Overview of Cardiovascular System Concepts

Hello, my name is Viola and this is a recording for ANPH1002, the topic on cardiovascular system. The reference used for this presentation is your recommended textbook by RISO. And the materials presented in this PowerPoint. from your recommended textbook if you go to chapter 14 you can read through the topic on cardiovascular system because this presentation is just a summary of what you are going to get from the book so i recommend that you go to chapter 14 read through the chapter as you read through the chapter make sure you do understand the concepts that are listed here as your learning outcomes so this is your checklist as you go through the chapter make sure you understand the concepts that are listed on this page the cardiovascular system consists of the heart the blood and the blood vessels the heart is the key pump which pumps blood as it circulate through the blood vessels. The heart is composed of a type of muscle known as cardiac muscle and it makes up the bulky of the heart and this is the muscle that provides the force that pumps blood through blood vessels to different parts of the body. In doing so, it will be carrying substances. It can be carrying supplies needed by the cells. and also waste products from the cells for excretion. On average, the heart beats at about 72 times a minute, but this is an average. Different people have different norm values, but on average it's about 72 times a minute. And the heart has got a series of valves that prevent backflow when it's doing its work. Again, even when you look at the veins, they also have valves to prevent backflow. Though when we are studying this anatomy and physiology, we study system by system just to help us follow the concepts on how each system works. But in reality, these systems work closely together. You cannot have a functional digestive system without a functional cardiovascular system. For example, after we eat food, the food is digested by the digestive system, which is primarily composed of the alimentary canal, which runs from the mouth to the anus, with some accessory structures. However, for the food that we eat, to get to the cells where it's needed we need a functional cardiovascular system that will absorb the nutrients and circulate them and bring them to to the cells then when we talk about cardiovascular system it consists of the heart the blood and blood vessels but whatever it transports it comes from other system for example it transport gases These gases are part of the respiratory system. It helps with issues of excretion and this is part of urinary system. So these systems are interconnected and the main function of the cardiovascular system is to make sure that it supplies nutrients that come from the digestive system. It also supplies the gases that are needed as part of the respiratory system. And at the same time it helps us to eliminate ammonia through the urinary system and carbon dioxide through the respiratory system. So the cardiovascular system's primary job is to pick and deliver substances to the cell and also pick waste materials from the body to respective systems that are responsible for excretion. So these systems are interconnected. So let's briefly talk about the structure and function of the heart. As I said earlier, the heart is primarily made up of muscle which is responsible for pumping the blood. However, we know the heart has got four chambers. It has got two upper chambers and two lower chambers. And when you look at the muscle, it's the myocardium which is the cardiac muscle which forms the balconies of the heart but lining the chambers inside the chambers that's where we have the endocardium. Covering the heart we have the epicardium which is composed of layers of the visceral and serous pericardium. The anatomical position of the heart we find it behind the bimidia sternum and is surrounded by layers of membranes. The pericardium as the name suggests peri meaning the outside. So the pericardium has got two layers. It has a layer of fibrous pericardium and a layer of serous pericardium. The fibrous pericardium as the name suggests is fibrous pericardium. fibrous it is connective tissues like a fiber with connective tissue its main function it helps to anchor the heart within the mid astina as you jump up and about doing your normal activities it's important that the heart remains in position for it to remain the position in position with a special type of connective tissue that helps to anchor the heart and that is the fibrous pericardium. Then the serous pericardium is kind of delicate and thin and it's also known as the parietal layer of the pericardium. This layer is continuous with the layer of the heart, the outermost layer of the heart. In other words, It touches the heart, it covers the heart muscle. I like this diagram because it shows the layers of the walls of the heart. If you look at it closely, we have the muscle which is the myocardium. Then the pericardium membrane that touches the heart muscle, covering the heart muscle is the serous. that serous is also known as the epicardium then between the serous and the the pericardium peri-h or pericardium is a pericardial cavity within the pericardial cavity this is where we have fluids that circulate is the heart pumps those fluids help to prevent friction then we have the fibrous pericardium the fibrous pericardium is the one that anchors the heart within the walls of the cavity to make sure that the heart stays in position. This diagram is a recap of what I have shown you before. This diagram is also found in a textbook. It shows the myocardium and the visceral pericardium which covers the heart muscle. The hat has got four chambers. It has got two upper chambers and two lower chambers. And then when you look at those chambers, we have a right side of the hat and a left side of the hat. Remember, this is a hat of somebody who is facing you. So the right side is to your left and the left is to your right. So this is kind of the normal visualization of the heart. The upper chambers are called atria and the lower chambers are called ventricles. In other words, so we have a right and a left atrium and a right and a left ventricle. It's also important to note that when you look at the heart from the outside, there are clear demarcations that separate the chambers. For example, between the atria and the ventricles, when you look at between the atria and ventricles, there is a clear separation and they are separated by the coronary sulcus. Then between the ventricles, there is an interventricular separation, also known as the sulci. so that you can tell that those four chambers are clearly separated or demarcated from the outside. Then when we look again at the inside, we can see that structure is related to function. The upper chambers which are the atrium are responsible for receiving the blood. Then the ventricles are responsible for pumping the blood so that it gets outside the heart. So to pump blood to go outside the heart, the ventricles they need more power that's why their walls are thicker. So if we're to compare the wall of an atrium as compared to the wall of a ventricle, the ventricle has got a thicker muscle because the atrium only pump blood to the lower chambers whereas the ventricles they need to pump blood to get outside the heart so they need more force they need more muscle that's why the ventricles tend to have thicker muscles as compared to the atrium then when we look at the great vessels of the heart to say how does blood get to the heart and how does blood leave the heart. The parts that are above the heart they drain deoxygenated blood and empty it into superior vena cava. The parts that are below the heart they drain deoxygenated blood and empty into inferior vena cava. So we can say inferior and superior vena cava they empt their blood into the right atrium the heart muscle is also tissue on its own so it also has a coronary supply of blood the deoxygenated blood