The Cardiovascular System PDF

THE CARDIOVASULAR SYSTEM introduction By Mr D.R Siwale (Human physiologist) MSc, BSc Biology, BSc.H Biology, Dip.Ed MBcHB  CONTENT OVERVIEW OF THE CARDIOVASCULAR SYSTEM. ANATOMY OF THE HEART. CORONARY CIRCULATION. INNERVATION OF THE HEART....

THE CARDIOVASULAR SYSTEM introduction By Mr D.R Siwale (Human physiologist) MSc, BSc Biology, BSc.H Biology, Dip.Ed MBcHB  CONTENT OVERVIEW OF THE CARDIOVASCULAR SYSTEM. ANATOMY OF THE HEART. CORONARY CIRCULATION. INNERVATION OF THE HEART. ANATOMY OF BLOOD VESSEL HOW THE HEART BEATs. CARDIAC CYCLE. BLOOD PRESSURE. SYSTEMIC CIRCULATION. PULMONARY CIRCULATION. CARDIOVASCULAR DISEASES MBcHB MBcHB CARDIOVASCULAR SYSTEM overview MBcHB Function of the heart The heart is a muscular double pump with two functions: (1) Its right side receives oxygen-poor blood from the body tissues and then pumps this blood to the lungs to pick up oxygen and dispel carbon dioxide, and (2) its left side receives the oxygenated blood returning from the lungs and pumps this blood throughout the body to supply oxygen and nutrients to the body tissues MBcHB  ANATOMICAL POSITION of THE HEART The human heart is located within the thoracic cavity, between the lungs in the space known as the mediastinum. A Normal heart is approximately the size of your fist: 12 cm in length, 8 cm wide, and 6 cm in thickness. The weight of a female heart is approximately 250–300 grams , and the weight of a male heart is approximately 300–350 grams MBcHB  Cont’d….. The heart is on a slant; the base is directed toward the right shoulder, and the apex points to the left hip. The base is deep to the second rib, and the apex is at the level of the fifth intercostal space. MBcHB Position of heart in the thorax MBcHB STRUCTURE OF THE HEART 4 chambers – 2 Atria – 2 Ventricles 2 systems – Pulmonary – Systemic MBcHB INTERNAL HEART ANATOMY MBcHB What layer covers the heart? The pericardium or pericardial sac (“around the heart”) is a triple- layered sac that encloses the heart. Pericardium is made up of; Fibrous pericardium (outer layer) and the serous pericardium (parietal pericardium + inner visceral pericardium/epicardium) MBcHB Pericardial Membranes and Layers of the Heart Wall MBcHB  State the 3 layers that makes up the walls of the heart? The wall of the heart has three layers: a superficial epicardium, a middle myocardium, and a deep endocardium.All three layers are richly supplied with blood vessels. The epicardium (“upon the heart”) is the visceral layer of the serous pericardium and is often infiltrated with fat, especially in older people. The myocardium (“muscle heart”) forms the bulk of the heart. It consists of cardiac muscle tissue and is the layer that actually contracts. The endocardium (“inside the heart”), located deep to the myocardium, is a sheet of simple squamous epithelium resting on a thin layer of connective tissue. Endocardium lines the heart chambers and covers the heart valves. MBcHB Layers of the heart MBcHB Foetal heart Blood is shunted from right atrium to left atrium, skipping the lungs. Only about one-tenth of right ventricular output passes the lungs (due to high flow resistance since the lungs are not yet expanded, and due to hypoxic MBcHB vasoconstriction  HEART VALVES Heart Valves ensure UNIDIRECTIONAL flow of BLOOD Tricuspid valve or right atrioventricular valve Pulmonary valve Mitral valve or bicuspid valve or left artrioventricular valve Aortic valve MBcHB  Heart Sounds are produced by the closing of heart Valves? The closing of the valves causes vibrations in the adjacent blood and heart walls that account for the familiar “lub-dup” sounds of each heartbeat: The “lub” sound is produced by the closing of the AV valves at the start of ventricular contraction; the “dup” is produced by the closing semilunar valves at the end of ventricular contraction. The mitral valve closes slightly before the tricuspid closes, and the aortic valve generally closes just before the pulmonary valve closes. Hence, all four valve sounds are discernible when the clinician listens through a stethoscope placed on the anterior chest wall. MBcHB  Heart Valves defects… Classified as: Incompetent Valve i.e