Physics of the Cardiovascular System (CVS) PDF

Physics of the Cardiovascular System (CVS) Assistant prof. Dr :Mohammed U. Hussein Department of Physiology and Medical Physics, College of Medicine, University of Anbar. [email protected]...

Physics of the Cardiovascular System (CVS) Assistant prof. Dr :Mohammed U. Hussein Department of Physiology and Medical Physics, College of Medicine, University of Anbar. [email protected] uoanbar.edu.iq Highlight Fetal heart Specialists in (CVS) Heart How does the heart work? Cardiac muscle: Cardiac output: Heart valves and artificial heart valves Blood volume: blood components : Physics of Blood Flow uoanbar.edu.iq Cardiovascular system (CVS): Blood, Vessels, Heart 1. Supply energy (fuel from food) 2. Supply O2 from the air we breathe 3. Dispose by-products of combustions (CO2, H2O, heat, etc) Blood: 7% of body mass: 4.5 kg or 4.4 liters in a 64 kg person Find : the blood volume for you (H.W) uoanbar.edu.iq  University of Anbar Fetal heart 1. Start blood circulation at the eighth week after conception 2. Obtain oxygenated blood from mother via umbilical cord 3. An opening between RA and LA NOTE: 1. 90% of blood flows from RA to LA through the opening 2. 10% circulates through fetal lungs 3. Within minutes after birth, the opening is closed in effect 4. Complete closure takes several months 5. Blue baby: inadequate closure of the opening, requires a surgery Notes on fetal heart: 1. Between the atria of the fetal heart is open because the period is incomplete for completion (10%) and after birth closes this hole. 2. The fetus's heart must be completed so that it will not be able to give up its mother's heart and cause its weakness and lack of age because it feeds on the blood through the umbilical cord and is formed in the first 7 weeks of its prenatal formation. Specialists in (CVS) 1. Hematologist 2. Cardiologist 3. Heart surgeon uoanbar.edu.iq uoanbar.edu.iq  Heart The heart is a hollow located in the chest between the lungs behind the sternum and above the diaphragm. It is surrounded by the pericardium. Its size is about that of a fist, and its weight is about 250-300 g. Its center is located about 1.5 cm to the left of the mid sagittal plane. Located above the heart are the great vessels: the superior and inferior vena cava, the pulmonary artery and vein, as well as the aorta. The aortic arch lies behind the heart. uoanbar.edu.iq  How does the heart work? - Enter the blood from the left atrium then to the left ventricle and then exit from the left ventricle to enter the right atrium and exit from the right ventricle to the lungs and then back to the left atrium. - Each cell needs 1 min. , In order to cut a full cycle in the body to pump blood - The capillary function gives O2 and takes CO2 uoanbar.edu.iq Four valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart as shown in Fig.():- 1- The tricuspid valve: - Is in the right side of the heart, between the right atrium and the right ventricle. 2- The pulmonary valve: - Is in the right side of the heart, between the right ventricle and the entrance to the pulmonary artery, which carries blood to the lungs. 3- The mitral valve: - Is in the left side of the heart, between the left atrium and the left ventricle. 4- The aortic valve:-Is in the left side of the heart, between the left ventricle and the entrance to the aorta, the artery that carries blood to the body. uoanbar.edu.iq Valves are like doors that open and close. They open to allow blood to flow through to the next chamber or to one of the arteries, and then they shut (close) to keep blood from flowing backward. Arteries of the heart The arteries are major blood vessels connected to heart. ++The pulmonary artery carries blood pumped from the right side of the heart to the lungs to pick up a fresh supply of oxygen. ++The aorta is the main artery that carries oxygen-rich blood pumped from the left side of the heart out to the body. ++The coronary arteries are the other important arteries attached to the heart. They carry oxygen-rich blood from the aorta to the heart muscle, which must have its own blood supply to function. Veins of the heart The veins also are major blood vessels connected to heart. ++The