[Music] hello everybody this is andy from med school eu today we are going to continue on with the anatomy and the physiology unit and we are going to start off with the circulatory system so i'm going to break this down into two separate videos this video will be primarily focused on the blood vessels and the circulation of the blood and the blood contents and the next video will be specif specifically focused on information about the heart so let's begin with a brief overview of the circulatory system we're going to see how the blood circulates all around the body and how it is pumped by two parts of the heart so we're going to begin with the numbering here we're going to start off with the right ventricle so the bottom part of the heart this this big one right here is the ventricle and the ones that are at the top there's two parts the top those are the atrium so the ventricles are going to be the chambers that pump the heart and they pump the blood out of the heart and it distributes throughout the body so we're going to begin here with number one and this part is is called the right ventricle so i'm just going to label it as as r for right ventricle and this is this is a circulatory system so it's it completes a full circle we can begin anywhere but um according to this diagram we're going to begin with the number one here so as you can see the blood is going to be the the heart is going to contract and the blood is going to be pumped out of the right ventricle and it's going to go right into the pulmonary artery so any blood vessel that leaves the heart doesn't matter if it's oxygenated or if it's deoxygenated it is going to be an artery anytime it leaves the heart it's an artery any time it arrives at the heart it's a vein so in this case we're going to have the right ventricle pumping over to number two and that's the pulmonary artery why it's pulmonary because it is going to pump the blood deoxygenated blood as you can see blue here is the deoxygenated blood doesn't have oxygen has plenty of carbon dioxide now this this blood is going to be pumped over to the right and the left pulmonary artery each is going to reach the right and the left lung so that's where the deoxygenated blood goes from the right ventricle a lot of the times students make the mistake that if it's an artery it must have oxygenated blood however that's not the case for the pulmonary artery because this one pumps deoxygenated blood to the lungs where it's going to get oxygenated as you can see the capillaries here so these are all capillaries capillaries they're going to be they're going to get oxygenated so the carbon dioxide is going to leave our body and oxygen is going to enter the circulatory system and the now the blood is going to be carried over to number four here and number four is going to be the left atria so left atrium atria is the pleural atrium is the singular so the left atrium is now going to receive blood from the pulmonary vein pull monary veins it's a vein because it arrives at the heart even though it's oxygenated it's still a vein and it's going to arrive at the left atrium now well of of course that's the right pulmonary vein here we got the left pulmonary vein it arrives both of them arrive at number four here left atrium now from the left atrium the heart is going to contract at the top so there's going to be a stimulus at the top in the atria and it's going to push the blood down to the left ventricle ventricle now at number five from the left ventricle the blood is this is now oxygenated blood is gonna be pumped out to the rest of the body is going to be distributed all over the body now it passes this very important artery it's called the aorta so we'll label it here a aorta and aorta is going to break off into of course smaller arteries then it's going to break off into arterioles and then it's going to break off into the capillaries so this is the lower body lower body is now going to get the oxygen it needs and this is the upper body excluding the lungs so now the rest of the body gets oxygenated blood for the cells where they receive the oxygen they're going to offload their carbon dioxide and it's going to travel back through the vena cavas the two major veins that where the deoxygenated blood arrives at the right atrium of the heart are called vena cavas so the one that's above here number nine is going to be superior superior vena cava i'm just going to label this as vc and the one at number 10 the one that's coming from the lower body is going to be the inferior vena cava so inferior vena cava so of course there's going to be all these little veins first and or venules then into bigger veins and it ends up in one of the biggest veins that are it called vena cavas from the top it's going to be superior from the bottom it's inferior vena cavas and finally they're going to arrive at 11 and that's the right atrium and then the whole cycle begins all over again next we're going to discuss the blood vessel anatomy so we're going to talk about the major arteries first and we're going to label some of these structures and they're going to be very similar to veins except for a couple of small differences so this is just gonna be like a cross section of uh so this would be the artery this this would be the general depiction of all arteries aorta pulmonary artery and so on and this would be a general depiction of veins so now we are going to begin from the outside and work our way inside so the structures are pretty much identical in terms of what they are from artery to vein except their thickness is going to differ so the outside part