blood moved by pressure changes – chamber contraction Valves function to prevent backflow & move blood in one direction: atria → ventricles → great blood vessels Cardiac diastole – chamber pressure low; AV valves open, semilunar valves closed Ventricular systole – ventricular pressure rises → AV valves close (1st heart sound) → pressure rises → blood ejected past semilunar valves → ventricular diastole → pressure drops → semilunar valves close (2nd heart sound) "Blood Flow Relaxed Ventricles" by OpenStax is licensed under CC BY 3.0 "Blood Flow Contracted Ventricles" by OpenStax is licensed under CC BY 3.0  Heart Sounds Auscultation with stethoscope Heart sounds due to valve closure: S1 & S2 (1st & 2nd) S1 – closure AV valves (1st heart sound) (ventricular systole) S2 – closure semilunar valves (2nd heart sound) (ventricular diastole) Murmur – abnormal heart sound; turbulent blood flow "Cardiac Cycle vs Heart Sounds" by OpenStax is licensed under CC BY 3.0 "Stethoscope Placement" by OpenStax is licensed under CC BY 3.0  17.3 Cardiac Muscle & Electrical Activity Cardiac muscle has autorhythmicity – ability to initiate electrical potential (APs) Cardiac muscle cells ( = Cardiomyocytes) – branched, 1-2 nuclei, intercalated discs (desmosomes, fasciae adherens, & gap junctions) Myocardial contractile cells (99%) – autorhythmic, stronger; contract chambers Myocardial conducting cells (1%) – autorhythmic, faster; generate APs & pace of chamber contractions "Cardiac Muscle" by Julie Jenks is licensed under CC BY 4.0 / A derivative from the original work / Micrograph provided by the Regents of the University of Michigan Medical School © 2012  Conduction System of the Heart Myocardial conducting cells – SA node, AV node, AV bundle, AV branches & Purkinje fibers SA node – establishes cardiac rhythm, sinus rhythm (pacemaker) → impulse to atria (internodal pathways, atrial systole) & AV node AV node – impulse delayed (~100 ms) → AV bundle (Bundle of His) → AV bundles → Purkinje fibers (ventricular systole) "Conducting System of the Heart" by Julie Jenks is licensed under CC BY 4.0 / A derivative from the original work  The Spread of the Conducting Signal through the Heart 1. Cardiac diastole 2. SA node impulse to atria & AV node 3. Atrial diastole 4. Impulse from AV node → AV bundle → bundle branches → Purkinje fibers 5. Impulse spreads to ventricles 6. Ventricular diastole "Cardiac Conduction" by OpenStax is licensed under CC BY 3.0  Electrocardiogram ECG (or EKG) – measures & graphs electrical activity of cardiac cycle P wave – SA node activity & atrial contraction QRS complex – AV node & AV bundle branches activity & ventricular contraction T wave – repolarization & relaxation of ventricles "Electrocardiogram" by OpenStax is licensed under CC BY 3.0  Disorders of the Conducting System Heart block – interruption of conduction pathway 1st degree (= Partial block) – delay in conduction between SA node & AV node → long interval to ventricular contraction 2nd degree (= Incomplete block) – some SA node impulses reach AV node, some do not → irregular or missed ventricular contraction 3rd degree (= Complete block) – no SA node impulses reach AV node → slower or irregular ventricular contraction Arrhythmias – irregular heartbeat, can be treated with artificial pacemaker "Cardiac Arrhythmias" by OpenStax is licensed under CC BY 3.0  Heart Rates Heart rates (HRs) vary – exercise, fitness level, age Resting HR – 60-100 bpm Maximum HR – 200-220 bpm HR adjusted by – endocrine system (hormones) & nervous system (ANS) Adrenal medulla (sympathetic stimulation, “fight-or-flight” response) → epinephrine ↑ strength of contraction & heart rate ANS (parasympathetic) – medulla → vagus nerve → slows heart rate ANS (sympathetic) – cardiac nerve → speeds up heart rate  17.4 Coronary Circulation Blood supply to cardiomyocytes (myocardium) Coronary arteries (L & R) branch from aorta: L coronary artery → circumflex & anterior interventricular arteries R coronary artery → marginal arteries & posterior interventricular artery Coronary veins: Great cardiac vein, posterior cardiac vein, middle cardiac vein, small cardiac vein → coronary sinus → R atrium "Coronary Blood Vessels" by OpenStax is licensed under CC BY 3.0  Skipping Section 17.5: Development of the Heart