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THE CARDIOVASCULAR SYSTEM VITAL FUNCTIONS • • • • pumps 7000 liters of blood / day beats ~2.5 billion times to carry O2 from the lungs to the body’s cells to carry nutrients from the digestive system to the cells • to remove cellular waste • to form clots / to coagulate (an anticoagulant prevents clotting) YOUR BLOOD: FLUID TRANSPORT • blood is a tissue made of fluid, cells, & fragments of cells – fluid = plasma, 55% of the total volume of blood – cells = red & white blood cells suspended in plasma • usually 45% of the total volume of blood • this percentage is called the hematocrit (HCT) – fragments = platelets suspended in plasma YOUR BLOOD: FLUID TRANSPORT • red blood cells (RBC’s): erythrocytes – round, disk-shaped cells – make up 44% of the total volume of blood – produced in the red bone marrow of the ribs, humerus, femur, sternum, and other long bones red blood cells (RBC’s): Erythrocytes – only have a nucleus in the early stages of development – active about 120 days, then broken down in the spleen & liver by macrophages via phagocytosis – contain hemoglobin, an iron-rich protein molecule that binds to O2 – oxygenated RBC’s carry oxygen from the lungs to the body’s cells Anemia: = too few RBC’s or too little hemoglobin. Person is pale & lacks energy. Caused by low iron intake. carbon dioxide in the blood: – 70% of the CO2 combines with water in plasma to form bicarbonate (affects the pH of blood) – 30% is attached to hemoglobin or dissolved in plasma white blood cells (WBC’s): leukocytes: – infection fighters – play a major role in protecting you from foreign substances, and from invading bacteria – make up 1% of total blood volume – they are larger than RBC’s & they have a nucleus blood clotting: – platelets help blood to clot by linking together a sticky network of protein fibers called fibrin – this forms a web over the wound to catch escaping RBC’s – platelets are produced in bone marrow & last only 1 week ABO BLOOD GROUPS • blood surface antigens determine blood group – antigen = substances that stimulate an immune response – antigens are on the surface of certain RBC’s – 2 types of antigens: A&B – blood plasma contains antibodies that are shaped to correspond with the different blood surface antigens – the antibodies react with the matching antigen if they are brought together, resulting in clumped blood – you don’t have antibodies for your own antigen type – type A blood has A antigens and anti-B antibodies – type B blood has B antigens and anti-A antibodies Rh factor = Rhesus factor: – another antigen which may be present (Rh+) or absent (Rh-) – Rh factor is an inherited characteristic – only 15% of the U.S. population is Rh- – may complicate pregnancies • an Rh- mother that is pregnant with a Rh+ baby will make anti-Rh+ antibodies when their blood mixes at birth • if she gets pregnant again with another Rh+ baby, her anti-Rh+ antibodies will destroy RBC’s in the fetus • prevention: mom is treated with a substance to prevent the production of antibodies in her blood at 28 weeks & again shortly after the birth of the first baby YOUR BLOOD VESSELS: PATHWAYS OF CIRCULATION • 3 main types: arteries, veins, capillaries + venules & arterioles • 62,000 miles of blood vessels in your body! arteries: – large, thick walled, muscular, elastic blood vessels – carry blood away from the heart under great pressure – main arteries divide into smaller arteries that divide into arterioles which eventually branch into capillaries capillaries: – microscopic blood vessels only 1 cell thick – enables nutrients & gases to diffuse easily between blood cells & surrounding tissue cells – form a dense network that reaches virtually every cell in the body – join to form venules as blood leaves tissues veins: – venules merge to form veins – carry blood from the tissues back to the heart – less pressure than the arteries – blood travels against gravity in some veins, so they are equipped with valves to prevent blood flowing backward YOUR HEART: THE VITAL PUMP • the heart – a large organ made of cardiac muscle cells rich in mitochondria – main function = to keep blood moving constantly thru the body • Myocardium = thick layer of muscle in the walls of the heart • Pericardium = serous membrane that encloses the heart all mammalian hearts have 4 chambers: • 2 upper chambers = L & R atria • 2 lower chambers = L & R ventricles • the atrial walls are thinner & less muscular than the ventricles because they perform less work • the L ventricle works harder than the R, so it’s bigger