D3.1 - Structures of the Circulatory System PDF

D3.1 - Structures of the Circulatory System Main Functions 1. Oxygen and nutrients are transported to our cells and waste is removed by the circulatory system 2. Internal temperature is regulated by the circulatory system 3. Protects us from blood loss due to injury and infection W...

D3.1 - Structures of the Circulatory System Main Functions 1. Oxygen and nutrients are transported to our cells and waste is removed by the circulatory system 2. Internal temperature is regulated by the circulatory system 3. Protects us from blood loss due to injury and infection William Harvey Suggested that the heart pumps blood throughout the body Determined that the body’s blood volume is circulated over and over throughout the body The Heart The heart is a muscular structure Is the size of a human fist Walls of heart are made up of muscle tissue (called cardiac muscle) ○ Contraction of cardiac muscle is involuntary - you cannot consciously affect your heartbeat The Heart Has four chambers: ○ Two top chambers, called atria (plural: atrium) Fill with blood returning from the body/lungs ○ Two bottom chambers, called ventricles Receive blood from atria and pump it out to body/lungs Atria and ventricles are separated from each other by septum, a thick muscular wall Circulation Within Heart - Right Side Receives blood coming back from body and pumps this blood out to the lungs The vena cava open into the right atrium ○ Superior vena cava: Collects deoxygenated blood coming from head, chest, and arms ○ Inferior vena cava: Collects deoxygenated blood coming from the rest of the body Circulation Within Heart - Right Side Deoxygenated blood flows from right atrium into right ventricle Blood then flows into pulmonary trunk before entering left and right pulmonary arteries ○ Pulmonary arteries: Only arteries in body that contain oxygen poor blood Circulation Within Heart - Left Side Receives oxygenated blood from left and right lungs and pumps this blood out to the body Oxygenated blood flows from lungs, through pulmonary veins, to the left atrium ○ Pulmonary veins: Only veins in the body that contain oxygenated blood Left atrium pumps blood into left ventricle, where blood is pumped to through the aorta (largest blood vessel in body) *Guide* Arteries: Brings blood away from heart Veins: Brings blood to heart Pulmonary: Refers to lungs Valves Ensures that blood flows in the correct direction Atrioventricular valves separate atria and ventricles ○ Right side: Tricuspid (3 flaps) ○ Left side: Bicuspid/mitral (2 flaps) Other two valves are called semilunar valves (half-moon shape) Structure of Blood Vessels Three main types: arteries, veins, capillaries 1. Arteries Carry oxygenated blood away from heart Highly elastic walls - allow artery to expand when blood surges through during contraction of ventricles, and then contract during relaxation of ventricle Elasticity keeps blood moving in right direction and helps force blood through vessels Pulse: Rhythmic expansion and contraction of an artery as blood moves through Structure of Blood Vessels 2. Veins Carries deoxygenated blood towards heart Thinner walls and larger inner circumference than arteries Contraction of muscles keep blood flowing towards heart Have one valve that prevents blood from flowing backwards Structure of Blood Vessels 3. Capillaries Join each artery and vein network Blood travels from arteries into capillaries, where gases, nutrients, and other materials are transferred to tissue cells and wastes move into blood, where they are moved into veins and back to the heart Unlike other blood cells, capillaries are only one layer of cells thick Blood cells must move through these capillaries single-file Thin walls and capillaries facilitate diffusion of nutrients, gases, and waste to and from the neighboring tissue Structure of Blood Vessels Arteries and Veins - 3 Layers Outer: Covering of connective tissue mixed with elastic tissue Middle: Alternating, circular bands of elastic tissue and smooth muscle tissue Inner: One cell thick, consists of flat, smooth cells ○ The shape and texture of these cells reduces friction as blood moves through it Video - How the heart actually pumps blood (TedED) https://www.youtube.com/watch?v=ruM4Xxhx32U The Beating Heart Electrical signals stimulate the heart to beat ○ Rate and strength of heartbeat is controlled by nervous system Sinoatrial (SA) node: Specialized muscle tissue stimulates muscle cells to contract and relax rhythmically ○ Also referred to as the “natural pacemaker” as it sets the pace for cardiac activity ○ Located in wall of right atrium ○ Generates electrical signal that spreads over two atria and causes them to simultaneously