3/7/2019 CARDIOVASCULAR SYSTEM WHAT IS THE CARDIOVASCULAR SYSTEM? POINTS TO PONDER SYSTEM COMPONENTS & FUNCTIONS. System overview

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1 POINTS TO PONDER CARDIOVASCULAR SYSTEM H E AR T AN D B L O O D V E S S E L S What are the functions of the cardiovascular system? What is the anatomy of the heart? Of blood vessels, such as veins and arteries? How is the heart beat regulated? What is blood pressure? What are common cardiovascular diseases and how might you prevent them? SYSTEM COMPONENTS & FUNCTIONS System overview Components Heart pumps blood Blood vessels blood flows through these Functions Circulation Performs exchanges Oxygen and nutrients are brought to cells Waste products are removed Kidneys, liver, lungs, intestines WHAT IS THE CARDIOVASCULAR SYSTEM? It includes the heart and blood vessels. It brings nutrients to cells and helps get rid of wastes. Blood is refreshed in the lung, kidneys, intestine, and liver. Lymphatic vessels help this system by collecting excess fluid surrounding tissues and returning it to the cardiovascular system. 1

2 WHAT ARE THE FUNCTIONS OF THE CARDIOVASCULAR SYSTEM? 1. Transport: oxygen, carbon dioxide and other wastes products, nutrients, and horomones 2. Protection: cells of the immune system are transported to help protect the body from infection 3. Regulation: maintain homeostasis of a variety of the body s conditions ARTERIES AND ARTERIOLES Arteries carry blood away from the heart. Their walls have 3 layers. Thin inner epithelium Thick smooth muscle layer Outer connective tissue Arterioles are small arteries that regulate blood pressure. ARTERIES AND ARTERIOLES CAPILLARIES The strong walls of an artery give it support when blood enters under pressure; The elastic tissue allows an artery to expand to absorb the pressure. The constriction or dilation of arterioles controls blood pressure. Microscopic vessels between arterioles and venules Made of one layer of epithelial tissue Form beds of vessels where exchange with body cells occurs Combined large surface area Blood Vessels VEINS AND VENULES Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. blood flow v. v. = vein; a. = artery Figure 5.2 Structure of a capillary bed. artery connective tissue arteriole precapillary sphincter elastic tissue endothelium smooth muscle valve venule blood flow (left): Ed Reschke; (right): Biophoto Associates/Photo Researchers capillary bed arteriovenous shunt vein Venules are small veins that receive blood from the capillaries. Venule and vein walls have 3 layers. Thin inner epithelium Thick smooth muscle layer Outer connective tissue Veins carry blood toward the heart. Veins that carry blood against gravity have valves to keep blood flowing toward the heart. 2

3 TYPES OF BLOOD VESSELS HOW CAN YOU TELL THE DIFFERENCE BETWEEN AN ARTERY AND VEIN? vein artery Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. artery connective tissue arteriole v. a. blood flow precapillary sphincter elastic tissue endothelium smooth muscle arteriovenous shunt valve blood flow venule vein v.=vein; a.=artery capillary Figure 5.2 Structure of a capillary bed. (left): Ed Reschke TYPES OF BLOOD VESSELS The Capillaries: exchange Arterioles branch into capillaries. The capillaries have walls that are only one cell thick and allow exchange of substances with tissue fluid. Not all capillary beds are open at the same time. Contraction of a precapillary sphincter muscle closes off the bed and then blood flows through an arteriovenous shunt, bypassing the capillary bed, going directly into a venule. TYPES OF BLOOD VESSELS arteriovenous shunt The Veins: To the Heart Venules drain into veins that return blood to the heart. Veins have much less smooth muscle and connective tissue than arteries. Veins often have valves that prevent the backward flow of blood due to gravity when closed. 3

4 THE HEART Located behind and slightly left of the breastbone(sternum) Cone-shaped Points slightly left Has 4 chambers 2 atria (sing. = atrium) 2 ventricles THE HEART Muscular Myocardium = cardiac muscle tissue Lies inside a fibrous pericardium ANATOMY OF THE HEART Large, muscular organ consisting of mostly cardiac tissue called the myocardium Surrounded by a sac called the pericardium Consists of 2 sides, right and left, separated by a septum Consists of 4 chambers: 2 atria and 2 ventricles 2 sets of valves: semilunar valves and atrioventricular valves (AV valves) Valves produce the lub and dub sounds of the heartbeat EXTERNAL ANATOMY OF THE HEART left subclavian artery left common carotid artery brachiocephalic artery superior vena cava aorta left pulmonary artery pulmonary trunk left pulmonary veins right pulmonary artery right pulmonary veins left atrium left cardiac vein right atrium right coronary artery left ventricle right ventricle left anterior descending coronary artery inferior vena cava apex 4

