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Cardiovascular System
The cardiovascular system is responsible for transporting blood throughout the body, essential for delivering oxygen, nutrients, and removing waste. The heart, which functions as a double pump, consists of four chambers and valves that regulate blood flow, with its contractions controlled by the autonomic nervous system and intrinsic conduction system. Heart physiology involves rhythmic contractions and various factors that affect heart rate and output, including hormonal and physical influences.
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Cardiovascular System
- 1. The Cardiovascular System Preparedby Mr.Abhay Rajpoot HOD (Dep. of Medical Surgical) [email protected]
- 2. The Cardiovascular System Cardiovascularsystem: organ system that distributes blood to all parts of thebody Major function – transportation, using blood as thetransport vehicle
- 3. The Cardiovascular System This system carries oxygen, nutrients, cell wastes, hormones and other substances vital for body homeostasis to and formcells The force to move blood around the body is provided by the pumping heart and blood pressure
- 5. The Heart Thehuman heart heart length, width, and thickness are 12 cm, 8.5 cm, and 6 cm, respectively. In addition, the mean weight of the heart is 280-340 g in males and 230-280 g in females. It is enclosed within the inferior mediastinum, the medial cavity of the thorax, and flanked on each side by the lungs
- 6. The Heart Thepointed apex is directed toward the left hipand restsat about the fifth intercostal space The broad aspect, or base, points towardthe right shoulder and lies beneath the second rib
- 7. The Heart Theheart is enclosed by a double-walled sac called the pericardium The superficial loosely fitted part is called the fibrous pericardium Protects and anchors theheart
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- 9. The Heart Deepto the fibrous pericardium is the slippery, two-layer serouspericardium The parietal layer lines the interior of the fibrous pericardium
- 10. The Heart Theparietal layerattaches to the large arteries leaving the heart and then makes a U-turn and continues inferiorly overthe heart surfaceas thevisceral layer, or epicardium
- 11. The Heart Aslippery lubricating fluid is produced by the serous pericardial membranes which allows the heart to beat easily in a relative frictionless environment
- 12. The Heart Inflammationof the pericardium, pericarditis,often results in a decrease in the serous fluid The cause the pericardial layers to stick, forming painful adhesions that interfere with heartmovements
- 13. The Heart Theheartwallsarecomposed of three layers: 1. outerepicardium 2. myocardium 3. endocardium
- 14. The Heart Themyocardium consists of thick bundles of the cardiac muscle twisted into ring like arrangements This is the layer ofthe heart that actually contracts Reinforced by dense, fibrous connectivetissue (“heart skeleton”)
- 15. The Heart Theendocardium is a thin, glistening sheetof endothelium that lines the heartchambers Continuouswith the liningsof the blood vessels leaving and entering theheart
- 16. The Heart Theheart has four hollowchambers: 2 atria – receivingchambers 2 ventricles – fillingchambers
- 17. The Heart Bloodflows intothe atria under low pressure from the veins, andcontinues into theventricles
- 18. The Heart Theventricles are thick- walled discharging chambers They are the pumpsof the heart When they contract, blood is propelled out of the heart and into circulation The right ventricle forms most of the heart’s anterior surface The left ventricle forms theapex
- 20. The Heart Theseptum that divides the heart longitudinally is the interventricular septum or theinteratrial septum based on the chambers itseparates
- 21. The Heart Theheart functionsas a doublepump The right sideworksas the pulmonarycircuit pump Receives relatively oxygen-poor blood from the veins of the body through the large superior and inferior vena cava
- 22.
