Heart Anatomy and Physiology PDF

THE HEART  The CARDIOVASCULAR SYSTEM This system is composed of the heart and the blood vessels The main functions of this system are: to transport oxygen, hormones and nutrients to the tissues and to transport waste products to the lungs and kidneys for excretion  The...

THE HEART  The CARDIOVASCULAR SYSTEM This system is composed of the heart and the blood vessels The main functions of this system are: to transport oxygen, hormones and nutrients to the tissues and to transport waste products to the lungs and kidneys for excretion  The Gross Anatomy of the Heart  The heart is located within the thorax behind the sternum in the compartment called MEDIASTINUM  The heart is commonly described as the size of a clenched fist The Gross Anatomy of the Heart  The shape is conical, with a base and an apex  The base is directed upward  The apex is directed downward to the left at the level of the 5th ICS LMCL  Heart Surface ANTERIOR SURFACE Right ventricle POSTERIOR SURFACE Left ventricle The Heart : Anatomy The heart has three layers The epicardium The myocardium The endocardium The heart is covered by the pericardium with a parietal and visceral layers The pericardial sac is a potential space in between the two pericardial layers with a minimal (15 cc) fluid The Heart: Anatomy The heart has four chambers The right atrium The right ventricle The left atrium The left ventricle  The Heart: Anatomy  The heart also has four valves that guard the openings in the chambers  The tricuspid valve – between the right atrium and right ventricle  The mitral or bicuspid valve- between the left atrium and left ventricle  The pulmonic valve- between the right ventricle and the pulmonary trunk  The aortic valve- between the left ventricle and the aorta  The Heart: Anatomy The blood supply of the heart:  The coronary arteries are the blood supply  There are two main coronary arteries- the right coronary artery and the left coronary artery  The venous drainage of the heart is the coronary sinus; the anterior cardiac vein and the smallest cardiac vein Blood Supply Venous Drainage Coronary sinus will collect all the venous blood from the heart into the RIGHT atrium The anterior cardiac vein drains NOT into the coronary sinus but DIRECTLY into the right atrium Circulation Fig. 12.11  The Heart : Physiology This consists of:  The conducting system  The cardiac cycle  The cardiac output and Blood pressure  The preload and afterload  The Starling’s law of the heart  The Heart: Physiology The conducting system of the heart is a group of specialized heart cells that functions to conduct electrical impulses independent of any nerve supply  The Heart: Physiology The parts of the conducting system of the heart are:  The SA (sino- atrial) node  The AV (atrio- ventricualr) node  The Bundle of His with its right and left bundle  The Purkinje fibers The Heart: Physiology The intrinsic conduction system causes the heart muscle to depolarize in one direction The rate of depolarization is around 75 beats per minute The SA node sets the pace of the conduction This electrical activity is recorded by the Electrocardiogram (ECG) The Heart: Physiology  The cardiac cycle consists of the contraction phase and the relaxation phase in each heartbeat  The SYSTOLE is the contraction phase  The DIASTOLE is the relaxation phase  The Heart: Physiology  Heart sounds can be auscultated  S1, S2, S3, and S4  S1 is due to the closure of the AV valves  S2 is due to the closure of the semilunar valves  S3 is due to the rushing of blood for ventricular filling  S4 is due to contraction of the atrium  The Heart: Physiology  The amount of blood the heart pumps out in each beat is called the STROKE VOLUME  When this volume is multiplied by the number of heart beat in a minute (heart rate), it becomes the CARDIAC OUTPUT When the Cardiac Output is multiplied by the Total Peripheral Resistance, it becomes the BLOOD PRESSURE Physiology of circulation Blood pressure is the measure of force exerted by blood against the blood vessel wall Measured by sphygmomanometer Normally BP is measured as systolic pressure and diastolic pressure PULSE PRESSURE = SP-DP Dependent on: Heart rate Heart contraction Blood volume Pressure on the walls of blood vessels The Heart: Physiology The PRELOAD is the volume of blood in ventricles at end of diastole The AFTERLOAD is the resistance to which the heart must pump to eject the blood  The Heart: Physiology  Starling’s Law of the Heart states that the force of contraction is proportional to the degree of stretching of the cardiac muscle fibers  As the length of the muscle fiber is stretched, the contractile force increases  But when the maximum length has been reach, any further stretching will impair the contraction  Anatomy & Terminology Physiology Chronotropic Refers to a change in heart rate effect A positive chronotropic effect refers to an increase in heart rate A negative chronotropic effect refers to a decrease in heart rate Dromotropic Refers to a change in the speed of conduction effect through the AV junction A positive dromotropic effect results in an increase in AV conduction velocity A negative dromotropic effect results in a decrease in AV conduction velocity Inotropic Refers to a change in myocardial contractility effect A positive inotropic effect results in an increase in myocardial contractility A negative inotropic effect results in a decrease in myocardial contractility Basic Electrophysiology Myocardial Cell Types Kinds of Where Primary Primary Cardiac Found Function Property Cells Myocardium Contraction and Contractility Myocardial cells Relaxation Electrical Generation and Automaticity Specialized cells conduction conduction of Conductivity of the system electrical electrical impulses conduction system Systemic circulation  The aorta- leaves the left ventricle to form the ascending aorta, aortic arch, descending aorta, thoracic aorta and abdominal aorta  The Vena cava ( superior and inferior) drains the whole body and returns the blood to the right atrium PULMONARY CIRCULATION Passage of blood from right ventricle to the lungs and from the lungs to the left atrium