Cardiovascularsystem 110221045748-phpapp02


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  • Oxygen rich and oxygen poor blood never mix.
  • supported by a thin layer of loose CT (basement membrane)
  • Arterioles (diameter of 0.3 mm or less) – tunica media almost entirely smooth muscle – close to capillaries - single layer of muscle spiralling around the endothelial lining vasoconstriction & dilation regulates blood flow to the local capillary bed
  • Cardiovascularsystem 110221045748-phpapp02

    1. 1. Cardiovascular System: Heart & Circulation
    2. 2. I. Anatomy of the Heart A. Coverings 1. Pericardium • fibrous pericardium • serous pericardium • parietal pericardium • visceral pericardium B. Heart wall layers 1. Epicardium – (visceral pericardium) • protects heart 2. Myocardium – cardiac muscle 3. Endocardium – epithelial/ connective/ fibers
    3. 3. C. Chambers, Vessels, and Valves 1. Four chambers • upper chambers – rt and left atria Collects blood • lower chambers – rt and left ventricle pumps blood from heart 2. Arteries • carry blood away from heart 3. Veins • blood toward heart
    4. 4. 4. Valves • AV valves Tricuspid – rt atrium Bicuspid or mitral - lt atrium • Semilunar valves Pulmonary semilunar (pulmonary trunk) Aortic semilunar (aortic arch)II. Pulmonary and Systemic Circulation A. Pulmonary pathway oxygenated blood –rt ventricle from rt atrium myocardium (rt ventricle) contracts
    5. 5. low oxygen blood through pulmonary semilunar pulmonary trunk -> arteries -> lungs oxygenated blood -> rt & lt pulmonary veins -> left atriumB. Systemic pathway Oxygenated blood -> Lt atrium to Lt ventricle Left ventricle contracts ->aortic semilunar Aortic arch -> arteries to tissues oxygen depleted blood from tissues -> veins to heart -> rt atrium (vena cava)
    6. 6. Passage of Blood Through the Heart Blood follows this sequence through the heart: superior and inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk and arteries to the lungs → pulmonary veins leaving the lungs → left atrium → bicuspid valve → left ventricle → aortic semilunar valve → aorta → to the body.
    7. 7. Direction of blood flow through the heart
    8. 8. The relationship between the systemic and pulmonary circulations
    9. 9. Blood supply to the heart orcoronary circulation The coronary arteries
    10. 10. Blood supply to the heart Arterial supply The heart is supplied with arterial blood by the right and left coronary arteries, which branch from the aorta immediately distal to the aortic valve The coronary arteries receive about 5% of the blood pumped from the heart, although the heart comprises a small proportion of body weight This large blood supply, especially to the left ventricle, highlights the importance of the heart to body function The coronary arteries traverse the heart, eventually forming a vast network of capillaries
    11. 11. Blood supply to the heart –Venous drainage Most of venous blood is collected into several small veins that join to form coronary sinus, which opens into right atrium The remainder passes directly into the heart chambers through little venous channels
    12. 12. THE CARDIAC CYCLEWhat is the cardiac cycleThe cardiac cycle is the sequence ofevents that occur when the heart beatsThere are two phases of this cycle:Diastole - Ventricles are relaxedSystole - Ventricles contract
    13. 13. The cardiac cycle Exercise increases blood flow through the heart so that the cardiac cycle accelerates to accommodate the increased demand for oxygen The normal cycle is around 0.8 seconds. This accelerates with faster and more powerful atrial and ventricular contraction, which is stimulated by the cardiac centre in the brain Heart rate:- is defined as the number of heart contractions in each minute# There are two distinct periods in the cardiac cycle- one of the heart muscle relaxation (cardiac diastole), the other of contraction (cardiac systole)
    14. 14. Cardiac diastoleDuring cardiac diastole• The bicuspid and tricuspid valves are closed and the atrium is full• Once full with blood, the atria forces the bicuspid and tricuspid valves to open and fill the ventricles• This lasts for around 0.4 seconds at rest
    15. 15. Cardiac systoleCardiac systole• The atria contract and send blood via the bicuspid and tricuspid valves into the ventricles• When full, these contract causing blood to be expelled from the heart via the semi- lunar valves• (the bicuspid and tricuspid valves are closed at this time)• This lasts around 0.4 seconds at rest
