Mais conteúdo relacionado


The cardiovascular system.pptx

  1. The Cardiovascular System • Presented by : Jagruti Marathe
  2. The Cardiovascular System  A closed system of the heart and blood vessels  The heart pumps blood  Blood vessels allow blood to circulate to all parts of the body  The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products
  3. The Heart and Homeostasis The heart contributes to homeostasis by pumping blood through blood vessels to the tissues of the body to deliver oxygen and nutrients and remove wastes.
  4. • Blood to reach body cells and exchange materials with them, it must be pumped continuously by the heart through the body’s blood vessels. • The heart beats about 100,000 times every day, which adds up to about 35 million beats in a year, and approximately 2.5 billion times in an average lifetime. • The left side of the heart pumps blood through an estimated 100,000 km (60,000 mi) of blood vessels, which is equivalent to traveling around the earth’s equator about three times. • The right side of the heart pumps blood through the lungs, enabling blood to pick up oxygen and unload carbon dioxide.
  5. Location of the Heart • The scientific study of the normal heart and the diseases associated with it is known as cardiology
  6. Location of the Heart  Location Thorax between the lungs Pointed apex directed toward left hip  About the size of your fist Less than 1 lb.
  7. • The heart is relatively small, roughly the same size (but not the same shape) as your closed fist. • It is about 12 cm (5 in.) long, 9 cm (3.5 in.) wide at its broadest point, and 6 cm (2.5 in.) • thick, with an average mass of 250 g (8 oz) in adult females and 300 g(10 oz) in adult males. • The heart rests on the diaphragm, near the midline of the thoracic cavity. • Recall that the midline is an imaginary vertical line that divides the body into unequal left and right sides. • The heart lies in the mediastinum (mē′-dē-as-TĪ-num), an anatomical region that extends from the sternum to the vertebral column, from the first rib to the diaphragm, and between the lungs.
  8. • The pointed apex is formed by the tip of the left ventricle (a lower chamber of the heart) and rests on the diaphragm. • It is directed anteriorly, inferiorly, and to the left . • The base of the heart is opposite the apex and is its posterior aspect. • It is formed by the atria (upper chambers) of the heart, mostly the left atrium .
  9. The Heart Position of the heart and associated structures in the mediastinum. The positions of the heart and associated structures in the mediastinum are indicated by dashed outlines. The heart is located in the mediastinum, with two-thirds of its mass to the left of the midline.
  10. • the heart has several distinct surfaces. • The anterior surface is deep to the sternum and ribs. • The inferior surface is the part of the heart between the apex and right surface and rests mostly on the diaphragm (Figure ). • The right surface faces the right lung and extends from the inferior surface to the base. • The left surface faces the left lung and extends from the base to the apex.
  11. The Heart: Coverings  Pericardium – a double serous membrane Visceral pericardium Next to heart Parietal pericardium Outside layer  Serous fluid fills the space between the layers of pericardium
  12. The Heart: Heart Wall  Three layers Epicardium  Outside layer  This layer is the parietal pericardium  Connective tissue layer Myocardium  Middle layer  Mostly cardiac muscle Endocardium  Inner layer  Endothelium
  13. External Heart Anatomy Figure 11.2a
  14. The Heart: Chambers  Right and left side act as separate pumps  Four chambers Atria  Receiving chambers  Right atrium  Left atrium Ventricles  Discharging chambers  Right ventricle  Left ventricle
  15. The Heart: Valves  Allow blood to flow in only one direction  Four valves Atrioventricular valves – between atria and ventricles  Bicuspid valve (left)  Tricuspid valve (right) Semilunar valves between ventricle and artery  Pulmonary semilunar valve  Aortic semilunar valve
  16. The Heart: Valves  Valves open as blood is pumped through  Held in place by chordae tendineae (“heart strings”)  Close to prevent backflow
  17. Operation of the Atrioventricular Valves • Because they are located between an atrium and a ventricle, the tricuspid and bicuspid valves are termed atrioventricular (AV) valves. • When an AV valve is open, the rounded ends of the cusps project into the ventricle. • When the ventricles are relaxed, the papillary muscles are relaxed, the chordae tendineae are slack, and blood moves from a higher pressure in the atria to a lower pressure in the ventricles through open AV valves . • When the ventricles contract, the pressure of the blood drives the cusps upward until their edges meet and close the opening . At the same time, the papillary muscles contract, which pulls on and tightens the chordae tendineae
  18. • This prevents the valve cusps from everting (opening into the atria) in response to the high ventricular pressure. • If the AV valves or chordae tendineae are damaged, blood may regurgitate (flow back) into the atria when the ventricles contract.