Valves that leak because they fail to close properly(or are said to exhibit insufficiency). An incompetent valve produces a distinct blowing sound after the valve closes. Stenotic i.e valves with narrowed openings, such as occur when cusps have fused or become stiffened by calcium deposits, are termed stenotic. Stenosis of the aortic valve produces a distinctive “click” sound during ventricular systole as blood passing through the constricted opening becomes turbulent and vibrates. MBcHB  Causes of heart Valves defects… Causes are: Congenital and genetic abnormalities Inadequate blood supply to the valves (due to a heart attack). Bacterial infection of the endocardium. MBcHB  CARDIOVASCULAR SYSTEM The Cardiovascular System; Discovered by the British physiologist William Harvey in 1628. Blood moves in two types of circulatory pathways: PULMONARY CIRCULATION. SYSTEMIC CIRCULATION MBcHB  Cont’d…. PULMONARY CIRCULATION involves blood moving from the right ventricle through the lungs and then to the left atrium. SYSTEMIC CIRCULATION blood moves from the left ventricle through all the organs and tissues of the body except the lungs and then to the right atrium. Arteries carry blood away from the heart and Veins carry blood toward the heart. MBcHB circuitry of the cardiovascular system. MBcHB  Circulation of blood…. 1. Oxygenated blood fills the left ventricle. 2. Blood is ejected from the left ventricle into the aorta. 3. Cardiac output is distributed among various organs. 4. Blood flow from the organs is collected in the veins. 5. Venous return to the right atrium. 6. Mixed venous blood fills the right ventricle. 7. Blood is ejected from the right ventricle into the pulmonary artery. 8. Blood flow from the lungs is returned to the heart via the pulmonary vein. MBcHB  CARDIAC OUTPUT Cardiac output is the amount of blood pumped from each ventricle per minute. Usually, it refers to left ventricular output through aorta. Cardiac output is the most important factor in cardiovascular system, because rate of blood flow through different parts of the body depends upon cardiac output. MBcHB  Cont’d….. Cardiac Output = Heart Rate x Stroke Volume. Stroke volume is the amount of blood pumped out by each ventricle during each beat. Normal value: 70 mL (60 to 80 mL) when the heart rate is normal (72/minute). MBcHB CARDIAC CYCLE MBcHB BLOOD VESSELS Blood vessels are the conduits through which blood is carried from the heart to the tissues and from the tissues back to the heart. Three types are Arteries, Veins MBcHB and Capillaries. Generalised structures of Arteries, Veins and Capillaries MBcHB Arteries and arterioles MBcHB Capillaries, Venules and Veins MBcHB Cont’d…. MBcHB BLOOD PRESSURE Blood pressure (BP) is the pressure exerted by circulating blood upon the walls of blood vessels. Blood Pressure (BP) usually refers to the arterial pressure in the systemic circulation. Normal BP is 120 mmHg/80 mmHg. MBcHB  Cont’d…Blood pressure. It is usually measured at a person's upper arm. BP is usually expressed in terms of the systolic (maximum) pressure over diastolic (minimum) pressure and is measured in millimeters of mercury (mmHg).  Inflate the Cuff and then reducing the pressure can be used to measure B.P. A MBcHB Pressure in systemic Vessel MBcHB HOW THE HEART BEATs. MBcHB Conducting system of the Heart MBcHB  Cont’d….anatomy SinoAtrial node (SA): is located at the junction of the superior vena cava with the right atrium. AtrialVentricular node (AV): is located in the right posterior portion of the interatrial. AtrialVentricular bundle (AV):This bundle, also known as the bundle of His, receives the muscle impulse from the AV node and extends into the interventricular septum before dividing into left and right bundle branches. Bundle Branches: conducts impulse through the interventricular septum. Purkinje Fibers: conducting fibers spreading to all parts of the ventricular myocardium MBcHB  Cont’d….physiology STEP 1: The heartbeat is initiated by the specialized cardiac muscle cells of the sinoatrial (SA) node. The cells of the SA node act as the pacemaker, the rhythmic center that establishes the pace for cardiac activity. STEP 2: The muscle impulse travels from the SA node to the atrioventricular (AV) node. The AV node normally slows conduction of the impulse as it travels from the atria to the ventricles, providing a delay between activation and contraction MBcHB of the ventricles.  