CVS: Heart PDF

CVS: Heart NAWALE RAJESH BHASKAR CVS ▪ CVS consist of ▪ Blood ▪ Heart ▪ Blood vessels ▪ Heart act as pump to circulate blood throughout body ▪ Heart beat 1,00,000 time in a day; 35 millions beats in a year and around 2.5 billion in lifetime. ▪ Left side of heart pump blood in around 1,00,000...

CVS: Heart NAWALE RAJESH BHASKAR CVS ▪ CVS consist of ▪ Blood ▪ Heart ▪ Blood vessels ▪ Heart act as pump to circulate blood throughout body ▪ Heart beat 1,00,000 time in a day; 35 millions beats in a year and around 2.5 billion in lifetime. ▪ Left side of heart pump blood in around 1,00,000 km of blood vessels ▪ Heart pump around 5 lit of blood per minute. 14,000 lit per day.  Heart: Anatomy ▪ Scientific study of heart – cardiology ▪ Size – own closed fist ▪ It is 12 cm long; 9 cm wide; 6 cm thick ▪ Weighing around 250 G (female) and 300 G in male ▪ Rest on diaphragm, located in mediastinum (sternum to vertebral column) ▪ About 2/3 mass lies at left side and 1/3 at right side of midline. ▪ Heart cone lies on its side, left ventricle rest on diaphragm Structure  Pericardium ▪ Protecting membrane on heart (outer sac) ▪ It confines the heart to its position ▪ And allowing sufficient freedom for vigorous and rapid contractile movement ▪ Contain two main layer ▪ Fibrous pericardium ▪ Serous Pericardium ▪ Superficial fibrous pericardium (tough, inelastic, dense irregular connective) ▪ Inner serous pericardium (thinner, more delicate, two layer) ▪ Parietal – fused with serous pericardium ▪ Visceral (epicardium) ▪ Space between two layer – pericardial cavity, filled with pericardial fluid; reduces friction between layers during heart movement  Layers of heart ▪ Heart contains three layers ▪ Epicardium ▪ Myocardium ▪ Endocardium ▪ Epicardium fused with visceral layer of serous pericardium, Is thin, transparent, composed of mesothelium, delicate fibroelastic tissue and adipose tissue. ▪ Myocardium is responsible for pumping action, composed of cardiac muscle tissue, make around 95% of heart wall. These are striated but involuntary ▪ Endocardium is innermost, thin, connective tissue layer. Provide smooth lining to chamber of heart, cover the valves, reduce friction with blood, Continue with large blood vessels attached to heart.  Chambers of Heart ▪ Heart has four chambers ▪ Two superior receiving chambers (atria) – receives blood from veins ▪ Two inferior pumping chamber (ventricles) – receives blood from arteries ▪ On anterior surface of each atria is wrinkled pouch structure – auricle (dog’s ear) ▪ Each auricle increases capacity of atria to accommodate blood ▪ Surface of heart has grooves (sulcus) – external marks / boundaries ▪ Coronary sulcus – marked between atria and ventricles ▪ Anterior intraventricular sulcus – groove on anterior surface of heart between right and left ventricle ▪ Posterior intraventricular sulcus – anterior intraventricular sulcus continues around posterior surface as posterior intraventricular sulcus.  Heart - Anatomy External Anatomy Internal Anatomy Right Atrium ▪ Thickness: 2 to 3 cm ▪ Received blood from three veins ▪ Superior vena cava ▪ Inferior vena cava ▪ Coronary sinus ▪ A thin partition between right and left atrium is called interatrial septum ▪ Prominent feature, oval depression – fossa ovalis, interatrial septum of fetal heart which close after birth. ▪ Blood passes from right atrium to right ventricle through a valve – tricuspid valve (three cups), also known as right atrioventricular valve. Right Ventricle ▪ Is about 4 to 5 cm average thickness. Forms anterior surface of heart ▪ Cups of tricuspid valves are connected with tendons like cord – cordae tendineae ▪ Right and left ventricle are separated by interventricular septum ▪ Blood passes from right ventricle through pulmonary valve into large pulmonary trunk which then divide in to right and left pulmonary artery. ▪ Arteries always take blood away from heart (although pulmonary artery contain deoxygenated blood) Left Atrium ▪ Same thickness - right atrium ▪ If forms base of heart ▪ Receives blood from four pulmonary veins ▪ Blood passes from left atrium to left ventricle