  19. Operation of the Semilunar Valves • The aortic and pulmonary valves are known as the semilunar (SL) valves because they are made up of three crescent moon–shaped cusps . • Each cusp attaches to the arterial wall by its convex outer margin. • The SL valves allow ejection of blood from the heart into arteries but prevent backflow of blood into the ventricles. • The free borders of the cusps project into the lumen of the artery. • When the ventricles contract, pressure builds up within the chambers.
  20. • The semilunar valves open when pressure in the ventricles exceeds the pressure in the arteries, permitting ejection of blood from the ventricles into the pulmonary trunk and aorta • As the ventricles relax, blood starts to flow back toward the heart. • This backflowing blood fills the valve cusps, which causes the free edges of the semilunar valves to contact each other tightly and close the opening between the ventricle and artery . • Surprisingly perhaps, there are no valves guarding the junctions between the venae cavae and the right atrium or the pulmonary veins and the left atrium. • As the atria contract, a small amount of blood does flow backward from the atria into these vessels. • However backflow is minimized by a different mechanism; as the atrial muscle contracts, it compresses and nearly collapses the weak walls of the venous entry points.
  21. Operation of Heart Valves Figure 11.4
  22. Blood Circulation Figure 11.3
  23. Systemic and Pulmonary Circulation
  24. Systemic and Pulmonary Circulation  In postnatal (aft er birth) circulation, the heart pumps blood into two closed circuits with each beat— systemic circulation and pulmonary circulation (pulmon- = lung)  The two circuits are arranged in series: The output of one becomes the input of the other. The left side of the heart is the pump for systemic circulation; it receives bright red oxygenated (oxygen-rich) blood from the lungs.
  25. Systemic and Pulmonary Circulation • The left side of the heart is the pump for systemic circulation; it receives bright red oxygenated (oxygen- rich) blood from the lungs. • The left ventricle ejects blood into the aorta . • From the aorta, the blood divides into separate streams, entering progressively smaller systemic arteries that carry it to all organs throughout the body—except for the air sacs (alveoli) of the lungs, which are supplied by the pulmonary circulation. • In systemic tissues, arteries give rise to smaller-diameter arterioles, which finally lead into extensive beds of systemic capillaries.
  26. Systemic and Pulmonary Circulation • Exchange of nutrients and gases occurs across the thin capillary walls. Blood unloads O2 (oxygen) and picks up CO2 (carbon dioxide). • In most cases, blood flows through only one capillary and then enters a systemic venule. Venules carry deoxygenated (oxygen-poor) blood away from tissues and merge to form larger systemic veins. • Ultimately the blood flows back to the right atrium.
  27. Systemic and Pulmonary Circulation • The right side of the heart is the pump for pulmonary circulation; it receives all of the dark-red deoxygenated blood returning from the systemic circulation. Blood ejected from the right ventricle flows into the pulmonary trunk, which branches into pulmonary arteries that carry blood to the right and left lungs. • In pulmonary capillaries, blood unloads CO2, which is exhaled, and picks up O2 from inhaled air. • The freshly oxygenated blood then flows into pulmonary veins and returns to the left atrium.
  28. Systemic and Pulmonary Circulation • walls of the two ventricles with oxygenated blood. The marginal branch beyond the coronary sulcus runs along the right margin of the heart and transports oxygenated blood to the wall of the right ventricle. • parts of the body receive blood from branches of more than one artery, and where two or more arteries supply the same region, they usually connect. These connections, called anastomoses (a- nas′-toˉ-MŌ-sēs), provide alternate routes, called collateral circulation, for blood to reach a particular organ or tissue. • .
  29. Systemic and Pulmonary Circulation • The myocardium contains many anastomoses that connect branches of a given coronary artery or extend between branches of different coronary arteries. • They provide detours for arterial blood if a main route becomes obstructed. This is important because the heart muscle may receive sufficient oxygen even if one of its coronary arteries is partially blocked.
  30. Systemic and Pulmonary Circulation • The right side of the heart is the pump for pulmonary circulation; it receives all of the dark-red deoxygenated blood returning from the systemic circulation. Blood ejected from the right ventricle flows into the pulmonary trunk, which branches into pulmonary arteries that carry blood to the right and left lungs. • In pulmonary capillaries, blood unloads CO2, which is exhaled, and picks up O2 from inhaled air. • The freshly oxygenated blood then flows into pulmonary veins and returns to the left atrium.
