Function of Human Heart

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 semilunarvalve 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 arte 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 valveso that's the essential anatomy we needto 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 other thing 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 outsideso because it's round about the outsideit'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 vascularendothelial cells this is a very thin layer but it goes all around about the inside of the heart 

this is very important to make sure you have smooth blood flow because you 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 allthis 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.