pulmonary veins carry oxygen-rich blood from the lungs to the left side of the heart so it can be pumped out to the body. ++The superior and inferior vena cava are large veins that carry oxygen-poor blood from the body back to the heart. uoanbar.edu.iq. Double pump. Provides the force needed to circulate the blood. Two major circulatory system 1. Pulmonary circulation (right side pump): RV (25 mmHg) →pulmonary artery →pulmonary capillary →pulmonary vein →LA (7 ~ 8 mmHg) →LV 2. Systemic circulation (left side pump): LV (125 mmHg) →arteries → arterioles →capillary bed (for a few seconds) →venules →veins → superior vena cava and inferior vena cava →RA (5 ~ 6 mmHg) →RV. Four chambers 1. Atrium collects returning blood 2. Ventricle generates high pressure Note //. Right ventricle pumps blood with constriction (80 ml) uoanbar.edu.iq Cardiac muscle:. Shares characteristics of skeletal and smooth muscle 1. Strong tension, (like skeletal muscle) 2. Not under direct conscious control, influenced by Autonomic Nervous System ANS (like smooth muscle). Cardiac muscle cells exhibit rhythmic self-excitation (!!!!). Long refractory period (~ 250 ms): prevents tetanus (sustained contraction) and limits heart rate Cardiac output:. Cardiac output = heart rate ×stroke volume. Cardiac output is determined by heart rate, contractility (contraction strength), and peripheral (external)flow resistance. Regulation of heart rate and contractility is very complex and involves CNS and hormonal influences, intrinsic cardiac mechanisms. For typical adult, about 5 l/min. Stroke volume ~ 80 ml. About 1 min for the average RBC to make one complete cycle of the body. Maximum cardiac output 1. 25 l/min for young men 2. 40 l/min for trained athletes uoanbar.edu.iq  Heart valves and artificial heart valves 1. One-way flow 2. Valve closing and turbulent blood flow →heart sound(!!!!) uoanbar.edu.iq  Blood volume Total volume of about 5 l - The blood is a bright red while in fact it is a dark red. Because most blood in the vein 1. 80% (4 l) in systemic circulation and (75%) and this does not contain O2 is dark red so when we are injured bright red to 20% (1 l) in pulmonary circulation contain O2 and blood comes out of the vein , not from artery. 2. Systemic circulation: 15% in arteries, - -The blood value as a percentage in the vein (75%) is more than the artery and capillary 10% in capillaries, 75% in veins because the blood is stagnant(static) and the pressure is greater , the diameter is larger in 3. Pulmonary circulation: 7% in pulmonary addition to containing the valves while the capillaries, 46.5% in pulmonary arteries, artery does not have valves and keeps the blood from returning , thus does not cause 46.5% in pulmonary veins varicose veins ….etc. uoanbar.edu.iq  Blood components 1. RBC (45%): It transfers oxygen and hemoglobin -(4.4 liters) of blood is not found 2. WBC is large size and contains several only in the heart, but in all types arteries, veins and capillaries 3. Platelet : be very small 4. Plasma contains ions, electrons, hormones, minerals and other substances - Blood fluidity varies on water fluidity !!!! -Each 100 ml of blood is 10 mg of calcium and if this is reduced, it leads to death (4-8 mg) because calcium is important in the work of nerves and muscles. uoanbar.edu.iq - The red color is caused by the red blood cells (erythrocytes), flat disks about 7μm in diameter, which Ex: If white blood cells have an average represent about 45% of the volume of the blood.There diameter of 12 μm, what percentage of the blood are about 5×106 red blood cells/mm3 of blood. volume is white blood cells? A nearly clear fluid called blood plasma accounts for the other 55%,. The white blood cells (leucocytes), present Solu.// in small amounts. White blood cells (~9 to 15 μm in Fraction of cells =No. of cells /mm3 ×Vol. of a cell in diameter) play an important role in combating disease. mm3 There are about 8000 white blood cells/mm3 of blood, =8000/mm3 × [(4/3)π (6×10-3)3 mm3 ]=7×10-3 when there is an infection in the body the number of =0.7% white blood cells (white count) increases.