Physics of CVS PDF

Physics of the circulatory system Arteries Physics of the circulatory system Introduction Circulatory system The circulatory system is a network consisting of blood, blood vessels, and the heart. This network supplies tissues in the body with oxygen and other nutrients, transports hormones, and remo...

Physics of the circulatory system Arteries Physics of the circulatory system Introduction Circulatory system The circulatory system is a network consisting of blood, blood vessels, and the heart. This network supplies tissues in the body with oxygen and other nutrients, transports hormones, and removes unnecessary waste products. The heart is a single organ, but it acts as a double pump. The first pump carries oxygen-poor blood to your lungs, where it unloads carbon dioxide and picks up oxygen. Physics of the circulatory system Introduction It then delivers oxygen-rich blood back to your heart. The second pump delivers oxygen-rich blood to every part of your body. The human cardiovascular system is composed of a heart which pumps blood through a closed system of blood vessels. The heart is composed mostly of cardiac muscle, or myocardium. Its primary function is to transport nutrients, water, gases, wastes, and chemical signals throughout the body. Physics of the circulatory system Introduction Bernoulli's : Bernoulli's Principle and Energetics of Flowing Blood. Because flowing blood has mass and velocity it has kinetic energy (KE). Furthermore, as the blood flows inside a vessel, pressure is exerted laterally against the walls of the vessel; this pressure represents the potential or pressure energy (PE) Blood is made up of liquid and solids. The liquid part, called plasma, is made of water, salts, and protein. Over half of your blood is plasma. Physics of the circulatory system Introduction Bernoulli's : The solid part of your blood contains red blood cells, white blood cells, and platelets. The blood is incompressible, that is the density ρ of the blood (mass per unit volume) is constant, and inviscid, that is there are no viscous forces. Steady, that is, it does not change with time. Organs are grouped into organ systems, in which they work together to carry out a particular function for the organism. For example, the heart and the blood vessels make up the cardiovascular system. Physics of the circulatory system Introduction Bernoulli's : In a human body, there are three types of circulation of blood: 1. Systemic (greater) circulation. 2. Pulmonary (lesser) circulation. 3. Portal circulation (Part of the systemic circulation). Physics of the circulatory system Introduction Fig 1: The heart & blood circulation a) The heart b) Pulmonary & Systemic Circuit. Physics of the circulatory system Cardiovascular system The essential components of the human cardiovascular system are the heart, blood and blood vessels. It includes the pulmonary circulation, a "loop" through the lungs where blood is oxygenated; and the systemic circulation, a "loop" through the rest of the body to provide oxygenated blood. The systemic circulation can also be seen to function in two parts – a macro circulation & a microcirculation. Physics of the circulatory system Cardiovascular system An average adult contains five to six quarts (roughly 4.7 to 5.7 liters) of blood, accounting for approximately 7% of their total body weight. Blood consists of plasma, red blood cells, white blood cells, and platelets. Also, the digestive system works with the circulatory system to provide the nutrients the system needs to keep the heart pumping. Physics of the circulatory system Cardiovascular system The cardiovascular systems of humans are closed, meaning that the blood never leaves the network of blood vessels. In contrast, oxygen and nutrients diffuse across the blood vessel layers and enter interstitial fluid, which carries oxygen and nutrients to the target cells, and carbon dioxide and wastes in the opposite direction. The other component of the circulatory system, the lymphatic system, is open. Physics of the circulatory system Cardiovascular system Arteries: Oxygenated blood enters the systemic circulation when leaving the left ventricle, through the aortic semilunar valve. The first part of the systemic circulation is the aorta, a massive and thick-walled artery. The aorta arches and gives branches supplying the upper part of the body after passing through the aortic opening of the diaphragm at the level of thoracic ten vertebras, it enters the abdomen. Later it descends down and supplies branches to abdomen, pelvis, perineum and the lower limbs. The walls of aorta are elastic. Physics of the circulatory system Cardiovascular system Arteries: This elasticity helps to maintain the blood pressure throughout the body. When the aorta receives almost five liters of blood from the