HLSC 120 BN04 W2025 Ch 13 Heart Class Notes Jan 26 2025 PDF

CHAPTER 13 The Heart  Heart Outline 1. Location of the Heart 2. Structure and Function 3. Blood Flow through the Hearts Chambers and Coronary Circulation Location of the Heart Closed Fist: heart roughly same size as closed fist. Heart rests on diaphragm (1) near...

CHAPTER 13 The Heart  Heart Outline 1. Location of the Heart 2. Structure and Function 3. Blood Flow through the Hearts Chambers and Coronary Circulation Location of the Heart Closed Fist: heart roughly same size as closed fist. Heart rests on diaphragm (1) near midline of thoracic cavity. lies in Mediastinum (dotted line). Between sternum and vertebrae From first rib to diaphragm 1 Between lungs Location of the Heart Location Terms Apex: (apex = forming point of left ventricle) inferior point of left ventricle (1) Base: (opposite of apex) Superior aspect of heart Surfaces: Anterior Surface Front facing surface (posterior 1 to sternum and ribs) Inferior Surface Rests on diaphragm Right and Left Surface Right surface faces right lung. Left surface faces left lung  Heart Outline 1. Location of the Heart 2. Structure and Function 3. Blood Flow through the Hearts Chambers and Coronary Circulation Pericardium Pericardium (“peri” means “surrounding”): triple-layered membrane that surrounds and protects heart. - Layer one (1): Fibrous pericardium: thick tough connective tissue that anchors heart in mediastinum - Layer two and three are the Serous pericardium: Double layer around heart. 1. Layer two (2): Parietal layer: outer 1 layer fused to fibrous pericardium 2 2. Layer three (3): Visceral layer (also 4 Epicardium): inner layer adheres tightly to heart surface 3 Pericardial Cavity (4) lies between layer 2 and 3 Pericardial fluid: fluid in pericardial cavity. 7 Layers of the Heart There are three (3) layers of the heart 1. Epicardium: external layer Epicardium composed of: Visceral pericardium, provides slippery surface to outermost surface of heart. Fibroelastic tissue and adipose tissue that houses major heart 1 blood vessels. 2 2. Myocardium: middle layer 3 Cardiac muscle layer responsible for heart pumping action 3. Endocardium: innermost layer. Provides smooth lining for heart “epi”= on or covering chambers “myo” = muscle “endo” = within, inner Chambers of the Heart Heart: four (4) Chambers Two Atria (= entry halls) Atria receive blood returning to heart from veins Two Ventricles (= little bellies) Ventricles eject blood from heart into arteries Atrial Auricle (1) on anterior surface of each atria, they slightly increases capacity of atria Coronary Sulcus (2): marks boundary 1 between atria and ventricles and contains the Coronary Sinus 2 Heart Chambers and Valves Mitral valve also called Bicuspid valve SVC: Superior Vena Cava IVC: Inferior Vena Cava Right Atrium Right Atrium (1): receives blood from three veins 1. Superior vena cava 2. Inferior vena cava 3. Coronary sinus Right Atrium Right Atrium (1): Veins always flow towards heart Posterior wall is smooth Anterior wall is rough due to muscle ridges called Pectinate Muscles. Interatrial septum: thin wall between left and 1 right atrium 2 Fossa Ovalis (yellow arrow): depression on interatrial septum Remnant of opening in fetal heart that closes during infancy Tricuspid valve (2): consists of three cusps (also called right atrioventricular valve) 2  Heart Chambers and Valves Tricuspid and Mitral (Bicuspid) also called atrioventricular valves Pulmonary and Aortic valves also called Semilunar valves Right Ventricle Right Ventricle: receives blood from right atria Papillary muscles (1): prevent inversion of the atrioventricular valves on systole (ventricular contraction) Trabeculae carneae (2): muscular columns that assist the papillary muscles to prevent inversion Chordae Tendineae (3): tendon-like cords connected to atrioventricular valve. 3 Together the papillary muscles and 1 chordae tendineae regulate the closure of 2 the atrioventricular valves Remember: Arteries flow away from heart / Veins flow toward heart Carneae means “ridges” / Papillary means “nipple-shaped” Right Ventricle Interventricular septum (4): wall between left and right ventricles Pulmonary valve (5): blood flows out right ventricle through pulmonary valve into arteries flowing to lungs. Also called a semilunar valve. 5 4 Left Atrium and Ventricle Left Atrium (1): receives blood through four pulmonary veins (two from left lung, two from right lung) Bicuspid valve (mitral valve or left 6 5 atrioventricular valve) (2) Blood passes to left ventricle 1 through bicuspid valve (has two 2 4 cusps) Left Ventricle (3): thickest chamber in heart 3 Aortic valve (4): blood passes from left ventricle through aortic valve into ascending aorta (5) Ligamentum arteriosum (6): ligament that connects aortic arch to pulmonary trunk. 