(In one type of blood cancer ,leukemia ,there is an excessive production of white blood cells) , The blood also contains platelets (~1 to 4 μm in diameter ) are involved in the clotting function of blood ,there are about 3×105 platelets /mm3 of blood. uoanbar.edu.iq Hb (Hemoglobin ) estimation: Hb is about 28% of red blood cells ,Hb molecule is spherical with maximum diameter 6.4 µm is composed of hem moiety which contents 1 ferrous iron carried in aporphyrin ring and globin tetramer of polypeptide chains which are bound to the hem moiety and is composed of 2 alpha and 2 beta chains. Normal range of Hb : For male (14-18g/dl) , For female (11.5-16 g/dl) , For children (11.5-14.5 g/dl) for (10-12 year) , For children (11-13 g/dl) for 1 year ………….. (dl=100ml) PCV estimation : PCV (packed cell volume)is the volume of RBC expressed as percentage of the volume of the whole blood in the sample Normal value of PCV: For male (40-54%) , For female (37-47%) ESR estimation: ESR (erythrocyte sedimentation rate) is the rate at which erythrocytes sediment on their native plasma Normal value of ESR: For male (0-15mm/hr) , For female (0-20mm/hr) uoanbar.edu.iq  How to calculate the number of blood cells, for example red blood cells ? -It is calculated by microscopy by taking a blood sample either by cell ,cell and this method is old, inaccurate and illogical (approximately 10%). - Another method is capillary where the rate of the diameter is taken. For example, (4-20 micrometers), the rate is approximately 7 micrometers, as much as a cell of RBC, a cell enters the capillary. A magnetic or electric field is placed on the tube causing attenuation (1), only in red blood cells and platelets, while in white blood cells, this device is not used because WBC contains several types that can not be distinguished and are calculated by microscopy. uoanbar.edu.iq  Physics of Blood Flow Conservation of flow rate:. Flow rate = blood volume/time, l/min. Blood flow rate is continuous under three assumptions 1. Blood is incompressible 2. Vessels are rigid 3. There are no sinks (leakage or hemorrhage) or sources (transfusion) of blood flow. Continuous flow →Ftotal = cardiac output = Farteries = Farterioles = Fcaps = Fvenules =Fveins Flow velocity 1. Flow rate = cross-sectional area ×velocity (F = A v) 2. For a group of n parallel blood vessels, + Atotal = n Aaverage + F = Atotal ×vaverage + F = Aarteries ×varteries = Aarterioles ×varterioles = Acaps ×vcaps =.Avenules ×vvenules = Aveins ×vveins = constant 3. Flow velocity is inversely related to total cross-sectional area: 4. varteries > varterioles > vcaps < vvenules < vveins uoanbar.edu.iq Physics of the Cardiovascular System (CVS) Assistant prof. Dr :Mohammed U. Hussein Department of Physiology and Medical Physics, College of Medicine, University of Anbar. [email protected] uoanbar.edu.iq Highlight Physics of Blood Flow Flow resistance Blood Vessels and Flow Regulation The Starling's law Arterial Blood Pressure Measurement of arterial BP Fluid flow and the continuity equation Bernoulli's equation The role of gravity on blood circulation Effect of acceleration on blood pressure uoanbar.edu.iq Hb (Hemoglobin ) estimation: Hb is about 28% of red blood cells ,Hb molecule is spherical with maximum diameter 6.4 µm is composed of hem moiety which contents 1 ferrous iron carried in aporphyrin ring and globin tetramer of polypeptide chains which are bound to the hem moiety and is composed of 2 alpha and 2 beta chains. Normal range of Hb : For male (14-18g/dl) , For female (11.5-16 g/dl) , For children (11.5-14.5 g/dl) for (10-12 year) , For children (11-13 g/dl) for 1 year ………….. (dl=100ml) PCV estimation : PCV (packed cell volume)is the volume of RBC expressed as percentage of the volume of the whole blood in the sample Normal value of PCV: For male (40-54%) , For female (37-47%) ESR estimation: ESR (erythrocyte sedimentation rate) is the rate at which erythrocytes sediment on their native plasma Normal value of ESR: For male (0-15mm/hr) , For female (0-20mm/hr) uoanbar.edu.iq  University of Anbar MCV : ( 80-100 fl ) ( normocytic Anemia ) WBC (4-11) ˂ 80 ( microcytic Anemia ) ( HB little ) decrease iron 1.Neutrophils ( 40-70) in ( infection) , >100 ( macrocytic Anemia ) bacteria infection 1. megaloblastic anemia ( Folic acid , B12) 2.Lymphocytes ( 20-40) in ( virus 2. Non- megaloblastic anemia ( Liver disease , Alcohl, infection ) cytotoxic ,hypothyroidism , pregnancy ) 3.Monocytes ( 2-8 %) in (Fungal disease or tuberculosis) MCH ( 28-32 pg) 4.Eosinophils (1-4 %) in (Allergy) ˂ 28 ( HB little ) decrease iron 5.Basophils (˂ 0.01 ) > 32 decrease (Folic acid , B12) If …….MCV ( 80-100 fl ) , MCH ( 28-32 pg) ( normocytic Anemia ) , HB ˂12.5 normocytic Anemia But may be disease for example increase acute bleeding or spleen work uoanbar.edu.iq How to calculate the number of blood cells, for example red blood cells ? -It is calculated by microscopy by taking a blood sample either by cell ,cell and this method is old, inaccurate and illogical (approximately 10%). - Another method is capillary where the rate of the diameter is taken. For example, (4-20 micrometers), the rate is approximately 7 micrometers, as much as a cell of RBC, a cell enters the capillary. A magnetic or electric field is placed on the tube causing attenuation (1), only in red blood cells and platelets, while in white blood cells, this device is not used because WBC contains several types that can not be distinguished and are calculated by microscopy. uoanbar.edu.iq uoanbar.edu.iq uoanbar.edu.iq  Physics of Blood Flow Conservation of flow rate:. Flow rate = blood volume/time, l/min. Blood flow rate is continuous under three assumptions 1. Blood is incompressible 2. Vessels are rigid 3. There are no sinks (leakage or hemorrhage) or sources (transfusion) of blood flow. Continuous flow →Ftotal = cardiac output = Farteries = Farterioles = Fcaps = Fvenules =Fveins Flow velocity 1. Flow rate = cross-sectional area ×velocity (F = A v) 2. For a group of n parallel blood vessels, + Atotal = n Aaverage + F = Atotal ×vaverage + F = Aarteries ×varteries = Aarterioles ×varterioles = Acaps ×vcaps =.Avenules ×vvenules = Aveins ×vveins = constant 3. Flow velocity is inversely related to total cross-sectional area: 4. varteries > varterioles > vcaps < vvenules < vveins uoanbar.edu.iq  Flow resistance 1. Laminar flow (v < critical velocity) - Silent - Maximum velocity at the center - Zero velocity at the wall 2. Turbulent flow (v > critical flow) - Audible →heart sound - Higher flow resistance than laminar flow - Most likely to occur at constrictions. uoanbar.edu.iq  Blood Vessels and Flow Regulation 1. Different vessels have distinct anatomy and physiology. This is due in part to large changes in blood pressure throughout the circulation A fast heart rate (tachycardia) increases the 2. Combined length of all blood vessels > earth’s circumference work load since the amount of time the heart muscles spend contracting increases. (~ 25,000 miles) Normocardia : is a normal heart rate that Mean arterial pressure : ( MAP) range between 60 and 100 beat /min. Normal ( 70-100 mmHg) Tachycardia : is a heart rate in excess of 100 𝑴𝑨𝑷 = 𝟐 𝟏 𝑫𝒊𝒂𝒔𝒕𝒐𝒍𝒊𝒄 + 𝑺𝒚𝒔𝒕𝒐𝒍𝒊𝒄 beats/min. 𝟑 𝟑 Bradycardia: is a heart rate that is less than 60 beats/min. If the pressure (180/60) ……Find MAP (2/3) 60+ (1/3) 180 = 40+ 60= 100 MAP is normal uoanbar.edu.iq Arteries. Thick, 1. Must withstand high BP 2. Puncture can be fatal (killer ) 3. High BP damages arterial walls, leading to vessel disease. Large diameter 1. Low flow resistance 2. Transmits entire heart pressure to arterioles. Arterioles. Large pressure drop →controls flow distribution. Local control 1. Meet local metabolic rate 2. Increase flow to muscles during exertion. Reflex (global) control 1. Regulate arterial BP 2. Maintain flow to vital organs (brain) uoanbar.edu.iq. Role of arterioles in hypertension 1. Autonomic nervous system innervates (stimuli ) smooth muscle surrounding blood vessels. 