this lecture is part two of the heart so chapter 20 um I've divided into the three sections the first sections was about heart circulation so now we need to know more about the heart in it of itself so the heart location inside the body is found in a place called The mediastinum the mediastinum is a space in a thoracic cavity that's going to extend from your top of your ribs to your diaphragm and basically the media stum space inside your thoracic cavity includes everything except for the lungs the heart is slightly tilted and so it kind of um has a slight Acuity to it meaning that the left side is located a little bit more posteriorly and the right side is located a little bit more anteriorly additionally it is somewhat of an inverted pyramid in the fact that the base is actually considered to be the Superior or the top part of the heart whereas the Apex is considered to be the bottom or the inferior conical end and that is going to be pointing slightly towards the left side of the body kind of right under the left lower part of the sternum so the dotted line in both of these images represent the medium so here's the mediastinum space mediastinum again is going to be that space inside a thoracic cavity that everything except for the lungs is found in and so the heart is positioned in that space with the medius then when we look at the heart itself again here is the Apex that is the bottom left location of it and then we have the base across the top and so it is an inverted pyramid in the positioning of the heart and so here you can see the star is the Apex and that line going straight across that's going to be considered the base of the heart both of these image um show you what the heart looks like in images versus what it looks like in real life so you can see that images do a wonderful job of adding color to represent oxygenated and deoxygenated blood making it all beautiful to be able to identify but in the bottom right you can see that the shades of the heart and heart tissue really are not that colorful at all it's kind of just a spectrum of brown and beige and so although those images are beautiful to be able to understand oxygenated and deoxygenated uh blood you need to understand that it's not actually what it looks like in real life so knowing the parts makes a difference so surrounding the heart is a piece of tissue that was talked about in a& P1 which is your pericardium peri means around cardi of course means heart um the challenging thing about the pericardium is it actually cons consists of two main divisions a piece called the fibrous pericardium and a piece called the Cirrus pericardium the fibrous pericardium is this very tough inelastic dense irregular connective tissue it's going to help connect the heart um down to the diaphragm and basically um close off near the top part of the heart the Cirrus pericardium is going to be a tissue that is more delicate kind of like a Saran Wrap and the seirus pericardium is a double layer around the heart the outer layer is called the parietal layer and the inner layer then is called the visceral layer we'll talk about how the visceral layer also has another name to it called the epicardium and so if we talk about the three layers of the pericardium that's going to be surrounding the heart the three layers are number one the fibrous pericardium then the parietal Cirrus pericardium number two and then the visceral Cirus pericardium number three so that's how they are defined in between the parietal and the visceral layers right here is where we're going to find a very small space called the paracardial cavity and the paracardial cavity is going to be where you find just a small amount of fluid as well and that's going to help to reduce the friction between the layers as the heart moves and pumps um in its location so if you're having trouble understanding how the paric cardium tissue Works here's a good image so the whole balloon represents a paracardial cavity this outer piece of tissue is a cirrus pericardium so once the heart is placed in into the balloon what happens is the balloon kind of gets smashed and so the remaining blue that surrounds here is the pericardial cavity when that part of the balloon is touching the heart that is known as the visceral layer and then the outer layer of the balloon is called the parial layer so visceral is directly on the heart itself parial is going to be outside of that and then in between that is going to be the paracardial space so here again looking at those three layers so we have the fibrous pericardium number one we have the parietal layer of the Cirus pericardium number two and we have the visceral layer of the seirs pericardium number three and then in between it of course is going to be the paracardial cavity now the visceral layer of the seirus pericardium what I want to point out to you here is that you can see in parentheses there's another name given to it that is the epicardium so we'll see this image coming up again because the visceral layer is the same thing the epicardium it just depends upon how you are looking at it whether you're looking at it through the paracardial layers or the layers of the heart superficially on the outside of the heart there's going to be a couple structures that you can recognize we have What's called the oracles Oracle means ear and so these are going to be structures that were once part of your developmental heart of the Atria but after the your heart is fly developed into its final position they become kind of extensions on the anterior surface of the heart so they look like little flaps so that's why we like say that they look like little um doggy ears additionally there will be some grooves on the surface of the heart that we call sulai You' remember sulky from talking