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THE CARDIOVASCULAR SYSTEM LECTURE 1: INTRODUCTION Eamonn O’Connor Applied Health Science Lecture Outline 1 Overview of the Cardiovascular System The Path of Blood Flow Through the Heart and Vasculature Anatomy of the Heart AHS Physiology - Cardiovascular System 11-12 1 Overview of the Cardiovascular System 2 AHS Physiology - Cardiovascular System 11-12 Overview of Cardiovascular System 3 Functions of CV system: Transport of substances Oxygen & nutrients to cells Wastes from cells to liver & kidneys Hormones, immune cells, clotting proteins to specific target cells Regulation of Cardiovascular system: interactions with nervous system, endocrine system and kidneys AHS Physiology - Cardiovascular System 11-12 2 The Heart 4 Four chambers 2 Atria: receive venous blood 2 Ventricles: pump blood to the circulation Septum: prevent mixture of blood from both sides (left and right) Interatrial Interventricular Base: upper end Apex: lower end Figure 13.1 AHS Physiology - Cardiovascular System 11-12 Blood Vessels 5 Heart →Arteries → Arterioles → Capillaries → Venules → Veins Vasculature Arteries – relatively large, branching vessels that conduct blood away from the heart Arterioles – small branching vessels with high resistance Capillaries – site of exchange between blood and tissue Venules – small converging vessels Veins – relatively large converging vessels that conduct blood to the heart Closed system AHS Physiology - Cardiovascular System 11-12 3 Blood 6 Arterial Blood Blood leaving the heart Bright Red High oxygen content (oxyhaemoglobin) Venous blood Blood returning to the heart Darker colour Lower oxygen content (deoxyhaemoglobin) Cellular portion of blood (45% blood volume) a) Erythrocytes (red blood cells): oxygen transport b) Leukocytes (white blood cells): immune function c) Platelets: Blood clotting Plasma (55% blood volume) a) Water (90%) b) Dissolved solutes eg. Ions, O2, CO2… c) Plasma proteins d) Other components eg. metabolites, hormones, enzymes, antibodies. Figure 15.1 AHS Physiology - Cardiovascular System 11-12 Path of Blood Flow through CVS 7 Pulmonary circuit Supplied by right heart Blood vessels from heart to lungs and lungs to heart Systemic circuit Supplied by left heart (rest of blood vessels) Blood vessels from heart to systemic tissues and tissues to heart Figure 13.2 AHS Physiology - Cardiovascular System 11-12 4 Oxygenation of Blood 8 Exchange between blood and tissue takes place in capillaries Pulmonary capillaries Blood entering lungs = deoxygenated blood Oxygen diffuses from tissue to blood Blood leaving lungs = oxygenated blood Systemic capillaries Blood entering tissues = oxygenated blood Oxygen diffuses from blood to tissue Blood leaving tissues = deoxygenated blood Figure 13.2 AHS Physiology - Cardiovascular System 11-12 Path of Blood Flow Through the CVS 9 Cardiovascular system = closed system Flow through systemic and pulmonary circuits are in series (has to go through both circuits and simultaneously) Left ventricle aorta systemic circuit vena cavae right atrium right ventricle pulmonary artery pulmonary circuit pulmonary veins left atrium left ventricle AHS Physiology - Cardiovascular System 11-12 Figure 13.2 5 10 Parallel Blood Flow Within the Systemic (or Pulmonary) Circuit Aorta arteries arterioles capillaries Oxygenated blood enters each capillary bed Parallel flow allows independent regulation of blood flow to organs Capillaries venules veins Exception: portal systems (i.e. kidneys, GI tract-liver) Figure 13.3 AHS Physiology - Cardiovascular System 11-12 Anatomy of the Heart: Location 11 Located in thoracic cavity Diaphragm separates abdominal & thoracic cavities Size of a fist Weight approx 250-350g AHS Physiology - Cardiovascular System 11-12 Figure 13.5 6 Pericardium 12 Membranous sac surrounding heart Lubricates heart decreasing friction Pericarditis = inflammation of pericardium AHS Physiology - Cardiovascular System 11-12 Myocardium & the Heart Wall 13 Three layers of the heart wall: Endocardium layer (inner) of endothelial cells Myocardium cardiac (middle) muscle Epicardium external (outer) membrane, connective tissue AHS Physiology - Cardiovascular System 11-12 7 Properties of Cardiac Muscle 14 Smaller fibres than skeletal muscle Sarcomeres: Striated Intercalated Disks Gap junctions: Contract as unit Desmosomes: Resist stress Atria & Ventricles: Separate units (separated by fibrous skeleton) Aerobic muscle 99% contractile cells / 1% autorhythmic cells Figure 12.32c AHS Physiology - Cardiovascular System 11-12 Walls of the Heart 15 Walls of ventricles thicker than walls of atria Wall of left ventricle thicker than wall of right Figure 13.1 Figure 13.6 AHS Physiology - Cardiovascular System 11-12 8 Function of Cardiac Muscle 16 Rhythmic contraction and relaxation generates heart pumping action Contraction increases the pressure within the chamber and pushes blood out of heart into vasculature Relaxation allows heart to fill with blood Heartbeat: Wave of contraction through cardiac muscle Atria contract as a unit Ventricles contract as a unit Atrial contraction precedes ventricle contraction AHS Physiology - Cardiovascular System 11-12 Valves and Unidirectional Blood Flow 17 Pressure within chambers of heart vary with heartbeat cycle Pressure High difference drives blood flow pressure to low pressure Normal direction of flow Atria to ventricles Ventricles to arteries Valves prevent backward flow of blood All valves open passively based on pressure gradient AHS Physiology - Cardiovascular System 11-12 9 Heart Valves: atrioventricular valves 18 AV valves: Right AV valve = tricuspid valve (3 flaps or cusps) Left AV valve = bicuspid valve = mitral valve Papillary muscles and chordae tendinae: keep AV valves from everting AHS Physiology - Cardiovascular System 11-12 Figure 13.7 Semilunar Valves 19 Semilunar valves: Aortic valve (L) Pulmonary valve (R) AHS Physiology - Cardiovascular System 11-12 Figure 13.8 10