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The Circulatory System & the anatomy of the heart The circulatory system • The link between all other body systems – the cells inside the body and the environment outside the body • The body’s transport system – blood is the medium Functions of the CV system • Transports/carries materials such as food and oxygen to the cells • Removes wastes from the cells (CO2 etc) • Role in protection of the body/immunity The Heart • A pump that pushes blood around the body • Located in the mediastinum (between the 2 lungs – slightly more on the left) • About the size of closed human fist • Enclosed by a membrane – pericardium (holds the heart in place, but also allows it to move as it beats, prevents it from overstretching) • Wall of the heart made up of a special type of muscle – Cardiac muscle. The chambers • The heart consists of four muscular chambers. • The two on the LHS are separated from the two on the right by the septum. • The upper chambers - the atria – receive blood. • The lower chambers - the ventricles – are the pumping chambers. The chambers Left atrium Right atrium Septum Right ventricle Left ventricle The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989) Exterior view of the heart Aorta Superior vena cava Right atrium Pulmonary artery Left atrium Pulmonary vein Right ventricle Inferior vena cava Left ventricle Image created by Patrick Lynch Section through the heart Superior vena cava Pulmonary artery Aorta Pulmonary vein Left atrium Right atrium Bicuspid valve Semilunar valve Tricuspid valve Septum Inferior vena cava Left ventricle Right ventricle The Miles Kelly Art library, Wellcome Images • • • • The Valves The direction of the blood flow is controlled by four valves. The atrioventricular valves are held in position by strong tendons, the chordae tendinae (tendineae). The other valves are the semi-lunar valves The heart sounds – “lubb dubb” – result from the valves snapping shut. The valves Pulmonic semilunar valve Tricuspid atrioventricular valve Chordae tendinae Aortic semilunar valve Bicuspid atrioventricular valve (mitral valve) The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989) The blood vessels Superior vena cava Pulmonary artery Aorta Pulmonary vein Inferior vena cava The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989) The blood vessels Carries From To Vena cava Deoxygenated blood The body Right atrium Pulmonary artery Deoxygenated blood Right ventricle The lungs Pulmonary vein Oxygenated blood The lungs Left atrium Aorta Oxygenated blood Left ventricle The body Blood circulation through the heart From the upper body To the lungs To the body From the lungs From the lungs From the lower body The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989) Heart Beat The heart contains specialised conductive tissue which regulates the heartbeat. • The sinoatrial node (SA node or pacemaker) is a cluster of specialised cardiac cells in the wall of the right atrium which initiates the heartbeat. • The atrioventricular node (AV node) is the secondary pacemaker which regulates the beating of the ventricles. Conductive tissue Sinoatrial (SA) node – the pacemaker Atrioventricular (AV) node Perkinje fibres The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989) The circulatory system The blood vessels & circulation Blood Vessels Basics • Arteries – carry blood away from the heart • Veins – carry blood back to the heart • Capillaries – small vessels where exchange of gases, nutrients and wastes takes place Circulation Double circulation Humans, like all mammals, have a double circulation: • The systemic circulation and • The pulmonary circulation. • This can be seen because there is two sides of the heart – each involved in a different circulation • Right side of the heart is involved in blood to and from the lungs (pulmonary circulation) • Left side of the heart is involved in blood to and from everywhere in the body (excluding the lungs) (systemic circulation) The pulmonary circulation • The pulmonary circulation takes deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium. • The right ventricle is the pump for the pulmonary circulation. Pulmonary circulation LUNGS Pulmonary artery Pulmonary circulation Left atrium HEART Right ventricle Pulmonary vein The systemic circulation • The systemic circulation takes oxygenated blood from the left ventricle to all the tissues of the body and returns deoxygenated blood to the right atrium. • The left ventricle is the pump for the systemic circulation. Systemic circulation Right atrium HEART Left ventricle Vena cava Aorta Systemic circulation ALL PARTS OF THE BODY Both together = Double circulation LUNGS Pulmonary circulation HEART Systemic circulation OTHER PARTS OF THE BODY • Therefore blood passes through the heart twice during one complete circuit of the CV system • This double circulation has the advantage that after blood goes through the lungs and losing much of its pressure, the heart pumps the blood again before going to the body cells • This means blood is kept moving rapidly and therefore the cells get the requirements they need Major arteries Carotid A Subclavian A Aorta HEART Celiac A Mesenteric A Renal A Common iliac A Femoral A The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989) Major veins Jugular V Subclavian V Superior vena cava HEART Inferior vena cava Hepatic V Renal V Common iliac V The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989) Stop here. The blood vessels • Arteries - muscular blood vessels that carry blood away from the heart. • Arterioles – small arteries that direct blood flow to various tissues. • Capillaries – microscopic blood vessels that connect arterioles and venules. They enable the exchange of substances between blood and surrounding tissues. • Venules – small veins. • Veins - blood vessels that carry blood toward the heart. Arteries, veins and capillaries Capillary bed Vein Arteriole Venule Artery The Miles Kelly Art library, Wellcome Images Blood vessels - structure Tunica interna (endothelium) Tunica externa Tunica media The Miles Kelly Art library, Wellcome Images • Arteries & veins have three layers (the tunicae) – the tunica externa, tunica media & tunica interna Blood vessels - structure Arteries Capillaries Veins Tunica interna Present Present Tunica media Well None developed Relatively thin Tunica externa Relatively thin Well developed None Present Arteries and veins VEIN ARTERY G. Meyer – ANHB, UWA Notice the relatively thin wall and large lumen. Notice the relatively thick, muscular wall and small lumen. Veins contain valves to prevent the back flow of blood Valve closed Valve open Section through a vein showing a valve Valve The Miles Kelly Art library, Wellcome Images Capillaries are where the exchange of materials takes place and consist of one layer of cells only The Miles Kelly Art library, Wellcome Images A capillary bed Capillaries Artery Vein Jean Wade and Linda Sharp, Wellcome Images Capillaries Capillary G. Meyer – ANHB, UWA L. Slomianka – ANHB, UWA Study Guide Read: • Our Human Species Chapter 10, sections 4-5, 8-13 Complete: • Workbook Topic 7, The heart and circulation