Cardiovascular System 1, Heart, Structure and Function

well welcome to today’s video where we’re going to be considering the heart and the hearts a hollow muscular organ located in the thoracic cavity and we need to learn the basic anatomical terminology and the basic anatomical structures in the heart before we go further so this is kind of an introductory session to cover that basic anatomy now of course in anatomy you remember you’re always looking at someone else’s so it’s as if you’re looking at my heart so this is my left hand here so that’s right left on that side of the board and right on this side of the board so we don’t get mixed up now I’ll start drawing the heart picture you can trees frame any time you want and draw your own so here we see the main bottom chambers in the heart and these bottom chambers are called the ventricles so we have a left ventricle on this side and the right ventricle on the other side and the left ventricle particularly has a thick muscular wall so here we see the thick muscular wall of the left ventricle and of course the right ventricle also has a muscular wall but it’s much thinner now why is it that the left ventricle has a thick muscular wall and the right ventricle has a thin muscular wall well as we’ll see it’s the left ventricle that’s pumping blood all around the body into the systemic circulation so the blood that’s pumped from the left ventricle goes to your ears down to your toes up to your brain absolutely everywhere around the body all of the systemic circulation so it needs to generate a fairly high pumping pressure with a large muscular mass on the left side whereas as we’ll see the right ventricle is only pumping blood to the lungs if the heart is here then the lungs are only so there’s not as far to pump the blood so the pressure doesn’t have to be as high so the amount of muscular mass required is less now the key thing about the heart is it’s in these four chambers now first of all we need to draw some arteries which are leaving the heart now this valve here guards the aorta which is the large vessel which leaves the left ventricle and the valve there points up the way and then between the ventricle at the bottom in the chamber on top there’s another valve and that one points down the way like that so here we see the left ventricle with one valve there and one valve there now the top chambers of the heart of a much thinner muscular wall so the muscle becomes thinner at that point and you can probably see here that we’re starting to draw an additional chamber one of the top chambers the atria and draining into the atria there are four large veins in humans I think in this diagram today I’ll just draw two so here we see two large veins draining blood into the top chamber the left atrium remember there are actually four in humans so now we see we have the left ventricle and here we can clearly see now there’s an additional chamber the left atrium so left ventricle left atrium pointing down the way valve pointing of the way and this valve between the atria and the ventricles below is called an atrial ventricular valve is between the atria and the ventricles so it’s atria atria ventricular valve or atrial ventricular valve and this particular valve has two cusps it opens like this the left atrioventricular valve just got two cusps so sometimes it’s called the bicuspid valve because it has two cusps but its proper name is the mitral valve

so the left atrial ventricular valve is the mitral valve and it has two cusps the valve between the left ventricle and the aorta that is the aortic valve and sometimes these are referred to as the semilunar valves because they look a bit like half a moon so the aortic arterial valve or the aortic semilunar valve that’s that one pointing up the way so as we’ve said this vessel is the aorta the large vessel leaving the left ventricle taking blood all around the systemic circulation and these bean veins here remember we said there was four veins taking blood into the left atrium there the pulmonary veins of course pulmonary means to do with the lungs and the terminology is very simple an artery is any vessel carrying blood away from the heart while a vein is any vessel carrying blood towards the heart so because these are veins we know they’re carrying blood towards the heart because their pulmonary veins we can know that these are the veins that are carrying blood towards the heart from the lungs they’re the pulmonary veins now we move on to the right side of the heart and in the same way here there’s a valve pointing up the way like this and this connects to a large arterial vessel which quickly divides into two quickly divides into two one branch of this vessel go into each lung because this large vessel leaving the right atrium is the pulmonary artery we know that pulmonary means to do with the lungs we know that an artery is any vessel carrying blood away from the heart therefore the pulmonary artery is the artery carrying blood from the heart to the lungs and we also notice this valve is pointing up the way and this is the pulmonary valve that is the pulmonary arterial valve also sometimes called the pulmonary arterial semilunar valve so both of these valves are sometimes described as semilunar valves now here we have a valve pointing down the way like this and the valve the left atrioventricular valve had two cusps this one has three cusps so I can’t do this has only got two hands but that’d be one there one there and another one from underneath three cusps so it’s called the tricuspid valve so the right atrial ventricular valve is called the tricuspid valve but just out of interest in passing we can notice that the aortic semilunar valve and the pulmonary semilunar valve also have three cusps but it’s this one that we call the tricuspid valve now what we need to put on now is the final chamber of the heart which is the right atrium so here we have the right atrium and there are two large vessels flowing into the right atrium the vessel coming from above draining the top part of the body is superior the vessel draining the bottom part of the body here is inferior and both of these are referred to as the vena cava so the vena cava is the largest vein in