through bicuspid valve (2 cups) ▪ Bicuspid valve is also known as mitral valve / left atrioventricular valve Left Ventricle ▪ Thickest chamber of heart wall (average 10 to 15 mm) ▪ Blood passes from left ventricle through aortic valve into ascending aorta ▪ Some blood from aorta flow into coronary arteries (first branch of aorta) ▪ Remaining blood passes from aortic arch to descending aorta to body ▪ During foetal life, temporary blood vessel ductus arteriosus shunts blood from pulmonary trunk to aorta. ▪ This ductus arteriosus close shortly after birth. ▪ Leaving ligamentum arteriosum. Myocardium ▪ Thickness of myocardium varies according to function of each chamber ▪ Thin walled atria deliver blood to ventricles under less pressure ▪ Ventricles pump blood under high pressure to greater distance ▪ Right and left ventricle are two separate pump but work simultaneously ▪ Right and left ventricle eject equal volume of blood ▪ Right side – small work load, pump short distance (pulmonary) ▪ Left side have – higher pressure, greater distance all part of body (systemic circulation) ▪ Left ventricle work much harder than right ventricle. Anatomy (thickness) confirm functional difference), Left ventricle wall is thicker than right ventricle  AV & SL valves ▪ Atrioventricular valves located between atria and ventricles (tricuspid and bicuspid) / AV valves ▪ When AV valve is open sups project into the ventricles ▪ When ventricle relax – papillary muscle relax. When ventricle contacts – cups upwards till edges meet and close opening. ▪ Aortic and pulmonary valves / Semilunar valves (SL valves) made of three moon shaped cups. ▪ SL valves allow ejection of blood from heart to arteries. Prevent backflow of blood into ventricles. ▪ Free border of cups project into lumen of artery  Flow of blood Systemic circulation - Superior & inferior vena cava - Right atrium - Tricuspid valve - Right ventricle - Pulmonary valve - Pulmonary trunk - Lung (pulmonary circulation) - Pulmonary veins - Left atrium - Bicuspid valve - Left ventricle - Aortic valve - Aorta - Systemic circulation Systemic & Pulmonary circulation  Coronary circulation ▪ Nutrients can not diffuse quickly enough from blood into chamber. ▪ Myocardium have own network of blood supply called coronary circulation ▪ Coronary artery (left & right) branch of assenting aorta encircle heart like crown. Coronary artery supply oxygenated blood to myocardium. ▪ Left coronary artery passes inferior to left auricle and distribute oxygenated blood to walls of left ventricle and left atrium. ▪ Right coronary artery is small branch, supply blood to right atrium divides and supply blood to walls of right side ventricle. ▪ Most part receives blood from branches of more than one artery (anastomoses). Blood passes from coronary artery to capillary and then moves in to coronary veins. ▪ These veins drain blood in to large vascular sinus called coronary sinus, which empty in to right atrium. Great, middle, small, anterior cardiac vein carry blood to sinus. Conducting system ▪ Inherent, rhythmic, electric activity is reason for lifelong beating of heart. ▪ The source of this electric activity is network of specialized cardiac muscle – autorhythmic fibers. ▪ They are self excited, autorhythmic, repeatedly generating action potential that trigger heart contraction. Continue heart to beat even after removed from body. ▪ During embryonic development 1% cardiac cells become autorhythmic. They act as pacemakers, setting rhythm of electric excitation. ▪ They forms cardiac conducting system. Network of specialized cardiac muscle fibers. ▪ Cardiac action potential propagate through – Sinoatrial / SA node; atrioventricular / AV node; atrioventricular / AV bundle and Purkinje fibers Conducting system  SA Node ▪ Cardiac excitation begins with sinoatrial (SA) node (located in right atrial wall, just inferior & lateral to the opening of superior vena cava) ▪ SA node spontaneous depolarisation is pacemaker potential. ▪ When this potential reaches threshold, it triggers an action potential. ▪ Each action potential from SA node propagate through atria. ▪ Following the action potential two atria contract at the same time  AV Node & AV Bundle ▪ By conducting atrial muscle fibers. Action potential reaches atrioventricular / AV node. AV node located in interatrial septum. Just inferior to opening of coronary sinus. ▪ At AV node action potential slow considerably. ▪ This delay provide time for atria to empty blood in ventricle. ▪ From AV node action potential reaches to atrioventricular (AV) bundle / Bundle of His. ▪ Is site where action potential conduct from atria to ventricle. ▪ Action potential enter right and left bundle branches. ▪ Bundle branches extend through intraventricular septum toward apex of heart.  Purkinje fibers ▪ Finally large diameter Purkinje fibers rapidly conduct the action potential beginning at the apex of heart upwards to the reminder of ventricular myocardium. ▪ The ventricle contracts. Pushing the blood upward towards semilunar valve. ▪ SA node initiate action potential at every 0.6 sec. ▪ SA node set a rhythm for contraction of heart (natural pacemaker) ▪ Nerve impulse from ANS, blood-born hormones (adrenaline) modify timing and strength of each heart beat. They do not establish fundamental rhythm. ▪ Ach from ANS slow SA mode pacing to 0.8 sec. Electrocardiogram (ECG) ▪ Action potential propagate through heart – generate electric current. Detected on surface of body. ▪ Recording of these electrical signals is known as electrocardiogram / Electrokardiogram / ECG / EKG ▪ Its is composed record of action potential produced by all heart muscle fiber during each heartbeat. ▪ Instrument used to record is electrocardiograph ▪ Electrodes are positioned on arms, legs and six position on chest (chest lead). ▪ Cardiograph amplifies signal and produce 12 different tracings form different combination of leads. ECG ▪ P wave: Small upward deflection on ECG. It represents atrial depolarization. ▪ Which spread through SA node through contractile fiber in both aria ▪ QRS Complex: Begins as downward deflection, large upward triangular wave, end as downward wave. Represents rapid ventricular depolarization. ▪ Action potential spreads through ventricular contractile fibers. ▪ T Wave: Dome shape upward deflection. Is ventricular repolarization. ▪ Occur just as ventricle start relaxing. T wave is smaller and wider than QRS complex. Because repolarization occur slow. ECG – Time span ▪ Analysis of ECG involves measurement of time span between waves, also called as intervals / segments. ▪ P-Q interval: time from beginning of P interval to beginning of QRS complex. ▪ Is conduction time from beginning of atrial excitation to beginning of ventricular excitation. Is time required for action potential to travel from atria to AV node ▪ S-T Segment: Begins at the S wave and ends at beginning of T wave. ▪ Elevation of S-T segment above baseline – myocardial infarction, and depression indicate heart muscle receives insufficient oxygen. ▪ Q-T Interval: extends from start of QRS complex to end of T wave. Time from beginning of ventricular depolarization to the end of ventricular repolarization. ▪ Q-T interval lengthened by myocardial damage, myocardial ischemia or conduction abnormalities ECG - Abnormalities ▪ In reading ECG size of wave provide clue regarding abnormalities. ▪ Large P wave - enlargement of atria ▪ Enlarge Q wave – myocardial infraction ▪ Enlarge R wave – enlarge ventricles ▪ T wave flattening – insufficient oxygen to cardiac muscle. ▪ Elevated T wave – hyperkalemia (high blood potassium level) Hear Sound ▪ Auscultation – act of listening to sound with in body. Done with stethoscope. Heartbeat sound come from turbulence caused by closing of heart valves. ▪ During each heart sound four sound occur. Normal heart first and second (S1 and S2) are loud enough to be heard through stethoscope. ▪ First sound (S1): describe as LUBB, louder bit longer, occur due to turbulence by closure of AV valves. ▪ Second sound (S2): describe as DUBB, not louder & shorter, occur due to turbulence by closure of SL valves. ▪ S3: turbulence during rapid ventricular filling. S4: turbulence during atrial systole ▪ Heart sound provide valuable