about the grooves of the brain so now we have sulky on the heart the suai and the heart are basically spaces or indentations where you can find the coronary vessels these are the vessels that are going to supply blood to the heart so there's What's called the coronary sulcus remember coronary means outside or crown and the coronary sulcus in particular is going to be a deeper Groove than others because this is going to separate your Atrium from your ventricles and goes around the circumference of the heart so it basically separates the superior portion from the inferior portion so those two structures are your oracles your right and your left Oracle hanging off the front or anterior surface of the heart and then this yellow line represents what would be the coronary sulcus so if the blood vessels were would be removed you would see a nice um indentation or a nice divot Groove about where those vessels would be positioned at all right so then we have the layers of the heart wall so the layer layers of the heart wall consist of three layers we have the epicardium The myocardium and the endocardium so the epicardium is composed of the outermost tissue this is also known as the visceral layer of that Cirrus pericardium which we talked about just a couple slides ago this piece of tissue is going to just be on the outermost superficial surface of the heart um on this tissue there's going to be a little bit of fibroelastic tissue some atopos tissue um it's going to create a smooth slippery texture on the outermost surface of the heart it's also where some blood vessels lymphatics and other vessels are going to be positioned at to supply blood the next layer is called The myocardium and myocardium hands down is the thickest layer of the heart because myocardium the prefix myo means muscle cardium referred to the heart it makes up about 95% of the heart wall and so this is a unique tissue called the cardiac muscle tissue which we talked about and looked at when we talked about muscles in& P1 um this is only found on the heart it is striated like skeletal muscle but it is involuntary and the purpose of The myocardium is it has to contract to pump the heart and then the innermost piece of tissue is called the endocardium endocardium is this very thin layer of endothelial tissue and that's going to be lining the inner surface of the heart of the chambers as well as continuation with the valves so that endocardium ensures that there is continuation of the inside of the blood vessels with the inside of the heart why that's important is if you can imagine two um hoses that are being linked together where they are linked together um that sometimes can spray out water because it's not going to create necessarily a cohesive link whereas the endocardium with having that lining being uh continuous with the major blood vessels connected to the heart it's not as if your hoses are hooked up on the heart it's all continuous so again the three main layers of the heart we saw this picture earlier in the lecture when we were talking about your paracardial tissue so the three layers are going to be the epicardium outermost layer myocardium thickest layer of the heart and then endocardium the inside of the heart so now we are inside the heart and inside the heart there are spaces that we call Chambers and so the chambers represent um these collections of spaces basically where the blood is going to be housed at and how it's going to be pumping um you have two receiving chambers that are called the Atria they are considered to be the entryway and then the two um inferior pumping Chambers are called the ventricles so you have two Superior Atria two inferior ventricles you also can um again know that you have one Atrium on the right one Atrium on the left one ventricle on the right one ventricle on the left between the chambers are going to be walls called the inter septums so if it's between the atrium it's called the interatrial septum inter means between and so that's a th wall separating your uh right and left atrium so here it is at this arrow that is the interatrial septum and then the interventricular septum is separating the two ventricles and so inter means between ventricles referring to those um ventricular spaces so the right and the left atrium um the right atrium is colorcoded here to represent that it has deoxygenated blood whereas the left atrium is going going to contain oxygenated blood when we look at both of the atriums you're going to see some unique structures that are only found in the atrium so the roughed walls of the atrium are called the pectinate muscles and we only find those in the atrium um the pectinate muscle is going to kind of help with a little bit of the turbulence of the blood as it enters your Atrium between your two Atrium is also going to be a prominent feature in the septum called the fossos ovalis it was once an opening called the frino valley and when you are born it actually closes off to ensure that the right side of your heart stays with the um deoxygenated blood and the left side of the heart contains the oxygenated blood so when you are in utero It's actually an open hole between the two Atrium to allow blood to bypass going through the lungs when you are a fetus then on the posterior surface of the heart is going to be the coronary sinus the coronary sinus is going to be draining all the blood from the surface of the heart and returning it specifically to the right atrium openings into the right atrium would be the superior and inferior vnea so those are the two largest veins remember veins bring blood back to the heart and opening into the uh left atrium are going to be the pulmonary veins those are going to be bringing blood back to the heart from the lungs and so those why is called the