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The Cardiovascular System. Structure of the heart Pericardium – encloses heart. Visceral pericardium – inner layer; parietal – outer layer. Wall of heart.

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Presentation on theme: "The Cardiovascular System. Structure of the heart Pericardium – encloses heart. Visceral pericardium – inner layer; parietal – outer layer. Wall of heart."— Presentation transcript:

1 The Cardiovascular System

2 Structure of the heart Pericardium – encloses heart. Visceral pericardium – inner layer; parietal – outer layer. Wall of heart – 3 layers: 1 Epicardium – protects heart (reduces friction) – visceral pericardium.

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4 2 Myocardium – cardiac muscle; thick middle layer. 3 Endocardium – contains blood vessels – inner lining of blood vessels.

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6 Heart divided into 4 chambers. 2 atria – upper chambers, thin- walled; receive blood returning to heart. 2 ventricles – lower chambers, thicker walled; pump blood into arteries.

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8 Septum divides atrium and ventricle on right from left side. R atrium receives blood from body from inferior vena cava and superior vena cava. R atrium separated from R ventricle by tricuspid valve.

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10 Developing fetus - hole between L and R atria. After birth - hole supposed to close. If hole does not close - hole in heart (atrial septal defect) Blood enters lungs - breathing problems.

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12 Chordae tendineae – attach cusps of tricuspid valve. Originate from papillary muscles on walls of ventricles. R ventricle pumps blood through pulmonary artery to lungs. Pulmonary valve leads into artery.

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14 * L atrium receives blood from lungs through pulmonary vein. L atrium and L ventricle separated by bicuspid (mitral) valve. L ventricle pumps through aorta to entire body. Aortic valve leads into aorta.

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16 Mitral valve prolapse – one or both cusps stretch and bulge into L atrium during contraction. Results in blood going back into L atrium.

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18 Blood flow Blood low in O 2, high in CO 2 enters R atrium. R atrium passes blood into R Ventricle. R ventricle contracts, blood flows into pulmonary artery (to lungs) Pulmonary vein brings blood high in O 2 back to L atrium.

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20 Blood passes to L ventricle. Pumped through aorta to body. 1 st 2 branches of aorta – R,L coronary arteries – supply blood to heart tissue. Cardiac veins – drain blood, join together to form coronary sinus – dump into R atrium.

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22 Cardiac cycle Heart sounds made from opening and closing of valves. 1 st sound made from recoil of blood against closed AV valves (“lub”) 2 nd sound made from recoil of blood against semilunar valves. (“dup”) Heart murmurs result of incomplete valve closure resulting in swishing noise.

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24 Sinoatrial node (SA node) – generates action potentials on its own (pacemaker). Impulse passes along fibers to mass of specialized tissue (atrioventricular node)

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26 From AV node, moves through bundle of His (AV bundle) Divide into L and R branches underneath endocardium. Give rise to Purkinje fibers. Causes ventricular walls to contract.

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28 ECG Electrocardiogram – recording of electrical changes in heart muscle. QRS complex – depolarization of ventricular fibers (ventricles contract) T wave – ventricular fibers repolarize.

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30 Heart rate – duration of cardiac cycle. Stroke volume – volume of blood ejected from ventricles during contraction. Cardiac output = heart rate X stroke volume.

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32 More cells stretched by incoming blood, more strongly heart walls contract to eject blood – Starling’s law of the heart. Cardiac output increases with increasing exercise and blood flow.

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34 Heart rate monitored in medulla oblongata of brain. Increase in blood pressure – stretch sensors send message to brain to slow heart rate down.

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36 Blood vessels Arteries – carry oxygenated blood away from heart. Branch into arterioles, then capillaries. Artery – 3-layered wall surrounding interior (lumen).

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38 1 Tunica intima – innermost layer. 2 Tunica media – thick smooth muscle layer (middle) 3 Tunica adventitia – outer layer; anchors artery to neighboring structures.