3. Excessive constriction of arterioles is primary mechanism responsible to high BP. 4. Constriction of arterioles →high peripheral resistance →BP increases to maintain flow uoanbar.edu.iq. Capillaries. Maximize exchange Arterial Blood Pressure BP during cardiac cycle: 1. Huge surface area 1. Systole: ventricles contract, arteries expand, hold 2. Thin walls to facilitate diffusion 2/3 of stroke volume 3. Low blood velocity (~ 1 mm/s) gives more time for exchange 2. Diastole: ventricles relax, arteries recoil,. Veins and venules squeezing blood to arterioles. Veins: very large radius and thin wall - Effect of gravity on arterial blood pressure: 1. Largest cross-sectional area - Arterial BP affected by gravity (P = ρgh) 1. Resistive losses are small 2. Negligible flow resistance 2. No blood to head for upward acceleration of a > 3. Large volume: holds 75% of blood and acts as blood reservoir 3g(!!!!). Pressure in veins governs ventricular filling (i.e. volume of blood filling heart), an 3. Adaptation to counteract( collision ) gravity: one- important determinant of cardiac output. If ventricular filling increases, the stretched heart responds with increased contractive force (Starling’s law), which way valve in veins, skeletal muscles squeeze veins, increases stroke volume and cardiac output. forcing blood back to heart. Veins have one-way valve. Constriction of the veins drives blood toward heart, increasing cardiac output via Starling mechanism. uoanbar.edu.iq  - Measurement of arterial BP: - Sphygmomanometer: inflatable cuff and pressure gauge 1. Inflate cuff at heart level until P > Psystole →no blood flow 2. Slowly deflate. Listen for Korotkoff sounds (K sounds, due to turbulent blood flow)(phonocardiogram) 3. First sound →P = Psystole 4. Last sound →P = Pdiastole uoanbar.edu.iq Fluid flow and the continuity equation: uoanbar.edu.iq  Bernoulli's equation: Bernoulli derived an important equation to describe the flow of fluids; this equation is stated that the work done on a fluid as it flows from one place to another is equal to the change in its mechanical energy. This equation is applicable for incompressible fluids ,nonviscous fluids (where no energy loss), laminar flow ,and for steady state flow (when the flow speed at any point is constant with time). uoanbar.edu.iq This can be generalized for any two points through the flow of the fluid, so Bernoulli's equation can be written as: Bernoulli's principle can explain the clogging (resistance) of arteries when the blood flows through an artery section of cross sectional area.According to Bernoulli Thus Bernoulli's equation can be stated as the pressure of the fluid plus its the pressure of blood within this section mechanical energy density (kinetic energy density+ potential energy will drop inside the arterial wall and on the density) is the same everywhere in the flow. other hand the pressure on the outside Rearrange the equation leads to the following: arterial wall will be larger than inside causing the clogging of the blood vessel. uoanbar.edu.iq Ex: The diameter of a horizontal blood vessel is reduced from 12 to 4 mm ,what is the flow rate of blood in the vessel ,if the pressure at the wide part is 8 Kpa. and 4 Kpa. at the narrow one.(Hint: The density of blood to be 1060kg.m-3). The flow rate is constant everywhere and can be calculated relation Q=πr2narr νnarr =3.14× (4×10-3 )2 ×2.76 =1.387×10-4 m3s-1 uoanbar.edu.iq  The role of gravity on blood circulation: From Bernoulli's ,the pressure of the fluid change according We can analyze the situation in the reclining position. to its kinetic energy density and as well as it potential -The velocities in the three main arteries (Brain,Heart ,and Feet) are energy density, because of that ,the blood pressure in small so that the term can be ignored human organs is affected by its location from earth.. During the blood circulation, the venous system is used to Furthermore in this position also the height of the brain , heart and return the blood from the lower extremities (maximum feet are almost equal so that the term ρgy can be ignored from terms ) to the heart.It is expected to have a problem of the formula. lifting blood long distances to the heart against the force of This results in equal blood pressure in the three parts gravity. PB =PH=PF ----If we have a person in the reclining (laying down) Note that B,H and F refer to the brain ,heart and feet. position, the measurement of blood pressure in the large -----In the standing position , the situation is different ,where only arteries are almost the same everywhere. the term can be ignored and the term ρgy has a The small drop in pressure between the heart and the feet or significant effect. the brain is due to the viscous