from the tissue of the heart is drained by coronary sinus which empty into the right atrium So we can say the right atrium receives blood from three veins. Superior vena cava which drains from upper parts. Inferior vena cava which drains from lower parts. And the sinus is not shown in this diagram. It drains from the heart tissue and ends into the right atrium. After receiving the deoxygenated blood from the different parts of the body, the right atrium simply squeezes this blood into the right ventricle. Then when the right ventricle squeezes blood, it goes into the pulmonary trunk. Then the pulmonary trunk will divide into the left and the right pulmonary arteries. The pulmonary arteries carry deoxygenated blood to the lungs for oxygenation. So the pulmonary arteries, they take blood from the heart to the lungs for oxygenation. After oxygenation, blood comes back to the heart so that it can be pumped to different parts of the body to bring blood from the lungs. to the heart we have pulmonary veins two from each side so in other words the left atrium receives blood from four veins two from the left lung and two from the right lung then after the left atrium has received blood it pumps it into the left ventricle the left ventricle it pumps into the ascending iota. On the ascending iota we have a branch which is the coronary artery which branches so that it feeds the tissue of the heart with blood. Then the ascending aorta will form an arc. The arc branches to supply the upper parts. Then the descending thoracic supplies the lower parts of the heart. So the coronary arteries are important because they make sure that the tissue of the heart muscle itself is supplied with the blood. So when you look at this diagram, where we had superior vena cava, now we have an aortic arc. Where we had inferior vena cava, now we have a descending thoracic. And then where we had a coronary sinus, we now have a coronary artery, which makes sure that the heart tissue is supplied. with oxygenated blood this is a branch that comes from the ascending iota then when you compare again the thicknesses I have already mentioned that the atrium are thinner than the ventricles the ventricles have thicker muscles as compared to the atrium the comparison is important because it's about the power needed by the muscles to pump blood from ventricle from atrium to ventricle the distance is short it's just squeezing blood into the lower chamber but when you are pumping out the blood to get to the extremities you need a thicker muscle that's why ventricles have a thicker muscles then when you compare the the sizes of the chambers The right atrium receives blood from different parts of the body. So when you are looking at it, it's slightly larger than the left. Slightly, not a lot because they pump about the same volume of the blood. Then when you look again at the ventricles, the left ventricle, the muscle is thicker than the right ventricle. This is because the right ventricle is pumping blood to the lungs and the lungs are not very far away from the heart. Whereas the left ventricle is to squeeze oxygenated blood to different parts of the body. So the blood from the left ventricle is to go to a longer distance. It needs more force, more pressure. That's why the left is bigger. is bigger muscle. So this slide is almost like a repeat of what I just said to say the left ventricle pumps blood to different parts of the body that blood needs more pressure hence the thick muscle which we find on the left ventricle is compared to the right ventricle which only pumps blood to the lungs. When blood is being pumped through the heart, we have deoxygenated blood being handled on the right side of the heart, oxygenated blood being handled on the left side of the heart. There are heart sounds, the lab-dub sounds that can be heard. These sounds are generated when the valves close. So between the atrium and the ventricle we have atrioventricular valves. On the blood vessels that leave the heart we have semilunar valves. So the heart sounds are generated when the valves close. The lab sound is generated when the atrophendicular valves close so when the valves between the atrium and ventricle close we have the lab sound the dab sound is heard when the semilunar valves close and semilunar valves are valves found on the arteries that leave the heart that is on the pulmonary trunk and on the ascending aorta there are cases where some members can be heard when you're listening at the heart sounds and this is typically caused by blood trying to squirt back through the the house then you can hear the this the hissing sounds or the heart memos. Another important aspect about the anatomy of the heart is that only veins go towards the heart and arteries they go away from the heart. Then when you look at this diagram pulmonary arteries are the only veins that carry deoxygenated blood and pulmonary veins. are the only veins that carry oxygenated blood to prevent backflow we said we have valves within the heart between each atrium and a ventricle we have valves those valves are known as atrial ventricular valves atrial for atrial ventricular for ventricle So between that we have atrioventricular valves. Then those atrioventricular valves, they are tricuspid if they are between the right ventricle and the right atrium. In other ways, a tricuspid valve is an atrioventricular valve between the right atrium and the right ventricle. Then a bicuspid is an atrioventricular valve. between the left atrium and the left ventricle. And to hold those valves in position, they have a series of tendons. When you look at this diagram, it has a series of tendons known as caudate tendineae. And when we say tricuspid, it's because they have three flaps. Bicuspid is because they have got two flaps. and the bicuspid are also named as the mitral valves and semilunar valves are valves that are found on the arteries that leave the heart so we have pulmonary semilunar which is found on the pulmonary trunk then on the ascending aorta we have the aortic semilunar valves so then in general the arteries that leave the heart have valves those valves are known as semilunar it's pulmonary if it's on the pulmonary trunk and it's aortic when it's on the aorta so we can say there is a pulmonary semilunar valve on the pulmonary trunk there is an aortic semilunar valve on the ascending aorta and just like the tricuspids the semilunar valves have three capsules so in other ways the mitral or the bicuspid are the only valves of the heart with two flaps all other valves the tricuspid the semilunar valves have three flaps As we talk about blood flow through the heart, it's important to note that what happens on the right is also happening on the left. In other words, these two atrium, they receive blood simultaneously. The right atrium receives deoxygenated blood from different parts of the body and the left atrium receives oxygenated blood from the lungs. So both atrium fill with blood. blood at the same time, they contract and squeeze blood into their respective ventricles. So when the right atrium and left atrium are contracting, the right and left ventricles will be relaxed. In other words, they will be opening up to receive the blood that is being squeezed to lower chambers by the upper chambers. After squeezing blood into the lower chambers, Both atrium relax as both ventricles contract at the same time to push blood to get outside the heart. The right will be pumping to the lungs and the left will be pumping to different parts of the body. Then all chambers relax before the next cycle and the valves will be closed before the next cycle. And that's important because it ensures maximum cardiac output. It helps to build pressure and ensures maximum cardiac output. So in sum, we can say deoxygenated blood from different parts of the body retains to the right atrium. Then the right atrium makes sure that it squeezes to the right ventricle. Then blood is squeezed via the pulmonary trunk and pulmonary arteries to the