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The Heart

Lecture Unit 2

Characteristics and Functions The pump. Mediates between the systemic & pulmonary circuit. On average beats 75/min, 108,000/day. Average cardiac output is 5.25L/min. 4-6 liters blood total in body.
Pulmonary circuit Vessels that carry blood to & from the lungs. Right atria & ventricle.
Systemic circuit Vessels that transport blood to & from the body tissues. Left atria & ventricle. Thicker muscle walls.
Heart orientation Left of body midline. Posterior to sternum. In mediastinum. Lies on diaphragm. Base-posterior & superior surface of the heart. Apex-anterior & inferior & points to the left hip.
Pericardium Triple layered sack. Encloses heart. Fibrous Pericardium-attached to diaphragm. Double layered serous membrane: parietal layer (underside of fibrous), visceral layer (epicardium). Pericarditis=inflammation of pericardium.
Pericaridal cavity Space between parietal & visceral layers. Contains serous fluid.
Pericardium functions Prevents undesired movement. Prevents overfilling of heart. Reduces friction.
Heart Wall Epicardium-most superficial. Myocardium-bulk. cardiac muscle. deep to epicarium. myocardial infarctions occur in this layer. Endocardium-lines heart chambers. covers valves. deepest.
External Anatomy Atria-auricle=flap. Ventricles. Coronary sinus (posterior). Superior & inferior vena cava (Last 3 empty into R. Atrium). Pulmonary trunk. Pulmonary arteries. Pulmonary veins. Aorta.
Fibrous Skeleton Region of connective tissue located between the atria & ventricles. Functions-separates atria & ventricles, anchors heart valves, electrical insulation between atria & ventricles, framework for attachment of cardiac muscle tissue.
Right Atrium Receiving chamber for O2 poor blood from systemic circuit. Superior & inferior vena cava, coronary sinus. interatrial septum. PECTINATE MUSCLES (muscle in wall of atria). FOSSA OVALIS-foramen ovale during fetal circulation. Conducting nodes-SA & AV nodes.
Right Ventricle Pump of pulmonary circuit. Interventricular septum. Trabeculae carnae-muscular ridges. Papillary Muscles-anchor chordae tendinae. Chordae tendinae-prevent valves form everting during contraction. Pulmonary SEMILUNAR valve.
Left Atrium Posterior surface of the heart. Receives O2 rich blood from lungs. Left atrioventricular (AV) valve or bicuspid or mitral valve.
Left Ventricle Most muscular of the chambers-3x thicker then right ventricle. Forms the apex and inferior surface of the heart. Pump of the systemic circuit. Aortic semilunar valve.
Valves Can be either cuspid or semilunar. Composed of dense connective tissue. 2 or 3 cusps. Permit passage of blood in one direction. Prevent backflow of blood.
Cardiac Muscle tissue Fibers are short, branched, stiated, & contain 1-2 nuclei. Cells are joined by intercalcated discs. Gap junctions increase flow of electrolytes. Desmomsomes prevent cardiac muscle from pulling apart. More mitochondira & ATP than skeletal muscle.
Cardiac cycle Period of time from start of 1 heartbeat to initiation of next. All chambers experience alternate periods of contraction & relaxation. Systole: contraction of a heart chamber. Diastole: relaxation phase. Both atria contract together. Ventricles too.
Conducting System Specialized cardiac muscle cells carry impulses throughout the heart musculature. 1. Sinoatrial (SA) node 2. Atrioventricular (AV) node 3. Atrioventricular (AV)- Bundle of His 4. R & L bundle branches. 5. Purkinje fibers LABEL!
Sinoatrial (SA) node Pacemaker. Tells cells when to contract.
Atrioventricular (AV) node Slow conduction of impulse as it travels from atria to ventricles. Pauses so atria can contract before ventricles do.
Atrioventricular(AV) bundle or Bundle of His Conduct impulse into the interventricular septum
Right and left bundle branches Conduct impulse down interventricular septum to the apex of the heart.
Purkinje fibers Ensures that the heart contracts from apex and up the walls of the ventricles.
Coronary Plexus Sympathetic innervation: T1-T5. Increases the rate & force of heart contraction. Parasympathetic innervation: Medulla oblongata & vagus nerve 10. Decreases the rate of heart contraction.
Heart Failure Progressive weakening of heart. Weakened ventricles, failure of ventricles to empty completely, overfilling of ventricles, congestive heart failure-heart enlarges greatly, pumping efficiency progressively declines, pulmonary edema. Cause unknown.
Myocardial Infarction Heart attack. Caused by blockage of a coronary artery. Lack of blood flow to a region of the myocardium can cause heart muscle to die. Due to O2 depravation.
Created by: punkaloo