5 INTERNAL ANATOMY OF THE HEART left subclavian artery left common carotid artery brachiocephalic artery superior vena cava aorta left pulmonary artery pulmonary trunk left pulmonary veins right pulmonary artery right pulmonary veins semilunar valve left atrium right atrium atrioventricular (bicuspid) valve atrioventricular (tricuspid) valve chordae tendineae papillary muscles right ventricle septum left ventricle inferior vena cava a. THE HEART THE HEART Right and left atria empty into the right and left ventricles respectively. Atrioventricular valves occur between the atria and ventricles Semilunar valves occur between the ventricles and the attached arteries. Chordae tendinae strengthen atrioventricular valves. Intercalated disks contain gap junctions and desmosomes which join neighboring fibers together and make sure that cardiac fibers contract simultaneously. CORONARY CIRCULATION Myocardium receives oxygen and nutrients from the coronary arteries. Right coronary artery Left coronary artery Circumflex artery Left anterior desending artery THE STRUCTURE OF THE VESSELS AND HEART MATCH THEIR FUNCTIONS The left ventricle is much more muscular than the right ventricle because it must pump blood to the entire body. The arteries are more muscular than veins to withstand the higher pressure exerted on them. The veins have a thinner wall and a larger center to contain blood. 5

6 VISUALIZING BLOOD FLOW THROUGH THE HEART PASSAGE OF BLOOD THROUGH THE HEART From the body through the heart Superior and inferior vena cava, right atrium, right ventricle, pulmonary arteries to the lungs. From the lungs Blood goes back to the heart via pulmonary veins, left atrium, left ventricle, and then to the body through the aorta. Oxygen-poor blood never mixes with oxygen-rich blood! Figure 5.4 The heart is a double pump. HOW DOES THE HEARTBEAT OCCUR? THE HEART During systole, the atria contract together followed by the ventricles contracting together. This is followed by diastole, a rest phase, when the chambers relax. This cardiac cycle, or heartbeat, occurs 70 times/minute on average. Each heartbeat is called a cardiac cycle. Systole refers to the contraction of heart chambers Diastole refers to their relaxation. Heart sounds, lub-dub Due to the closing of the atrioventricular valves Followed by the closing of the semilunar valves. WHAT IS THE CARDIAC CYCLE? semilunar aortic semilunar valve bicuspid valve valves close ( dup ) pulmonary trunk semilunar superior aorta valves vena cava HEARTBEAT IS CONTROLLED Internal Control of Heartbeat right atrium left atrium right atrium Sinoatrial (SA) node (pacemaker) initiates the beat and causes the atria to contract. a. right ventricle left ventricle aorta inferior vena cava c. pulmonary trunk atrioventricular (AV) valves close d. Atrioventricular (AV) node conveys the stimulus and initiates contraction of the ventricles. The signal for the ventricles to contract travels from the AV node through the atrioventricular bundle to the smaller Purkinje fibers. b. ( lub ) represents contraction d: Biophoto Associates/ Photo Researchers These impulses travel between gap junctions at intercalated disks. Figure 5.5 The stages of the cardiac cycle. 6

7 5.3 The Heart is a Double Pump VISUALIZING THE GAP JUNCTIONS AT THE INTERCALATED DISKS gap junction Figure 5.4b The heart is a double pump. HEARTBEAT IS CONTROLLED ELECTROCARDIOGRAM External Control of Heartbeat Cardiac control center in the medulla oblongata regulates the heartbeat by way of the parasympathetic nervous system (slows heart rate) The sympathetic nervous system (increases heart rate) systems. Hormones of the adrenal medulla also stimulate the heart. Electrocardiogram (ECG) is a recording of the electrical changes that occur in the myocardium during a cardiac cycle. ECG pattern P wave signals the atria are about to contract when stimulated by the SA node; QRS complex signals contraction of the ventricles; Recovery of the ventricles produces the T wave. ECG can also detect various types of abnormalities, including ventricular fibrillation. ELECTROCARDIOGRAM WHAT DOES A NORMAL ECG LOOK LIKE? R P T SA node Q S AV node b. Normal ECG b: Ed Reschke branches of atrioventricular bundle Purkinje fibers a. Figure 5.6a-b An electrical signal pathway through the heart. 7

