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Transcript
Features of a good transport system • A fluid to carry nutrients and gases • A pump to create pressure that will push fluid around the body • Exchange surfaces • Tubes or vessels – to carry fluid (a) Single circulation (b) Double circulation: Pulmonary cirulation – carries blood to the lungs to pick up oxygen Systemic circulation – carries the oxygen and nutrients around the body to tissues. © Pearson Education Ltd 2008 This document may have been altered from the original Advantages of a Double Circulation • Heart increases the pressure on blood after it has passed through the lungs so blood flows more quickly to the body tissues. • Systemic circulation can be at a higher pressure than the pulmonary circulation • Blood pressure in pulmonary system cannot be too high as it could damage lungs. AORTA VENA CAVA RIGHT ATRIUM PULMONARY ARTERY PULMONARY VEIN SEMI LUNAR VALVE LEFT ATRIUM LEFT VENTRICLE ATRIOVENTRICULAR VALVES RIGHT VENTRICLE Valves in the heart prevent the backflow of blood The internal structure of the heart © Pearson Education Ltd 2008 This document may have been altered from the original Structure of the Heart Why is a mammalian heart is divided into a right and left side? • Keeps oxygenated and deoxygenated blood separate • Allows as much oxygen as possible to be carried to the tissues • Allows different pressures to exist – left more pressure required to force blood to body whereas right side requires less as forcing blood a shorter distance to lungs Main adaptations of the heart • Composed of cardiac muscle A specialised tissue that can contract automatically, powerfully and without fatigue. All cells in cardiac muscle are connected by specialised junctions called intercalated discs. This allows the rapid spread of impulses through the muscle ensuring that all cells contract at the same time Main adaptations of the heart • Thickness of the walls The thickness of the walls in the different heart chambers reflects their function. Atria: thin muscle as only pumps blood a short distance Right Ventricle: thicker muscle than atria – forcing blood a further distance to lungs. Left Ventricle: thickest walls – has to force blood all the way round body Main adaptations of the heart • Valves Ensure unidirectional flow through the heart and prevent backflow. The AV valves Location: between atria and ventricle Function: to prevent blood flowing back into atria when ventricles contract The Semilunar valves Location: found at the openings of the aorta and pulmonary artery Function: prevent backflow of blood into ventricles during diastole Valve structures The cardiac cycle © Pearson Education Ltd 2008 This document may have been altered from the original Atrial Systole AV valves open semi-lunar valves closed Filling of ventricles atrial systole Ventricular Diastole Ventricle muscles contract Pressure increases Ventricular Systole Semi-lunar valves close Ventricles relax Pressure in the ventricles falls AV valves open AV valves close Semi-lunar valves open Blood enters arteries Action of the atrioventricular valves © Pearson Education Ltd 2008 This document may have been altered from the original Describe the sequence of events involved in one heart beat 1. atrial systole / atria contract ; 2. blood passes into ventricles ; 3. atrioventricular / AV valves open ; 4. ventricular systole / ventricles contract ; 5. blood to, the arteries /Aorta and Pulmonary Artery; 6. via open, semilunar valves ; 7. Atrioventricular (AV) valves shut to stop backflow ; 8. relaxation / diastole, of ventricles (and atria) ; 9. semilunar, valves shut to stop backflow ; Pressures changes in the aorta, left ventricle and left atrium during one heartbeat © Pearson Education Ltd 2008 This document may have been altered from the original Week 8 • Describe how heart action is coordinated with reference to the sinoatrial node, the atrioventricular node and the Purkyne tissue. • Interpret and explain electrocardiogram (ECG) traces with reference to normal and abnormal heart activity. © Pearson Education Ltd 2008 This document may have been altered from the original The pathway followed by the wave of excitation © Pearson Education Ltd 2008 This document may have been altered from the original Week 8 A normal ECG trace compared with others indicating an unhealthy heart © Pearson Education Ltd 2008 This document may have been altered from the original