  31. Valve Pathology • Incompetent valve = backflow and repump • Stenosis = stiff= heart workload increased • May be replaced • Lup Dub Heart Sound
  32. The Heart: Associated Great Vessels  Aorta Leaves left ventricle  Pulmonary arteries Leave right ventricle  Vena cava Enters right atrium  Pulmonary veins (four) Enter left atrium
  33. Coronary Circulation  Blood in the heart chambers does not nourish the myocardium  The heart has its own nourishing circulatory system Coronary arteries Cardiac veins Blood empties into the right atrium via the coronary sinus
  34. • Nutrients are not able to diff use quickly enough from blood in the chambers of the heart to supply all layers of cells that make up the heart wall. • For this reason, the myocardium has its own network • of blood vessels, the coronary circulation or cardiac circulation (coron- = crown). • The coronary arteries branch from the ascending aorta and encircle the heart like a crown encircles the head. • While the heart is contracting, little blood flows in the • coronary arteries because they are squeezed shut. • When the heart relaxes, however, the high pressure of blood in the aorta propels blood through the coronary arteries, into capillaries, and then into coronary veins .
  35. The principal tributaries carrying blood into the coronary sinus are the following: • Great cardiac vein in the anterior interventricular sulcus, which drains the areas of the heart supplied by the left coronary artery (left and right ventricles and left atrium) • Middle cardiac vein in the posterior interventricular sulcus, which drains the areas supplied by the posterior interventricular branch of the right coronary artery (left and right ventricles) • Small cardiac vein in the coronary sulcus, which drains the right atrium and right ventricle • Anterior cardiac veins, which drain the right ventricle and open directly into the right atrium
  36. The coronary circulation. The views of the heart from the anterior aspect in (a) and(b) are drawn as if the heart were transparent to reveal blood vessels on the posterior aspect. The left and right coronary arteries deliver blood to the heart; the coronary veins drain blood from
  37. Cardiac Pathology • Rapid heart beat • = Inadequate blood • = Angina Pectoris
  38. The Heart: Conduction System  Intrinsic conduction system (nodal system) Heart muscle cells contract, without nerve impulses, in a regular, continuous way
  39. The Heart: Conduction System Special tissue sets the pace Sinoatrial node (right atrium)  Pacemaker Atrioventricular node (junction of r&l atria and ventricles) Atrioventricular bundle (Bundle of His) Bundle branches (right and left) Purkinje fibers
  40. The Heart: Conduction System Cardiac action potentials propagate through the conduction system in the following sequence : • Cardiac excitation normally begins in the sinoatrial (SA) node, located in the right atrial wall just inferior and lateral to the opening of the superior vena cava. SA node cells do not have a stable resting potential. Rather, they repeatedly depolarize to threshold spontaneously. The spontaneous depolarization is a pacemaker potential. When the pacemaker potential reaches threshold, it triggers an action potential . Each action potential from the SA node propagates throughout both atria via gap junctions in the intercalated discs of atrial muscle fibers. Following the action potential, the two atria contract at the same time.
  41. The Heart: Conduction System • By conducting along atrial muscle fibers, the action potential reaches the atrioventricular (AV) node, located in the interatrial septum, just anterior to the opening of the coronary sinus. At the AV node, the action potential slows considerably as a result of various differences in cell structure in the AV node. This delay provides time for the atria to empty their blood into the ventricles. • From the AV node, the action potential enters the atrioventricular (AV) bundle (also known as the bundle of His, pronounced HIZ). This bundle is the only site where action potentials can conduct from the atria to the ventricles. (Elsewhere, the fibrous skeleton
  42. The Heart: Conduction System • Aft er propagating through the AV bundle, the action potential enters both the right and left bundle branches. The bundle branches extend through the interventricular septum toward the apex of the heart. • Finally, the large-diameter Purkinje fibers (pur-KIN-jē) rapidly conduct the action potential beginning at the apex of the heart upward to the remainder of the ventricular myocardium. Then the ventricles contract, pushing the blood upward toward the semilunar valves.