pulmonary veins so here's a picture the pectinate muscles what you will see inside a heart we can see that rough wall look to them and then the structure of the um fosa oval right there is a very thin spot because again when you are developing in your mom's uterus this is an opening between the two Atrium to bypass going to the lungs and so that ensures that these two Atrium are going to have um blood that is going to be shunted to avoid the fetal lungs they don't work to be oxygenated and then when you are born it will close off to create compartments then to the ventricles so the V ventricles are also going to contain some unique structures that are to them we have the right and left ventricle right again is going to contain deoxygenated blood left is going to contain oxygenated in blood so in both of them we're going to find their rough wall which is called tribula caret tribula car is only found in the ventricles just as pectinate was only found in the atrium additionally projecting up in the ventricles is going to be these muscle projections called pap Ary muscles so papillary muscles are also only found in the right and the left atrium they help with the opening and closing of your AV valves that we'll talk about in just a little bit so extending from the papillary muscles then are going to be the cordate tendon and cordate tendon look like little parachute strings to attach to the AV valves your right AV valve and your left AV valve then are going to attach to the cord tonate pap muscles neither of the semi lunar valves are going to have that attached to them so here we see in the top left that is the cord tendon and the probe is moving over what is considered the rough wall of the ventrical called tabic carne and then in the bottom right here's a papillary muscle projection and attach to the papillary muscle then are the string-- like structures called the cord a tendon and that again is going to attach to both of the AV valves so this is a illustration as opposed to a picture of the real heart to show you the two papillary um well actually be three on one side here and then oh maybe even four because there's one back there and then two over here those are the papillary muscles and the strings are the cord a tendon everybody kind of has a different number of papillary muscles so it's not something that we say that there's a specific number [Music] between the atrium and the ventricles there is a difference in the thickness of the walls ventricles overall have a much thicker wall um spec specifically The myocardium um because these are going to be pumping to places outside the heart the right ventricle pumps to the lungs and left ventricle pumps to the rest of the body and so therefore their walls definitely going to be thicker than atrial walls and then when we compare your right ventricle and your left ventricle the left ventricle is much much thicker than the right ventricle because your left ventricle is pumping everywhere in the body whereas your right ventricle only pumps to your heart so it does not require as much pumping Force nor thickness of the walls of the heart in order to um pump so here we can see the left ventricle wall thickness right there and and then the right ventricle right there and so both of them are going to be pumping um to the body right ventricle pumps the lungs which is why is much thinner left ventricle pumps to the rest of the body structurally inside the heart there is also going to be valves valves are used inside the heart to ensure that there is a one-way flow of blood and so there are total of four valves in the heart valves open and close in response to pressure changes do to the heart Contracting and relaxing and each of the valves are going to ensure again a one-way flow of blood through the heart and so the images here we can see the AV valves so reason we know that these are AV valves atrioventricular valves is that there's the papillary muscles and the cordate tendon so these are going to be either your bicuspid or your tricuspid because both of those are the AV valves and then down here we can see an image of the semi lunar valve semi lunar valves have three tiny little flaps to them and they do not have cord tendon or papillary muscles and then over here this image is what we call the um fibrous skeleton because we can see all four valves there uh we can see your two semi lunar valves here and then your tricuspid and bicuspid valves there the two um valves that are between the atrium and the ventricles are called the atrioventricular valves the atrio ventricular valves are commonly abbreviated the AV valves the right AV valve is also called the tricuspid because there's three flaps to it these again are going to open and close based upon the papillary muscles in the cord a tendon and that's on the right side the left side of the heart is going to contain your left AV valve another name for this is called bicuspid because there's two flaps it also is most commonly referred to as the mitro valve so there's more than one name for this particular valve both of these valves again are attached to the cord tendon or those tiny little string structures and the papillary muscles so here we can see an illustration of the cord a tendon and then the papillary muscles that are there the pulmonary semi lunar Valves and aortic semi lunar valves these are considered to be your semi lunar valves and so semi lunar semi means half lunar means Moon shaped these are going to be between your ventricles and the big vessels that are taking blood away from the heart so the pulmonary artery and um the aorta from the right ventricle the opening is going to be the pulmonary valve the pulmonary valve will open up to the pulmonary trunk which then divid with a pulmonary artery and so