- 23. The Heart Theblood then pumps out through the pulmonary trunk which splits into the left and right pulmonary arteries The pulmonary arteries carry blood to thelungs, where oxygen is picked up and carbon dioxideis unloaded Oxygen-rich blood drains from the lungs and is returned tothe leftsideof the heart through the four pulmonaryveins
- 24. The Heart Thiscircuit is call pulmonarycirculation Itsonly function is tocarry blood to the lungs forgas exchange and then return it to the heart
- 26. The Heart Bloodreturned to the leftside of the heart is pumped out of the heart into the aorta The systemicarteries branch from theaorta tosupply the body tissues withblood Oxygen-poor blood circulates from the tissues back to the right atrium via the systemic veins, which empty their blood into either the superior or inferior vena cava
- 27. The Heart Thissecond circuit, from the left side of the heart through the body tissuesand back to the right side of the heart is called systemiccirculation Itsuppliesoxygen and nutrient-rich blood toall body organs Because the left ventricle is the systemic pump that pumps blood overa much longerpathway through the body, its walls are thicker than those of the right ventricle It is a more powerfulpump
- 29. The Heart The heartalso has four valves: 2 that separatethe atria from the ventricles 2 that separate the ventricles fromtheir arteries All of these valves prevent back flow
- 30. The Heart Theatrioventricular (AV) valves are between the atria and ventricles On the left is the bicuspid or mitral valve On the right is the tricuspid valve
- 31. The Heart Whenthe heart is relaxed and blood is passively filling its chambers, the AV-valve flaps hang limply into the ventricles As the ventricles contract, they press on the blood in theirchamber, and the intraventricular pressure rises
- 32. The Heart Thesemilunar valves guard the bases of the large arteries leavingthe ventricularchambers On the right isthe pulmonary valve On the left is theaortic valve When the ventricles are contracting these valves are forced openand flattened againstthe arterial walls When the ventricles are relaxed the blood flows back towards theheart This prevents arterial blood fromreentering the heart
- 33. The Heart Thecoronary arteries branch from the base of the aortaand encircle the heart in thecoronary sulcus (AV groove) at the junctionof theatriaand ventricles
- 34. The Heart Thecoronary arteries and their major branches are compressed when the ventricles are contracting and fill when the heart is relaxed
- 35. The Heart Themyocardium is drained by several cardiacveins, which empty into thecoronary sinus The coronary sinus, in turn, empties into the right atrium
- 36. The Heart Whenthe heart beats rapidly the myocardiumcan received an inadequate amount of blood This can result in crushing chest pain called angina pectoris
- 37. The Heart Paindue toangina pectoris is a warningsign If angina is prolonged, oxygen-deprived heartcells may die forming aninfarct The resulting myocardial infarction is a “heart attack”
- 39. Heart Physiology Althoughcardiac muscle can beat independently, the muscle cells on different areas of theheart have differentrhythms Atrial cells – 60 bpm Ventricular cells –20-40 bpm
- 40. Heart Physiology Twosystemsact toregulate heartactivity: 1. Autonomic nervoussystem – brakes and accelerator Acts todecrease or increase heart rate 2. Intrinsic conduction system (nodalsystem) Composed of specialized tissue that is across between muscle and nervoustissue Causes heart muscledepolarization from theatria to theventricles Enforces contraction rate ~ 74bpm
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- 42. Heart Physiology Components ofthe Intrinsic ConductionSystem include: The sinoatrial (SA) node is acrescentshaped node in the rightatrium Theatrioventricular (AV) node is at the junctionof the atria andventricles The atrioventricular (AV) bundle (bundle ofHis) Branch bundles in the interventricular septum Purkinje fibers which spread with the muscleof the ventriclewalls
- 43.
- 44. Heart Physiology TheSA node has the highest rate of depolarization in the wholesystem It starts each heartbeat and sets the pace forthe whole heart and is therefore called the pacemaker
- 45.
- 46. Heart Physiology Theimpulse travels from the SA node through the atria to the AV node, causing theatria tocontract At the AVnode, the impulse is delayed togive the atria time to finish contracting It then passes rapidly through the AVbundle,the bundle branches, and the Purkinje fibers, causing a “wringing” contraction of the ventricles that begins at the apex and moves toward theatria
- 47. Heart Physiology Thiscontraction effectivelyejects blood superiorly into the large arteries leaving theheart
- 48. Heart Physiology Tachycardiais a rapid heart rate (> 100bpm) Bradycardia is a slow heart rate (< 60 bpm) Neither condition is pathological, butprolonged tachycardia may progress tofibrillation
- 49. Fibrillation isa rapid, uncoordinated shuddering of the heart muscle Fibrillation makes the heart totallyuselessasa pump and is a major cause of death from heart attacks inadults Heart Physiology
- 50. Heart Physiology Apacemaker is a small device, about the sizeof a half dollar piece, placed under the skin near the heart to help control the heartbeat. A pacemaker isimplanted as part of what's often referred to as "cardiac resynchronization therapy."