information about mechanical operation of heart. Heart murmur is abnormal clicking, rushing, gurgling, noise between normal heart sound. ▪ Murmur common in children, mask normal heart sound indicate poor health condition Cardiac Cycle ▪ All events associated with 1 heart beat ▪ Consist of three phases ▪ Atrial systole ▪ Ventricular systole ▪ Complete cardia diastole (relaxation) ▪ Atria and ventricle alternately contract and relax. ▪ It show relationship between ECG, contraction and relaxation pattern of heart, heart sound and time taken by each event etc. ▪ One cardiac cycle lasts for 0.8 sec. (72 beats per min.) Events of cardiac cycle  ECG Event Timing Name Sound  0.0 0.7 S4 0.1 P Cardiac Auricular Contraction S1 Cycle Complete (0.1) Cardiac QRS Relaxation 0.6 (0.4) 0.2 Ventricular Contraction (0.3) S3 T S2 0.5 0.3 0.4 Atrial systole ▪ Last for 0.1 sec. Atria contracts. At the same time ventricles were relaxing ▪ Depolarization of SA node. Atrial depolarization. P wave in ECG. ▪ Atrial depolarization cause atrial contraction (systole) and forces blood through opened AV valve in to ventricle. ▪ Atrial systole contribute final 25 ml blood to volume in ventricle. About 105 ml already in each ventricle due to filling during relaxation. Total 130 ml. ▪ This 130 ml is called end-diastolic volume. ▪ QRS complex in ECG marks onset of ventricular depolarization. Ventricular systole ▪ Last for 0.3 sec. Ventricles were contracted. At same time atria are relaxed. ▪ Ventricular depolarization causes ventricular contraction (systole). ▪ Pressure rises and push blood against AV valve. This is isovolumetric contraction. ▪ Cardiac muscle fibers are contracting and exerting force. ▪ Continued contraction of ventricle causes pressure inside chamber rises sharply. ▪ SL valve open, ventricular ejection, around 70 ml of blood in aorta. ▪ The volume remaining in ventricle (around 60 ml) is end-diastolic volume. ▪ T wave in ECG marks onset of ventricular repolarization (relaxation) Relaxation period ▪ Last for 0.4 sec. atria and ventricle both relaxes. Increased heart beat shorten this period. ▪ Ventricular repolarization causes ventricular diastole. As ventricle relaxes, pressure within chamber falls. ▪ Blood from aorta and pulmonary trunk begin to backflow but SL valve close and prevent back flow. This is isovolumetric relaxation. ▪ Ventricle continue to relax and pressure drop below atrial pressure. AV valve open and ventricular filling starts. The major filling occur during this phase only. ▪ At the end of this phase ventricle are almost 2/3 filled. ▪ P wave appear in ECG and signaling start of another cardiac cycle. Cardiac output ▪ Is volume of blood ejected from left ventricle (or right) into aorta (pulmonary trunk) each minute. ▪ Stroke volume (SV) is volume of blood ejected by ventricle during each contraction. ▪ Heart rate (HR) is number of beats per minute so Cardiac out put (CO = SV x HR) ▪ Typically for adult it is 70 x 75 = 5250 i.e. 5.25 lit/min. This is volume close to total blood volume. ▪ Thus entire blood volume flow through pulmonary &system circulation per min. ▪ Factors that increases SV and/or HR increases CO ▪ Cardiac reserve is difference between maximum CO and CO at rest. Average cardiac reserve is 4 to 5 time of CO at rest. Top athletes have cardiac reserve 7 to 8. Regulation of stroke volume ▪ More blood return to heart, more blood will eject during next cardiac cycle. ▪ At the rest SV is only 50 to 60% of end-diastolic volume. 40 to 50% blood remain in ventricle after each contraction i.e. ESV. Three factors contributes ESV ▪ Preload: Degree of stretch before it contract. ▪ Key factor 1. Duration of ventricular diastole 2. venous return. ▪ Contractility: Forcefulness of contraction. ▪ Positive ionotropic agent increases force of contraction. ▪ Afterload: Pressure that must be excided before ejection of blood from ventricle. ▪ When afterload increases – more emptying of ventricle occur Regulation of Heart Rate ▪ Adjustment in HR is important in short term control of CO ▪ HR can be adjusted by following three ways ▪ Autonomic regulation: Nervous system