2 17 18 Myocardial Thickness Myocardial thickness: thickness of muscle in heart varies from chamber to chamber Thickness is related to amount of pressure chamber needs to produce. Atria = thin walls because they don’t create much pressure pushing blood to ventricles Ventricles push against greater pressure (to lungs or to rest of body) than atria Left ventricle produces greatest pressure = has greatest myocardial thickness Fibrous Skeleton In addition to cardiac muscle, heart walls contain dense connective tissue called “fibrous skeleton of heart”. Function: provides foundation for, and prevents overstretching of heart valves Pulmonary and Aortic rings (1) (semilunar rings) Tricuspid and Bicuspid rings (2) (atrioventricular rings) 1 1 2 2  Heart Outline 1. Location of the Heart 2. Structure and Function 3. Blood Flow through the Hearts Chambers and Coronary Circulation Heart Valves and Circulation of Blood Valves open and close in response to pressure changes. Valves ensure one-way flow of blood through heart. Aortic and pulmonary valves are called semilunar (SL) valves (1) (shaped like a half- moon) Tricuspid and bicuspid valves are called atrioventricular (AV) valves (2) 1 1 2 2 Heart Valves and Circulation of Blood When atria contract blood flows into relaxed ventricles through AV valves. AV valves close when ventricles contract (pressure pushes against AV valves and closes them). SL valves: Allow ejection of blood from ventricles Also prevent backflow of blood into ventricles Systemic and Pulmonary Circulations Two circulations are arranged in series: output of one becomes input of other Heart is really two pumps: right pump and left pump Right pump collects deoxygenated blood from systemic circulation and pumps it to the lungs for oxygenation Left pump collects oxygenated blood from lungs and pumps it to systemic circulation. Coronary Circulation Heart cells require a blood supply to provide oxygen, nutrients, etc., therefore the heart wall (myocardium) has its own blood supply Arteries and veins that provide blood to heart muscle, etc. are called Coronary Circulation. Called “Coronary” because arteries circle heart “like a crown” (corona = crown) Coronary Arteries provide oxygenated blood to heart myocardium Anastomoses (a-na-sto-mo-sis) Most myocardium cells receive blood from more than one artery (fail safe) Anastomoses: where two supply arteries connect Coronary veins: bring back deoxygenated blood to right atria through coronary sulcus Coronary Circulation: Bypass Surgery Blocked coronary artery = heart cells (not receiving oxygen) die quickly. Treatment: Bypass Surgery An internal mammary artery (often saphenous vein = longest vein in body) provide new connections from major aorta to damaged coronary artery.  Heart Outline 1. Location of the Heart 2. Structure and Function 3. Blood Flow through the Hearts Chambers and Coronary Circulation 4. Conduction System Conduction System: Autorhythmic Fibers and Pacemaker Rhythmical electrical activity = reason for hearts lifelong continuous beating. Continuous beat due to specialized fibers which are self-excitable = autorhythmic Thus: heart continues to beat even if removed from body Self-excitable fibers act as pacemaker: setting rhythm of heart beats. Conduction System: Cardiac Action Potentials Cardiac action potentials flow through conduction system in five (5) step sequence. 1. Sinoatrial (SA) node: Located in right atrial SA nodes are unstable and repeatedly depolarize initiating action potentials Action potential travels to both left and right atria. Result: both atria contract at the same time. Conduction System: Cardiac Action Potentials 2. Atrioventricular (AV) node: Action potential initiated at SA node reaches AV node Located in interatrial septum At AV node, action potential slows down which allows the atria to empty blood into ventricles 3. AV bundle: Action potential enters AV bundle (Bundle of His) AV bundle is where action potential gets conducted to ventricles. Conduction System: Cardiac Action Potentials 4. Right and left bundle branches: Action potential enters two bundles and extends through interventricular septum towards heart apex. 5. Purkinje fibers: Finally, large-diameter Purkinje fibers conduct action potential throughout ventricles Contraction starts at apex and moves upward through ventricles. Purkinje fibers offshoots ensure all ventricle cells contract simultaneously. Conduction System: Electrocardiogram Electrocardiogram: Detects action potential electrical signals of heart. Electrocardiograph: machine that records electrocardiogram (a recording of heart beat electrical changes) Three (3) recognizable waves appear. 1. P wave: represents atrial depolarization which spreads from SA node to contractile fibers 2. QTS complex (second wave): represents rapid ventricle depolarization. 3. T wave: indicated ventricular repolarization. Atrial repolarization is not represented because it occurs at a similar time to ventricular depolarization. Conduction System: Heart Sounds Heart sounds comes from turbulence caused by closing of heart valves. Four heart sounds / only two are loud enough to be heard through a stethoscope: Two audible heart sounds 1. Lubb sound = first sound (louder and longer than second) = closure of atrioventricular valves soon after ventricular systole begins. 2. Dubb sound = closure of semilunar valves which occurs as ventricular diastole begins. Therefore: two sounds related to ventricular function. Lubb: when ventricles begin to contract (ventricular systole) Dubb: when ventricles begin to relax (ventricular diastole).  Heart Phonological Visuospatial chunks chunks Pericardium Peri = surround / Fibrous, Serous (parietal-cavity- visceral) Heart layers Epicardium (visceral, adipose and blood) / Myocardium (myo=muscle) / Endocardium (smooth inner layer) Circulation SVC + IVC + CS – RA –Tricuspid – RV –Pulmonary valve –pulmonary artery – LUNGS –pulmonary veins –LA –mitral (bicuspid) –LV –aortic valve –cells of the body. Conduction SA node (RV, self-excitable, pacemaker) – AV node (interatrial septum, AP slows down) –AV Bundle of His (left and right branches) – Purkinje fibers (contraction starts at apex, ensures all ventricle cells contract at same time)