the body the superior vena cava is draining the top half of the body and the inferior vena cava is draining the bottom half of the bobbling both draining blood into the right atrium so what we can actually do now is start to describe the flow of blood through the heart now the blood coming back from the lungs is going to come back in the pulmonary veins and this blood is oxygenated and if you do an oxygen saturation test on yourself you’ll probably find your oxygen saturations are about 98 or 99 percent anywhere between 96 and 100% and if you’re young and fit you put an oxygen saturation probe on your finger you find it’s 98% take a few deep breaths and it will go up to 100% meaning your lungs are completely saturating the blood passing through them with oxygen and this highly oxygenated blood containing the oxyhemoglobin is going to return from the lungs in the four pulmonary veins into the left atrium from here the blood will go through the mitral valve into the left ventricle when the left ventricle contracts that blood will be ejected through the aortic semilunar valve into the aorta from there into smaller arteries perfusing all of the systemic arterial circulation and then as the blood goes around the tissues of the body it’s going to give up some of its oxygen not all of it but some of it so when it arrives back from the systemic venous circulation from the top half of the body it’s going to arrive back via the superior vena cava and from the bottom half of the body it’s going to arrive back via the inferior vena cava and this partly deoxygenated blood which traditionally in biology we draw as blue even though it’s not blue still dyed red drained back into the right atrium from there the blood will go through the tricuspid valve into the right ventricle when the right ventricle contracts that blood will be ejected through the pulmonary arterial semilunar valve and it will go to each lung so the blood flow through the heart is regulated by the four valves and it’s going through thee from the atria to the ventricles to the body back to the right atrium right ventricle pulmonary artery and off to the lungs and we’ll look at how this happens in more detail shortly but just before we do that I want to finish off the anatomy so let’s just summarize the basic anatomy we’ve got so far we’ve got the four pulmonary veins we’ve got the superior and inferior vena cava a otter pulmonary artery left atrium right atrium left ventricle right ventricle the left atrial ventricular valve is the mitral this is the aortic valve or the aortic semilunar valve this is the tricuspid valve which is the right atrial ventricular valve this is the pulmonary arterial semilunar valve so that’s the essential anatomy we need to know now the valves we don’t want the valves to over expand or over open so connecting to the valves there are tendons these are called tenderness cords or sometimes you see them referred to by their latin name of chord e tendon e but these days we normally call them the tendinous cords and what they are is

tissue which holds the valves strands which holds the valves and stops them flapping back the way into the Adria because the whole point of a valve it is a a structure to ensure one-way flow so we want this blood to go from the atria to the ventricle but not back again that would be regurgitated which is a pathological situation so what Tim they’re very open that way that they’re not go too far back and to stop them going too far back we have these tenderness cords and these tendinous cords are routed into the wall of the heart via specialized muscles that route the tendinous cords into the wall of the heart so that the valves can’t over expand and these muscles that connect the tendinous cords to the wall of the heart are papillary muscles the papillary muscles so we looked at the Chamber’s we’ve looked at the vessels we’ve looked at the valves the other thing we need to learn when we’re starting to learn about the heart are the layers of the heart now round about the outside of the heart surrounding all of the outside there is a fibrous sag this fibrous sac is very important because it provides physical protection to the heart in addition to the ribs and the vertebrae in the sternum it’s made of tough fibrous tissue and what it also does is it stops the heart from over expanding so the heart can expand so much when blood returns to it but not over expand which would damage the heart and this fibrous sac facilitates that protection and this is round about the outside so because it’s round about the outside it’s the pericardium so peri means perimeter it’s around about the outside car diem is the heart it’s the pericardium and it forms a sac in which the heart sits to protect the heart now lining the inside of the heart we have a layer of squamous vascular endothelial cells this is a very thin layer but it goes all around about the inside of the heart and this is very important to make sure we have smooth blood flow because we don’t want any turbulence in the blood flow through the heart so it’s a nice smooth surface of squamous vascular endothelial cells and this is called the endocardium endo means in the endocardium is this inner layer of the heart and of course as you’ll see this is left out the thick muscular layer in the middle and all this area here thick muscular wall of the left ventricle this bit that goes up the middle the wall of the left atrium the wall of the right ventricle and the right atrium all of this contains bands of a specialized muscle called cardiac muscle it’s a striated muscle it’s arranged in various bands that allow the heart to contract in the most optimum possible way and this vital muscle of course is the myocardium Myo means muscle the muscle of the heart is the myocardium so what we see is that

the heart is in two sides the left side and the right side and this structure separating the two sides now a structure in anatomy which separates is called a septum and of course this is the heart so that structure in the middle there is the cardiac septum cardiac because it’s heart septum because it’s a tissue that divides so here we have the cardiac septum separating the left heart from the right heart and to put it in very simple terms we see that the left ventricle is pumping blood to the body so very often we call the left side of the heart the body pump so the left side of the heart is the body pump we see that the right ventricle is pumping blood into the pulmonary artery going to the lungs so the right side of the heart is the lung pump so the left is the body pump the right is the lung pump so they’re the basic anatomical structures of the heart that we need to learn and that is the basic pattern of blood flow through the heart