lungs. Then oxygenated blood will come back. to the heart via the pulmonary vein which feeds into the left atrium. Left atrium squeezes its blood to the left ventricle then when the left ventricle contracts it goes through different parts of the body. So to initiate the cardiac cycle the heart has its own intrinsic factors that initiate the cardiac cycle. through the generation of electrical activity. This is done by the pacemaker also known as the sino-arterial node. This is the center which generates the impulse electrical activity that stimulates contraction. This activity can also be shown on the ECG. So the sino-arterial node When it initiates the cardiac cycle, it generates an electrical activity which is distributed to both atrium, the right and the left. Then both atrium will contract at the same time and squeeze blood into relaxed ventricles. Meanwhile, impulse will be traveling to the atrioventricular node. There is a slight delay on the atroventricular node and that's important because it ensures that the ventricles fill with blood before they contract. Thereafter, it travels rapidly down the septum, the histobandals, and gets to the apex and then goes to the walls of the ventricle to the Purkinje fibers. Once the Purkinje fibers receive the electrical impulse, they stimulate the ventricles to contract at the same time. So in short, both atrium receive electrical activity at the same time, they simultaneously contract to squeeze blood to their respective ventricles, and both ventricles receive electrical activity from the purkinje simultaneously, and they contract to push blood to get outside of the heart. So in summary, that's the conduction system of the heart. The cardiac cycle is innervated by the ANS, Autonomic Nervous System. The ANS does not initiate the cardiac cycle, it only innervates either by speeding it up as part of the sympathetic system or to slow it down or restore it as part of the parasympathetic system. In other words, the initiation of the cardiac cycle is within the heart itself through the pacemaker. The nervous system is there to innovate either to make it go faster or slower or to just regulate the heartbeat. So the generation, as I said before, is important because it stimulates the cardiac muscle to contract. As I said earlier, the electrical activity that takes place during the heart conduction system can be recorded on an ECG. So on the ECG, each different wave represents a certain part of the heart which is being activated to contract. For example, when you see these flow diagrams, the part that is colored in purple is the part that will be receiving the impulse. The first part is the generation of electrical impulse from the sinoarterial node. It goes to both atrium. So when both atrium are receiving electrical activity to stimulate them to contract, this is shown by the first. wave of the ECG. Then when information gets to the atrial ventricular node, that's the second part of the graph. Then when the information travels down the septum, these bundles to the Purkinje fibers, this is this part of the ECG. Remember, once the Purkinje fibers receive electricity, they stimulate the ventricles to contract and when ventricles are contracting it gives us this this big wave so the reason why the sino arterial node is also known as the pacemaker is because it kind of says the pace of the the cardiac cycle it initiates the cardiac cycle and it's called sinoarterial because it's found on the atrium specifically the right atrium so the function of the ans is just to innervate either by speeding it up or slowing it down or to restore if there was a notion of flea or flight so in other ways hormones for flea or flight can also help to speed up the pace of the heart so when we look at this diagram you can actually put the sequence of events in some order to say number one you start with the sign arterial node initiating the cardiac circle number two is the right and left atrium receiving impulse then to receive it number three will be the atrioventricular node number four will be the the his bundles on the septum number five will be the purkinje fibers receiving the impulse receiving last will be our ventricles they receive it simultaneously So what's happening on the left side of the heart is also happening on the right side of the heart. It happens simultaneously. Both atrium receive electrical activity at the same time and contract at the same time to squeeze blood into their respective ventricles. Both ventricles receive electrical activity at the same time and contract at the same time to push blood outside of the heart. So a cardiac cycle actually is from the time the heart receives blood up to the time when it pumps blood from the heart. So the cardiac cycle can be measured from the time the heart is receiving blood, it's squeezed into the lower ventricles and then squeezed out of the heart to initiate another next cycle. So we can talk again in terms of systole and diastole. Systole is basically contraction phase and diastole is basically relaxation phase. And blood pressure is measured in systolic and diastolic pressure. The systolic number is the number above and the diastolic is the number below which is the smaller number. And when we are measuring blood pressure, it's all by the... pressure generated by our left ventricle because we are measuring arterial pressure and arterial pressure is generated by the left ventricle is the one which pumps blood to the periphery our right side of the heart only pumps blood to to the lungs the left is the one which pumps to different parts of the body so when you are measuring the pulse It's about pressure generated specifically by the left ventricle. So this slide here gives you an idea on the categories of blood pressure. To see, we see blood pressure is normal when the systolic, which is the bigger number, the top number, is less than 120. Or the diastolic is less than... 80. Prehypertensive again ranges between 120 and 139 for systolic and 80 for 89 to diastolic. Then stage 1 blood pressure. The systolic is 140 to 159, diastolic will be 90 to 99. Then stage 2 hypertensive is 160 and above for systolic and 100 or higher for diastolic. It is also important to note that when staging, the number that matters the most is the number that is off the range. For example, if a patient is a blood pressure of 140 over 89. 89 as you can see is pre-hypertensive but 140 is stage 1 hypertensive. So the patient is classified as stage 1 hypertensive because of the 140. Then you can have a patient who has say 120 for their systolic and then maybe for some reason they have hand reach. for their dystolic. For when the dystolic is 100 it's stage 2 but 120 is kind of in the normal range but that patient will be classified as stage 2 hypertensive because of their dystolic which is off the chart. So let's talk about some major circulatory route to say when blood leaves the heart where does it go to? So we say circulation is systemic when it includes all the blood that leaves the heart and all the blood that is returning to the heart. So it's almost like saying is the total circulation when we are distributing oxygen to different parts of the body and the total circulation in. when we are bringing carbon dioxide for oxygenation. So the total circulation is systemic circulation. Then there are some subdivisions that are important. For example, we have coronal circulation. Coronal circulation is about circulation that takes place within the heart muscle itself. The heart is a tissue that requires a constant supply of oxygen and nutrients because for the heart muscles to contract and relax they also need ATP that ATP comes from glycolysis so they need a continuous supply of oxygen so from the ascending iota we have a special branch of coronary arteries which branch so that they can feed the heart muscle so that's another special circulator route the coronary circulation and in most cases when you hear that a patient has got a heart attack or they have a clot in their