D3.1 - Structures of the Circulatory System PDF

D3.1 - Structures of the Circulatory System I can… Identify the principal structures of the heart and describe their purpose (atria, ventricles, septa, valves, aorta, venae cavae, pulmonary arteries and veins, sinoatrial node, atrioventricular node, Purkinjie fibres) Describe the...

D3.1 - Structures of the Circulatory System I can… Identify the principal structures of the heart and describe their purpose (atria, ventricles, septa, valves, aorta, venae cavae, pulmonary arteries and veins, sinoatrial node, atrioventricular node, Purkinjie fibres) Describe the action of the beating heart Trace the flow of blood through the heart to the rest of the body Describe the structure and function of blood vessels (arteries, veins and capillaries) Define blood pressure and describe factors which influence it Describe the general circulation of blood through coronary, pulmonary and systemic pathways Describe associated cardiovascular disorders along with their symptoms and causes Main Functions of the Circulatory System 1. Transports gases, nutrients, and waste materials throughout the body 2. Regulates internal temperature and distribution of hormones 3. Protects the body against disease Components of the Circulatory System The Heart Types of Muscle Cardiac Muscle The heart is a notably powerful muscle with an extremely important role in providing our cells with energy Cardiac muscle is found only in the heart Cardiac muscle is controlled by the autonomic nervous system (involuntary control) William Harvey (1578-1657) William Harvey was an English physician who suggested that the heart pumps blood throughout the body He determined that the body’s blood volume is circulated over and over throughout the body The Heart The heart is a muscular structure that is the size of a human fist Organization of the Heart Composed of 4 chambers: two atria (top chambers) and two ventricles (bottom chambers) Right atrium and ventricle handle deoxygenated blood Left atrium and ventricle handle oxygenated blood Organization of the Heart The left and right sides of the heart are separated from each other by the septum, a thick muscular wall The septum prevents oxygenated blood from mixing with deoxygenated blood. The muscle surrounding the left ventricle is much thicker than the muscle that surrounds the right ventricle. This is because the left ventricle is responsible for pumping blood out to the entire body, while the right ventricle only needs to pump blood out to the lungs. Other Important Characteristics Often, arteries are thought of as blood vessels that carry oxygenated blood, while veins carry deoxygenated blood. However, this is not always the case The pulmonary arteries carry deoxygenated blood (from the right ventricle to the lungs) The pulmonary veins carry oxygenated blood (from the lungs to the left atrium) The better way to define an artery is any blood vessel that carries blood AWAY from the heart Conversely, veins are best defined as any blood vessel that carries blood TOWARDS the heart Path of Blood Flow Through the Heart 1. Once depleted of oxygen, blood returns to the right atrium of the heart through the superior and inferior vena cava. 2. Blood moves through the right atrium to the right ventricle, where it is then pumped out of the heart via pulmonary arteries to the lungs. Here, CO2 will be exchanged for O2. 3. Oxygenated blood travels back to the heart where it enters the left atrium through pulmonary veins. 4. Blood flows into the left ventricle and is pumped out of the heart via the aorta, where it then travels to other areas of the body. Path of Blood Flow Through the Heart Terminology Arteries: Brings blood away from heart Veins: Brings blood towards the heart Pulmonary: Refers to lungs Valves Valves ensure that blood flows in the correct direction Atrioventricular valves separate the atria and ventricles ○ Right side: Tricuspid valve (3 flaps) ○ Left side: Bicuspid/mitral valve (2 flaps) Other two valves are called semilunar valves (half-moon shape) Blood Vessels Three main types: arteries, veins, capillaries 1. Arteries Typically carry oxygenated blood Carry blood away from the heart Thick, highly elastic walls to keep blood flowing in right direction (allows arteries to contract) Composed of three layers Branch into smaller arterioles Pulse: Rhythmic expansion and contraction of an artery as blood moves through Structure of Blood Vessels 2. Veins Typically carry deoxygenated blood Carry blood back to the heart Thin, rigid walls (do not contract on their own) One-way valves (important to counteract the force of gravity) Composed of three layers Branch off into smaller venules Structure of Blood Vessels Varicose veins occur when the leaflets of valves fail to close properly, causing blood to flow backwards and pool in the veins. This is common in veins of the legs. Why? Structure of Blood Vessels 3. Capillaries Capillaries Connect arteries and veins to tissues Composed of a single layer of cells