1 SSN College of Engineering ( An Autonomous Institution, Affiliated to Anna University) Academic Year -2021-22 Department of EEE Class : III Year /VI Sem EEE UEE 1623-Biomedical Instrumentation (elective) Course Instructor-Dr.R.Deepalaxmi, Asso.Prof/EEE, SSNCE Cardiovascular System Module Objectives • To know the parts present in cardiovascular system • To understand the structure of heart • To know about the function of heart Introduction: • Cardio vascular system can be viewed as complex closed hydraulic system with 4 chamber pump. • It is mainly used for transportation of oxygen, Carbon dioxide, numerous chemical compounds and the blood cells to maintain optimum environment and for cellular function. • In some part of the system, diameter of the arteries are changed to control pressure. Heart is the power source which provides energy to move the blood through the body and at the same time removes waste products ( products of metabolism ) from the cell. • Structurally, the heart is divided into right and left parts. • Each part has two chambers called atrium and ventricle. • Heart has four valves. Structure of the heart 2 3 Heart has 4 valves • Tricuspid/Right Atrio-Ventricular valve: Between Right A and V, Prevents blood flow from right V to A 2. Bicuspid/ left Atrio-Ventricular valve (or) Mitral valve: Between left A and V, Prevents blood flow from left V to A 3. Pulmonary valve: At right ventricle, It has 3 cusps 4. Aortic Valve: Between left ventricle and aorta, It has 3 cusps. 1. Tricuspid valve (or) right atrio-ventricular valve * exist between the right atrium and right ventricle * consists of three flaps (or) cusps * prevents backward flow of blood from right ventricle to right atrium 2. Bicuspid/ left Atrio-Ventricular valve (or) Mitral valve: * exist between the left atrium and left ventricle * consists of two flaps (or) cusps * prevents backward flow of blood from left ventricle to left atrium 3.Pulmonary valve at the right ventricle • Consists of three half-moon shaped cusps. • Does not allow blood to come back to the right ventricle 4.Aortic Valve • between left ventricle and aorta. • construction is similar to pulmonary valve. • Prevents the return of blood back to the left ventricle from aorta. Heart wall consists of three layers • Pericardium: Outer most layer, keeps outer surface moist, prevents friction as the heart beats. • Myocardium: Middle layer, main muscle of heart, made up of short cylindrical fibres . 4 This muscle is automatic in action, contracting and relaxing rhythmically throughout the life. 3. Endocardium: Inner layer of heart, provides smooth lining for blood flow One of the two stage pump (Right side) collect fluid from the system and pump it through oxygenation system (Lungs). § Other side pump receives blood from oxygenation system (Lungs) and pump blood to main hydraulic system. § Blood act as communication and supply network for all parts of the body. The blood is carried out to the various parts of the body through blood vessels which are hollow tubes. There are three types of blood vessels • Arteries--- Thick walled, carry oxygenated blood away from the heart • Veins--- Thin walled, carry de-oxygenated blood towards the heart • Capillaries---Smallest, Last level of blood vessels, They are so small that the blood cells which make blood, actually flow one at a time through them. • There are estimated to be over 8,00,000 km of capillaries in human beings that include all the arteries and veins, which carry blood. 5 Circulatory system Heart which drives the blood through the blood vessels of the circulatory system consists of four chamber muscular pump that beats about 72 times per minute (on an average for a normal adult) , sending blood through every part of the body. The pump acts as two synchronized but functionally isolated two stage pumps. Heart is an isolated two stage synchronized chamber The first stage of each pump (the atrium) collects blood from the hydraulic system and pumps it into second stage ( the ventricle). The second stage then pump these blood to the system Heart pumps blood through the pulmonary circulation to the lungs and through the systemic circulation to the other parts of the body. 1) Pulmonary circulation 2) Systemic circulation 6 Pulmonary circulation • In pulmonary circulation system, the pressure difference between the arteries and veins is small. • As is the resistance to flow, so the right heart may be considered as volume pump. • In pulmonary circulation, venous blood (de-oxygenated) flows from right ventricle through pulmonary artery to lungs, where it is oxygenated and gives off carbon-dioxide. • The arterial ( oxygenated) blood then flows through the pulmonary veins to the left atrium. Systemic circulation The systemic circulation system is a high resistance circuit with a large pressure gradient between the arteries and veins. • The pump constituting the left heart may be considered as pressure pump • In systemic circulation, the blood is forced through the blood vessels, which are somewhat elastic. • The blood flows from the left atrium to the left ventricle and is pumped through the aorta and its branches, the arteries, out into the body. • Through the arterioles ( small arteries), the blood is distributed to the capillaries in the tissues, where it gives up its oxygen and chemical compounds, takes up carbon-dioxide and products of combustion. • The blood returns to the heart along different routes from different parts of the body. • It usually passes from the venous side of the capillaries directly via superior vena cava (or) inferior vena cava, both of which empty into the right atrium. • The heart itself is supplied by two small but highly important arteries, the coronary arteries. • They branch from the aorta just above the heart. • If they are blocked by coronary thrombosis, myocardial infarction follows, often leading to a fatal situation. Note: • The muscle contraction of the left heart is larger and stronger than that of the right heart because of great pressures required for the systemic circulation. • The volume of blood delivered per unit of time by the two sides is the same when measured over a sufficiently long interval. 