this is carrying deoxygenated blood the left one is going to be called the aortic semi lunar valve and the aortic semi lunar valve will open up into the aorta neither of these valves have the cordate tendon or the papillary muscles attached to them so they basically open and close just upon pressure changes based upon blood that's all that they do so when the pressure behind the valve is forceful enough it will push the valve open and when that pressure d s the blood flow is going to stop from going back into the heart because the flaps will come together of the cusps so for the heart valves um when one set of valves is open the other set is closed and that again is going to ensure that there's only a one-way flow of blood through the body through the body through the heart and so you can see that in the left image your tricuspid and your bicuspid valves are open while your pulmonary semi lunar valves and aortic semilunar valves are closed and then when those semilunar valves are open your bicuspid and tricuspid valves are closed so when one set of valves is open the other set is closed so now we need to talk a little bit about The myocardium so again The myocardium myo means muscle um myocardial TI tissue is going to demand a lot of energy um for pumping the body rightfully so it's going to be a a a engine that doesn't want to stop pumping because it's really important to pump blood to the rest of the body so therefore when we look at myocardial tissue we notice that there's lots of blood supply we also know that there's lots of mitochondria because of what the heart's going to be doing of needing to produce energy your heart relies mainly on upon that aerobic metabolism meaning having plenty of oxygen available to go to the mitochondria so the mitochondria can produce ATP when your myocardium has low oxygen getting to it because of some sort of interference some sort of blockage that can cause damage or death pretty quickly because The myocardium really relies on a lot of that oxygen being delivered to them um the unique structure that is of cardiac muscle is called that inter cated discs and again the intercalated discs are going to allow the heart muscle to be much more sturdier um and strengthwise than your skeletal muscle so illustration here of cardiac muscle we can see lots of mitochondria shown in the yellow here and then we can see that there is a jagged edge representing those intercalated discs through here right through there again identifying that that is going to be where the edges of those heart cells are going to be and another image of the mitochondria um of the cardiac muscle in the yellow there mitochondria mitochondria mitochondria and we can see the organization that we talked about of the muscle way back in A1 so your zisk your ab band um hzone mline and the structure of the sarle mirror with those thick and thin filaments so why we reviewed going over the heart muscle again is that the heart muscle is going to be supplied by important vessels on the surface of the heart that we call the coronary circulation there are two divisions of the coronary circulation there's the coronary arteries and the coronary veins so coronary refers to Crown and these are going to be on the surface of the heart supplying that um myocardia again because The myocardium needs lots of oxygen that's why there's going to be lots of vessels on the surface of the heart so the ones that are transporting oxygenated blood are called the coronary arteries arteries taking blood away from the heart and in this case it's taking it to the surface of the heart the ones that are going to be containing deoxygenated blood are called the coronary veins and these are going to be collecting all that deoxygenated blood to bring it back to the inside of the heart actually so there's lots of branches of the coronary arteries we're going to know the main branches um coming straight off of the aorta are the right and the left coronary branches these are going to immediately come off and Supply oxygenated blood to The myocardium the right coronary already branches into the two main branches for you to know here which is the right marginal branch and then the posterior interventricular marginal means border and so it's going to run along the right margin of the heart or the right border of the heart and posterior interventricular posterior means backside inter means between ventricles what that's referring to the left coronary artery is going to come off and Supply a circumflex circumflex means basically a round this is going to distribute blood to the left side of the heart and then it's also going to have the anterior intraventricular anterior meaning the front surface of the heart inter meaning between the ventricles there this is also commonly known as the Widowmaker because this is the branch that when someone has a heart attack is the most likely one that is blocked um and because it is gentlemen that tend to have heart attacks over women that makes women the widows so that is the Widowmaker part to why the speciel is called that so off of the aorta aorta is right here we're going to find your right coronary artery and the right coronary artery will come off and run along the border of the heart it's then going to give off the right marginal which will give off to the right border of the heart and go around the back side where it's then going to turn into the posterior interventricular there the left coronary artery will come off and it will give off the anterior one known as the anterior interventricular branch and that will also give off the circumflex now many images make it seem like these uh vessels only are positioned here and there's no other vessels but they actually Anastos together meaning that they will combine with other