regulates CV centre in medulla oblongata ▪ centre receives input from variety of sensory receptors. It give appropriate output to increase / decrease frequency of sympathetic / parasympathetic branch of ANS. ▪ Chemical regulation: Hypoxia, acidosis, alkalosis, depress HR. Hormones and cations also alters HR. ▪ Hormones: adrenaline / noradrenaline (adrenal medulla, ANS) enhances pumping. ▪ Cations like Na, K and Ca have large effect on cardiac function via HR. Na & K decreases HR. Ca level increases HR. ▪ Other factors: Age, gender, physical fitness, body temperature, influences HR. Elevated body temperature increases HR, Heart disorders ▪ Coronary artery disease (CAD) ▪ Congenital heart defect (CHD) ▪ Arrythmia CAD ▪ Result from accumulation of atherosclerotic plague in coronary artery. Reduction of blood flow to myocardium. ▪ Greater risk with smoking, high blood pressure, diabetes, high cholesterol, obesity, life style, family history of CAD etc. ▪ Development of atherosclerotic plagues – thickening of wall, loss of elasticity, formation of plague. LDL and HDL play important role. ▪ Diagnosis – stress test. Radio nuclear imaging, echocardiogram, coronary computed tomography radiography, cardiac catheterization, angiography ▪ Treatment – coronary artery bypass, coronary angioplasty, stent, CHD ▪ Defect in heart by birth ▪ Coarctation of aorta ▪ Segment of aorta too narrow, flow of blood is reduced, left ventricle to pump harder ▪ Surgical removal of obstruction, balloon dilation, insertion & inflation of device, stent ▪ Patent ductus arteriosus ▪ Ductus arteriosus remain open, arterial blood flow in pulmonary trunk, ▪ Increases pulmonary trunk blood pressure & overflow of ventricle ▪ Surgical intervention ▪ Septal defect ▪ Fetal foramen ovale between left and right atria fail to close after birth. ▪ Oxygenated blood flow back to deoxygenated blood. Surgical intervention is required. CVS Blood Vessels Structure & Function ▪ Five main types of blood vessels ▪ Arteries ▪ Arterioles ▪ Capillaries ▪ Venules ▪ Vein ▪ Arteries carry blood away from heart. Divide in to medium size arteries, then to small size, which in turn divide into arterioles. ▪ Arterioles enter tissue and branch into number of tiny vessels known as capillaries, where exchange takes place. ▪ Group of capillary unit together to form venules. These venules in turn merge to form progressively larger veins. ▪ Veins are blood vessels that convey blood from tissue back to heart  Basic Structure ▪ Wall of blood vessel consists of three layers / tunics ▪ Epithelial – innermost (Tunica interna/intima) ▪ Smooth muscle – middle (Tunica media) ▪ Connective tissue – outermost (Tunica Externa / adventitia) ▪ Modification in these three layers make different five types of blood vessels. ▪ These modification are in the form of structural and functional difference. ▪ Structural difference correlate to the difference in function. Layers of Blood vessels ▪ Tunica Interna: Direct contact with blood. Contribute minimal in thickness of wall. ▪ Also call endothelium. These are flat cell with smooth luminal surface. ▪ Deep in basement membrane, physical support. Anchor to underlying connective tissue. Internal elastic lamina facilitate diffusion thorough opening ▪ Tunica media: Is muscular & connective tissue. Great variation in thickness of various type. The primary role of encircled smooth muscle cell is to regulate diameter of lumen. ▪ Contraction of smooth muscle squeeze vessel, reducing diameter – vasoconstriction. It also help small blood vessel to loss blood through injured vessels. ▪ Tunica externa: Is outer covering of blood vessel. Made of elastic and collagen fibers. It contains number of nerves (specially large blood vessels). Arteries ▪ Found empty at death. ▪ Wall contain typical three layer. ▪ Thick muscular elastic. ▪ Wall stretches easily, expand without tearing in response to pressure. ▪ Elastic arteries – largest in body, aorta, pulmonary trunk. ▪ Well defined internal and external elastic lamina. ▪ Muscular arteries – medium size, more smooth muscle, fewer elastic fibers. ▪ From total thickness around ¾ relative thickness in smooth muscle. Anastomoses ▪ Most tissue receive blood from more than one artery ▪ Union of branches supplying the same body region. ▪ Provide alternative routes for blood to reach tissue / organ. ▪ If blood flow stop due to normal movement, disease, injury, surgery. ▪ Alternative route flow blood through anastomose. Also known as collateral circulation. ▪ Anastomoses also occur in between artery and vein. Arterioles ▪ Is a small arteries, abundant microscopic vessels. Regulate blood flow in capillaries. ▪ The wall thickness of arterioles is ½ of total vessel diameter. ▪ Have thin tunica interna. Tunica media contain 1 to 2 layers of smooth muscle cells of circular orientation. ▪ Tunica externa of arterioles consists of areolar connective tissue containing abundant sympathetic nerves. This nerve with local chemical mediators alters diameter of vessel. ▪ Play key role in regulation of blood to capillaries by regulating resistance (friction of blood with vessel). ▪ Vasoconstriction enhances friction, increases resistance, reduces blood flow  Capillaries ▪ Are smallest blood vessels. Diameter 5 to 10 micro meter. Connect arterial outflow to venous return. RBC fold themselves to squeeze through capillary. ▪ They form extensive network. Around 20 billion, short, branched, interconnecting, individual cell body. ▪ Provide enormous surface area to make contact with each body cell. Found near almost every cell of body. Number vary as per metabolic activity. ▪ High metabolic activity require more nutrient and O2, have more capillary network. Brain, liver, kidney, nervous system. ▪ Flow of blood through capillary is call microcirculation. ▪ Primary function – exchange of substances between blood and interstitial fluid. ▪ Capillary lack tunica media and tunica externa. Have only epithelial cells with basement membrane. Substance passes one cell layer. ▪ Three types – Continuous (CNS, lung, skin), Fenestrated (kidney, small intestine), sinusoid (Liver, spleen, anterior pituitary, parathyroid, adrenal gland) Venules ▪ Thin wall as compared to arteries. Do not maintain their shape. ▪ Diameter 10 to 50 micro meter. ▪ It drain blood from capillary and flow back to heart. ▪ Venules receiving blood from capillary called postcapillary venules. ▪ Function as site of exchange, WBC emigration – part of microcirculation. ▪ They have one to two layer of circular smooth muscle cells. ▪ Thin wall and muscular venules allow to expand and serve as large reservoir for accommodation of large volume of blood. Blood volume increases of 360%.  Veins ▪ Have very thin wall in relation with diameter. Have same three player. ▪ Tunica interna is thinner than artery. Tunica media is much thinner (relatively little smooth muscles and elastic fibers), Tunica externa is thickest layer amongst contain collagen fiber and elastic fibers. ▪ Vein lack internal and external elastic laminae. Lumen of vein is larger as compared to artery. Appeared collapsed / flattened when sectioned. ▪ Contraction of skeletal muscle in lower limb help boost venous return. Blood flow in vein slow, even. ▪ Many veins (specially in limb) have valves. Valves are cup like projection in lumen pointing towards heart. Low blood pressure allow blood returning to heart slow and valve aid preventing backflowing. ▪ Vascular sinus is vein with thin epithelial wall that has not smooth muscle to alter diameter. Surrounding connective tissue replaces tunica media. ▪ Veins are more numerous than arteries. Veins are mostly superficial (also dipper). Blood distribution ▪ Large portion of blood at the rest (64%) is system vein & venules ▪ Arteries hold around 13% of total blood volume. ▪ Systemic capillary hold around 7%, ▪ Pulmonary blood vessels hold around 9%, ▪ Heart hold around 7% ▪ Veins and venules contain large % of blood – function as blood reservoir. ▪ This blood can be diverted quickly if need arises (muscular activity, haemorrhage) Capillary exchange ▪ Is movement of substances between blood and interstitial fluid ▪ The 7% of blood at any given time is continuously exchanging material ▪ Exchange occur by three mechanisms ▪ Diffusion: capillary exchange is simple diffusion (high to low concentration) O2, CO2, Glucose, amino acid, hormones, wastes. Substance diffuses through intercellular cleft or fenestrations. ▪ Transcytosis: Substances in blood plasma become enclosed within tiny pinocytic vessels and transported across capillary wall. Lipid soluble molecules, hormones ▪ Bulk flow (filtration & reabsorption): Is passive process, large number of ions, molecules, move together in same direction. Occur from high to low pressure area. Is solute exchange. Blood hydrostatic & interstitial fluid osmotic pressure promot filtration. Factors affecting blood flow ▪ Hemodynamics is force involved in circulating blood throughout body. ▪ Blood flow is volume of blood that flow through any tissue in given period of time (ml/min). ▪ Total blood flow is cardiac output (CO), volume of blood circulated through systemic and pulmonary circulation vessels each minute. ▪ Factor that affect blood flow are ▪ Blood Pressure - Pressure difference that drives blood flow through tissue ▪ Blood flow from region of high pressure to low pression ▪ Greater the pressure difference – greater will be blood flow ▪ Resistance to flow blood in blood vessel. ▪ Higher the resistance – smaller the blood flow Blood pressure (BP) ▪ Is hydrostatic pressure exerted by flowing blood on wall of blood vessels. ▪ BP is determined by cardiac output, blood volume & vascular resistance. ▪ Systolic blood pressure is highest pressure attained in arteries during systole ▪ Diastolic blood pressure is lowest pressure attained in arteries during diastole. ▪ Blood pressure continue to drop when is passes from arteries to veins. ▪ Blood pressure reaches to zero when it flow into right atrial and ventricle. ▪ Mean arterial pressure – average blood pressure in artery. It is roughly 1/3 way between diastolic and systolic pressure.  Vascular resistance ▪ Is opposition to blood flow due to friction between blood & wall of blood vessels. ▪ Vascular resistance depends on ▪ Size of lumen: Small lumen will give greater resistance (inversely proportional). Vasoconstrictor narrow lumen increases resistance. ▪ Blood viscosity: Depends on ratio of RBC to plasma. Higher viscosity – more resistance. Dehydration, polycythemia increases blood pressure by increasing viscosity. ▪ Total blood vessel length: Resistance to flow of blood is directly proportional to length of blood vessel. Longer blood vessel – more resistance. Obese peoples have hypertension because of additional blood vessels in adipose tissue. Around 650 km of blood vessel develop for each kg. of fat. ▪ Systemic vascular resistance (total peripheral resistance) – all vascular resistance offered by systemic blood vessels. ▪ Large diameter of arteria and veins – resistance will be small because most of blood will not come in physical contact with wall of blood vessels. ▪ Small blood vessels contributes more systemic vascular resistance Control of blood pressure & blood flow ▪ Several interconnected feedback system controls blood pressure by adjusting ▪ Heart rate ▪ Stroke volume ▪ Systemic vascular resistance ▪ Blood volume ▪ Some system allow rapid adjustment to cope with sudden change in BP ▪ Other act more slowly to provide long-term regulation. ▪ Blood pressure is regulated by ▪ Cardio vascular center ▪ Neural regulation – Baroreceptor and chemoreceptor ▪ Hormonal regulation – RAA, adrenaline, ADH, ANP ▪ Auto regulation – Physical change, vasodilation & vasoconstriction Cardio vascular center (CV) ▪ CV center in medulla oblongata regulate HR and stroke volume. ▪ It also control neural, hormonal and local negative feedback system that regulate BP. ▪ Group of neurons in CV center control HR and contractility, blood vessel diameter. ▪ CV center receive input from higher brain region, and sensory receptors. ▪ Output from CV center flow along sympathetic impulse and reach heart. ▪ CV center send impulse to smooth muscle of blood vessels via vasomotor nerve.  