8 FEATURES OF THE CARDIOVASCULAR SYSTEM FEATURES OF THE CARDIOVASCULAR SYSTEM Pulse Rate Equals Heart Rate The surge of blood entering the arteries following a heartbeat causes their elastic walls to stretch and then recoil. This is felt as a pulse. The pulse rate of the radial or carotid artery indicates the heart rate. Blood Flow Is Regulated Beating of the heart is necessary for homeostasis because it creates the pressure that propels blood in the arteries and the arterioles Blood Pressure Moves Blood in Arteries Blood pressure is the pressure of blood against the wall of a blood vessel. Usually measured in the brachial artery of the arm with a sphygmomanometer Higher number is the systolic pressure and the lower number is the diastolic pressure Normal blood pressure is less than 120/80. High blood pressure is called hypertension and low blood pressure hypotension. What is blood pressure? BLOOD PRESSURE READINGS Figure 5.7 Sphygmomanometers measure blood pressure. Systolic The top number, which is also the higher of the two numbers, measures the pressure in the arteries when the heart beats (when the heart muscle contracts). Diastolic The bottom number, which is also the lower of the two numbers, measures the pressure in the arteries between heartbeats (when the heart muscle is resting between beats and refilling with blood). FEATURES OF THE CARDIOVASCULAR SYSTEM Am. Heart Assoc. values 2012 When the left ventricle contracts, a surge of blood flows through the arteries. BP is highest in the aorta BP is lowest in the superior and inferior vena cavae. 8

9 Relative magnitude BLOOD FLOW What is important about blood flow? Blood Flow Is Slow in the Capillaries Blood moves slowly in capillaries because there are more capillaries than arterioles. Slow pace allows time for exchanges between capillary blood and tissue cells. arteries arterioles capillaries venules veins total blood cross-sectional pressure area of vessels velocity Blood flow (starting from heart) 49 Figure 5.8 Blood velocity and pressure in the blood vessels. BLOOD FLOW Blood Flow in Veins Returns Blood to Heart Venous return is dependent upon skeletal muscle contraction, the presence of valves in veins, and respiratory movements. Once blood has moved past a valve it closes preventing backward return. TWO CARDIOVASCULAR PATHWAYS Blood flows in two circuits: Pulmonary Systemic circuits The Pulmonary Circuit: Exchange of Gases Pulmonary arteries take blood from the right ventricle to the lungs Carbon dioxide is given off Oxygen is picked up Pulmonary veins return it to the left atrium. Pulmonary arteries carry oxygen-poor blood while pulmonary veins carry oxygen-rich blood. TWO CARDIOVASCULAR PATHWAYS The Systemic Circuit: Exchanges with Tissue Fluid Aorta is largest artery in the systemic circuit Receives blood from the heart Superior and inferior venae cavae Ascending Aorta Descending Aorta Trace the Path of Blood see following figure 9

10 FIG BLOOD FLOW THE HEART S BLOOD SUPPLY: CORONARY CIRCULATION There are small coronary arteries that supply the heart. They are separate from the systemic and pulmonary pathways of the body. HEPATIC PORTAL SYSTEM Hepatic Portal System: Specialized for Blood Filtration Drains blood from the capillary beds of the digestive tract to a capillary bed in the liver Purifies blood of toxins and pathogens Blood returns via hepatic vein to inferior vena cava HEPATIC PORTAL SYSTEM A system that brings amino acid- and glucose-rich blood from the digestive tract to the liver. The liver synthesizes blood proteins and stores the glucose as glycogen. The liver also plays a role in purifying blood from the digestive tract. Finally, the blood will return to the heart via the inferior vena cava. EXCHANGE AT THE CAPILLARIES Movement of fluid through the capillary wall controlled by Osmotic pressure Blood pressure control Arterial End Blood pressure is higher than osmotic pressure and water exits capillary Venule End Osmotic pressure is greater than blood pressure, and water tends to move into capillary 10

11 Exchange at the capillary beds is primarily a result of osmotic and blood pressure Exchange at the capillaries from heart arteriole Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arterial End Blood pressure is higher than osmotic pressure. Net pressure out. smooth muscle fiber water salt oxygen amino acids plasma protein osmotic pressure blood pressure Tissue Fluid glucose carbon dioxide wastes Venous End Osmotic pressure is higher than blood pressure. Net pressure in. water to heart venule Lymphatic capillary beds lie alongside capillary beds. When lymphatic capillaries take up excess fluid it becomes lymph. Lymph returns to the cardiovascular veins in the chest. Precapillary sphincters can shut down a blood capillary, and blood then flows through the shunt. Figure 5.12 The movement of solutes in a capillary bed EXCHANGE AT THE CAPILLARIES EXCHANGE AT THE CAPILLARIES Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Excess tissue fluid left behind in capillary beds is collected by lymphatic vessels. This fluid is called lymph and is returned to the venous blood in the shoulder region. arteriole tissue cells lymphatic capillary Figure 5.13 Interaction of lymphatic and capillary beds. blood capillary lymphatic duct venule Cardiovascular Disorders Cardiovascular Disease Cardiovascular disease (CVD) is the most common cause of death in the Western world. DISORDERS OF THE BLOOD VESSELS Hypertension/high blood pressure Atherosclerosis Stroke Heart attack Aneurysm 65 11