coronary circulation it will be clots found on the arteries that feed the heart tissue with oxygenated blood Another second special circulator route is the hepatic portal circulation. This is a special circulator route which goes back and forth between intestines and the liver. Remember after a meal we need to store excess carbohydrates in the liver. So we have a special circulator route where nutrients are absorbed and it goes to the liver for storage. and also the liver is a detoxifying organ when the absorbed nutrients or the absorbed substances from the intestine when they get to the liver, the liver also detoxifies it before it's distributed to different parts of the body. Other circulations that are worth mentioning is the pulmonary circulation. Pulmonary circulation is important because this is the route that ensures that we oxygenate our blood and also we get rid of the carbon dioxide. So this is the route which occurs between our heart and our lungs. Another important route which is worth mentioning is the cerebral. which ensures that our brain is supplied with with oxygen and nutrients and also to take the waste materials from the brain. Then another important circulatory route is the renal. To say each time we have a cardiac output about 25 percent of the blood goes to the kidneys where it's filtered That filtration process is the formation of urine to make sure that we get rid of ammonia. Another route which is worth mentioning is the fetal circulation route. This is the temporal route which is formed between a developing fetus and a mother when she is pregnant to ensure that the fetus is supplied with blood. There is a special circulator route which attaches the placenta to the mother's cardiovascular system to ensure the umbilical cord to ensure that the nutrients are supplied to the developing fetus and also waste materials are removed from the developing fetus. The heart is the major organ for the cardiovascular system because it's the one who is responsible for pumping blood into different parts of the body. However, the blood vessels carry a major part because these are the tubes that penetrate the organs and tissue. So their structure and function is important. When you look at the blood vessels, they have a lumen which is a hole within them. But then they have layers, layers of muscle tissue, smooth muscle. The innermost layer is the intima. The middle layer is the media. The outer layer is the advecta. So they have three layers. Structure is related to function. Same with arteries and veins. Veins typically carry sluggish blood because this is blood which is now returning in general, returning to the heart. Then the arteries carry blood which is under high pressure. So the muscles tend to be thicker and they are stronger. so that they can withstand the the pressure that comes from the heart when the left ventricle is pumping blood to different parts of the body it generates a lot of pressure and the blood vessels should be strong enough to withstand that pressure that's why the arteries are built for for that then when blood gets to its destination there is need to drop oxygen and nutrients and peak carbon dioxide and to enable that from happening that's where we have capillaries which are about one centimeter thick to ensure diffusion and these penetrate into the tissue so in other ways our venous system connects with the arterial system through the capillary network this is where the magic of dropping and picking substance okay Then once there's dropping and picking to begin its journey back, it goes through the venous system but now the blood is moving towards the heart, it has less pressure. Then to prevent backflow, the veins have valves which prevent backflow as the blood is moving towards the heart so that it goes to the lungs for oxygenation. The venules connect to the veins via the capillaries. This diagram is kind of a repeat of what I just said before to say the arteries are built so that the hair can withstand the pressure of the blood that travels through them. The blood is under high pressure. The pump pumps blood so that it gets to the periphery. It needs to push it hard. so the blood vessels need to be strong enough to withstand the pressure then the veins they don't need a thicker muscle because the blood is now under less pressure under less pressure and it risks the idea of flowing back but to prevent that from happening there are valves which prevent back flow Again, this is a diagram which is showing the valves found in the veins to prevent backflow. Then when you look at the thickness of this muscle, it's different from the thickness of that muscle because the arteries need a stronger, thicker muscle. Then the capillaries are only one centimeter thick and that's important so that it's easy for substances to diffuse. in and out. This diagram is similar to what you have in your textbook. Remember we said blood coming from the left ventricle it goes via the ascending aorta. As it goes via the ascending aorta there are coronary branches which help to supply oxygenated blood to the tissue. of the heart. Then we have aortic arc. Then branches of the aortic arc supply the parts that are above the heart including the branchiocephalic which supplies the hands. Same as the branchioartary. Then the descending thoracic. The descending aorta makes sure that it supplies parts that are below the heart so they continue to branch to supply parts that are below the heart so in some we can say parts below the heart are supplied by the descending aorta parts above the heart are supplied by the branches of the aortic arc then the heart muscle itself are supplied by the coronary arteries it's also important to take note of the three major branches of the aortic arc the first one being the branchiocephalic which supplies the right side of the neck and the head and the right subclavian then the second branch is the common carotid which goes to the head then the third branch is the left subclavian Then the parts that are below the heart, they are supplied by branches from the descending thoracic. So the descending thoracic branches, it has got 10 pairs of intercostal arteries. The bronchial arteries, as the name suggests, they go to the lungs. The oesophageal goes to the oesophagus. The phrenic goes to to the diaphragm so we have branches it keeps branching as it descends to supply different organs i want you to stop and reflect on the major blood vessels that empty into the superior vena cava in which blood vessels empty their blood into the superior vena cava which in turn ends into the right atrium and which major blood vessels empty into the inferior vena cava which in turn empty into the right atrium. So there are some significant changes that take place as we age. For example, there is a general decrease in calcium transport. Calcium is important because remember calcium binds to troponin, which is a protein inhibitor. When it binds to troponin, it initiates muscle contraction. So when we have a decrease in the transportation of calcium, it leads to longer relaxation and contraction rates. And as we age again, the left ventricle muscle enlarges because it's now working harder there is less volume of blood because of less volume of blood the little blood that we have as we age it also means that the heart is to work harder to push that blood to different parts of the body such that the muscles tend to enlarge And the cardiac output also decreases. As we age there's a decrease in the volume of blood. For example, a 70 year old's volume of blood is way less than the volume of blood of a 30 year old. So there is a general decrease in the volume of blood as we age. So there is a 75% decrease of the cardiac output by age 70. that's a significant decrease in cardiac output so in sum i can say these are the highlights of the topic on cardiovascular system please go to your chapter on cardiovascular system and read through the chapter using the essay laws as your guide or a checklist. Thank you.