Other Control ▪ Neural regulation: Control by negative feedback system ▪ Baroreceptor: Pressure sensitive sensory receptor located in aorta, internal carotid arteries, other large arteries of neck and arm. Send impulse to CV center to help regulate BP. ▪ Chemoreceptor: Sensory receptor that monitor chemical composition of blood located close to baroreceptor. They sense change in level of O2, CO2, H+, acidosis and stimulate chemoreceptor to send impulse to CV center. ▪ Hormonal regulation ▪ RAA: Decrease in blood volume regulate Renin angiotensin aldosterone system. ▪ Adrenaline: Adrenal medulla release adrenaline increases cardiac output and vasoconstriction ▪ ADH: Produced by hypothalamus, manipulate blood volume. ▪ ANP: Atrial natriuretic peptide released by atria of heart lowers BP by vasodilation ▪ Auto regulation: Local changes regulate vasomotion. Vasodilators produces local dilation of capillary, increase blood flow, increase O2 level. Opposite vasoconstriction. This ability to adjust blood flow as per metabolic demand is autoregulation. Governed by ▪ Physical change: Warming promote vasodilation, Cooling causes vasoconstriction. ▪ Vasodilation & vasoconstriction: Blood cell produces chemicals (K+, H+, lactate, ATP, NO) that alters blood-vessel diameter. Tissue trauma / inflammation releases vasodilating substances like kinins, histamine, thromboxane, serotonin, superoxide radicals, endothelin etc. BP and its measurement ▪ In clinical practice blood pressure refers to pressure in arteries generated by left ventricle during systole. ▪ BP is measured in brachial artery in left hand using device sphygmomanometer ▪ Systolic BP is the force of blood pressure on arterial wall just after ventricular contraction. ▪ Diastolic BP is force exerted by blood remaining in artery during ventricular relaxation. ▪ Normal systolic BP in adult is less than 120 mmHg and diastolic BP is less than 80 mmHg. (written as 120/80). ▪ In young adult females BP are 8 to 10 mmHg less. Peoples who exercise regularly and of good physical condition have lower BP. Slight low BP is sign of good health. ▪ Difference between systolic and diastolic BP is pulse pressure. (normally 40 mmHg) Circulatory Route Heart Lung machine  Systemic circulation ▪ Arteries, arterioles, capillary, venules, veins are organized in circular route. ▪ Include all arteries & arterioles that carries oxygenated blood from left ventricle to systemic capillaries and veins and venules that returns deoxygenated blood to the right atrium. ▪ Some subdivision of system circulation are ▪ Coronary circulation – myocardium of heart ▪ Cerebral circulation – supply to brain ▪ Hepatic portal circulation – supply from GIT to liver ▪ Fetal circulation - - only in special circumstances ▪ Systemic circulation carry oxygen and nutrient to the body tissue and remove carbon dioxide, waste products and heat from tissue. ▪ All systemic arteries branched from aorta ▪ All systemic veins drain in to superior, inferior vena cava or coronary sinus.  Hepatic & Portal circulation ▪ Carry venous blood from GIT and spleen to liver ▪ A vein that carries blood from one capillary network to another is called portal vein. ▪ Hepatic portal vein receives blood from GIT & spleen and deliver it to liver. ▪ After meal hepatic portal blood (coming from GIT) is rich in nutrients. Liver stores some of them, modify other and then passes to general circulation. ▪ E.g. Liver converts glucose to glycogen and stores it, reduces blood glucose level shortly after meal. ▪ Liver also detoxifies harmful substances, alcohols that are absorbed from GIT Pulmonary circulation ▪ Carry deoxygenated blood from right ventricle to air sac in lungs. ▪ Oxygenated blood return from sac to the left atrium through 4 pulmonary veins. ▪ Pulmonary trunk emerges from right ventricle & divide in to right and left artery (to the right and left lung) ▪ Arteries enter in lung and subdivide to form capillary network around sac (alveoli) ▪ In lungs exchange of O2 and CO2 take place. Pulmonary capillary unit to form venules and eventually pulmonary vein. Which exit lungs and carry oxygenated blood to left atria. ▪ Contraction left atria and subsequently ventricle eject the oxygenated blood into the systemic circulation. Thanks