Much smaller and more widespread than arteries and veins The site of gas exchange in the circulatory system Thin walls and capillaries facilitate diffusion of nutrients, gases, and waste to and from the neighboring tissue Structure of Blood Vessels Video - How the heart actually pumps blood (TedED) https://www.youtube.com/watch?v=ruM4Xxhx32U The Beating Heart Electrocardiogram (ECG) An electrocardiogram (ECG) can be used to record the electrical activity of the heart. In a healthy heart rhythm, there are three waves: ○ P-wave: Contraction of atria ○ QRS-wave: Contraction of ventricles ○ T-wave: Recovery of ventricle Note: Because ventricular contraction occurs at the same time as atrial recovery, recovery of the atria cannot be detected Dead heart tissue: Will create an ECG with abnormal peaks and lines Practice What would the ECG of a person who is exercising look like? Heart Sounds Familiar sounds of a heartbeat are due to opening and closing of valves As ventricles contract, blood is forced up the sides of ventricle and the AV valve closes, which produces a “lub” sound As ventricles relax, blood pressure decreases and semilunar valves close, which causes a ”dub” sound If valve doesn’t close properly, a heart murmur is detected ○ Murmur sound (similar to a gurgle) is due to blood rushing backwards through a valve Blood Pressure (BP) Blood pressure is the pressure exerted against the walls of the heart as blood is transported throughout the body Measured as a ratio of systolic/diastolic pressure (120/80 is normal) Maximum pressure during ventricular contraction = systolic pressure Minimum pressure before ventricular contraction = diastolic pressure BP is measured using sphygmomanometer (pressure cuff) Cardiac Output Cardiac output: The amount of blood pumped by the heart per unit of time ○ Indicates level of oxygen delivered to tiddues Affected by: ○ Stroke volume: Amount of blood pumped by each beat of the heart ○ Heart rate: Beats per minute Brainstorm What are some variables that may affect heart rate? Pathways of Circulatory System Blood vessels are organized to carry blood Three different pathways: ○ Pulmonary pathway: Circulates blood from the heart to the lungs and back ○ Systemic pathway: Circulates blood from the heart to the body and back ○ Coronary pathway: Oxygen and nutrients are delivered to the heart through capillaries embedded directly in the heart wall. These capillaries are supplied by two small arteries that branch off of the aorta. Deoxygenated blood is carried away in coronary veins. Supplies the heart itself with oxygen Common Cardiovascular Disorders 1. Arteroschlerosis 2. Heart Arrhythmia 3. Congenital Heart Defects 4. Heart Attack 1. Arterioschlerosis Arteriosclerosis: Describes conditions in which walls of arteries thicken and lose elasticity due to buildup of plaque, thus becoming hard Caused by lack of exercise, smoking, and/or a diet high in fat Leads to decreased blood flow and increased blood pressure Symptoms include chest pain, blood clots, shortness of breath, and heart failure Arteriosclerosis Treatments Aspirin prevents platelets from sticking together and reduces the formation of blood clots Angioplasty: Surgical procedure wherein a tube is inserted into a clogged artery and inflated, forcing the artery to open 2. Heart Arrythmia Heart arrhythmia results in an abnormal rhythm of the heart: too slow, too fast, or at an irregular beat or tempo Without proper rhythm, the heart doesn’t work as effectively and may not be able to pump enough blood to deliver oxygen and nutrients to other organs Arrhythmia can be prevented by maintaining a healthy diet, exercising regularly, limiting or managing stress, caffeine, and alcohol 3. Congenital Heart Defects Congenital heart defects are structural defects present from birth May be genetic, or due to drug/alcohol use during pregnancy. Examples: ○ Valve defects (leaky valve leads to heart murmur) ○ Septal defects (hole in septum leads to mixing of oxygenated and deoxygenated blood) Primarily corrected through surgery 4. Heart Attack Occurs when the heart muscle is cut off from the oxygen it needs to operate ○ The blood flow delivering the oxygen has been significantly reduced or stops entirely Due to atherosclerosis (slow buildup of plaque, fat, cholesterol, other substances) in coronary arteries. Blood clots form around the plaque, which can slow or block the blood flow and cause a heart attack, Someone in the USA has a heart attack about every 40 seconds. 4. Heart Attack The symptoms of a heart attack in women have only recently been studied We now know that women experience symptoms that are often not associated with a heart attack Because women experience more subtle symptoms than men, they are less likely to seek help/call 911 (many don’t even realize they are having a heart attack) As a result, women are more likely to die of a heart attack than men. So, it is important that you know the symptoms, as it could save your life one day (or the life of a loved one)!