Cont’d…..physiology STEP 3: The AV node communicates with the next part of the conduction system, the atrioventricular (AV) bundle. This bundle, also known as the bundle of His, receives the muscle impulse from the AV node and extends into the interventricular septum before dividing into left and right bundles. STEP 4: The left and right bundle conduct the impulse to conduction fibers called Purkinje cells that begin within the apex of the heart and extend through the walls of the ventricles. Purkinje fibers are larger than other cardiac muscle cells. Muscle impulse conduction along the Purkinje fibers is extremely rapid, consistent with the large size of the cells, and the impulse spreads immediately throughout the ventricular myocardium. MBcHB INNERVATION OF THE HEART The heart is innervated by the autonomic nervous system This innervation consists of sympathetic and parasympathetic components, collectively referred to as the coronary plexus MBcHB CORONARY CIRCULATION MBcHB ECG-Electrocardiogram MBcHB Normal ECG pattern MBcHB MBcHB Cont’d……..Coronary veins MBcHB  Cont’d… The coronary circulation provides blood flow to the heart. The HEART works continuously, so it needs Oxygen and Nutrients. It is the shortest Circulation in the Human Body. MBcHB  Cont’d…. The Left and Right Coronary Arteries originate at the Base of the Aorta. Blood enters the Coronary artery when the Left Ventricles are Relaxing and not when they are contracting MBcHB  Cont’d……. The heart is Supplied with Arterial blood (OXYGENATED blood) by the Right and Left Coronary arteries which branch from the AORTA. The left coronary Artery supply to the Left Ventricles and the Right Coronary supply to the Right ventricles. Coronary Sinus returns de- Oxygenated blood into the Right atrium. MBcHB DISORDER OF THE HEART MBcHB Cardiovascular disease MBcHB  Reducing Risk of HEART DISEASE –Avoid tobacco –Cut back on saturated fat and cholesterol –Maintain a healthy weight –Modify dietary habits –Physical activity MBcHB  CARDIOVASCULAR DISEASES Atherosclerosis/Arteriosclerosis Hypertension SHOCK Stroke Arrhythmias. Congestive heart failure. Valvular heart disease. Coronary artery disease. Pericarditis. MBcHB What are the most important diseases of the blood vessels? Arteriosclerosis, which includes changes induced by aging and hypertension Atherosclerosis, a multifactorial disease Vasculitis, an inflammatory disease that occurs in several clinicopathologic forms Varicose veins Vascular tumors MBcHB  Do vascular diseases occur at any age? Yes, but they occur most often in the elderly. MBcHB  What are the consequences of vascular diseases? The most important consequences include disturbances of blood flow, such as hypoxia and infarction. MBcHB  What is the difference between arteriosclerosis and atherosclerosis? Arteriosclerosis is a generic term used for hardening of arteries and arterioles. Atherosclerosis is a multifactorial disease of arteries affected by atheromas. It should be noted that atherosclerosis affects only the aorta and its major branches. Arteriosclerosis may involve any artery in the body and also may affect arterioles. MBcHB  ATHEROSCLEROSIS FEATURES: - Hyperlipidemia – abnormally high blood lipid level. This causes hardening of the arteries that progress with age. Atherosclerosis is associated with damage to the endothelial lining and the formation of lipid deposits in the tunica media. Atherosclerosis is the most common form arteriosclerosis. MBcHB Deposits of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of the artery. The commonly affected arteries are those in the HEART, Abdomen and Pelvis. MBcHB MBcHB  HYPERTENTION Hypertension is generally defined as an arterial pressure greater than 140/90 mm Hg in adults on at least three consecutive visits to the doctor's office. Hypertension is not a single disease but a syndrome with multiple causes. MBcHB  What are the determinants of blood pressure? Blood pressure