from your recommended textbook if you go to chapter 14 you can read through the topic on cardiovascular system because this presentation is just a summary of what you are going to get from the book so i recommend that you go to chapter 14 read through the chapter as you read through the chapter make sure you do understand the concepts that are listed here as your learning outcomes so this is your checklist as you go through the chapter make sure you understand the concepts that are listed on this page the cardiovascular system consists of the heart the blood and the blood vessels the heart is the key pump which pumps blood as it circulate through the blood vessels. The heart is composed of a type of muscle known as cardiac muscle and it makes up the bulky of the heart and this is the muscle that provides the force that pumps blood through blood vessels to different parts of the body. In doing so, it will be carrying substances.

It can be carrying supplies needed by the cells. and also waste products from the cells for excretion. On average, the heart beats at about 72 times a minute, but this is an average.

Different people have different norm values, but on average it's about 72 times a minute. And the heart has got a series of valves that prevent backflow when it's doing its work. Again, even when you look at the veins, they also have valves to prevent backflow. Though when we are studying this anatomy and physiology, we study system by system just to help us follow the concepts on how each system works. But in reality, these systems work closely together.

You cannot have a functional digestive system without a functional cardiovascular system. For example, after we eat food, the food is digested by the digestive system, which is primarily composed of the alimentary canal, which runs from the mouth to the anus, with some accessory structures. However, for the food that we eat, to get to the cells where it's needed we need a functional cardiovascular system that will absorb the nutrients and circulate them and bring them to to the cells then when we talk about cardiovascular system it consists of the heart the blood and blood vessels but whatever it transports it comes from other system for example it transport gases These gases are part of the respiratory system. It helps with issues of excretion and this is part of urinary system.

So these systems are interconnected and the main function of the cardiovascular system is to make sure that it supplies nutrients that come from the digestive system. It also supplies the gases that are needed as part of the respiratory system. And at the same time it helps us to eliminate ammonia through the urinary system and carbon dioxide through the respiratory system.

So the cardiovascular system's primary job is to pick and deliver substances to the cell and also pick waste materials from the body to respective systems that are responsible for excretion. So these systems are interconnected. So let's briefly talk about the structure and function of the heart. As I said earlier, the heart is primarily made up of muscle which is responsible for pumping the blood. However, we know the heart has got four chambers.

It has got two upper chambers and two lower chambers. And when you look at the muscle, it's the myocardium which is the cardiac muscle which forms the balconies of the heart but lining the chambers inside the chambers that's where we have the endocardium. Covering the heart we have the epicardium which is composed of layers of the visceral and serous pericardium.

The anatomical position of the heart we find it behind the bimidia sternum and is surrounded by layers of membranes. The pericardium as the name suggests peri meaning the outside. So the pericardium has got two layers. It has a layer of fibrous pericardium and a layer of serous pericardium.

The fibrous pericardium as the name suggests is fibrous pericardium. fibrous it is connective tissues like a fiber with connective tissue its main function it helps to anchor the heart within the mid astina as you jump up and about doing your normal activities it's important that the heart remains in position for it to remain the position in position with a special type of connective tissue that helps to anchor the heart and that is the fibrous pericardium. Then the serous pericardium is kind of delicate and thin and it's also known as the parietal layer of the pericardium. This layer is continuous with the layer of the heart, the outermost layer of the heart.

In other words, It touches the heart, it covers the heart muscle. I like this diagram because it shows the layers of the walls of the heart. If you look at it closely, we have the muscle which is the myocardium.

Then the pericardium membrane that touches the heart muscle, covering the heart muscle is the serous. that serous is also known as the epicardium then between the serous and the the pericardium peri-h or pericardium is a pericardial cavity within the pericardial cavity this is where we have fluids that circulate is the heart pumps those fluids help to prevent friction then we have the fibrous pericardium the fibrous pericardium is the one that anchors the heart within the walls of the cavity to make sure that the heart stays in position. This diagram is a recap of what I have shown you before.

This diagram is also found in a textbook. It shows the myocardium and the visceral pericardium which covers the heart muscle. The hat has got four chambers.

It has got two upper chambers and two lower chambers. And then when you look at those chambers, we have a right side of the hat and a left side of the hat. Remember, this is a hat of somebody who is facing you.

So the right side is to your left and the left is to your right. So this is kind of the normal visualization of the heart. The upper chambers are called atria and the lower chambers are called ventricles.

In other words, so we have a right and a left atrium and a right and a left ventricle. It's also important to note that when you look at the heart from the outside, there are clear demarcations that separate the chambers. For example, between the atria and the ventricles, when you look at between the atria and ventricles, there is a clear separation and they are separated by the coronary sulcus. Then between the ventricles, there is an interventricular separation, also known as the sulci.

so that you can tell that those four chambers are clearly separated or demarcated from the outside. Then when we look again at the inside, we can see that structure is related to function. The upper chambers which are the atrium are responsible for receiving the blood.

Then the ventricles are responsible for pumping the blood so that it gets outside the heart. So to pump blood to go outside the heart, the ventricles they need more power that's why their walls are thicker. So if we're to compare the wall of an atrium as compared to the wall of a ventricle, the ventricle has got a thicker muscle because the atrium only pump blood to the lower chambers whereas the ventricles they need to pump blood to get outside the heart so they need more force they need more muscle that's why the ventricles tend to have thicker muscles as compared to the atrium then when we look at the great vessels of the heart to say how does blood get to the heart and how does blood leave the heart.

The parts that are above the heart they drain deoxygenated blood and empty it into superior vena cava. The parts that are below the heart they drain deoxygenated blood and empty into inferior vena cava. So we can say inferior and superior vena cava they empt their blood into the right atrium the heart muscle is also tissue on its own so it also has a coronary supply of blood the deoxygenated blood from the tissue of the heart is drained by coronary sinus which empty into the right atrium So we can say the right atrium receives blood from three veins.

Superior vena cava which drains from upper parts. Inferior vena cava which drains from lower parts. And the sinus is not shown in this diagram. It drains from the heart tissue and ends into the right atrium. After receiving the deoxygenated blood from the different parts of the body, the right atrium simply squeezes this blood into the right ventricle.

