Chapter 15 Lecture PowerPoint Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15.1: 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 Systemic circuit

Systemic circuit delivers oxygen to all Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Systemic circuit delivers oxygen to all body cells and carries away wastes. Deoxygenated blood Pulmonary circuit eliminates carbon dioxide via the lungs and oxygenates the blood. Oxygenated blood Oxygenated blood pumped to all body tissues via aorta Deoxygenated blood pumped to lungs via pulmonary arteries O2 O2 CO2 CO2 CO2 O2 CO2 O2 CO2 CO2 CO2 O2 O2 Alveolus O2 O2 CO2 Oxygenated blood returns to heart via pulmonary veins Deoxygenated blood returns to heart via venae cavae Left atrium Right atrium Left ventricle Right ventricle

15.2: 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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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 © McGraw-Hill Companies, Inc./Photo and dissection by Christine Eckel

Base of heart Sternum Heart Apex of heart Diaphragm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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) Myocardium (middle layer) Endocardium (inner layer) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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: 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

c: © The McGraw-Hill Companies, Inc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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) c: © The McGraw-Hill Companies, Inc.

13 Right atrium Cusps of tricuspid valve Chordae tendineae Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Right atrium Cusps of tricuspid valve Chordae tendineae Interventricular septum Papillary muscles Muscular ridges © McGraw-Hill Higher Education, Inc./University of Michigan Biomedical Communications Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13 © McGraw-Hill Higher Education, Inc./University of Michigan Biomedical Communications

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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pulmonary valve Aortic valve Opening of left coronary artery Tricuspid valve Mitral valve Fibrous skeleton Posterior 14

Path of Blood Through the Heart Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Systemic capillaries Tissue cells CO2 Superior vena cava O2 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

Alveolar capillaries (lungs) Blood to systemic circuit Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aorta Right coronary artery Left coronary artery Posterior interventricular artery Anterior interventricular artery Marginal artery Circumflex artery Myocardial capillaries in ventricular walls Myocardial capillaries in walls of right atrium and right ventricle Myocardial capillaries in walls of left atrium and left ventricle Myocardial capillaries in ventricular walls Cardiac veins Coronary sinus Right atrium

Aorta Part of aorta removed Aortic valve cusps Right coronary artery Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aorta Part of aorta removed Aortic valve cusps Right coronary artery Opening of left coronary artery

Anterior interventricular artery (left anterior descending artery) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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

15.3: 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) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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

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

Aortic area Pulmonary area Tricuspid Mitral area area Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aortic area Pulmonary area Tricuspid area Mitral area

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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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

26 Interatrial septum Left bundle branch SA node AV node Junctional Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Interatrial septum Left bundle branch SA node AV node Junctional fibers AV bundle Right bundle branch Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Purkinje fibers Interventricular septum Myocardial muscle fibers (a) (b) 26

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

R Q S (a) 1.0 1.0 .5 .5 Millivolts Millivolts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) 1.0 1.0 .5 .5 Millivolts Millivolts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. –.5 –.5 200 400 600 200 400 600 (b) Milliseconds (f) Milliseconds R 1.0 1.0 .5 .5 Millivolts Millivolts Q –.5 –.5 200 400 600 200 400 600 S (c) Milliseconds (g) Milliseconds 1.0 1.0 .5 .5 Millivolts P T Millivolts –.5 –.5 200 400 600 200 400 600 (d) Milliseconds (h) Milliseconds 1.0 R .5 QRS complex Millivolts Q –.5 S 200 400 600 (e) Milliseconds

R R P P T T Q Q S S Atrial systole Atrial diastole Atrial systole Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atrial systole Atrial diastole Atrial systole Atrial diastole Ventricular diastole Ventricular systole Ventricular diastole Ventricular systole Ventricular diastole Pressure changes 0.3 0.6 0.9 seconds 120 Aortic semilunar Aortic semilunar valve closes 100 valve opens 80 Aortic pressure Pressure (mm Hg) 60 Ventricular pressure 40 AV valve closes AV valve opens 20 Atrial pressure Ventricular volume 160 Volume (mL) 120 Ventricular volume 80 Electrocardiogram (ECG) R R +1 Millivolts P P T T Q Q –1 S S One cardiac cycle Heart sounds Lubb: AV valves close Dupp: Semilunar valves close

Regulation of the Cardiac Cycle The SA node controls the heart rate There are also sympathetic and parasympathetic fibers that control the heart rate as well There are also regulatory reflex centers that influence heart rate Additional factors that may influence heart rate include: Physical exercise Body temperature Concentration of various ions including: Potassium Calcium Parasympathetic impulses decrease heart action Sympathetic impulses increase heart action Cardiac center regulates autonomic impulses to the heart

(transverse sections) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Receptor Sensory or afferent neuron Central Nervous System Motor or efferent neuron Effector (muscle or gland) (a) Carotid baroreceptors Carotid sinus Cerebrum (frontal section) Common carotid artery Sensory fibers Hypothalamus Aorta Medulla (transverse section) Aortic baroreceptors Parasympathetic vagus nerve Cardiac center SA node AV node Spinal cord (transverse sections) Sympathetic nerve (b) Sympathetic trunk