This muscle never stops working It works when you are asleep The HEART It works when you eat It really works when you exercise. What is it???? Located between the lungs in the mid thoracic region Apex points toward the left hip Surrounded by a membrane called the pericardium Composed of cardiac muscle tissue Heart Facts Hold out your hand and make a fist. If you're a kid, your heart is about the same size as your fist, and if you're an adult, it's about the same size as two fists. Your heart beats about 100,000 times in one day and about 35 million times in a year. During an average lifetime, the human heart will beat more than 2.5 billion times. Give a tennis ball a good, hard squeeze. You're using about the same amount of force your heart uses to pump blood out to the body. Even at rest, the muscles of the heart work hard--twice as hard as the leg muscles of a person sprinting. The human heart can create enough pressure that it could squirt blood at a distance of thirty feet. Scientists have discovered that the longer the ring finger is in boys the less chance they have of having a heart attack. The chambers: Left & Right Atria Left & Right Ventricles The vessels: Pulmonary artery & vein Superior & inferior vena cava Aorta The valves: Atrioventricular valves = Tricuspid, Mitral, Semilunar valves = Pulmonary & Aortic HEART Membrane sac Surrounds the heart Protection Anchors Contains serous fluid Pericarditis inflammation of the pericardium decreases serous fluid causing painful adhesions interfering with heart movements 1
The Valves Allow blood to flow in only one direction The pulmonary semilunar valve is the doorway between the right ventricle and the pulmonary artery which carries dirty blood to the lungs The aortic semilunar valve is the doorway between the left ventricle and the aorta which carries clean blood to the body The Valves Allow blood to flow in only one direction The tricuspid valve separates the right atrium and right ventricle Composed of 3 flaps The mitral valve (sometimes called the bicuspid valve) separates the left atrium and left ventricle Composed of 2 flaps Valves open as blood is pumped through Held in place by chordae tendineae ( heart strings ) Superior vena cava enters right atrium Rt Pulmonary veins enters left atrium Inferior vena cava enters right atrium Aorta leaves left ventricle Pulmonary artery leaves right ventricle L Pulmonary veins enters left atrium Superior Vena Cava Inferior Vena Cava Carry deoxygenated blood from the upper and lower parts of the body into the heart Pulmonary Arteries Carry deoxygenated blood from the heart to the lungs The Vessels Pulmonary Veins Carry oxygenated blood from the lungs to the heart Aorta Carries oxygenated blood from the heart out to the body Cardiovascular System A DOUBLE PUMP system Pulmonary Circuit RA RV Pulmonary artery capillary beds of the alveoli Systemic Circuit capillary beds of the alveoli LA LV Aorta Body Functions to deliver oxygen and nutrients and to remove carbon dioxide and other waste products Oxygen-poor blood (shown in blue) flows from the body into the right atrium. Blood flows through the right atrium into the right ventricle. The right ventricle pumps the blood to the lungs, where the blood releases waste gases and picks up oxygen. The newly oxygen-rich blood (shown in red) returns to the heart and enters the left atrium. Blood flows through the left atrium into the left ventricle. The left ventricle pumps the oxygen-rich blood to all parts of the body. 2
Lub Dub If you listen to your heartbeat, it makes a lub dub sound. The lub is when blood is pushed out of the heart into the body and the dub is the reloading of the heart with more blood ready to push it out to the body The Heart s External Anatomy & Conduction System Heart at rest Blood flows from large veins into atria Passive flow from atria into ventricles Atria (R & L) contract simultaneously Blood forced into ventricles Ventricles (R & L) contract simultaneously Atrioventricular valves close lub sound Blood forced into large arteries Ventricles relax Semilunar valves close dub sound Heart at rest HEART Membrane sac Surrounds the heart Protection Anchors Contains serous fluid Pericarditis inflammation of the pericardium decreases serous fluid causing painful adhesions interfering with heart movements Heart Wall Epicardium (outside) visceral layer of the serous pericardium. Myocardium (muscle) cardiac muscle layer forming the bulk of the heart. Endocardium (within) endothelial layer of the inner myocardial surface. Cardiac Muscle Specialized muscle cells Involuntary Striated Cushioned by endomysium Joined by intercalated discs Cardiac cell metabolism Areobic Large mitochondria Organic fuels: fatty acids & glucose Fatigue resistance 3
Coronary Arteries Branch off aorta above aortic semilunar valve Left coronary artery supplies left atrium and left ventricle Anterior interventricular artery supplies both ventricles Right coronary artery supplies right ventricle Posterior interventricular artery supplies both ventricles Coronary Veins Collects wastes from cardiac muscle Drains into a large sinus on posterior surface of heart called the coronary sinus Coronary sinus empties into right atrium The heart beats because of the spread of electrical impulses to the heart muscle, causing it to contract. Cardiac Conduction System Cardiac muscle tissue exhibits autorhythmicity = generates its own stimulation. This is possible because of an internal cardiac conduction system which can initiate and distribute electrical impulses. Cardiac Conduction System Sinoatrial (SA) Node Comprised of interconnected structures Sinoatrial node Atrioventricular node Atrioventricular Bundle Bundle Branches Purkinje Fibres 4
Atrioventricular (AV) Node Linked to the nervous system Junction of atria and ventricles Spread of depolarisation - from atrial myocardium Delay 0.15 seconds Atrioventricular Time atria to expel blood node Time for ventricular filling Protection to ventricles Less autonomic nervous control than SA node Sympathetic conduction time Parasympathetic conduction time Depolarization The heart is autorhythmic Depolarization begins in sinoatrial (SA) node Spread through atrial myocardium Results in myocardial contration of the atria Delay in atrioventricular (AV) node To the Bundle of His AKA atrioventricular bundle Depolarization The heart is autorhythmic Separates into 2 main branches left & right Located in the interventricular septum Left bundle antero-superior division Right bundle postero-inferior division Bundle branches divide - small, dense network of conduction tissue called the Purkinje Fibers Entire musculature depolarizes quickly Electrocardiogram Variations in electrical potential radiate from the heart ECG records electrical events in the heart. P wave Depolarization of atria Followed by contraction QRS complex 3 waves (Q, R, & S) Depolarization of ventricles Followed by contraction T wave Repolarization of ventricles P-Q interval Time atria depolarize & remain depolarized Q-T interval P-P = one cardiac cycle P-Q = time for atrial depolarization Q-T = time for ventricular depolarization T-P = time for relaxation Time ventricles depolarize & remain depolarized 5
P T PR QRS SA node Represented on the ECG as P wave AV node conduction is represented on the ECG as the PR Interval The Bundle Branch and purkinje fibre depolarisation constitutes ventricular depolarisation Represented on the ECG as the QRS Atrial repolarization occurs within the QRS & therefore is masked Ventricular repolarization is represented on the ECG as a T wave 1) atrial depolarization begins 2) atrial depolarization complete (atria contracted) 3) ventricles begin to depolarize at apex; atria repolarize (atria relaxed) 4) ventricular depolarization complete (ventricles contracted) 5) ventricles begin to repolarize at apex 6) ventricular repolarization complete (ventricles relaxed) 6