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40 Vasoconstriction – vessel decreases in diameter. Vasodilation – vessel increases in diameter. Pulmonary artery – carries deoxygenated blood away from heart (toward lungs)

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42 Capillaries – smallest vessels. Permit exchange of nutrients, removal of wastes at tissue level. Thin, permeable walls to allow diffusion to occur.

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44 Veins – carry deoxygenated blood back to heart. Capillaries join venules, join to form veins. Same 3 layers; tunica media not very thick.

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46 Blood pressure in veins not high, so veins need valves to prevent backflow. Blood must flow against gravity back to heart.

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48 Blood Pressure Blood pressure – force exerted by blood against walls of vessels. Systolic pressure – stretch of arteries to allow for blood flow pumped from heart. Diastolic pressure – relaxation.

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50 Pulse – expanding, recoiling of arterial walls. Represents # of heartbeats per minute.

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52 Factors affecting blood pressure 1 Cardiac output – increase in cardiac output increases blood pressure. 2 Peripheral resistance – friction + drag in vessels; increases blood pressure. Vasoconstriction increases b.p.

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54 3 Blood volume – decrease causes drop in b.p. Sympathetic nervous system – causes rise in b.p, heart rate. Parasympathetic – decrease.

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56 Hormones regulate b.p. Epinephrine, norephinephrine – rise, fall of b.p. Antidiuretic hormone – rise in b.p. Kidneys aid in regulation – drop in b.p. releases renin; renin causes formation of angiotensin.

57 Angiotensin – vasoconstriction. Stimulates release of aldosterone – increases b.p.

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59 Circulatory Pathways 1 Pulmonary circulation – pulmonary trunk carries blood from R ventricle. Divides into R and L pulmonary artery, into capillaries. O 2 picked up in lungs, brought back to heart via pulmonary veins.

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61 Arteries 2 Systemic – blood leaves L ventricle into ascending aorta. Branches into R, L coronary arteries (supply heart wall). Aorta curves to back (aortic arch) 3 branches – brachiocephalic, L common carotid, L subclavian.

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63 Aorta turns downward (descending aorta). Section above diaphragm – thoracic aorta; branch into intercostal arteries (supply thoracic wall). Below diaphragm – abdominal aorta.

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65 Branches into celiac artery (liver, spleen, stomach, pancreas), superior mesenteric artery (small intestine), suprarenal arteries (adrenal glands), renal arteries (kidneys), inferior mesenteric artery (large intestine). Divides into R, L iliac (to lower legs)

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67 Pelvis, lower limbs – common iliac divides into internal, external iliac. External iliac – becomes femoral. Forms deep femoral artery (flexor muscles of thigh), popliteal artery (knee), anterior, posterior tibial arteries.

68 Head, neck – from common carotid, subclavian. R common carotid arises from brachiocephalic. R, L common carotid branch into external, internal carotid.

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70 Shoulder, upper limbs – from subclavian. Axillary artery – near armpit. Continues down arm as brachial artery; divides into ulnar, radial arteries.

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72 Veins Head, face veins – blood drained into R, L external jugular. Merge with subclavian veins  internal jugular  brachiocephalic vein  superior vena cava.

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74 Upper limbs – ulnar, radial vein  brachial vein  axillary vein. Major superficial arm veins – basilic (forearm to middle of upper arm), cephalic (wrist to shoulder), median cubital vein (where blood is drawn).

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76 Inferior vena cava – longest vein in body – great saphenous vein, joins with femoral vein. Abdomen – hepatic portal system – blood from capillaries of digestive tract to liver only. Dumps blood into superior, inferior mesenteric veins.

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78 Diseases 1 Congestive heart failure – can’t pump blood to body. Bad circulation to body  increased pressure, fluid leaking in lungs. Caused by damage to cardiac muscle. Symptoms – shortness of breath, swelling in lower legs.

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80 2 Hypertension – increase in blood pressure. Due to narrowing of blood vessels (atherosclerosis) or hardening of vessels (arteriosclerosis)

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82 3 Endocarditis – infection of lining of heart due to bacterial infection. Can cause embolus (blood clot) 4 Aneurysm – sac formation in vessel or heart chamber; can produce tear in vessel (hemorrhage)

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