Cardiovascular System 7, Circulation of the blood

we want to follow on now and consider the heart and the chambers and valves in the heart in relation to the systemic and the pulmonary circulation the systemic circulation going to the body the pulmonary circulation going to the lungs now if you've watched the previous video you'll be aware that that is the mitral or the bicuspid valve pointing down the way and you'll be aware that that represents the pulmonary veins left atrium left ventricle that would make this the aortic semilunar valve and this vessel coming out here the aorta this would represent the inferior and superior vena cava the right atrium and the right ventricle that would make this atrial ventricular valve here pointing down the way that would make that the tricuspid valve this will be the pulmonary arterial semilunar valve pointing up the way into the pulmonary artery now the left ventricle has got a thicker myocardial wall because it has to pump blood to all of the systemic circulation and the muscle in the septum is also heavily involved in generating this contractile force the right ventricle has a relatively thinner muscular wall because it only has to pump blood from the pulmonary artery to the lungs and that's not so far the atria also has a myocardial wall but again it's thinner because that's just pumping blood from the atria down into the ventricles now the aorta will divide into smaller arteries and this will take blood to all of the body so we can represent that like this this is the body so that's your brain your kidneys liver all of the major organs and once the blood is circulated through the body it's going to return via the inferior and superior vena cava draining back into the chamber there which is the right atrium so the left side of the pump or the heart acting as a pump the left side is the body pump pumping blood to the body into the systemic circulation now the right atrium I'm sorry the right ventricle that's the right atrium there the blood goes from the right atrium to the right ventricle when the right ventricle contracts the blood is ejected into the pulmonary artery and that's going to take the blood to the lungs which we can represent here so here we have the lungs this is the pulmonary arteries that are taking blood to the lungs in order to be oxygenated as the blood goes through the lungs it's going to be oxygenated and give up its carbon dioxide or most of it and then the blood is going to drain back via these pulmonary veins back into the left atrium so there we see the full circulatory system in all its splendor and yet great simplicity now the blood in the left ventricle is going to the systemic circulation so that's going to be bright red it's going to go through the aortic semilunar valve a into the large arteries as the blood pumps into the large arteries they're going to dilate and then elastically they're going to recoil down smoothing out the blood flow to the body so oxygenated blood is going to go into the systemic circulation to all parts of the body and when it arrives in the tissues of the body it's going to be highly oxygenated therefore bright red but as this blood goes through the tissues of the body the percentages of oxygen in it are going to be reduced down to 70 to 80 percent saturations and the blood is going to appear dark red because it's carrying less oxygen now traditionally when we're doing physiology the dark red blood we do is blue it's not blue of course it's dark red but the blood is going to become darker red as it goes through the body then dark red blood is going to drain in the large veins eventually going into the inferior and superior vena cava taking blood to the right atrium this deoxygenated blood will then go through the tricuspid valve into the right ventricle when the right ventricle contracts that blood will be ejected out into the pulmonary artery and it is the pulmonary arterial system taking blood to the lungs so when the blood arrives in the lungs it's going to be dark red relatively deoxygenated blood as it goes through the lungs is going to become progressively oxygenated and it will progressively become brighter red until it's 95 to 100% saturated and then this bright red blood rich in oxyhemoglobin we'll go back in the pulmonary veins a vein being any vessel which carries blood back towards the lungs there's actually four main pulmonary veins in humans carrying the blood back into the left atrium the blood will go from the left atrium through the mitral or the bicuspid valve back to the right ventricle which is where we started this account so the circulation of the blood in essence is very simple and very straightforward and yet a very intricate well-designed parsimonious system of circulation now I've got a diagram here which shows us a bit more detail on how this circulation of the blood works so I'm just going to put that up there and we'll have a look at it now I think we'll start with the heart here in the middle and again if we start with the left ventricle which is this chamber here that's going to pump oxygenated blood into the aorta and some of that blood is going to go to the is all oxygenated blood here some is going to go to the arms via the brachial arteries the large artery in the top of the arm is the brachial artery carrying the oxygenated blood to the arms and the hands of course as that goes through the tissues it will give up its oxygen and become deoxygenated and will drain as dark red partially deoxygenated blood into the veins we notice one of the large veins in the arm is called the calf Ali vain and that is eventually going to drain back into the superior vena cava to go back to the right atrium and we notice that other blood from the aorta is going to go up towards the brain in the head two of the large arteries carrying blood towards the brain are the carotid arteries that you can feel pulsating in the neck this is going to take oxygenated blood to the head and indeed to the brain again as that goes through the tissues it's going to become somewhat deoxygenated it's going to become darker red two of the large veins in the neck accord the jugular veins they're going to bring the blood back down to the superior vena cava back to the right atrium now from the right atrium the blood is going to go through to the right ventricle and from there to the lungs and as the blood arrives in the lungs it's going to be dark red deoxygenated but then as it goes through the lungs is going to become oxygenated and bright red again draining back via the pulmonary veins to the right atrium sorry to the left atrium ready to go to the left ventricle to be pumped out again into the systemic circulation and we notice that blood also goes down through the body towards the liver and it's the hepatic artery that's taking blood to the liver again as the blood goes through the liver it will be partly deoxygenated meaning the hepatic veins are carrying deoxygenated dark red blood back and in this case it's to the inferior vena cava which is also draining back into the right atrium ready to go to the right ventricle to go back to the lungs to be oxygenated now oxygenated blood is also going to go to the organs of the gastrointestinal tract and one of the vessels involved there is the mesenteric artery that's going to take blood to the gut this tube here represents the gut so the oxygenated blood will go into the gut the gastrointestinal tract and it will become deoxygenated but here we notice a very interesting thing this blood does not drain directly back into the venous circulation it drains via this small vein here directly into the liver and this is the hepatic portal vein because we don't want bacterial breakdown products and we don't want digested food going directly into the systemic circulation we wanted to go to the liver first where it can be processed so this hepatic portal vein is unusual in that it begins and ends with capillaries ending with capillaries in the liver so the apat a portal vein is taking blood from the gut directly back to the liver for processing oh the blood goes down through the abdominal aorta to the kidneys again going through the kidneys giving up some of this oxygen draining into the inferior vena cava other blood goes down arteries such as the femoral arteries to the legs giving up oxygen to the tissues of the legs and draining Y veins such as the femoral veins back into the inferior vena cava to go back to the right atrium prior to go into the right ventricle prior to go into the pulmonary artery to going back to the lungs so there we see a little more detail about the nature of the circulatory system with some of the names of the major blood vessels involved taking blood in arterial vessels away from the heart to the tissues and returning blood from the tissues to the heart in the veins

Channel: Dr. John Campbell

Views: 142,461

Keywords: heart, cardiovascular system, anatomy, physiology, NCLEX, cardiovascular, CVS, circulation, circulatory system

Id: Kr5q2sZoV0Q

Length: 14min 4sec (844 seconds)

Published: Sat Aug 08 2015