Then when the right ventricle squeezes blood, it goes into the pulmonary trunk. Then the pulmonary trunk will divide into the left and the right pulmonary arteries. The pulmonary arteries carry deoxygenated blood to the lungs for oxygenation.

So the pulmonary arteries, they take blood from the heart to the lungs for oxygenation. After oxygenation, blood comes back to the heart so that it can be pumped to different parts of the body to bring blood from the lungs. to the heart we have pulmonary veins two from each side so in other words the left atrium receives blood from four veins two from the left lung and two from the right lung then after the left atrium has received blood it pumps it into the left ventricle the left ventricle it pumps into the ascending iota.

On the ascending iota we have a branch which is the coronary artery which branches so that it feeds the tissue of the heart with blood. Then the ascending aorta will form an arc. The arc branches to supply the upper parts. Then the descending thoracic supplies the lower parts of the heart.

So the coronary arteries are important because they make sure that the tissue of the heart muscle itself is supplied with the blood. So when you look at this diagram, where we had superior vena cava, now we have an aortic arc. Where we had inferior vena cava, now we have a descending thoracic.

And then where we had a coronary sinus, we now have a coronary artery, which makes sure that the heart tissue is supplied. with oxygenated blood this is a branch that comes from the ascending iota then when you compare again the thicknesses I have already mentioned that the atrium are thinner than the ventricles the ventricles have thicker muscles as compared to the atrium the comparison is important because it's about the power needed by the muscles to pump blood from ventricle from atrium to ventricle the distance is short it's just squeezing blood into the lower chamber but when you are pumping out the blood to get to the extremities you need a thicker muscle that's why ventricles have a thicker muscles then when you compare the the sizes of the chambers The right atrium receives blood from different parts of the body. So when you are looking at it, it's slightly larger than the left. Slightly, not a lot because they pump about the same volume of the blood.

Then when you look again at the ventricles, the left ventricle, the muscle is thicker than the right ventricle. This is because the right ventricle is pumping blood to the lungs and the lungs are not very far away from the heart. Whereas the left ventricle is to squeeze oxygenated blood to different parts of the body. So the blood from the left ventricle is to go to a longer distance.

It needs more force, more pressure. That's why the left is bigger. is bigger muscle. So this slide is almost like a repeat of what I just said to say the left ventricle pumps blood to different parts of the body that blood needs more pressure hence the thick muscle which we find on the left ventricle is compared to the right ventricle which only pumps blood to the lungs.

When blood is being pumped through the heart, we have deoxygenated blood being handled on the right side of the heart, oxygenated blood being handled on the left side of the heart. There are heart sounds, the lab-dub sounds that can be heard. These sounds are generated when the valves close.

So between the atrium and the ventricle we have atrioventricular valves. On the blood vessels that leave the heart we have semilunar valves. So the heart sounds are generated when the valves close.

The lab sound is generated when the atrophendicular valves close so when the valves between the atrium and ventricle close we have the lab sound the dab sound is heard when the semilunar valves close and semilunar valves are valves found on the arteries that leave the heart that is on the pulmonary trunk and on the ascending aorta there are cases where some members can be heard when you're listening at the heart sounds and this is typically caused by blood trying to squirt back through the the house then you can hear the this the hissing sounds or the heart memos. Another important aspect about the anatomy of the heart is that only veins go towards the heart and arteries they go away from the heart. Then when you look at this diagram pulmonary arteries are the only veins that carry deoxygenated blood and pulmonary veins. are the only veins that carry oxygenated blood to prevent backflow we said we have valves within the heart between each atrium and a ventricle we have valves those valves are known as atrial ventricular valves atrial for atrial ventricular for ventricle So between that we have atrioventricular valves.

Then those atrioventricular valves, they are tricuspid if they are between the right ventricle and the right atrium. In other ways, a tricuspid valve is an atrioventricular valve between the right atrium and the right ventricle. Then a bicuspid is an atrioventricular valve.

between the left atrium and the left ventricle. And to hold those valves in position, they have a series of tendons. When you look at this diagram, it has a series of tendons known as caudate tendineae.

And when we say tricuspid, it's because they have three flaps. Bicuspid is because they have got two flaps. and the bicuspid are also named as the mitral valves and semilunar valves are valves that are found on the arteries that leave the heart so we have pulmonary semilunar which is found on the pulmonary trunk then on the ascending aorta we have the aortic semilunar valves so then in general the arteries that leave the heart have valves those valves are known as semilunar it's pulmonary if it's on the pulmonary trunk and it's aortic when it's on the aorta so we can say there is a pulmonary semilunar valve on the pulmonary trunk there is an aortic semilunar valve on the ascending aorta and just like the tricuspids the semilunar valves have three capsules so in other ways the mitral or the bicuspid are the only valves of the heart with two flaps all other valves the tricuspid the semilunar valves have three flaps As we talk about blood flow through the heart, it's important to note that what happens on the right is also happening on the left. In other words, these two atrium, they receive blood simultaneously.

The right atrium receives deoxygenated blood from different parts of the body and the left atrium receives oxygenated blood from the lungs. So both atrium fill with blood. blood at the same time, they contract and squeeze blood into their respective ventricles.

So when the right atrium and left atrium are contracting, the right and left ventricles will be relaxed. In other words, they will be opening up to receive the blood that is being squeezed to lower chambers by the upper chambers. After squeezing blood into the lower chambers, Both atrium relax as both ventricles contract at the same time to push blood to get outside the heart. The right will be pumping to the lungs and the left will be pumping to different parts of the body.

Then all chambers relax before the next cycle and the valves will be closed before the next cycle. And that's important because it ensures maximum cardiac output. It helps to build pressure and ensures maximum cardiac output.

So in sum, we can say deoxygenated blood from different parts of the body retains to the right atrium. Then the right atrium makes sure that it squeezes to the right ventricle. Then blood is squeezed via the pulmonary trunk and pulmonary arteries to the lungs. Then oxygenated blood will come back.

to the heart via the pulmonary vein which feeds into the left atrium. Left atrium squeezes its blood to the left ventricle then when the left ventricle contracts it goes through different parts of the body. So to initiate the cardiac cycle the heart has its own intrinsic factors that initiate the cardiac cycle.

through the generation of electrical activity. This is done by the pacemaker also known as the sino-arterial node. This is the center which generates the impulse electrical activity that stimulates contraction.

