Cardiovascular System Chapter 13 Cardiovascular System Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Introduction The heart pumps 7,000 liters of blood through the body each day The heart contracts 2.5 billion times in an average lifetime The heart and all blood vessels make up the cardiovascular system The blood vessels make up two circuits: Pulmonary circuit sends oxygen depleted blood to the lungs to pick up oxygen and unload carbon dioxide Systemic circuit sends oxygen rich blood and nutrients to all the body cells and removes wastes

Systemic capillaries Tissue cells CO2 O2 Superior vena cava Pulmonary artery Alveolus CO2 CO2 Alveolar capillaries Alveolar capillaries O2 O2 Alveolus Pulmonary veins Right atrium Left atrium Tricuspid valve Mitral valve Pulmonary valve Left ventricle Right ventricle Aortic valve Inferior vena cava Aorta Oxygen-poor blood O2 Oxygen-rich blood CO2 Systemic capillaries Tissue cells

Structure of the Heart The heart is a hollow, cone-shaped, muscular pump There are four chambers: Two atria (for blood storage) Two ventricles (one low pressure pump and one high pressure pump)

Size and Location of the Heart The heart size varies with body size The heart lies in the thoracic cavity The average size of the heart is: 14 cm long 9 cm wide The heart is: Posterior to the sternum Medial to the lungs Anterior to the vertebral column The base lies beneath the 2nd rib The apex at the 5th intercostal space It lays just above the diaphragm 1 2 3 4 5 cm

Base of heart Sternum Heart Apex of heart Diaphragm

Coverings of the Heart The coverings of the heart include the pericardium: Fibrous pericardium Visceral pericardium Parietal pericardium Right lung Left lung Superior vena cava Aorta Pulmonary trunk Diaphragm Auricle of left atrium Fibrous pericardium Auricle of right atrium Cut edge of parietal pericardium Heart (covered by visceral pericardium) Right ventricle Left ventricle Anterior interventricular sulcus Pericardial cavity

Wall of the Heart The heart wall has three distinct layers: Epicardium (outer layer) also called visceral pericardium Myocardium (middle layer) Endocardium (inner layer) Pericardial cavity Parietal pericardium Fibrous pericardium Endocardium Coronary blood vessel Myocardium Epicardium (visceral pericardium)

Heart Chambers and Valves The heart is divided into four chambers (2 upper atria and 2 lower ventricles): Right atrium: Receives blood from the: Inferior vena cava Superior vena cava Coronary sinus Right ventricle Receives blood from the right atrium Left atrium Receives blood from the pulmonary veins Left ventricle Receives blood from the left atrium

Mitral (bicuspid) valve Chordae tendineae Pulmonary valve Aorta Superior vena cava Left pulmonary artery Right pulmonary artery Pulmonary trunk Left pulmonary veins Right pulmonary veins Left atrium Right atrium Mitral (bicuspid) valve Chordae tendineae Pulmonary valve Left ventricle Tricuspid valve Papillary muscle Right ventricle Interventricular septum Inferior vena cava (a) Aorta Superior vena cava Left pulmonary artery Aortic valve Right pulmonary artery Pulmonary trunk Left pulmonary veins Right pulmonary veins Left atrium Mitral (bicuspid) valve Right atrium Opening of coronary sinus Chordae tendineae Left ventricle Tricuspid valve Papillary muscle Right ventricle Interventricular septum Inferior vena cava (b) (c)

Skeleton of the Heart The fibrous rings, together with other masses of dense connective tissue in the portion of the septum between the ventricles (interventricular septum), constitute the skeleton of the heart Pulmonary valve Aortic valve Opening of left coronary artery Tricuspid valve Mitral valve Fibrous skeleton Posterior 13

Path of Blood Through the Heart Systemic capillaries Tissue cells CO2 O2 Superior vena cava Pulmonary artery Alveolus CO2 CO2 Alveolar capillaries Alveolar capillaries O2 O2 Alveolus Pulmonary veins Right atrium Left atrium Tricuspid valve Mitral valve Pulmonary valve Left ventricle Right ventricle Aortic valve Inferior vena cava Aorta O2 CO2 Systemic capillaries Tissue cells