  43. Heart Contractions
  44. Heart Contractions
  45. • Three formations – P wave: impulse across atria – QRS complex: spread of impulse down septum, around ventricles in Purkinje fibers – T wave: end of electrical activity in ventricles Electrocardiograms (EKG/ECG)
  46. Electrocardiograms (EKG/ECG) (cont.) Figure 8.15B, C
  47. Electrocardiograms (EKG/ECG) (cont.)
  48. Pathology of the Heart • Damage to AV node = release of ventricles from control = slower heart beat • Slower heart beat can lead to fibrillation • Fibrillation = lack of blood flow to the heart • Tachycardia = more than 100 beats/min • Bradychardia = less than 60 beats/min
  49. The Heart: Cardiac Cycle  Atria contract simultaneously  Atria relax, then ventricles contract  Systole = contraction  Diastole = relaxation
  50. The Heart: Cardiac Cycle  Atrial Systole = contraction(Systole During atrial systole, which lasts about 0.1 sec , the atria are contracting. At the same time, the ventricles are relaxed.) • Ventricular Systole = relaxation(During ventricular systole, which lasts about 0.3 sec, the ventricles are contracting. At the same time, the atria are relaxed in atrial diastole.)
  51. The Heart: Cardiac Cycle  Atrial Systole 1Depolarization of the SA node causes atrial depolarization, marked by the P wave in the ECG. 2 Atrial depolarization causes atrial systole. As the atria contract, they exert pressure on the blood within, which forces blood through the open AV valves into the ventricles. 3 Atrial systole contributes a final 25 mL of blood to the volume already in each ventricle (about 105 mL). The end of atrial systole is also the end of ventricular diastole (relaxation). Thus, each ventricle contains about 130 mL at the end of its relaxation period (diastole). This blood volume is called the end-diastolic volume (EDV). 4 The QRS complex in the ECG marks the onset of ventricular depolarization.
  52. The Heart: Cardiac Cycle  Ventricular Systole 5 Ventricular depolarization causes ventricular systole. As ventricular systole begins, pressure rises inside the ventricles and pushes blood up against the atrioventricular (AV) valves, forcing them shut. For about 0.05 seconds, both the SL (semilunar) and AV valves are closed. This is the period of isovolumetric contraction(ī-soˉ-VOL-ū-met′-rik; iso- = same). During this interval, cardiac muscle fibers are contracting and exerting force but are not yet shortening. Thus, the muscle contraction is isometric (same length). Moreover, because all four valves are closed, ventricular volume remains the same (isovolumic). 6 Continued contraction of the ventricles causes pressure inside the chambers to rise sharply. When left ventricular pressure surpasses aortic pressure at amillimeters of mercury (mmHg) and right ventricular pressure rises above the pressure in the pulmonary trunk (about 20 mmHg), both SL valves openbout 80. At this point, ejection of blood from the heart begins. The period when the SL valves are open is ventricular ejection and lasts for about 0.25 sec. The pressure in the left ventricle continues to rise
  53. The Heart: Cardiac Cycle  Ventricular Systole to about 120 mmHg, and the pressure in the right ventricle climbs to about 25–30 mmHg. 7 The left ventricle ejects about 70 mL of blood into the aorta and the right ventricle ejects the same volume of blood into the pulmonary trunk. The volume remaining in each ventricle at the end of systole, about 60 mL, is the end-systolic volume (ESV). Stroke volume, the volume ejected per beat from each ventricle, equals end-diastolic volume minus end-systolic volume: SV = EDV − ESV. At rest, the stroke volume is about 130 mL − 60 mL = 70 mL (a little more than 2 oz). 8 The T wave in the ECG marks the onset of ventricular repolarization.
  54. The Heart: Cardiac Cycle  Relaxation Period • During the relaxation period, which lasts about 0.4 sec, the atria and the ventricles are both relaxed. As the heart beats faster and faster, the relaxation period becomes shorter and shorter, whereas the durations of atrial systole and ventricular systole shorten only slightly.
  55. The Heart: Cardiac Cycle • Ventricular repolarization causes ventricular diastole. As the ventricles relax, pressure within the chambers falls, and blood in the aorta and pulmonary trunk begins to flow backward toward the regions of lower pressure in the ventricles. Backflowing blood catches in the valve cusps and closes the SL valves. The aortic valve closes at a pressure of about 100 mmHg. Rebound of blood off the closed cusps of the aortic valve produces the dicrotic wave on the aortic pressure curve. Aft er the SL valves close, there is a brief interval when ventricular blood volume does not change because all four valves are closed. This is the period of isovolumetric relaxation. 10 As the ventricles continue to relax, the pressure falls quickly. When ventricular pressure drops below atrial pressure, the AV valves open, and ventricular filling begins. The major part of ventricular filling occurs just aft er the AV valves open. Blood that has been flowing into and building up in the atria during ventricular systole then rushes rapidly into the ventricles. At the end of the relaxation period, the ventricles are about three-quarters full. The P wave appears in the ECG, signaling the start of another cardiac cycle.