7 • The left heart develops a pressure head sufficient to cause blood to flow to all the extremities of the body. • The pumping action itself is performed by contraction of the heart muscles surrounding each chamber of the heart. • These muscles receive their own blood supply from the coronary arteries, which surround the heart like a crown (corona). • The coronary arterial system is a special branch of the systemic circulation. • The heart rate is partly controlled by autonomic nervous system and partly by hormone action. • These control the heart pump’s speed, efficiency and the fluid flow pattern through the system. • The circulatory system is the transport system of the body by which food, oxygen, water and other essentials are transported to the tissue cells and their waste products are transported away. • This happens through a diffusion process in which nourishment from the blood cell diffuses through the capillary wall into interstitial fluid. • Similarly, carbon-di-oxide and some waste products from the interstitial fluid diffuse through the capillary wall into the blood cell. • The condition of the cardiovascular system is examined by haemodynamic measurements and by recording the electrical activity of the heart muscle ( electrocardiography) and listening to the heart sounds ( phonocardiography). • For assessing the performance of the heart as a pump, measurement of the cardiac output ( amount of blood pumped by the heart per unit time), blood pressure, blood flow rate and blood volume are made at various locations throughout the circulatory system. Piping diagram for cardiovascular circulation 8 Operation of circulatory system Blood enters the heart on the right side through two main veins - superior vena cava leads from the body’s upper extremities (head, arms) - inferior vena cava leading from the body’s organs and extremities below the heart ( internal organs, legs) The incoming blood fills the storage chamber, the right atrium. Coronary sinus empties into the right atrium Coronary sinus contains the blood that has been circulating through the heart itself via the coronary loop. 9 When the right atrium is full, it contracts and forces blood through the tricuspid valve into the right ventricle, which then contracts to pump the blood into the pulmonary circulation system. • When the ventricular pressure exceeds arterial pressure, the tricuspid valve closes and the pressure in the ventricles forces the semilunar pulmonary valve to open, thereby causing blood to flow into the pulmonary artery, which divides into two lungs. • In the alveoli of the lungs, an exchange takes place. • Red blood cells are recharged with oxygen and give up their carbon-di-oxide. • The pulmonary artery bifurcates (divides) many times into smaller and smaller arteries, which become arterioles with extremely small cross sections. • These arterioles supply blood to the alveolar capillaries, in which exchange of oxygen and carbon-di-oxide takes place. • On the other side of the lung mass is a similar construction in which the capillaries feed into tiny veins (or) venules. Venules combine to form larger veins , which in turn combine until ultimately all the oxygenated blood is returned to the heart via the pulmonary vein. Blood enters the heart on the left atrium from the pulmonary vein, and from there it is pumped through the mitral (or) bicuspid valve, into the left ventricle by contraction of the atrial muscles. • When the left ventricular muscles contract, the pressure produced by the contraction mechanically closes the mitral valve, and the build up of pressure in the ventricle forces the aorta valve to open, causing the blood to rush from the ventricle into aorta. • This action takes place synchronously with the right ventricle as it pumps blood into the pulmonary artery. Heart pumping cycle • Heart pumping cycle is divided into two major parts Systole period of contraction of the heart muscles specifically the ventricular muscle at which time blood is pumped into the pulmonary artery and the aorta. Diastole period of dilation of the heart cavities as they fill with blood. Note: • Once the blood has been pumped into the arterial system, the heart relaxes, the pressure in the chamber decreases, the outlet valve close, and in a short time inlet valves open again to restart the diastole and initiate a new cycle in the heart 10 Assessment questions: 1. Draw the structure of human heart. Explain the parts present in it. 2. Explain the operation of human circulatory system 3. Write a short note on valves present in heart. 4. Write a short note on heart wall. 5. Differentiate arteries, veins and capillaries 6. Draw and explain the piping diagram for cardiovascular circulation 7. Write a short note on heart pumping cycle. 8. Write about a) Pulmonary circulation ,b) Systemic circulation