force , according to Hence the gauge pressure at the brain PB at the heart PH and the Bernoulli's equation. foot PF are related by: PF = PH + ρghH=PB+ ρghB Note that hF=0 in the standing position. uoanbar.edu.iq -Typical values for adults standing upward hH=1.3 m and hB=1.7m - Typical value of the blood pressure at heart is PH=13.3KPA and take the blood density to be 1060 kg.m- 3 ,we find: PF = PH + ρghH = 13.3×103+(1060)(10)(1.3) ≈ 27.1kpa -In a similar way , we find that: PF = PH + ρghH= PB+ρghB PB = PH + ρg(hH-hB)=13.3×103+(1060)(10)(-0.4)=9.06KPa -This explains why the pressures in the lower and upper parts of the body are very different when the person is standing , although they are about equal in the reclining. -The high blood pressure at the foot explain the possibility of lifting blood uphill (increase.) to the heart and in addition the muscles surrounding the veins contract and cause constriction. uoanbar.edu.iq  Effect of acceleration on blood pressure : It is a common system for some people having hypotension to fell dizziness when they exist in an elevator of upward acceleration. Downward acceleration: If a man in an upright position experience Q //Is the blood pressure at organs affected when man under upward or downward downward acceleration then his effective weight becomes acceleration? m(g-a). Ans.// Applying Bernoulli's equation to the foot, brain and heart with g replaced by g-a , so we have: When a person experiences an upward or downward acceleration his weight will be different. Upward acceleration :If a man experience upward acceleration a ,then his effective weight PB=PH+ρ(g-a)(hH-hB) or PB=PH-ρ(g-a)( hB -hH) becomes m(g +a). Thus the blood pressure at the brain will increase even farther by Applying Bernoulli's equation to the foot ,brain and heart with g replaced by g +a ,so we have : increasing the downward acceleration a ,which opposite to PB=PH+ρ(g+a)(hH-hB) Or PB=PH-ρ(g+a)( hB -hH) what occurs by the upward acceleration. For stand person the term ( hB -hH) is positive and also the same for (g+a). This increase should be controlled and observed, where at certain The blood pressure at the brain will be reduced even farther by increasing the upward value of a the blood pressure at the brain may cause an acceleration a. explosion (rupture ) of the arteries in the brain, which is so dangerous. At certain value of a , the human will losses consciousness (or dizziness) because the collapse of the arteries in the brain when the blood pressure at the brain equal zero. The same calculation for the blood pressure at the foot results in a Put PB =0 in the above equation ,we get: decrease of the blood pressure by increasing the downward acceleration. 0= PH - ρ(g+a)( hB -hH) ` uoanbar.edu.iq Physics of the Cardiovascular System (CVS) Assistant prof. Dr :Mohammed U. Hussein Department of Physiology and Medical Physics, College of Medicine, University of Anbar. [email protected] uoanbar.edu.iq Highlight Viscosity (η) Reynolds Number (NR) Cardiovascular Disease (Congestive Heart Failure (CHF), Risk factors, promoters of vessel disease, Heart attack) uoanbar.edu.iq Ex: The diameter of a horizontal blood vessel is reduced from 12 to 4 mm ,what is the flow rate of blood in the vessel ,if the pressure at the wide part is 8 Kpa. and 4 Kpa. at the narrow one.(Hint: The density of blood to be 1060kg.m-3). uoanbar.edu.iq The role of gravity on blood circulation: From Bernoulli's ,the pressure of the fluid change according to its kinetic energy density and as well as it potential energy density, because of that ,the blood pressure in human organs is affected by its location from earth. During the blood circulation, the venous system is used to return the blood from the lower extremities (maximum terms ) to the heart.It is expected to have a problem of lifting blood long distances to the heart against the force of gravity. ----If we have a person in the reclining (laying down) position, the measurement of blood pressure in the large arteries are almost the same everywhere. The small drop in pressure between the heart and the feet or the brain is due to the viscous force , according to Bernoulli's equation. uoanbar.edu.iq We can analyze the situation