  56. Cardiac cycle. (a) ECG. (b) Changes in left atrial pressure (green line), left ventricular pressure (blue line), and aortic pressure (red line) as they relate to the opening and closing of heart valves. (c) Heart sounds. (d) Changes in left ventricular volume. (e) Phases of the cardiac cycle. A cardiac cycle is composed of all of the events associated with one heartbeat
  57. Filling of Heart Chambers – the Cardiac Cycle Slide Figure 11.6
  58. The Heart: Cardiac Output  Cardiac output (CO) Amount of blood pumped by each side of the heart in one minute CO = (heart rate [HR]) x (stroke volume [SV])  Stroke volume Volume of blood pumped by each ventricle in one contraction
  59. Cardiac output, cont. • CO = HR x SV • 5250 ml/min = 75 beats/min x 70 mls/beat • Norm = 5000 ml/min • Entire blood supply passes through body once per minute. • CO varies with demands of the body.
  60. Cardiac Output Regulation Figure 11.7
  61. The Heart: Regulation of Heart Rate  Stroke volume usually remains relatively constant Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction  Changing heart rate is the most common way to change cardiac output
  62. Regulation of Heart Rate  Increased heart rate Sympathetic nervous system Crisis Low blood pressure Hormones Epinephrine Thyroxine Exercise Decreased blood volume
  63. The Heart: Regulation of Heart Rate  Decreased heart rate Parasympathetic nervous system High blood pressure or blood volume Dereased venous return In Congestive Heart Failure the heart is worn out and pumps weakly. Digitalis works to provide a slow, steady, but stronger beat.
  64. Congestive Heart Failure (CHF) •Decline in pumping efficiency of heart •Inadequate circulation •Progressive, also coronary atherosclerosis, high blood pressure and history of multiple Myocardial Infarctions •Left side fails = pulmonary congestion and suffocation •Right side fails = peripheral congestion and edema
  65. Blood Vessels: The Vascular System  Taking blood to the tissues and back Arteries Arterioles Capillaries Venules Veins
  66. The Vascular System Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.8b
  67. Blood Vessels: Anatomy  Three layers (tunics) Tunic intima Endothelium Tunic media Smooth muscle Controlled by sympathetic nervous system Tunic externa Mostly fibrous connective tissue
  68. Differences Between Blood Vessel Types  Walls of arteries are the thickest  Lumens of veins are larger  Skeletal muscle “milks” blood in veins toward the heart  Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue
  69. Movement of Blood Through Vessels  Most arterial blood is pumped by the heart  Veins use the milking action of muscles to help move blood Figure 11.9
  70. Capillary Beds  Capillary beds consist of two types of vessels Vascular shunt – directly connects an arteriole to a venule Figure 11.10
  71. Capillary Beds True capillaries – exchange vessels Oxygen and nutrients cross to cells Carbon dioxide and metabolic waste products cross into blood Figure 11.10
  72. Diffusion at Capillary Beds Figure 11.20
  73. Vital Signs • Arterial pulse • Blood pressure • Repiratory Rate • Body Temperature • All indicate the efficiency of the system
  74. Pulse  Pulse – pressure wave of blood  Monitored at “pressure points” where pulse is easily palpated Figure 11.16
  75. Blood Pressure  Measurements by health professionals are made on the pressure in large arteries Systolic – pressure at the peak of ventricular contraction Diastolic – pressure when ventricles relax  Pressure in blood vessels decreases as the distance away from the heart increases
  76. Measuring Arterial Blood Pressure Figure 11.18
  77. Blood Pressure: Effects of Factors  Neural factors Autonomic nervous system adjustments (sympathetic division)  Renal factors Regulation by altering blood volume Renin – hormonal control
  78. Blood Pressure: Effects of Factors  Temperature Heat has a vasodilation effect Cold has a vasoconstricting effect  Chemicals Various substances can cause increases or decreases  Diet
  79. Variations in Blood Pressure  Human normal range is variable Normal 140–110 mm Hg systolic 80–75 mm Hg diastolic Hypotension Low systolic (below 110 mm HG) Often associated with illness Hypertension High systolic (above 140 mm HG) Can be dangerous if it is chronic
  80. Thank-You Jagruti Marathe