    16. 16. The Cardiac CycleHeart at rest– Blood flows from large veins into atria– Passive flow from atria into ventriclesAtria (R & L) contract simultaneously– Blood forced into ventriclesVentricles (R & L) contract simultaneously– Atrioventricular valves close  “lubb” sound– Blood forced into large arteriesVentricles relax– Semilunar valves close  “dub” soundHeart at rest
    17. 17. Heart valves• Valves are flap-like structures that allow blood to flow in one direction• The heart has two kinds of valves, atrioventricular and semilunar valvesHeart sounds The audible sounds that can be heard from the heart are made by the closing of the heart valves These sounds are referred to as the “lub-dupp” sounds The “lub” sound is made by the contraction of the ventricles and the closing of the atria-ventricular valves The “dupp” sound is made by the semi-lunar valves closing
    18. 18. Conducting system of Heart
    19. 19. Stimulation of the heart originates in thecardiac centre, in the “medulla oblongata.”The “sympathetic and parasympatheticnervous systems” work antagonistically andprovide the stimulation for acceleration anddeceleration of the heart rateCardiac systole (contraction) is initiated bythe electrical cardiac impulse from the “sinu-atrial node” (the pace-maker found in theright atria wall)This distributes electrical stimulus throughthe “myocardial” (heart muscle) wallbetween the heart chamberswhere the “atrio-ventricular node” (betweenthe right atrium and right ventricle)continues distribution of the electrical signalacross the ventricles
    20. 20. The SA node• In the upper part of the right atrium of the heart is a specialized bundle of neurons known as the sino-atrial node (SA node)• Acting as the hearts natural pacemaker, the SA node "fires" at regular intervals to cause the heart of beat with a rhythm of about 60 to 70 beats per minute for a healthy, resting heart• The electrical impulse from the SA node triggers a sequence of electrical events in the heart to control the orderly sequence of muscle contractions that pump the blood out of the heart The AV node • The AV node (AV stands for atrioventricular) is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart) • Electrical signals from the atria must pass through the AV node to reach the ventricles
    21. 21. AV node (bundle of his)The bundle of His is located in the proximal interventicular septumIt emerges from the AV node to begin the conduction of the impulse from the AVnode to the ventricles
    22. 22. Purkinje fibersPurkinje fibers are heart muscle tissues that are specialized toconduct electrical impulses to ventricular cells, which induce thelower chambers of the heart to contractImpulses from the upper chambers of the heart are relayed by thisnode to large bundles of Purkinje fibers referred to as the Bundleof HisThese bundles branch into smaller elements and eventually formterminal ends that burrow into left and right ventricular chambermusclesAs the impulse is passed to the ventricles, the muscles contract andpump bloodThe contraction caused by the specialized fibers begins from thebottom of the ventricles and move upwards so that the blood leavesthe lower chambers through the pulmonary arteries and the aorta
    23. 23. Signal Conduction Pathway • SA action potentials -> contraction in atrium • AV action potentials (slower) -> bundle of HIS-> through septum -> Purkinje fibers -> contractionC. Electrocardiography • electrical events corresponding to mechanical • P wave: atrial fibers depolarize • QRS complex: ventricles depolarize • T wave: ventricles repolarize
    24. 24. Electrocardiography
    25. 25. Cardiac Output (CO) CO is the amount of blood pumped by each ventricle in one minute CO is the product of heart rate (HR) and stroke volume (SV) HR is the number of heart beats per minute SV is the amount of blood pumped out by a ventricle with each beat
    26. 26. Cardiac Output: Example CO (ml/min) = HR (75 beats/min) x SV (70 ml/beat) CO = 5250 ml/min (5.25 L/min)
    27. 27. Regulation of Stroke Volume SV = end diastolic volume (EDV) minus end systolic volume (ESV) EDV = amount of blood collected in a ventricle during diastole ESV = amount of blood remaining in a ventricle after contraction
    28. 28. Factors Affecting Stroke Volume Preload – amount ventricles are stretched by contained blood Contractility – cardiac cell contractile force due to factors other than EDV Afterload – back pressure exerted by blood in the large arteries leaving the heart