This activity can also be shown on the ECG. So the sino-arterial node When it initiates the cardiac cycle, it generates an electrical activity which is distributed to both atrium, the right and the left. Then both atrium will contract at the same time and squeeze blood into relaxed ventricles. Meanwhile, impulse will be traveling to the atrioventricular node. There is a slight delay on the atroventricular node and that's important because it ensures that the ventricles fill with blood before they contract.

Thereafter, it travels rapidly down the septum, the histobandals, and gets to the apex and then goes to the walls of the ventricle to the Purkinje fibers. Once the Purkinje fibers receive the electrical impulse, they stimulate the ventricles to contract at the same time. So in short, both atrium receive electrical activity at the same time, they simultaneously contract to squeeze blood to their respective ventricles, and both ventricles receive electrical activity from the purkinje simultaneously, and they contract to push blood to get outside of the heart. So in summary, that's the conduction system of the heart. The cardiac cycle is innervated by the ANS, Autonomic Nervous System.

The ANS does not initiate the cardiac cycle, it only innervates either by speeding it up as part of the sympathetic system or to slow it down or restore it as part of the parasympathetic system. In other words, the initiation of the cardiac cycle is within the heart itself through the pacemaker. The nervous system is there to innovate either to make it go faster or slower or to just regulate the heartbeat.

So the generation, as I said before, is important because it stimulates the cardiac muscle to contract. As I said earlier, the electrical activity that takes place during the heart conduction system can be recorded on an ECG. So on the ECG, each different wave represents a certain part of the heart which is being activated to contract.

For example, when you see these flow diagrams, the part that is colored in purple is the part that will be receiving the impulse. The first part is the generation of electrical impulse from the sinoarterial node. It goes to both atrium.

So when both atrium are receiving electrical activity to stimulate them to contract, this is shown by the first. wave of the ECG. Then when information gets to the atrial ventricular node, that's the second part of the graph. Then when the information travels down the septum, these bundles to the Purkinje fibers, this is this part of the ECG. Remember, once the Purkinje fibers receive electricity, they stimulate the ventricles to contract and when ventricles are contracting it gives us this this big wave so the reason why the sino arterial node is also known as the pacemaker is because it kind of says the pace of the the cardiac cycle it initiates the cardiac cycle and it's called sinoarterial because it's found on the atrium specifically the right atrium so the function of the ans is just to innervate either by speeding it up or slowing it down or to restore if there was a notion of flea or flight so in other ways hormones for flea or flight can also help to speed up the pace of the heart so when we look at this diagram you can actually put the sequence of events in some order to say number one you start with the sign arterial node initiating the cardiac circle number two is the right and left atrium receiving impulse then to receive it number three will be the atrioventricular node number four will be the the his bundles on the septum number five will be the purkinje fibers receiving the impulse receiving last will be our ventricles they receive it simultaneously So what's happening on the left side of the heart is also happening on the right side of the heart.

It happens simultaneously. Both atrium receive electrical activity at the same time and contract at the same time to squeeze blood into their respective ventricles. Both ventricles receive electrical activity at the same time and contract at the same time to push blood outside of the heart. So a cardiac cycle actually is from the time the heart receives blood up to the time when it pumps blood from the heart. So the cardiac cycle can be measured from the time the heart is receiving blood, it's squeezed into the lower ventricles and then squeezed out of the heart to initiate another next cycle.

So we can talk again in terms of systole and diastole. Systole is basically contraction phase and diastole is basically relaxation phase. And blood pressure is measured in systolic and diastolic pressure.

The systolic number is the number above and the diastolic is the number below which is the smaller number. And when we are measuring blood pressure, it's all by the... pressure generated by our left ventricle because we are measuring arterial pressure and arterial pressure is generated by the left ventricle is the one which pumps blood to the periphery our right side of the heart only pumps blood to to the lungs the left is the one which pumps to different parts of the body so when you are measuring the pulse It's about pressure generated specifically by the left ventricle. So this slide here gives you an idea on the categories of blood pressure. To see, we see blood pressure is normal when the systolic, which is the bigger number, the top number, is less than 120. Or the diastolic is less than...

80. Prehypertensive again ranges between 120 and 139 for systolic and 80 for 89 to diastolic. Then stage 1 blood pressure. The systolic is 140 to 159, diastolic will be 90 to 99. Then stage 2 hypertensive is 160 and above for systolic and 100 or higher for diastolic.

It is also important to note that when staging, the number that matters the most is the number that is off the range. For example, if a patient is a blood pressure of 140 over 89. 89 as you can see is pre-hypertensive but 140 is stage 1 hypertensive. So the patient is classified as stage 1 hypertensive because of the 140. Then you can have a patient who has say 120 for their systolic and then maybe for some reason they have hand reach. for their dystolic.

For when the dystolic is 100 it's stage 2 but 120 is kind of in the normal range but that patient will be classified as stage 2 hypertensive because of their dystolic which is off the chart. So let's talk about some major circulatory route to say when blood leaves the heart where does it go to? So we say circulation is systemic when it includes all the blood that leaves the heart and all the blood that is returning to the heart. So it's almost like saying is the total circulation when we are distributing oxygen to different parts of the body and the total circulation in.

when we are bringing carbon dioxide for oxygenation. So the total circulation is systemic circulation. Then there are some subdivisions that are important.

For example, we have coronal circulation. Coronal circulation is about circulation that takes place within the heart muscle itself. The heart is a tissue that requires a constant supply of oxygen and nutrients because for the heart muscles to contract and relax they also need ATP that ATP comes from glycolysis so they need a continuous supply of oxygen so from the ascending iota we have a special branch of coronary arteries which branch so that they can feed the heart muscle so that's another special circulator route the coronary circulation and in most cases when you hear that a patient has got a heart attack or they have a clot in their coronary circulation it will be clots found on the arteries that feed the heart tissue with oxygenated blood Another second special circulator route is the hepatic portal circulation.