12 CARDIOVASCULAR DISORDERS HYPERTENSION Disorders of the Blood Vessels High Blood Pressure (Hypertension) Can lead to heart disease Best defense against hypertension is a life-style that lowers the risk of hypertension Often seen in individuals with atherosclerosis, an accumulation of plaque in the linings of arteries. These clots can dislodge and lodge in a small blood vessel, forming a thromboembolism, which is life-threatening. High blood pressure results when blood moves through vessels at a rate higher than normal, often due to arterial plaque. 120/80 mmhg is considered prehypertensive. It is a silent killer because there are few symptoms. It can lead to a heart attack, stroke, or kidney failure. 5.7 Cardiovascular Disorders ATHEROSCLEROSIS Atherosclerosis It is a build up of plaque in blood vessels. Plaque that is stationary is called a thrombus, and an embolus when it detaches and can move to distant sites. coronary artery Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ulceration lumen of vessel It is associated with a stroke, heart attack, and aneurysm. fat cholesterol crystals atherosclerotic plaque Biophoto Associates/Photo Researchers Figure 5B Coronary arteries and plaque. CARDIOVASCULAR DISORDERS STROKE Stroke, Heart Attack, and Aneurysm Stroke Blood clot lodges in a cerebral blood vessel or a cerebral blood vessel bursts, and a portion of the brain dies. Heart attack Blood clot lodges in a coronary blood vessel Aneurysm Ballooning of a blood vessel If a major blood vessel like the aorta bursts, death is likely A stroke is also known as a cerebrovascular accident (CVA). It usually occurs when a cranial artery is blocked or bursts. Part of the brain dies dues to lack of oxygen. Symptoms may include numbness of hands or face, difficulty speaking, and inability to see in one eye. 12

13 HEART ATTACK A heart attack is also known as a myocardial infarction (MI). Part of the heart dies due to lack of oxygen. It can begin with angina pectoris, a pain that radiates down the left arm due to a blockage of a coronary artery. ANGINA Chest pain or discomfort caused when your heart muscle doesn't get enough oxygenrich blood. Usually happens because one or more of the coronary arteries is narrowed or blocked, also called ischemia. Symptom of an underlying heart problem ANGINA ANEURYSM Symptoms May feel like pressure or squeezing in your chest. The discomfort also can occur in your shoulders, arms, neck, jaw, or back. Angina pain may even feel like indigestion. Treatments Lifestyle changes Medicines vasodilators (nitroglycerine) Cardiac procedures Cardiac Rehab It is a ballooning of a blood vessel. Atherosclerosis and hypertension can weaken a vessel and cause ballooning. The most commonly affected is the abdominal artery or the arteries leading to the brain. CARDIOVASCULAR DISORDERS Treatments for blood vessel disorders Angina pectoris. Blockage of a coronary artery Dissolving Blood Clots t-pa drug dissolves clots Aspirin reduces chance of clots Treating Clogged Arteries Coronary bypass operation Angioplasty Gene therapy has also been used to grow new blood vessels Treating clogged arteries Bypass surgery: usually a vein from the leg is taken and used to bypass a clogged artery Stents: wire mesh cylinder inserted into a clogged artery to hold it open Angioplasty: a tube with a balloon is inserted into the clogged area and the balloon is then inflated to open the vessel A stent and angioplasty may be used in combination 13

14 TREATMENTS FOR ATHEROSCLEROTIC PLAQUE IN CORONARY ARTERIES DISORDERS OF THE HEART AND ITS TREATMENT Disorders Heart failure is when the heart no longer pumps properly. Treatments Left ventricular assist device (LVAD) Heart transplant either natural or artificial CARDIOVASCULAR DISORDERS CARDIOVASCULAR DISORDERS Heart Failure Heart no longer pumps as it should Implantation of a cardioverter-defibrillator senses fast or slow heart beat Heart Transplants Routinely performed but there is a shortage of human hearts Left ventricular assist device (LVAD), implanted in the abdomen, Alternative to a heart transplant. Work still goes forward on an artificial heart. Artificial Heart Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CARDIOVASCULAR DISEASE PREVENTION wireless energytransfer system external wireless driver Figure 5.15 An artificial heart. internal controller external battery pack (right): Courtesy SynCardia Systems, Inc. replacement heart rechargeable internal battery photograph of artificial heart 83 Preventable risk factors include: use of tobacco products. drug and alcohol abuse. obesity and a sedentary lifestyle. poor diet. stress. poor dental hygiene. 14

15 HOMEOSTASIS All body systems work together to maintain homeostasis. How Body Systems Work Together The cardiovascular system delivers oxygen and nutrients to, and takes away metabolic wastes from, the tissue fluid that surrounds cells. The lymphatic system returns tissue fluid to the bloodstream. The muscular system makes essential contributions to body movement. In the skeletal system, bones contribute calcium ions, which are important to blood clotting. The urinary system regulates acid-base and water-salt balance of blood and tissue fluid. 15