contract ○ When atria contracts, the signal reaches atrioventricular (AV) node AV node transmits electrical signal through specialized fibres, called Bundle of His Bundle of His fibres relay the signal through two branches that divide into Purkinje fibres Purkinje fibres initiate almost simultaneous contractions of all cells in the right and left ventricle Electrocardiogram (ECG) Records electrical activity of heart as it contracts and relaxes In a healthy heart rhythm, there are three waves: ○ P-wave: Indicates contraction of atria ○ Large spike: Records ventricular contractions, known as QRS wave, ○ T-wave: Indicates recovery of ventricle Dead heart tissue: Will create an ECG with abnormal peaks and lines 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 - produces a “lub” sound As ventricles relax, blood pressure decreases and semilunar valves close, - 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) Pressure exerted against vessel walls as blood passes through them Changes in BP correspond to different phases of heartbeat Ventricles contract, forcing blood into pulmonary arteries and aorta, increasing pressure ○ Systolic pressure: Maximum pressure during ventricular contraction Ventricles then relax and pressure drops in pulmonary arteries and aorta ○ Diastolic pressure: Lowest pressure reached before ventricles contract again BP is measured using sphygmomanometer (pressure cuff) Cardiac Output Cardiac output: The amount of blood that flows from each side of the heart per minute ○ Indicates level of oxygen delivered to body and the amount of work the body can perform Two factors affect cardiac output: ○ Stroke volume: Amount of blood pumped by each beat of the heart ○ Heart rate: Beats per minute Cardiac Output - Calculation cardiac output = heart rate x stroke volume Average person’s cardiac output is 5 L per minute (total amount of blood in body that circulates throughout heart) ○ AV stroke volume: 70 mL ○ AV heart rate (at rest): 70 beats/min People with lower resting heart rate = more muscular heart ○ Can pump greater volume with each beat Pathways of Circulatory System Blood vessels are organized to carry blood Three different pathways: ○ Pulmonary pathway ○ Systemic pathway ○ Coronary pathway Pulmonary Pathway Transports oxygen-poor blood into lungs Blood reaches lungs, oxygen and CO2 are exchanged by diffusion between blood in capillaries and air in alveoli of lungs Oxygen-rich blood returns to left side of the heart via pulmonary veins Systemic Pathway Moves oxygen-rich blood from left ventricle of heart to body tissues Oxygen and nutrients move into tissue cells Waste produced moves out of tissue cells, into blood Tracing Blood Flow Through Pulmonary and Systemic Pathways 1. Oxygen-poor blood returns to heart from body. 2. Oxygen-poor blood enters pulmonary pathway by flowing through vena cava (either superior or inferior) in the right atrium 3. Atria contracts, blood is pumped into right ventricle 4. Ventricle contracts and pumps blood out into pulmonary trunk (divides into left and right pulmonary arteries) 5. Pulmonary arteries lead to capillaries in left and right lungs, where gas exchange occurs 6. Blood picks up oxygen from alveoli in lungs and gives up CO2 7. Oxygen-rich blood continues through capillaries of lungs and into left and right pulmonary veins 8. Blood enters left atrium of heart 9. Blood enters systemic pathway 10. Atria contracts, left atrium pumps blood into left ventricle 11. Blood goes into aorta 12. Aorta divides into several large arteries that supply blood to body tissues Coronary Pathway Provide blood to muscle tissue of heart Cardiovascular Disorders and Treatments If diet contains too much fat, it can build up in the arteries Arteriosclerosis: Describes conditions in which walls of arteries thicken and lose elasticity, thus becoming hard Cardiovascular Disorders and Treatments Atherosclerosis: Condition where there is a buildup of plaque (fatty deposits, calcium, fibrous tissue) on inside of artery walls ○ Artery narrows due to buildup and decreases blood flow - therefore, increasing pressure ○ Artery can become completely blocked ○ Can lead to angina (chest pain), blood clots, shortness of breath, heart attack/failure ○ Aspirin can prevent/reduce clots ○ Angioplasty (surgical treatment): Procedure where surgeon inserts tube into clogged artery Once tube reaches site of clogged artery, tiny balloon is inflated, forcing the artery open ○ Stent (permanent metal tube): Can be placed in artery, holds vessel open Cardiovascular Disorders and Treatments Angioplasty Cardiovascular Disorders and Treatments Coronary bypass surgery: Grafted veins are used to provide route through which blood may travel around blocked vessels