The Cardiovascular System

Transcription

1 Essentials of Human Anatomy & Physiology Elaine N. Marieb Slides Seventh Edition Chapter 11 The Cardiovascular System Functions of the Cardiovascular system Function of the heart: to pump blood Function of the blood vessels: to provide the conduits within which blood circulates to all body tissues Function of the lymphatic system: to return leaked plasma to the blood vessels after cleansing it of bacteria and other foreign matter Lecture Slides in PowerPoint by Jerry L. Cook Slide 11.2a Circulatory System vs. Cardiovascular system Circulatory system = cardiovascular system and the lymphatic system Cardiovascular system: muscular pump with one way valves (heart) and contains large and small plumbing tubes that the blood travels through (vessels). The Heart Location and size: Heart size of a person s fist Weighs less than a pound Flanked by the lungs Apex (point) is pointed towards the left hip Rests on the diaphragm Base points toward the right shoulder Slide 11.2a Slide 11.2b The Heart The Heart: Coverings Pericardium double sac of serous membrane providing a nearly frictionless for the heart to beat in. A slippery lubricating fluid is produced by the pericardial membrane and allows the heart to beat easily. Figure 11.1 Slide 11.2b Slide

2 The Heart: Heart Wall External Heart Anatomy 3 layers Epicardium Outer layer of the heart part of the pericardium Myocardium Thick bundles of cardiac muscle Reinforced by thick connective tissue Endocardium Thin sheet of endothelium Lines chamber of heart Continues with the lining of blood vessels leaving and entering the heart. Slide 11.4 Figure 11.2a Slide 11.5 The Heart: Chambers Two atria and two ventricles Lined with endocardium Atria Receiving chambers Not important in the pumping activity of the heart Blood flows from the veins through the atria and usually straight to the ventricles Ventricles Discharge Chambers Pumps of the heart The Heart: Septum Septum divides the left and the right side of the heart Interventricular divides ventricles Interatrial divides atrium Slide 11.6 Slide 11.6 The Heart works as a double pump Heart is twisted Right side is for the pulmonary circuit (lungs) Pulmonary circuit Receives blood from inferior and superior vena cava Pumps blood out through the pulmonary trunk Splits into right and left pulmonary arteries To right and left lung Oxygen is picked up and Carbon dioxides Pulmonary vein returns blood to the left atria Blood Circulation Systemic circulation Left atria Left ventricle Aorta Systemic arteries branch to supply all body tissue Slide 11.6 Slide

3 Blood Circulation The Heart: Valves Four valves Allows blood to flow in one direction Atrioventricular valves (AV Valves) Between atria and ventricles Left AV Valve Bicuspid Two cusps Figure 11.3 Slide 11.7 Slide 11.8 The Heart: Valves Right AV Valve Tricuspid Three cusps Chordate tendineae Tiny chords that anchor the cusps to the heart wall. The Heart: Valves AV valve hangs into ventricle Ventricle contracts AV valve forced up and closes Blood does not go into atria Heart is relaxed blood passively fills atria Semilunar valve Operation of Heart Valves Valves that leave the ventricles Pulmonary Valve Aortic semilunar valve When ventricles contract cusps are forced open and blood moves through As blood pressure decreases blood flows back and gathers in cusps causing them to close AV valves open when heart relaxes and closed when ventricles contract Figure 11.4 Slide

4 Operation of Heart Valves Figure 11.4 Semilunar valves are closed during relaxation and open during contraction Slide Problems with valves Problems with valves Leaky valves OK as long as small Incompetent valve forces the heart to pump and repump the same blood Valvular stenosis Valve flaps are stiff Caused by repeated bacterial infections of the endocardium Coronary Circulation Blood in heart does not nourish the myocardium Right and left coronary arteries (off of the aorta) nourish the heart Compress when the ventricles are contracting and fill when the heart is relaxed Myocardium is drained by cardiac vein Cardiac vein empties into the coronary sinus Coronary sinus empties into the right atrium Problems with Coronary circulation Heart beats rapidly Myocardium receives inadequate blood Not enough relaxation to get blood to the heart Myocardium is deprived of oxygen Angina pectoris results Crushing chest pains Angina Physiology Angina is prolongs cells may die and a infarct can occur = myocardial infarct Heart attack or coronary Heart not receiving adequate blood One day 6 quarts of blood through your body over 1,000. 4

5 The Heart: Conduction System Regulation of Heart Rate Regular, spontaneous, independent contractions of the heart Atrial cells beats about 60 times/minute Ventricular cells beat about times/minute Therefore they need a mechanism, that will synchronize the cells Autonomic nervous system Increases and decreases the heart rate Slide 11.13a Built into the heart tissue Cross between muscle and heart tissue Heart depolarizes in one direction Atria to ventricles Heart rate is set at about 75 beats/minute Heart beats as a coordinated unit measured with Electrocardiography Sinoatrial nodes (SA nodes) Right atrium Highest rate of depolarization Starts each heart beat Sets the pace for the whole heart Often called the pacemaker Atrioventricular node (AV node) Junction of the atria and ventricle Atrioventricular bundle (AV bundle) or Bundle of His Right and left bundle branches into the interventricular septum Purkinje fibers spread between the muscle of the ventricle wall SA node through the atria to the AV node = atria contracts AV node delays impulse briefly to allow atria to finish contraction Through the AV bundle, the bundle branches, and the Purkinje fibers = wringing contraction Begins at the heart apex and moves toward the atria Page 334 5

6 Heart Contractions Figure 11.5 and Heart Sounds Atria contract simultaneously, and as they relax, contraction of the ventricles begin Systole Contraction of the ventricles Diastole Relaxation of the ventricles Slide 11.14b Slide Cardiac cycle = one complete heart beat Average heart beat is about 75 times/minute Length of the cardiac cycle is about.8 seconds Mid to late diastole Heart in complete relaxation Heart pressure is low Blow flows passively through the atria to the ventricles Semilunar valves are closed AV valves are open Atria contracts and remaining blood moves into the ventricles Ventricular systole Shortly after ventricular contraction (systole) Ventricular pressure increases and AV valves close Semilunar valves are forced open and blood rushes through them and out the ventricles Atria are relaxed and begin to fill with blood Early diastole Ventricles relax Semilunar valves shut Interventricular pressure drops AV Valves are forced open and the ventricles again begin to refill rapidly with blood 6

7 Filling of Heart Chambers the Cardiac Cycle Figure 11.6 Slide Heart sounds + lub dup Lub Closing of AV valve Dup Semilunar valves shut Abnormal heart sounds Murmurs Usually indicate valve problems Not fully shut swishing sound after the valve should have shut The Heart: Cardiac Output Amount of blood pumped out by each side of the heart in 1 minute Product of the heart rate and stroke volume Average 75 beats/minutes X 70 ml/beat = 5250 ml/min All of the blood in the body circulates in about 1 minute Slide The Heart: Cardiac Output Regulation of Stroke volume Healthy heart pumps about 60% of blood in it 70 ml (2 ounces) with each heartbeat Slide The Heart: Cardiac Output Cardiac Output Regulation More the heart walls stretch stronger the contraction More venous return Amount of blood entering the heart and distending the ventricles Anything that increases volume or speeds venous return increases stroke volume and force of contraction Slide Figure 11.7 Slide