heart, it recoils and is responsible for pulsating blood pressure. Moreover, as aorta branches into smaller arteries, their elasticity goes on decreasing and their compliance goes on increasing Physics of the circulatory system Cardiovascular system Capillaries: Arteries branch into small passages called arterioles and then into the capillaries. The capillaries merge to bring blood into the venous system. Physics of the circulatory system Cardiovascular system Veins: Capillaries merge into venules, which merge into veins. The venous system feeds into the two major veins 1. the superior vena cava - which mainly drains tissues above the heart 2. the inferior vena cava - which mainly drains tissues below the heart. These two large veins empty into the right atrium of the heart. Physics of the circulatory system Cardiovascular system Portal veins: The general rule is that arteries from the heart branch out into capillaries, which collect into veins leading back to the heart. Portal veins are a slight exception to this. In humans the only significant example is the hepatic portal vein which combines from capillaries around the gastrointestinal tract where the blood absorbs the various products of digestion; rather than leading directly back to the heart, the hepatic portal vein branches into a second capillary system in the liver. Physics of the circulatory system Cardiovascular system Heart : The heart pumps oxygenated blood to the body and deoxygenated blood to the lungs. In the human heart there is one atrium and one ventricle for each circulation, and with both a systemic and a pulmonary circulation there are four chambers in total: left atrium, left ventricle, right atrium and right ventricle. The right atrium is the upper chamber of the right side of the heart. Physics of the circulatory system Cardiovascular system Heart : The blood that is returned to the right atrium is deoxygenated (poor in oxygen) and passed into the right ventricle to be pumped through the pulmonary artery to the lungs for re-oxygenation and removal of carbon dioxide. The left atrium receives newly oxygenated blood from the lungs as well as the pulmonary vein which is passed into the strong left ventricle to be pumped through the aorta to the different organs of the body. Physics of the circulatory system Cardiovascular system Heart : coronary circulation The heart itself is supplied with oxygen and nutrients through a small "loop" of the systemic circulation and derives very little from the blood contained within the four chambers. The coronary circulation system provides a blood supply to the heart muscle itself. The coronary circulation begins near the origin of the aorta by two coronary arteries: the right coronary artery and the left coronary artery. Physics of the circulatory system Cardiovascular system Heart : coronary circulation After nourishing the heart muscle, blood returns through the coronary veins into the coronary sinus and from this one into the right atrium. Back flow of blood through its opening during atrial systole is prevented by the besian valve. The smallest cardiac veins drain directly into the heart chambers Physics of the circulatory system Cardiovascular system Heart : Systemic circulation Is the portion of the cardiovascular system which transports oxygenated blood away from the heart through the aorta from the left ventricle where the blood has been previously deposited from pulmonary circulation, to the rest of the body, and returns oxygendepleted blood back to the heart. Physics of the circulatory system Cardiovascular system Heart : Pulmonary circulation The pulmonary circulation as it passes from the heart. Showing both the pulmonary and bronchial arteries. The circulatory system of the lungs is the portion of the cardiovascular system in which oxygendepleted blood is pumped away from the heart, via the pulmonary artery, to the lungs and returned, oxygenated, to the heart via the pulmonary vein. Physics of the circulatory system Cardiovascular system Heart : Pulmonary circulation Oxygen deprived blood from the superior and inferior vena cava enters the right atrium of the heart and flows through the tricuspid valve (right atrioventricular valve) into the right ventricle, from which it is then pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs. Gas exchange occurs in the lungs, whereby CO₂ is released from the blood, and oxygen is absorbed. The pulmonary vein returns the now oxygen-rich blood to the, left atrium. A separate system known as the bronchial circulation supplies blood to the tissue of the larger airways of the lung. Physics of the circulatory system Cardiovascular system Heart : Cerebral circulation The brain has a dual blood supply that comes from arteries at its front and back. These are called the "anterior" and "posterior" circulation