making the heart lopsided • a solid septum separates the whole R side from the L, so blood never mixes Valves of the heart: - the tricuspid valve sits between the R atrium & the R ventricle & it permits blood to flow thru while preventing backflow – the bicuspid (mitral) valve sits between the L atrium & the L ventricle, & does the same job as the tricuspid – the bicuspid & tricuspid valves are called atrioventricular – the pulmonary & aortic valves are called semilunar because their cusps are shaped like half moons – the aortic valve sits at the entrance to the aorta & prevents backflow into the L ventricle – the pulmonary valve sits at the entrance to the pulmonary trunk & prevents backflow into the R ventricle blood’s path through the heart: – blood enters the heart thru the atria & leaves thru the ventricles – both atria fill up at the same time – the R atrium receives O2 poor - CO2 rich blood from the head & body via 2 large veins, the vena cava blood’s path through the heart: – the L atrium receives O2 rich blood from the lungs via 4 pulmonary veins (the only veins to carry oxygen-rich blood) – after the atria fill with blood, they contract & push it into the ventricles – after the 2 ventricles are full, they contract simultaneously – the R ventricle pushes O2 poor blood out of the heart & towards the lungs thru the pulmonary arteries (the only arteries to carry oxygen-poor blood) – the L ventricle pushes O2 rich blood out of the heart thru the aorta (the largest blood vessel in the body) to the arteries PATH OF BLOOD: • • • • • • • Vena cava (superior / inferior) Right atrium Tricuspid valve Right ventricle Pulmonary semi-lunar valve Pulmonary arteries Capillaries of lungs * * * * * * * Pulmonary veins Left atrium bicuspid valve left ventricle aortic semi-lunar aorta all body cells the heart acts as 2 separate pumps, following 2 pathways : – pulmonary circulation = the right side of the heart pumps blood from the heart to the lungs – systemic circulation = the left side of the heart pumps blood from the heart to the rest of the body heartbeat regulation – each heartbeat causes a surge of blood to flow from the L ventricle into the aorta & then into the arteries = pulse – best felt in the arm’s radial artery or the neck’s carotid artery heartbeat regulation – heart rate is set by the pacemaker in the top of the R atrium • sends an impulse to the atria • triggers another impulse to contract the ventricles – electrocardiograph = a machine that measures & records these electrical signals heartbeat regulation – electrocardiogram = the reading produced by this machine – the ECG is an important tool used to diagnose abnormal heart rhythms & patterns blood pressure = the force that the blood exerts on the blood vessels – it rises & falls as the heart contracts & relaxes – it rises sharply when the ventricles contract = systolic pressure / systole – it drops dramatically as the ventricles relax = diastolic pressure / diastole blood pressure • hypertension = high blood pressure = persistently elevated arterial pressure. Can be caused by kidney disease, high sodium intake, obesity, psychological stress, or arteriosclerosis (hardening of the arteries) control of the heart – the medulla oblongata regulates the rate of the pacemaker – sensory cells in the arteries become stretched when the heart beats too fast which sends a signal to the medulla oblongata control of the heart • if the heart slows too much, blood pressure drops which signals the medulla oblongata to speed up the pacemaker RELEVANT VOCABULARY: • Pericarditis = inflammation of the pericardium • Pulmonary circulation = a circuit transporting blood between the heart & lungs • Systemic circulation = a circuit transporting blood between the heart & body tissues • Myocardial infarction = a heart attack • Tachycardia = rapid heart rate (100+ beats / min) • Bradycardia = abnormally slow heart rate (<60) • Heart murmur = abnormal or unusual heart sounds, can be due to valve incompetence • Cardiac output = the volume of blood pumped out by each side of the heart in 1 min • Stroke volume = the volume of blood pumped out a ventricle with each heartbeat • Congestive heart failure = a progressive condition occurring when the pumping efficiency of the heart is depressed so that circulation is inadequate to meet tissue needs • Pulmonary edema = blood vessels leak fluid into the air sacs and tissues of the lungs • Atherosclerosis = fatty deposits / plaque clogs the blood vessels, leads to arteriosclerosis (hardening of the arteries) • Leukemia = cancer of the white blood cells