- 51. Heart Physiology Peoplemay need a pacemaker fora variety of reasons — mostly due to one of a group of conditions called arrhythmias, in which the heart's rhythm isabnormal They can be implantedtemporarily to treat a slow heartbeat after a heartattack, surgeryoroverdoseof medication Pacemakers can also be implanted permanently to correctbradycardia or to help treat heart failure
- 52. Cardiac Cycle andHeart Sounds
- 53. Cardiac Cycle andHeart Sounds In a healthy heart, theatria contractsimultaneously When theystart torelax, contraction of theventricles begins Systoleand diastole mean heartcontraction and relaxation respectively
- 54. Cardiac Cycle andHeart Sounds Because most of the pumping work is done by the ventricles, these terms always refer to the contraction and relaxation of theventricles unlessotherwisestated
- 55. Cardiac Cycle andHeart Sounds The term cardiac cycle refers to the events of one complete heartbeat, during which both atria and ventricles contract and then relax
- 56. Cardiac Cycle andHeart Sounds The average heart beats 74 times perminute Theaverage length of a cardiac cycle is 0.8 seconds Thecardiac cycleoccurs in three majorsteps: 1. mid-to-latediastole 2. ventricularsystole 3. earlydiastole
- 57. 1. Mid-to-late diastole The heart is in complete relaxation Pressure in the heart islow Blood is flowing passively into and through the atria and into theventricles from pulmonaryand systemic circulations
- 58. 1. Mid-to-late diastole The semilunarvalvesareclosed The AVvalves are open Then theatria contractand force the blood into the ventricles
- 59.
- 60. 2. Ventricular systole The pressure within the ventricles increases rapidly, closing the AVvalves When the intraventricular pressure is higher than the pressure in the large arteries leaving the heart, the semilunar valves are forced open, and blood rushes out of theventricles The atriaare relaxed, and again are filling with blood
- 61.
- 62. 3. Early diastole At the end of systole, the ventricles relax, the semilunarvalvessnapshut, and fora moment the ventricles are completelyclosed chambers
- 63. 3. Early diastole During early diastole, the intraventricular pressure drops When it drops below the pressure in the atria, the AV valves are forced open. And the ventricles again begin to refill rapidly withblood
- 64. Heart Sounds Whenusing a stethoscope, the heart beat usually has two distinct sounds – “lup” and“dup” Thesearecaused by theclosing of the twosets of valves “lup” – AVvalves “dup” – semilunarvalves
- 66. Cardiac Output CardiacOutput (CO) is the amount of blood pumped out by eachside of the heart in 1 minute It is the product of heart rate (HR) and stroke volume (SV)
- 67. Cardiac Output Ingeneral, strokevolume increases as the forceof ventricular contractionincreases Let’s look at normal resting heart rateand volume: CO = HR x SV CO = (74 bpm) x (70 ml perbeat) CO = 5180 ml/min
- 68. Cardiac Output Ahealthy heart pumps out about 60% of blood in the ventricles (~70ml) per heart beat The critical factor is how much the cardiac muscle cells stretch just before contracting
- 69. Cardiac Output Theimportant factor stretching the heart muscle is venous return, the amountof blood entering the heart and distending theventricles The more the heart muscles stretch,the stronger the contraction
- 70. Cardiac Output Ifone side of the heart suddenly begins to pump more blood than the other, the increased venous return to the opposite ventricle will force it to pump out an equal amount, thus preventing backup of blood in the circulation
- 71. Cardiac Output Theenhanced squeezing action of active skeletal muscles from exercisespeeds upvenousreturn Severe blood loss or rapidheart rate, decreases stroke volume, creating less venousreturn
- 72. Factors Modifying BasicHeart Rate Heart contraction does not depend on the nervous system, but itcan bechanged temporarily by the ANS It is also modified bychemicals, hormones and ions
- 73. Neural (ANS) Control During times of physical or emotional stress, the nervesof sympatheticdivision stimulatethe SA and AVnodes and the cardiacmuscles The heart beats morerapidly
- 74. Neural (ANS) Control When the demand declines, the heart adjusts, the parasympathetic nerves slowand steady the heart rate Gives the heart time to recoverand rest
- 75. Neural (ANS) Control In patientswith Congestive Heart Failure (CHF), or other heartdisease the heart pumpsweakly Some medicationscan be used toenhance contractile force and stroke volume of the heart, improving cardiac output
- 76.
- 77. Neural (ANS) Control Various hormonesand ions havea dramaticeffecton heartactivity Epinephrine – mimics sympathetic nerves,increases heart rate Thyroxine – increase heartrate Electrolyte imbalance – prolongedcontractions, arrhythmias, decreaseoutput
- 78. Physical Factors Restingheart rate is fastest in the fetusand then graduallydecreases Faster heart rate in females thanmales High body temperaturealso increase heart rate, Low body temperature decreases heartrate