respectively. The anterior circulation arises from the internal carotid arteries and supplies the front of the brain. The posterior circulation arises from the vertebral arteries, and supplies the back of the brain and brainstem. The circulation from the front and the back join together (anastomise) at the Circle of Willis. Physics of the circulatory system Cardiovascular system Heart : Cerebral circulation Physics of the circulatory system Cardiovascular system Heart : Renal circulation Receives around 20% of the cardiac output. It branches from the abdominal aorta and returns blood to the ascending vena cava. It is the blood supply to the kidneys, and contains many specialized blood vessels. Physics of the circulatory system Cardiovascular system Heart : Lymphatic system Part of the circulatory system. It is a network of lymphatic vessels and lymph capillaries, lymph nodes and organs, and lymphatic tissues and circulating lymph. One of its major functions is to carry the lymph, draining and returning interstitial fluid back towards the heart for return to the cardiovascular system, by emptying into the lymphatic ducts. Its other main function is in the adaptive immune system. Physics of the circulatory system Cardiovascular system Heart : Portal circulation Is the flow of blood from one organ to another, without going through the heart. The term is most often used to refer to how blood moves through the network of veins in the gut and digestive organs, such as the spleen and pancreas, and is carried to the liver. This particular system is known as the hepatic portal system, although it's also sometimes called the portal venous system. Physics of the circulatory system Cardiovascular system Mechanism Blood within the hepatic portal system contains all the nutrients absorbed by the digestive tract, which can then be processed by the liver. Useful substances may be adapted for use or stored, while harmful substances are removed and may be converted into less toxic forms. Sometimes, obstructions occur in the portal circulation and pressure builds up, leading to a condition known as portal hypertension. Physics of the circulatory system Cardiovascular system Mechanism Networks of tiny blood vessels, known as capillaries, form the beginning of the portal circulation. These capillaries drain blood from the digestive system, all the way from the lowest part of the esophagus to the last section of gut which leads to the anus. Similar networks of capillaries drain the pancreas, spleen and gallbladder. Physics of the circulatory system Cardiovascular system Mechanism: Fig 2: Portal circulation: Physics of the circulatory system Factors affect the flow of blood in the body The rate, or velocity, of blood flow varies inversely with the total cross-sectional area of the blood vessels. As the total cross-sectional area of the vessels increases, the velocity of flow decreases. Blood flow is slowest in the capillaries, which allows time for exchange of gases and nutrients. Fig 3: velocity of blood flow Physics of the circulatory system Factors affect the flow of blood in the body Average peak and mean blood velocities were 66 and 11 cm/sec in the ascending aorta, 57 and 10 cm/sec in the pulmonary artery, 28 and 12 cm/sec in the superior vena cava, and 26 and 13 cm/sec in the inferior vena cava. The velocity of blood is an inverse law to the cross-sectional area of the blood vessel: Flow rate Velocity = Cross section The average velocity in the aorta is about 30 cm/sec, but in the capillary is only about 1mm/sec. This low velocity allows time for exchange O₂ & CO₂ to occur. Physics of the circulatory system Factors affect the flow of blood in the body The viscosity of blood depends on temperature. As the blood gets colder, the viscosity increased and this reduces the blood supply to hands and feet. Medical Definition of Poiseuille's law: A statement in physics: the velocity of the steady flow of a fluid through a narrow tube (as a blood vessel or a catheter) varies directly as the pressure and the fourth power of the radius of the tube and inversely as the length of the tube and the coefficient of viscosity. Flow rate = 𝝅 𝑹⁴)𝟐𝐏−𝟏𝐏( 𝐋𝛈 𝟖 Physics of the circulatory system Factors affect the flow of blood in the body Fig 4: Poiseuille law. Q: flow rate. ∆𝑝 =(P1-P2): pressure difference on the ends. R: the radius. L: length of tube. η: The viscosity Physics of the circulatory system Factors affect the flow of blood in the body: Ex2: What is the rate of blood flow if the pressure difference throw two points is 50 dyne/cm² along 3 cm in aorta of 1cm radius? If η 4× 10¯³ (Pa·s). Solution: Flow rate = 3.3 (50)(10¯²)⁴/8×3 (4× 10¯³) (10¯²) = 0.5 cm/sec. Physics of the circulatory system Blood Pressure Blood pressure (BP) is the pressure of circulating blood on the walls of blood vessels. Most of