This is a special circulator route which goes back and forth between intestines and the liver. Remember after a meal we need to store excess carbohydrates in the liver. So we have a special circulator route where nutrients are absorbed and it goes to the liver for storage. and also the liver is a detoxifying organ when the absorbed nutrients or the absorbed substances from the intestine when they get to the liver, the liver also detoxifies it before it's distributed to different parts of the body.

Other circulations that are worth mentioning is the pulmonary circulation. Pulmonary circulation is important because this is the route that ensures that we oxygenate our blood and also we get rid of the carbon dioxide. So this is the route which occurs between our heart and our lungs. Another important route which is worth mentioning is the cerebral.

which ensures that our brain is supplied with with oxygen and nutrients and also to take the waste materials from the brain. Then another important circulatory route is the renal. To say each time we have a cardiac output about 25 percent of the blood goes to the kidneys where it's filtered That filtration process is the formation of urine to make sure that we get rid of ammonia.

Another route which is worth mentioning is the fetal circulation route. This is the temporal route which is formed between a developing fetus and a mother when she is pregnant to ensure that the fetus is supplied with blood. There is a special circulator route which attaches the placenta to the mother's cardiovascular system to ensure the umbilical cord to ensure that the nutrients are supplied to the developing fetus and also waste materials are removed from the developing fetus.

The heart is the major organ for the cardiovascular system because it's the one who is responsible for pumping blood into different parts of the body. However, the blood vessels carry a major part because these are the tubes that penetrate the organs and tissue. So their structure and function is important. When you look at the blood vessels, they have a lumen which is a hole within them. But then they have layers, layers of muscle tissue, smooth muscle.

The innermost layer is the intima. The middle layer is the media. The outer layer is the advecta. So they have three layers.

Structure is related to function. Same with arteries and veins. Veins typically carry sluggish blood because this is blood which is now returning in general, returning to the heart. Then the arteries carry blood which is under high pressure. So the muscles tend to be thicker and they are stronger.

so that they can withstand the the pressure that comes from the heart when the left ventricle is pumping blood to different parts of the body it generates a lot of pressure and the blood vessels should be strong enough to withstand that pressure that's why the arteries are built for for that then when blood gets to its destination there is need to drop oxygen and nutrients and peak carbon dioxide and to enable that from happening that's where we have capillaries which are about one centimeter thick to ensure diffusion and these penetrate into the tissue so in other ways our venous system connects with the arterial system through the capillary network this is where the magic of dropping and picking substance okay Then once there's dropping and picking to begin its journey back, it goes through the venous system but now the blood is moving towards the heart, it has less pressure. Then to prevent backflow, the veins have valves which prevent backflow as the blood is moving towards the heart so that it goes to the lungs for oxygenation. The venules connect to the veins via the capillaries. This diagram is kind of a repeat of what I just said before to say the arteries are built so that the hair can withstand the pressure of the blood that travels through them.

The blood is under high pressure. The pump pumps blood so that it gets to the periphery. It needs to push it hard. so the blood vessels need to be strong enough to withstand the pressure then the veins they don't need a thicker muscle because the blood is now under less pressure under less pressure and it risks the idea of flowing back but to prevent that from happening there are valves which prevent back flow Again, this is a diagram which is showing the valves found in the veins to prevent backflow.

Then when you look at the thickness of this muscle, it's different from the thickness of that muscle because the arteries need a stronger, thicker muscle. Then the capillaries are only one centimeter thick and that's important so that it's easy for substances to diffuse. in and out. This diagram is similar to what you have in your textbook.

Remember we said blood coming from the left ventricle it goes via the ascending aorta. As it goes via the ascending aorta there are coronary branches which help to supply oxygenated blood to the tissue. of the heart.

Then we have aortic arc. Then branches of the aortic arc supply the parts that are above the heart including the branchiocephalic which supplies the hands. Same as the branchioartary. Then the descending thoracic. The descending aorta makes sure that it supplies parts that are below the heart so they continue to branch to supply parts that are below the heart so in some we can say parts below the heart are supplied by the descending aorta parts above the heart are supplied by the branches of the aortic arc then the heart muscle itself are supplied by the coronary arteries it's also important to take note of the three major branches of the aortic arc the first one being the branchiocephalic which supplies the right side of the neck and the head and the right subclavian then the second branch is the common carotid which goes to the head then the third branch is the left subclavian Then the parts that are below the heart, they are supplied by branches from the descending thoracic.

So the descending thoracic branches, it has got 10 pairs of intercostal arteries. The bronchial arteries, as the name suggests, they go to the lungs. The oesophageal goes to the oesophagus. The phrenic goes to to the diaphragm so we have branches it keeps branching as it descends to supply different organs i want you to stop and reflect on the major blood vessels that empty into the superior vena cava in which blood vessels empty their blood into the superior vena cava which in turn ends into the right atrium and which major blood vessels empty into the inferior vena cava which in turn empty into the right atrium.

So there are some significant changes that take place as we age. For example, there is a general decrease in calcium transport. Calcium is important because remember calcium binds to troponin, which is a protein inhibitor. When it binds to troponin, it initiates muscle contraction. So when we have a decrease in the transportation of calcium, it leads to longer relaxation and contraction rates.

And as we age again, the left ventricle muscle enlarges because it's now working harder there is less volume of blood because of less volume of blood the little blood that we have as we age it also means that the heart is to work harder to push that blood to different parts of the body such that the muscles tend to enlarge And the cardiac output also decreases. As we age there's a decrease in the volume of blood. For example, a 70 year old's volume of blood is way less than the volume of blood of a 30 year old.

So there is a general decrease in the volume of blood as we age. So there is a 75% decrease of the cardiac output by age 70. that's a significant decrease in cardiac output so in sum i can say these are the highlights of the topic on cardiovascular system please go to your chapter on cardiovascular system and read through the chapter using the essay laws as your guide or a checklist. Thank you.

Transcript for:Overview of Cardiovascular System Concepts

Transcript for:
Overview of Cardiovascular System Concepts