in the reclining position. -The velocities in the three main arteries (Brain,Heart ,and Feet) are small so that the term can be ignored. Furthermore in this position also the height of the brain , heart and feet are almost equal so that the term ρgy can be ignored from the formula. This results in equal blood pressure in the three parts PB =PH=PF Note that B,H and F refer to the brain ,heart and feet. -----In the standing position , the situation is different ,where only the term can be ignored and the term ρgy has a significant effect. Hence the gauge pressure at the brain PB at the heart PH and the foot PF are related by: PF = PH + ρghH=PB+ ρghB Note that hF=0 in the standing position. uoanbar.edu.iq -Typical values for adults standing upward hH=1.3 m and hB=1.7m - Typical value of the blood pressure at heart is PH=13.3KPA and take the blood density to be 1060 kg.m-3 ,we find: PF = PH + ρghH = 13.3×103+(1060)(10)(1.3) ≈ 27.1kpa -In a similar way , we find that: PF = PH + ρghH= PB+ρghB PB = PH + ρg(hH-hB)=13.3×103+(1060)(10)(-0.4)=9.06KPa -This explains why the pressures in the lower and upper parts of the body are very different when the person is standing , although they are about equal in the reclining. -The high blood pressure at the foot explain the possibility of lifting blood uphill (increase.) to the heart and in addition the muscles surrounding the veins contract and cause constriction. uoanbar.edu.iq Effect of acceleration on blood pressure : It is a common system for some people having hypotension to fell dizziness when they exist in an elevator of upward acceleration. Q //Is the blood pressure at organs affected when man under upward or downward acceleration? Ans.// When a person experiences an upward or downward acceleration his weight will be different. Upward acceleration :If a man experience upward acceleration a ,then his effective weight becomes m(g +a). Applying Bernoulli's equation to the foot ,brain and heart with g replaced by g +a ,so we have : PB = PH + ρ(g+a)(hH-hB) Or PB = PH - ρ(g+a)( hB -hH) For stand person the term ( hB -hH) is positive and also the same for (g+a). The blood pressure at the brain will be reduced even farther by increasing the upward acceleration a. At certain value of a , the human will losses consciousness (or dizziness) because the collapse of the arteries in the brain when the blood pressure at the brain equal zero. Put PB =0 in the above equation ,we get: 0= PH - ρ(g+a)( hB -hH) ` uoanbar.edu.iq Downward acceleration: If a man in an upright position experience downward acceleration then his effective weight becomes m(g-a). Applying Bernoulli's equation to the foot, brain and heart with g replaced by g-a , so we have: PB=PH+ρ(g-a)(hH-hB) or PB=PH-ρ(g-a)( hB -hH) Thus the blood pressure at the brain will increase even farther by increasing the downward acceleration a ,which opposite to what occurs by the upward acceleration. This increase should be controlled and observed, where at certain value of a the blood pressure at the brain may cause an explosion (rupture ) of the arteries in the brain, which is so dangerous. The same calculation for the blood pressure at the foot results in a decrease of the blood pressure by increasing the downward acceleration. uoanbar.edu.iq  Viscosity (η): The quantity that describes a fluid's resistance to flow. The cgs unit used to measure viscosity is the poise, the SI unit for viscosity is the Pascal second (Pa.s) ,which equals (10 poises). The viscosity of water is about (10-3pa.s) at 200C ,the viscosity of blood typically (3×10-3-4×10-3pa.s) ,but depends on the percentage of red blood cells in the blood (the hematocrit). The percentage of the blood that is cells is called the hematocrit. thus if a person has hematocrit of 40,40 percent of the blood volume is cells and the remainder is plasma. The hematocrit of men averages about 42 where as that of women averages about 38. These values vary tremendously ,depending on:- 1-whether or not the person has anemia. 2-The degree of bodily activity. 