vessels to create large branches that are microscopic that we can't see to allow all of the coronary vessels to provide blood to the surface of the heart but there are of course certain coronary vessels that are going to be supplying more blood to certain areas of the heart and when they're blocked that's when the heart muscle can die then there's the coronary veins veins again bring blood back to the heart and so these are going to be be bringing deoxygenated blood from the surface of the heart and draining it into that coronary sinus that we talked about previously that will eventually empty into the right atrium there are three main cardiac veins for you to know the great cardiac vein middle cardiac vein small cardiac vein a lot of times where you find veins in the body you're going to find arteries because it's very efficient the great cardiac vein runs right next to your anterior interventricular artery the middle cardiac vein runs right next to the posterior in posterior intraventricular artery and it's also going to um oh and then there's also the small cardiac vein which is going to be draining basically right next to the right marginal all three of those then are going to combine and empty into the coronary sinus which is on the posterior surface of the heart and that will take all that De oxidated Blood from the surface of the heart and empty it into the [Music] right so here's the great cardiac vein right on the anterior interventricular um part of the heart then we have the small cardiac vein which is going to be running right next to the marginal we have the middle cardiac vein which is running right next to the posterior ventricular artery and all three are draing into the coronary sinus this large space of blood collection on the posterior surface and that's going to empty into your right atrium ultimately okay so the top left image is showing you a posterior uh view of the heart so you can see the um left atrium left ventricle right atrium and we see the large coronary sinus that's collecting that deoxygenated blood from the surface of the heart and right there it's emptying into the right atrium this image on the top right then shows you what a heart looks like in real life so again not a whole lot of color coding to it and the yellow that you see is the fat that's on the surface of the heart down here of course is a beautiful image to show you the color coordination and we see on the anterior surface of the heart in particular we can make out the anterior interventricular artery and the great cardiac vein running right next to it so both of them are sitting in a beautiful sulcus that you can see there with that color coordination now this is of course the part where we talk about um a condition which you most likely have heard of if not familiar with which is atherosclerosis and atherosclerosis is the narrowing in this case of the coronary arteries you can have artherosclerosis and other vessels of the heart as well as other vessels of the body um but in this case we are referring to them in the sense of what they what happens as they become uded causing and angin pectoris so angin pectoris means strangled chest it's the severe pain that's going to come with when someone is going to have um a heart attack which is known as a myocardia esia this um angion aorus can show up in people's having severe chest pain or it can be pained down the left arm or pain in the jaw uh various people have talked about how it can show up differently in them I've also heard of it being in the upper back between the shoulder blades what this is is this is referred pain because the pain isn't actually in the necessarily in the chest the arm the jaar between the shoulder blades it is often it is in a heart but it's being referred to the surface of the skin via this way often times angin pectoris comes before somebody's having a heart attack which is known as a myocardial infarction myo meaning muscle cardia referring to Heart and infarction means basically stop or death of tissue because of interrupted blood supply what happens here is that the coronary artery has become either completely uded most commonly due to plaque buildup but there are other things that can cause a blockage and then as a result of that that causes hypoxia or low oxygen to the heart muscle and then that tissue can die and so the pain comes from the lactic acid that's built up and the muscle can't do what it normally does which is taking all that oxygen in to make enough ATP and so for people there can be a sudden one or it can be a slow one there's even silent um heart attacks but common with symptoms with it are going to be pain at the chest level down the arm that also might be some nausea some vomiting um large amounts of sweating involved if large amount of the tissue has died then the person also might die from it um because your heart needs the blood supply here's a picture of a test known as a coronary angiogram and a coronary angiogram allows a cardiologist to be able to see how open your blood vessels are and so they inject dye into the arteries and the arteries will pump the blood to the heart and then that allows them to see where there's might be blockages and in this case you can see at both of the arrows that the blockages have created a narrowing there and that is probably why the person is feeling tightness um in the chest if not having a heart attack because of those vessels being blocked and then there's various mechanisms that can be done to open them such as a stint um a bypass surgery if necessary um sometimes yeah the stin the main one that's usually uh going to help alleviate it initially they can take medication toin the blood so the doctor will decide what's the best course in order to help open up these vessels again