this pressure is due to work done by the heart by pumping blood through the circulatory system. Blood pressure usually refers to the pressure in large arteries of the systemic circulation. Blood pressure is highest as its leaves the heart through the aorta and gradually decreases as it enters smaller and smaller blood vessels (arteries, arterioles, and capillaries). Physics of the circulatory system Blood Pressure Blood returns in the veins leading to the heart, aided by gravity and muscle contraction. Fig 5: Blood Pressure: Physics of the circulatory system Blood Pressure Doctors call them systolic (the top No.) and diastolic (the bottom No.)Blood pressure. Knowing both is important and could save your life. When your heart beats, it squeezes and pushes blood through your arteries to the rest of your body. This force creates pressure on those blood vessels, and that's your systolic blood pressure. A normal systolic pressure is below 120 Physics of the circulatory system Blood Pressure A reading of 120-129 is elevated. 130-139 is stage 1 high blood pressure (also called hypertension). 140 or more is stage 2 hypertension. 180 or more is a hypertensive crisis. The diastolic reading, or the bottom number, is the pressure in the arteries when the heart rests between beats. This is the time when the heart fills with blood and gets oxygen. Physics of the circulatory system Blood Pressure Hypertension: Is the medical term for high blood pressure. It is known as the "silent killer" since it has no initial symptoms but can lead to longterm disease and Complications Many people have high blood pressure and don't know it. Physics of the circulatory system Blood Pressure Hypertension: Important complications of uncontrolled or poorly treated high blood pressure include heart attack, congestive heart failure, stroke, kidney failure, peripheral artery disease, and aortic aneurysms (weakening of the wall of the aorta, leading to widening or ballooning of the aorta). Fig 6: Systolic &Diastolic Pressure Physics of the circulatory system Blood Pressure Hypertension: A normal diastolic blood pressure is lower than 80. But even if your diastolic number is lower than 80, you can have elevated blood pressure if the systolic reading is 120-129. 80-89 is stage 1 hypertension. 90 or more is stage 2 hypertension. 120 or more is a hypertensive crisis. Physics of the circulatory system Blood Pressure Table 1: Blood Pressure Category: Blood pressure Systolic mmHg (Upper No.) Diastolic mmHg (Lower No.) Normal Less than 120 and Less than 80 Elevated 120-129 and Less than 80 High Blood pressure (Hypertension )stage 1 130-139 or 80-90 High Blood pressure (Hypertension stage) 2 140 or Higher or 90 or Higher Hypertensive Crisis (consult doctor immediately) Higher than 180 And/or Higher than 120 Physics of the circulatory system Blood Pressure Hypertension: If your blood pressure is extremely high, there may be certain symptoms to look out for, including 1. Severe headache 2. Fatigue or confusion. 3. Vision problems. 4. Chest pain. 5. Difficulty breathing. 6. Irregular heartbeat. 7. Blood in the urine. 8. Pounding in your chest, neck, or ears. Physics of the circulatory system Blood pressure characteristics. Blood pressure is one of the vital signs, along with respiratory rate, heart rate, oxygen saturation, and body temperature. Normal resting blood pressure, in an adult is approximately 120 millimeters of mercury systolic, and 80 millimeters of mercury diastolic, abbreviated "120/80 mmHg“ A sphygmomanometer (blood pressure meter). Is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner. And a mercury or mechanical manometer to measure the pressure. Physics of the circulatory system Blood pressure characteristics. Table 7: Sphygmomanometer. (Manual and digital) Physics of the circulatory system Blood pressure characteristics. In adults each contraction of the heart muscles forces a bout 80ml of blood through the lung from the right ventricle and similar volume to the systemic circulation from the left ventricle. In this process the heart does work due to pressure which has the following characteristics: 1. The pressure in the two pumps of the heart is not the same. 2. The pressure varies throughout the circulatory system. 3. The pressure throughout the pulmonary system is quite low because of the low resistance of blood vessels in the lung. 4. 80% of the blood is through the systematic circulation and the rest through the pulmonary circulation. Physics of the circulatory system Blood pressure characteristics. 