3-The altitude(h) at which the person resides. When the hematocrit rises to 60 or 70 , which it often does in polycythemia uoanbar.edu.iq  Reynolds Number (NR): We remember that Poiseulle's is applicable for laminar flow ,so it is necessary to determine whether the flow is laminar or turbulent.There is a dimensionless quantity called Reynolds Number (NR) used to distinguish the type of the flow. It is found experimentally that if : -consider a fluid of density ρ and viscosity NR3000 ………flow is turbulent through a tube of radius R ,hence the Reynolds 2000< NR 140 mmHg 4. Two types: LDL (low density lipoprotein) and HDL 5. LDLs deposit on vessel walls →bad cholesterol 2. Diastolic BP > 90 mmHg 6. HDLs reduce the amount of LDLs →good cholesterol 3. Leading cause of stroke and heart disease 4. Arterioles constricted, regulation goes awry (deflection) 5. 10% (50% in US) are sodium sensitive (salt elevates BP) 6. No obvious (not clear ) symptoms →silent killer 7. Damages arteries →hardening of arteries→ narrowing (atherosclerosis) uoanbar.edu.iq 1.Bad cholesterol LDL (Low Density Lipoprotein) : Bad fats, with low density, deposited in the arteries, causing narrowing of blood vessels and the occurrence of atherosclerosis. Its percentage rises in the blood when eating foods that contain a high percentage of cholesterol, or because of diabetes mellitus, hypothyroidism, or a genetic reason. Its blood level should not exceed (100-130 mg/dL) 2. Useful cholesterol HDL (High Density Lipoprotein) : loving fats, or called scavengers, of high density responsible for carrying cholesterol deposited in the arteries to the liver for disposal.... Its increase in the blood is a good sign, and its percentage can be increased by eating unsaturated oils and also by reducing weight. Its normal blood level ranges between (35-55 mg/dL.( uoanbar.edu.iq. Smoking 1. Increases BP 2. Smoke contains CO →stresses heart 3. Increases platelet clumping →promotes atherosclerosis (viscosity ) 4. Effects are reversible. Other factors 1. Salt: not certain except effect on hypertension 2. Caffeine: no strong link to heart disease 3. Chronic stress: may increase risk in some individuals uoanbar.edu.iq Vessel disease. Arteries surrounded by tough (solid) connective tissue. However, high blood pressure can damage the tissue, leading to vessel disease.. Arteriosclerosis: hardening of arteries. Atherosclerosis: plaque (fat, calcium) deposits on and within lining of damaged vessel. Vessel wall damage →blood clots →clog arteries 3. Heart attack. 0.5 million deaths annually in US. Infarction: death of heart muscle due to blockage of coronary arteries 1. Heart uses 5/6 of blood oxygen 2. Often little or no collateral circulation 3. Coronary arteries are first to suffer complete blockage (SaO2 ~ 0% in venous return from heart). Partial blockage 1. Angina pectoris: pain during exertion 2. Develop collateral (width )circulation in a few days. Sudden (acute) blockage 1. Blood clot forms rapidly on rough surface 2. Clot or deposit breaks off, blocks vessel downstream uoanbar.edu.iq uoanbar.edu.iq. Symptoms of heart attack 1. The most common symptom (> 80%) is a heavy, persistent pressure in the center of the chest, lasting 10 min or more. 2. The pain often radiates upward to the neck, jaw, or left arm and shoulder. Weakness and profuse sweating are also common. 3. Sometimes the pain is a burning sensation, similar to heartburn. 4. Rarely associated symptoms: brief and sharp pain, pain on breathing. Precautions for high-risk persons 1. Sensible diet, life style 2. Avoid overexertion, especially after eating. Treatments 1. Angina: nitroglyerin (vasodilator) can relieve symptoms 2. Drugs →dissolve clot 3. Angioplasty →clean out vessel 4. By-pass surgery uoanbar.edu.iq 4. Stroke, cerebrovascular accident (200,000 deaths annually in US). Blockage or rupture of brain blood vessel ,. Stroke symptoms ,. One-sided numbness or weakness ,. Blurred or decreased vision ,. Sudden severe headache ,. Problems speaking or understanding ,. Dizziness, loss of balance (aneurysm) An aneurysm is a weakening in the wall of an artery resulting in an increase in its diameter. The increased diameter increases the tension in the wall proportionately.If an aneurysm does rupture it is often fatal-especially if the rupture is in the brain ,a type of cerebrovascular accident (CVA). uoanbar.edu.iq uoanbar.edu.iq