Three Types of Blood Vessels Transport Blood Summary Chapter 8 Carry blood away from the heart Transport blood under high pressure Arteries Capillaries Veins Exchange solutes and water with cells of the body Return blood to the heart Blood Vessels Arteries Structure Thick walled three layers Innermost layer endothelium Middle layer smooth muscle Outer layer connective tissue Function Arteries carry blood away from heart Carry blood under pressure Arterioles and Pre capillary Sphincters Blood flow Heart Arteries Arterioles Capillaries Arterioles smallest arteries Pre capillary sphincters control blood flow into capillaries Vasodilation increases blood flow to capillaries Vasoconstriction decreases blood flow to capillaries Capillaries Structure Smallest blood vessels Thin walled one cell layer thick Porous Capillary beds extensive networks of capillaries Function selective exchange of substances with the interstitial fluid Blood Vessels Veins Structure Three layers thin walled Larger lumen than arteries High distensibility Functions Carry blood toward the heart Blood flow Capillaries Venules Veins Heart Serve as blood volume reservoir Three Mechanisms Assist Venous Return to the Heart Mechanisms in blood return Contraction of skeletal muscles One way valves Pressure changes associated with breathing Also functions in immune system Lymphatic System Function Maintains blood volume Structure Blind ended capillaries Lymphatic vessels Lymph derives from interstitial fluid The Heart Layers Surrounded by fibrous sac pericardium Layers of the heart Epicardium thin layer of epithelial and connective tissue Myocardium thick layer of cardiac muscle Endocardium thin layer of endothelial tissue The Heart Chambers and Valves Four Chambers Two atria Two ventricles Valves prevent back flow Two atrioventricular valves Tricuspid valve Bicuspid mitral valve Two semilunar valves Pulmonary valve Aortic valve Pulmonary Circuit Oxygenation of Blood Deoxygenated blood from the body travels through the vena cava to the right atrium Through the right atrioventricular valve to the right ventricle Through the pulmonary semilunar valve to the pulmonary trunk and the lungs Blood is oxygenated within pulmonary capillaries Oxygenated blood travels through the pulmonary veins to the left atrium Through the left atrioventricular valve to the left ventricle Systemic Circuit Delivery of Oxygenated Blood to Tissues Oxygenated blood travels from the left ventricle through the aortic semilunar valve to the aorta Through branching arteries and arterioles to tissues Through the arterioles to capillaries From capillaries into venules and veins To the vena cava and into the right atrium Cardiac Cycle The heart contracts and relaxes AV valves open semilunar valves are closed Atrial systole Both atria contract Ventricles fill Ventricular systole Both ventricles contract AV valves close semilunar valves open Diastole Both atria and ventricles relax Semilunar valves close Heart Sounds and Heart Valves Lub dub heart sound Lub closing of both AV valves during ventricular systole Dub closing of both semilunar valves during ventricular diastole Cardiac Conduction System Coordinates Contraction Heart murmurs Causes when blood flow is disturbed May be a sign of a defective valve SA node Cardiac pacemaker Initiates the heartbeat Pace can be modified by nervous system AV node Relays impulse AV bundle and Purkinje fibers Carry impulse to ventricles Electrocardiogram EKG ECG Tracks the electrical activity of the heart A healthy heart produces a characteristic pattern Three formations P wave impulse across atria QRS complex spread of impulse down septum around ventricles in Purkinje T wave end of electrical activity in ventricles The force that the blood exerts on the wall of the blood vessels Systolic pressure highest pressure as blood is ejected during ventricular Diastolic pressure lowest pressure during ventricular diastole fibers EKGs can detect Arrhythmias Ventricular fibrillation Blood Pressure systole Measurement Sphygmomanometer Normal readings Systolic pressure 120 mmHg Diastolic pressure 80 mmHg Hypertension high blood pressure The silent killer Hypotension blood pressure too low Clinical signs dizziness fainting Causes orthostatic severe burns blood loss Regulation of the Cardiovascular System Baroreceptors Baroreceptors pressure receptors in aorta and carotid arteries Steps in mechanism 1Blood pressure rises vessels stretched 2Signals sent to the cardiovascular center in the brain 3Heart signaled to lower heart rate and force of contraction 4Arterioles vasodilate increasing blood flow to tissues 5Combined effect lowers blood pressure Regulation Nervous and Endocrine Factors Medulla oblongata signals Sympathetic nerves constrict blood vessels raising blood pressure Parasympathetic nerves dilate blood vessels lowering blood pressure Hormones epinephrine adrenaline Local requirements dictate local blood flow Exercise increased blood flow and cardiac output Cardiovascular Disorders Angina pectoris narrowed coronary arteries impair blood flow Myocardial infraction heart attack permanent cardiac damage due to blockage in a coronary artery Congestive heart failure decrease in pumping efficiency Intense chest pain nausea heaviness in the chest difficulty breathing pain radiating to left arm jaw back upper abdomen Embolism blockage of blood vessels Stroke impaired blood flow to the brain Heart Attack Also known as myocardial infraction Permanent damage to myocardium Symptoms Diagnosis EKG Blood test for cardiac enzymes Prevention Treatment Clot busting medications CABG Reducing the Risk of Cardiovascular Disease Smoking dont Blood lipids monitor cholesterol levels Exercise regular and moderate Blood pressure treat hypertension Weight being overweight increases risk of heart attack and stroke Control of diabetes mellitus early diagnosis and treatment delays onset of related problems Stress avoid chronic stress