Blood from systemic circuit Venae cavae and coronary sinus Right atrium Tricuspid valve Right ventricle Pulmonary valve Pulmonary trunk Pulmonary arteries Alveolar capillaries (lungs) Pulmonary veins Left atrium Mitral valve Left ventricle Aortic valve Aorta Blood to systemic circuit

Blood Supply to the Heart The left and right coronary arteries supply blood to the tissues of the heart Aorta Part of aorta removed Aortic valve cusps Right coronary artery Opening of left coronary artery

Aorta Right coronary artery Left coronary artery Posterior interventricular artery Anterior interventricular artery Marginal artery Circumflex artery Myocardial capillaries in walls of left atrium and left ventricle Myocardial capillaries in walls of left atrium and left ventricle Myocardial capillaries in ventricular walls Myocardial capillaries in ventricular walls Cardiac veins Coronary sinus Right atrium

Aorta Superior vena cava Right pulmonary artery Left pulmonary artery Pulmonary trunk Right pulmonary veins Left pulmonary veins Left auricle Left coronary artery Right auricle Great cardiac vein Right coronary artery Anterior interventricular artery (left anterior descending artery) Anterior cardiac vein Small cardiac vein Left ventricle Inferior vena cava Right ventricle Apex of the heart (a) Superior vena cava Aorta Right pulmonary artery Left pulmonary artery Left pulmonary veins Right pulmonary veins Left auricle Circumflex artery Cardiac vein Left atrium Right atrium Inferior vena cava Coronary sinus Middle cardiac vein Left ventricle Posterior interventricular artery (b) Right ventricle Apex of the heart

Heart Actions The heart chambers function in coordinated fashion Heart actions are regulated so that atria contract (atrial systole) while ventricles relax (ventricular diastole); followed by ventricles contract (ventricular systole) while atria relax (atrial diastole) Pulmonary valve closed Aortic valve closed Pulmonary valve open Aortic valve open RA LA Atrial systole Atrial diastole Ventricular systole Tricuspid and mitral valves open LV Tricuspid and mitral valves closed Ventricular diastole RV (a) (b)

Cardiac Cycle During a cardiac cycle, the pressure in the heart chambers rise and falls In atrial systole and ventricular diastole: Blood flows passively into the ventricles The remaining 30% of blood is pushed into the ventricles The A-V valves open and the semilunar valves close The ventricles relax This causes an increase in ventricular pressure In ventricular systole and atrial diastole: The A-V valves close The chordae tendinae prevent the cusps of the valves from bulging too far into the atria The atria relax The blood flows into atria The ventricular pressure increases and opens the semilunar valves The blood flows into pulmonary trunk and aorta

Animation: The Cardiac Cycle Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 21

Heart Sounds A heart beat through a stethoscope sounds like “lubb-dupp” The “lubb” The first heart sound It occurs during ventricular systole The A-V valves are closing The “dupp” The second heart sound It occurs during ventricular diastole The pulmonary and aortic semilunar valves are closing A murmur – abnormal heart sound from the cusps not completely closing

Cardiac Muscle Fibers Cardiac muscle fibers form a functional syncytium This is a mass of cells that function as a unit Two such areas exist in the heart: In the atrial walls called the atrial syncytium In the ventricular walls called the ventricular syncytium

Cardiac Conduction System Clumps or strands of specialized cardiac muscle tissue which initiate and distribute impulses throughout the myocardium The cardiac conduction system coordinates the events of the cardiac cycle SA node Atrial syncytium Junctional fibers AV node AV bundle Bundle branches Purkinje fibers Ventricular syncytium

Animation: Conducting System of the Heart Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 25 25

Electrocardiogram An electrocardiogram or ECG is a recording of electrical changes that occur in the myocardium during the cardiac cycle It is used to assess the hearts ability to conduct impulses The deflections in the normal ECG, or waves, include: P wave – atrial depolarization QRS complex (three waves) – ventricular depolarization T wave – ventricular repolarization