depends on the cardiac output and peripheral resistance. Blood pressure may result from increasing the cardiac output or peripheral vascular resistance: Factors increasing cardiac output: Increased heart rate (hyperthyroidism); water and sodium retention. Factors increasing peripheral resistance: Neural alpha-adrenergic effect on arterioles; catecholamines, angiotensin II, aldosterone, and atrial natriuretic factor MBcHB  What is the difference between primary and secondary hypertension? The cause of primary hypertension (also known as idiopathic or essential hypertension) is not known. It accounts for 95% of all cases of hypertension. Secondary hypertension can be related to an underlying disease. In most instances, it is related to diseases of the kidneys, endocrine glands, neural disorders, and diseases of the aorta. MBcHB  What are complications of hypertension? The most commonly affected organs are the heart, aorta, brain, eyes, and kidneys: MBcHB  What are aneurysms? An aneurysm is a localized dilatation of an artery. Aneurysms may occur in the ventricles of the heart. Dilatations of the veins are called varicosities. MBcHB  SHOCK It refers to an abnormality of the circulatory system in which there is inadequate blood supplied to tissue because of a relatively or absolutely inadequate cardiac output. The causes are divided into four groups: (1) inadequate volume of blood to fill the vascular system (hypovolemic shock); (2) increased size of the vascular system produced by vasodilation in the presence of a normal blood volume (distributive, vasogenic, or low-resistance shock). (3) inadequate output of the heart as a result of myocardial abnormalities (cardiogenic shock); (4) inadequate cardiac output as a result of obstruction of blood flow in the lungs or heart (obstructive shock). MBcHB  STROKE Stroke occurs when the supply of blood to the brain is either interrupted or reduced. When this happens, the brain does not get enough oxygen or nutrients which causes brain cells to die. There are three main kinds of stroke; ischemic, hemorrhagic and Transient Ischemic Attack. MBcHB  Ischemic strokes Ischemic strokes are the most common form (85% of strokes being of this type). They are caused by the arteries that connect to the brain becoming blocked or narrowed, resulting in ischemia - severely reduced blood flow. MBcHB  These blockages are often caused by blood clots, which can form either in the arteries connecting to the brain, or further away before being swept through the bloodstream and into narrower arteries within the brain. Clots can be caused by MBcHB Stroke... MBcHB  ARRYTHMIAs It is an abnormal heart rhythm. There are two basic kinds of arrhythmias. (a)Bradycardia is when the heart rate is too slow — less than 60 beats per minute. (b)Tachycardia is when the heart rate is too fast — more than 100 beats per minute. An ECG machine is usually used to detect Arrhythmias. MBcHB  Congestive Heart Failure Inadequate pump function of the heart, which leads to congestion resulting from fluid in the lungs and peripheral tissues, is a common end result of many cardiac disease processes. In congestive heart failure, blood volume may increase 15 to 20 %, and extracellular fluid volume sometimes increases by 200 per cent or more. Initially, heart failure reduces cardiac output and, consequently, decreases arterial pressure. MBcHB  Valvular Heart Disease Dysfunctional cardiac valves can be classified as either narrow (stenosis) or leaky (regurgitation). Tricuspid and pulmonary valves dysfunction are relatively rare. Most dysfunction are found on aortic and mitral (bicuspid) valves. Stenosis: Narrow or constricted. Regurgitation: backflow of blood caused by a malfunctioning valve. MBcHB  Coronary artery Disease The Term coronary artery disease (CAD) refers to degenerative changes in the coronary circulation. Cardiac muscle fibers need a constant supply of oxygen and nutrients, and any reduction in coronary circulation produces a corresponding reduction in cardiac performance. Such reduced circulatory Supply, known as coronary ischemia, usually results from partial or complete blockage of the coronary arteries MBcHB ………….END… MBcHB