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CHAPTER 23 Circulation Artery and vein, cross-section •Blood smear It transports O2 and nutrients to cells It takes away CO2 and other wastes Circulatory system made up of 3 parts organ heart tissues & cells blood vessels arteries veins capillaries blood red blood cells plasma The circulatory system associates intimately with all body tissues Capillaries are microscopic blood vessels They form an intricate network among the tissue cells Capillary Red blood cell The circulatory system associates intimately with all body tissues II No substance has to diffuse far to enter or leave a cell Capillary INTERSTITIAL FLUID Tissue cell Diffusion of molecules The cardiovascular system has two circuits The pulmonary circuit conveys blood between the heart and gas-exchange tissues The systemic circuit carries blood between the heart and the rest of the body Circulation of Blood Circulatio to lungs 2 part system Circulation to lungs(pulmonary) blood gets O2 from lungs drops off CO2 to lungs brings O2-rich blood from lungs to heart lungs heart Circulation to body(systemic) pumps O2-rich blood to body picks up nutrients from digestive system collects CO2 & cell wastes body Circulatio to body The human heart 4-Chambered heart atria (atrium) thin wall collection chamber receive blood left atrium ventricles thick wall pump pump blood out right atrium right ventricle left ventricle Lub-dub, lub-dub 4 valves in the heart flaps of connective tissue prevent backflow Heart sounds closing of valves “Lub” force blood against closed AV valves SL AV AV “Dub” force of blood against semilunar valves Heart murmur leaking valve causes hissing sound blood squirts backward through valve Blood’s path through the heart 1. vena cavae 2. right atrium 3. valve 4. right ventricle 5. valve 6. pulmonary artery (to lungs) 7. pulmonary veins 8. left atrium 9. valve 10. left ventricle 11. valve 12. aorta largest blood vessel in the body. Blood vessels arteries veins artery venules arterioles arterioles capillaries venules veins Arteries: Built for their job Arteries blood flows away from heart thicker walls provide strength for high pressure pumping of blood elastic & stretchable maintains blood pressure even when heart relaxes Major arteries aortacarotid = to head to brain & left arm to right arm pulmonary artery coronary arteries to body pulmonar y artery = to lungs Veins: Built for their job Veins Blood flows toward heart blood returns back to heart Open valve thinner-walled blood travels back to heart at low speed & pressure why low pressure? far from heart blood flows because muscles contract when we move squeeze blood through veins valves in large veins Closed valve in larger veins one-way valves allow blood to flow only toward heart Major Veins superior vena cava = from upper body pulmonary vein = from lung pulmonary vein = from lung inferior vena cava = from lower body Structure-function relationship Capillaries very thin walls allows diffusion of materials across capillary waste body cell O2, CO2, H2O, food, waste CO2 O2 food The heart contracts and relaxes rhythmically Diastole Blood flows from the veins into the heart chambers Systole The atria briefly contract and fill the ventricles with blood Then the ventricles contract and propel blood out The pacemaker sets the tempo of the heartbeat The SA node (pacemaker) generates electrical signals that trigger the contraction of the atria The AV node then relays these signals to the ventricles heart pumping controlled by electrical impulses signal also transmitted to skin = EKG electrocardiogram Connection: What is a heart attack? A heart attack is damage that occurs when a coronary feeding the heart is blocked Right coronary artery Aorta Left coronary artery Blockage Dead muscle tissue Cardiovascular diseases are the leading cause of death in the United States Blood vessel blockage is usually due to blood clots Atherosclerosis: Growths called plaques develop in the inner wall of the arteries, narrowing their bore In some cases, plaques also become hardened by calcium deposits, leading to arteriosclerosis, commonly known as hardening of the arteries Connective tissue Smooth Epithelium muscle Plaque Women & Heart Disease Death rates for heart disease per 100,000 women, 2002 Risk factors Smoking Lack of exercise High fat diet Overweight Heart disease is 3rd leading cause of death among women aged 25–44 years & 2nd leading cause of death among women aged 45–64 years. Blood exerts pressure on vessel walls Blood pressure depends on cardiac output resistance of vessels Pressure is highest in the arteries It drops to zero by the time the blood reaches the veins Systolic pressure Diastolic pressure Relative sizes and numbers of blood vessels Three factors keep blood moving back to the heart muscle contractions breathing one-way valves Connection: Measuring blood pressure can reveal cardiovascular problems Blood pressure is measured as systolic and diastolic pressures Hypertension is persistent systolic pressure higher than 140 mm Hg and/or diastolic pressure higher than 90 mm Hg It is a serious cardiovascular problem STRUCTURE AND FUNCTION OF BLOOD Blood consists of cells suspended in plasma Plasma is an aqueous solution of various substances Blood Cell production ribs, vertebrae, breastbone & pelvis Stem cells “parent” cells in bone marrow differentiate into many different types of cells white blood cells white blood cells red blood cells Blood & blood cells Blood is a tissue of fluid & cells plasma liquid part of blood dissolved salts, sugars, proteins, and more cells red blood cells (RBC) transport O2 in hemoglobin white blood cells (WBC) defense & immunity platelets blood clotting Red blood cells transport oxygen Small round cells produced in bone marrow 5 liters of blood in body 5-6 million RBC in drop of human blood last 3-4 months (120 days) filtered out by liver ~3 million RBC destroyed each second Hemoglobin Protein which carries O2 250,000 hemoglobins in 1 red blood cell O2 O2 O2 O2 White blood cells help defend the body White blood cells (leukocytes) function both inside and outside the circulatory system They fight infections and cancer Blood clots plug leaks when blood vessels are injured When a blood vessel is damaged, platelets respond They help trigger the formation of an insoluble fibrin clot that plugs the leak Connection: Stem cells offer a potential cure for leukemia and other blood cell diseases All blood cells develop from stem cells in bone marrow Such cells may prove valuable for treating certain blood disorders Have a heart? 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