    29. 29. Preload and Afterload
    30. 30. Regulation of Heart Rate Positive chronotropic factors increase heart rate Negative chronotropic factors decrease heart rate Autonomic nervous system Hormones
    31. 31. Blood Pressure & its regulation Blood pressure is the force or pressure that the blood exerts on the walls of the blood vessels BP = CO x TPR CO= SV x HR BP = Blood Pressure CO = Cardiac Output TPR = Total Peripheral Resistance SV = Stroke Volume HR = Heart rate
    32. 32. Control of Arterial Blood Pressure
    33. 33. Control of Blood Pressure Short term control :  Baroreceptors  Chemoreceptors  Higher centres in the brain Long term control: RAAS system
    34. 34. Summary of the main mechanisms in blood pressure control
    35. 35. Baroreceptors Located in walls of aortic arch and left and right carotid sinus Mechanical stretch receptors Neuronal circuits in brainstem compare actual value of BP provided by the baroreceptors with the set point or optimal value
    36. 36. The baroreceptor reflex
    37. 37. Chemoreceptor  Nerve ending situated in the carotid and aortic bodies  control of respiration  Sensitive to changes in the levels of Co2 , O2 and acidity of the bloodThe relationship between stimulation ofchemoreceptors and arterial blood pressure
    38. 38. Higher centres in the brain  Fear  Anxiety  Pain  Anger
    39. 39. Long term Blood pressure regulation Renin-angiotensin-aldosterone system (RAAS) Anti-diuretic harmone (ADH) Atrial natriuretic peptide (ANP) harmone released by heart sodium and water loss from the kidney reduces blood pressure
    40. 40. RAAS System
    41. 41. Disorder of CVS• Hypertension• Hypotension• Congestive heart failure• Cardiac Arrhythmia• Angina Pectoris• Arteriosclerosis• Myocardial Infarction
    42. 42. Hypertension Essential hypertension Benign (chronic ) hypertension Malignant ( accelerated) hypertension Secondary hypertension Kidney disease Endocrinal disorders
    43. 43. Heart failure Acute heart failure Chronic heart failureRight-sided (congestive) heart failureLeft-sided (left ventricular) heart failure
    44. 44. Cardiac arrhythmia Sinus bradycardia Sinus tachycardia Asystole Fibrillation Atrial fibrillation Ventricular fibrillation Heart block
    45. 45. Blood VesselsFunctions: Distribution of blood Exchange of materials with tissues Return of blood to the heartStructure: Most have the same basic structure: – 3 layers surrounding a hollow lumen
    46. 46. General Structure of Blood VesselsArteries and veins are composed of three tunics: tunica interna tunica media tunica externa Capillaries are composed of endothelium
    47. 47. General Structure
    48. 48. The Vessels1. Tunica Intima innermost smooth layer simple squamous epithelium continuous with the endocardium present in all vessels
    49. 49. The Vessels2. Tunica Media layer of smooth muscle - circular arrangement – contains elastin supplied by sympathetic division of the ANS depending on body’s needs – lumen is narrowed (vasoconstriction) or widened (vasodilation)
    50. 50. The Vessels3. Tunica Externa (Adventitia) thin layer of CT elastic & collagen fibres
    51. 51. The VesselsTypes of Vessels: Arteries – carry blood away from the heart Veins – carry blood towards the heart Capillaries – the most important part of the vascular system; site of exchange of materials
    52. 52. Types of Blood vessels: Arteries Elastic Arteries:  Thick-walled arteries near the heart; the aorta and its major branches  Large lumen allows low-resistance conduction of blood  Contain lots of elastin in all three tunics  walls stretch and recoil to propel blood  Withstand and regulate large blood pressure fluctuations
    53. 53. Types of Blood vessels: ArteriesMuscular (distributing) arteries medium sized vessels tunica media more smooth muscle; less elastin major area of vaso-constriction & dilation to regulate blood flow
    54. 54. The VesselsArterioles (diameter of 0.3 mm or less) - smallest arteries; lead to capillary beds - close to capillaries - single layer of muscle spiralling around the endothelial lining - regulates blood flow to capillary
    55. 55. The VesselsCapillaries Smallest vessels – diameter just large enough for a red blood cell walls consist of tunica intima only (i.e. layer of endothelium) thinness facilitates exchange of materials