Cardiovascular System 8, Heart with labels

in this video we want to look at the basic structures of the heart and the heart is going to be lying in the thoracic cavity at about that kind of angle and this surface here where my hand is would actually be the diaphragm and round about the heart there's the pericardial sack the outer layer of which is made of tough fibrous tissue and the pericardial Sac actually connects onto the diaphragm below and we see there's an arrangement of small blood vessels around about the heart these are called the coronary vessels because the idea is they look like a crown crowning the heart so in red we see the coronary arteries and in blue we see the coronary veins so these form a crown around the heart if you've got the imagination to see that and then what we notice now is that this is the left side here and this is the right side here and the first thing we want to look at are the chambers on the top the left and the right atrium so we can take off this side here and what we're looking into here now is the right atrium so this space is the right atrium sometimes when you start learning about the heart you learn that the heart is a hollow muscular organ located in the thoracic cavity and we see it's Hollow because it contains four chambers so the right atrium here the other Atria can be visualized at the back here it's not actually at the back this is actually the left atrium here this is the left atrium now the Atria are the collecting Chambers they collect blood so blood is going to go into the right atrium via the superior venne caver and we might be able to see the entrance in red there to the superior venne Cava so blood from the superior venne Cava is draining downwards back into the right atrium and also draining the bottom half of the body this orifice here is representing the inferior venne Cava coming from below and we can see that this also from my finger also drains into the right Atrium and round about the right atrium we can see that there's a thin muscular wall this is made of myocardial tissue and this is the atrial myocardium and on the left side on the left atrium we can see the same thing a thin layer of contractile cardiac muscle forming the atrial myocardium now we saw that the superior and inferior venne Cava fill the right atrium what about the vessels that drain into the left atrium well these are the vessels that come from the lungs and there's actually four of them and they're in red on this model because they carry oxygenated blood and these are the pulmonary veins so pulmonary means to do with lungs these are the four pulmonary veins draining oxygenated blood back into the left atrium now the heart actually contains four chambers and the two bottom Chambers are the ventricles and here we see a cutaway section of the ventricles now what we notice here is that The myocardium is thicker so this is the right ventricular wall this is the left ventricular wall and actually when you see a real heart the left ventricular wall looks even thicker than it is on this model here and here we see another area of cardiac muscle another area of myocardium this is the cardiac septum so this space here is the right ventricle this space here is the left ventricle and we can see that the wall of the ventricles are thrown up into folds here on the left for example and here on the right these are papillary muscles and they're connected to these tenderous cords Cordy tendon so the cordi tendon here are these tendonous cords connecting the papillary muscles to these structures here which are the valves and this valve here I think you can see is between The ventricle and the Atria so that is the right atrio ventricular valve and you can see that that allows passage from the right atrium through to the right ventricle and this right atrio ventricular valve has got three cusps so it's referred to as the tricuspid valve in the same way connecting the left ventricle and the left atrium and again we can see that this is communicating through I put my finger through there and this valve here is the mitro valve and because it contains two cusps it sometimes called the bicuspid valve but its correct name is the mitro valve so blood will return from the vena cavers into the right side of the heart from the pulmonary veins into the left side side of the heart and when the heart is relaxing this blood will just go straight through starting to fill up the ventricles that will allow the ventricles to expand stretching The myocardium around about the ventricular wall then when the next cardiac cycle starts the atrio will both contract forcing blood under pressure through from the Atria to the ventricles at the same time so atrial contraction will fill up the ventricles with blood stretching the ventricular myocardium further then the ventricles will contract and they contract in the way and up the way and also the heart will twist a little bit when it contracts and as the ventricles cont ract that's going to increase the pressure of the blood within the ventricles now when the pressure of the blood in the ventricles increases that's going to slam shut the atrio ventricular valves so the increas in blood pressure in the ventricles will shut the mitro valve and will simultaneously shut the tricuspid valve and that makes a sound that's traditionally referred to as a Lu that will eject the blood through the arteries through the arterial valves so here we can see this valve here with three cusps is between the right ventricle and this artery here on top which is in blue because it carries relatively deoxygenated blood this is the pulmonary artery this is the main trunk of the ponary artery leaving the right ventricle and we see this divides into two because one branch goes to each of the two lungs at the same time the left ventricle is going to contract ejecting blood through another valve with three cusps this is the aortic valve so the pulmonary valve is between the right ventricle and the pulmonary artery and the aortic valve is between the left ventricle this space here and this vessel here the main artery supplying blood to the body which is the aort and from there blood goes into all of the systemic circulation and we actually notice here there's a small connection between the pulmonary artery here and the aorta here this is called the ligamentum arteriosum ligamentum arteriosum and that's not actually active in adults but in prenatal life before you were born when you were a fetus then that was patent and referred to as the ductus arteriosis and the ductus arteriosis would carry right ventricular blood into the aorta so the blood will go from the right ventricle to the pulmonary artery to the aorta or a lot of it would because you don't want a lot of blood going around the fetal lungs but when the baby starts to breathe that should close off and in later life it's the ligamentum arterio the thicker left ventricle is going to generate systemic blood pressure and you probably know that systemic blood pressure is going to be about 120 millim of mercury over 80 mm of mercury so when that contracts it's developing a pressure of 120 mm of mercury but the right ventricular myocardium which is much thinner generates a much lower blood pressure in the order of 25 mm of mercury so the pressure in the pulmonary artery is going to be about 25 over 8 millim of mercury we've already mentioned there's a tough pericardial sack around about the heart and a smoother pericardial layer under that there's The myocardium and the inside of the heart is lined with smooth vascular endothelium and this is the endocardium so the layers are the pericardium myocardium and endocardium so we see the four chambers of the heart and we've described the blood flow from the Atria through to the ventricles when the ventricles are contracted the blood is ejected into the major arteries but actually just after that some of the blood does try and get back it tries to flow back and that's what these arterial valves are for to stop the blood flowing back from the arteries into the ventricles and the back pressure of blood slams shut these slams these atrial so it slams these arterial valves shut and that makes a noise called a dub so the atrio ventricular valve shut causing a Lu and when these contract that causes a dub so it's Lu dub Lu dub are the heart sounds so there we have the basic structure of the heart and the basic flow of blood through the right side of the heart pumping blood to the lungs and through the left side of the heart pumping blood to the body via the systemic circulation

Channel: Dr. John Campbell

Views: 38,182

Keywords: heart, anatomy

Id: htS7UkUCUU4

Length: 14min 27sec (867 seconds)

Published: Thu Feb 19 2015