5. During strenuous work or exercises the blood pressure may rise by 50% and the blood volume pumped per minutes may increase by a factor of 5, leading to increase of 7.5 times in the work done by the heart per min. 6. The work (w) done by the a heart working at a constant pressure (p) is equal to the product of the pressure and the volume pumped ∆𝑣 or: W= P∆𝑣 Ex3: Let assume that the average pressure is 100mmHg or about 1.4×10⁵ dy/cm².if 80 ml of blood is pumped each second, the work per second is: Solution: W= P∆𝑣 = 80× 1.4×10⁵ = 1.1× 10⁷ ergs or 1.1 J/sec or power of 1.1 W Physics of the circulatory system Blood pressure characteristics. There are commonly used methods for measuring blood pressure for clinical purposes: clinic readings, self-monitoring by the patient at home, and 24-hour ambulatory readings. Self-monitoring is generally carried out using electronic devices that work on the oscillometric technique. Two methods for measuring a blood pressure exist, the direct and indirect method. Physics of the circulatory system Blood pressure characteristics. The direct : Method is the criterion standard and consists of using an intra-arterial catheter to obtain a measurement. It is used more commonly in the intensive care or operative settings. The indirect: Method involves collapsing the artery with an external cuff, providing an inexpensive and easily reproducible way to measure blood pressure. The indirect method can be performed using a manual cuff and sphygmomanometer, a manual cuff and Doppler ultrasound, or with an automated oscillometric device. Physics of the circulatory system Blood pressure characteristics. The indirect: Oscillometric technique: With an oscillatory device, a cuff is inflated over the upper arm or wrist. When the cuff pressure falls below the patient's diastolic pressure, blood flows smoothly through the artery in the usual pulses, without any vibration being set up in the wall. Physics of the circulatory system Power produced by the heart The pressure of the heart is about 10⁴ pascal. Making the heart's power about one watt. This is the power of a typical human heart, but it's different for everyone. The average heart beats about 75 times per minute, which is about five liters of blood per minute. The fact that each beat of a human heart is about 1 joule. Physics of the circulatory system Power produced by the heart Fig 8: Produced heart rate (HR) & corresponding estimation of power. Physics of the circulatory system Power produced by the heart The energy in the flowing blood is provided by the pumping action of the heart. The power generated by the heart to keep the blood flowing in the circulatory system. The power PH produced by the heart is the product of the flow rate Q and the energy E per unit volume of the blood; that is: Cm ³ PH = Q 𝑐𝑒𝑠 𝑔𝑟𝑒 x E = Q × E erg/sec cm³ Physics of the circulatory system Power produced by the heart At rest, when the blood flow rate is 5 liter/min, or 83.4 cm³/sec, the kinetic energy of the blood flowing through the aorta is 3.33 × 10³ erg/cm³. The energy corresponding to the systolic pressure of 120 torr is 160 × 10³ erg/cm³. The total energy is 1.63× 10⁵ erg/cm³. Sum of kinetic energy & energy due to fluid pressure Therefore, the power P produced by the left ventricle of the heart is, P = 83.4 cm³/sec × 1.63× 10⁵ erg/cm³ = 1.35 × 10⁷ erg/sec = 1.35 W. Physics of the circulatory system Instruments Echography Echocardiography or echo is a painless test that uses sound waves to create moving pictures of your heart. The pictures show the size and shape of your heart. A type of echo called Doppler ultrasound shows how well blood flows through your heart's chambers and valves. An echocardiogram is an ultrasound image of the heart. Physics of the circulatory system Instruments Echography Doctors use echocardiograms to help them diagnose heart problems, such as damaged cardiac tissue, chamber enlargement, stiffening of the heart muscle, blood clots in the heart, fluid around the heart, and damaged or poorly functioning heart valves Fig 9: Echocardiogram Physics of the circulatory system Instruments Echography Doppler ultrasound Similar to an echocardiogram, Doppler ultrasound (or Doppler echocardiography) is a test in which very high frequency sound waves are bounced off your heart and blood vessels. The returning sound waves (echoes) are picked up and turned into pictures showing blood flow through the arteries or the heart itself. Echo: Is a repetition or imitation of sound. When sound waves hit a hard surface they might reflect, making the sound bounce and repeat. Physics of the circulatory system Instruments ECG ECG (electrocardiogram) and high blood pressure. An electrocardiogram (ECG) is a test which measures the electrical activity of your heart to show whether or not it is working normally. An ECG records the heart's rhythm and activity on a moving strip of paper or a line on a screen. Electrocardiogram to assess the heart rate and rhythm. This test can often detect heart disease, heart attack, an enlarged heart, or abnormal heart rhythms that may cause heart failure. Physics of the circulatory system Instruments ECG Chest X-ray to see if the heart is enlarged and if the lungs are congested with fluid. Fig 10: Electrocardiograph. Physics of the circulatory system The physics of cardiovascular disease Most of heart disease has a physical component due to the physical aspect of the cardiovascular system. These aspects may relate to work, tension, pressure, power, energy, and/or fluid laws. Physics of the circulatory system The physics of cardiovascular disease Hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP). Is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure typically does not cause symptoms. Long-term high blood pressure, however, is a major risk factor for coronary artery disease, stroke, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia. Physics of the circulatory system The physics of cardiovascular disease Hypertension Fig 11: High blood pressure. Physics of the circulatory system The physics of cardiovascular disease Hypertension High blood pressure is classified as primary (essential) hypertension or secondary hypertension. About 90–95% of cases are primary, defined as high blood pressure due to nonspecific lifestyle and genetic factors. Lifestyle factors that increase the risk include excess salt in the diet, excess body weight, smoking, and alcohol use. Physics of the circulatory system The physics of cardiovascular disease Hypertension The remaining 5–10% of cases are categorized as secondary high blood pressure, defined as high blood pressure due to an identifiable cause, such as chronic kidney disease, narrowing of the kidney arteries, an endocrine disorder, or the use of birth control pills. Physics of the circulatory system The physics of cardiovascular disease Arrhythmia An arrhythmia is a problem with the rate or rhythm of your heartbeat. It means that your heart beats too quickly, too slowly, or with an irregular pattern. When the heart beats faster than normal, it is called tachycardia. Fig 12: Cardiac arrhythmia Physics of the circulatory system The physics of cardiovascular disease Aneurysm An aneurysm refers to a weakening of an artery wall that creates a bulge, or distention, of the artery. Most aneurysms do not show symptoms and are not dangerous. However, at their most severe stage, some can rupture, leading to life-threatening internal bleeding. Physics of the circulatory system The physics of cardiovascular disease Aneurysm Fig 13: Brain aneurysm. Physics of the circulatory system The physics of cardiovascular disease Congestive heart failure Congestive heart failure (CHF) is a chronic progressive condition that affects the pumping power of your heart muscles. While often referred to simply as “heart failure,” CHF specifically refers to the stage in which fluid builds up around the heart and causes it to pump inefficiently. You have four heart chambers. There are 4 stages of heart failure (Stage A, B, C and D). The stages range from "high risk of developing heart failure" to "advanced heart failure," and provide treatment plans. Physics of the circulatory system The physics of cardiovascular disease Congestive heart failure Fig 14: Healthy & congested hearts Physics of the circulatory system The physics of cardiovascular disease Heart attack A heart attack is the death of a segment of heart muscle caused by a loss of blood supply. The blood is usually cut off when an artery supplying the heart muscle is blocked by a blood clot. If some of the heart muscle dies, a person experiences chest pain and electrical instability of the heart muscle tissue. Physics of the circulatory system The physics of cardiovascular disease Heart attack These 4 silent signs of a heart attack: 1. Chest Pain, Pressure, Fullness, or Discomfort. 2. Discomfort in other areas of your body. 3. Difficulty breathing and dizziness. 4. Nausea and cold sweats. Physics of the circulatory system The physics of cardiovascular disease Fig 15: Healthy & congested hearts Physics of the circulatory system The physics of cardiovascular disease Varicose veins Varicose veins are enlarged, swollen, and twisting veins, often appearing blue or dark purple. They happen when faulty valves in the veins allow blood to flow in the wrong direction or to pool. More than 23 percent of all adults are thought to be affected by varicose veins Physics of the circulatory system The physics of cardiovascular disease Fig 16: Varicose veins Physics of the circulatory system The physics of cardiovascular disease Varicose veins Treatment may involve life-style changes or medical procedures with the goal of improving symptoms and appearance. Life-style changes may include compression stockings, exercise, elevating the legs, and weight loss. Medical procedures include sclerotherapy, laser surgery, and vein stripping. Following treatment there is often reoccurrence.