right here the outside is going to be called connective tissue this is connective connective tissue and and we had a brief introduction about connective tissue in our previous lectures now looking at the inner more inner structure the one that's in the middle here it's called tunica media in in latin however this is made up of smooth muscles and elastic fibers so let's make labels for that as well these ones right here so this this is made up of smooth muscle so the important thing to notice here is that arteries have gigantic smooth muscle and elastic fibers compared to the veins so the veins still have smooth muscle and elastic fibers in in one of these layers however this the thickness of the artery is is almost three times more simply due to having more volume of the smooth muscles and the elastic fibers meaning that the artery is more flexible it's able to sustain higher blood pressure and it only makes sense because arteries come right off from the heart where the blood pressure is at its peak so the aorta has to sustain very strong blood pressure before it slows down to the veins because blood pressure in the veins is going to be quite low it could get high if there is lots of blood buildup in for example in the legs if you're standing for a long time the veins in the legs are going to have in the inferior vena cava is going to build up quite a lot however there is a mechanism to push the blood along and the blood flow in the artery is going to be much much higher than in the veins because artery comes right off the heart whereas veins kind of slowly drain into the heart to get the blood back in there and let's label the final layer the one that's on the the innermost layer here and this one is going to be called endothelium endo see liam an endothelium exists in all types of blood vessels so this would include capillaries it would include venules it would include arterials the inner layer of every single blood vessel in our body is made up of endothelium and endothelium is simply connective tissue that we discussed here however it is specialized connective tissue in a sense that it makes the surface extremely smooth so it's very smooth surface to reduce friction because you don't want blood clots you don't want anything attaching to the surface of the the blood vessels so you do not get any blood clots and the red blood cells and other substances in the blood can flow smoothly now if the endothelium is damaged if the endothelium gets gets rough in its inner surface it's going to have a great impact and it's going to increase the likelihood of many diseases now another thing that is very unique to veins compared to other blood vessels is that they have these valves these one-way one-way valves and the purpose of one one-way valves is to prevent backflow of the blood so if you could imagine that there is a very low blood pressure very low blood flow going through your legs however somehow the blood is supposed to make it from all the way from your toes and your ankles all the way up to the heart so it could circulate again now how is that going to happen how how are we going to achieve this without having any backup or or backflow because if you are standing upright for 8 hours you don't want to be getting any blood clots or or any back flow in the veins the way to prevent that is to have one-way valves where the blood is going to flow in one way so it's going to flow this way here and it's the valves are going to be shut for the blood if it if it's if it wants to return now one way to have the blood pushed over faster and this is why it's encouraged that people do some walking or do some exercising or even when you run imagine somebody's running a marathon for four hours and how does the blood make make their way all the way up to their veins if you're constantly pumping the blood down to your legs or how is the blood going to make it all the way up to the heart from the veins when all the blood is going and pulling down in the legs well the the reason why we don't have blood pooling in a healthy individual is because we have muscles that push the blood upwards so the veins are situated in places where there are muscles that are in constant work so if you have a vein going like this and you have muscle belly right there and muscle belly here now imagine you're going to be walking now these muscles are going to be activating they're going to be contracting each time they contract it's going to push the blood flow up because if it pushes but it cannot go backwards it can only go one way because of these one-way valves so here we're gonna label some of the structures that are associated with each type of blood vessel so we got artery we talked about artery and vein so as you can see here it's pretty much a similar depiction is that the elastic fibers of the arteries so these blue ones this is elastic fibers the elastic fibers are much thicker and the artery contains a lot more smooth muscle so this is i'm going to label this as sm smooth muscle right here as you can see the artery has the most smooth muscle compared to any other blood vessel now another thing to note is that uh the this is this is going to be the endothelium i'm just going to label this as endo right here and the endothelium exists that's the most inner part it exists in all types of blood vessels in equal proportions so in arterials in capillaries and venules they exist in the same proportion as the arteries in the vein now another thing to note here is that the arterioles which are basically designed to slow down blood flow before it enters capillaries because arterioles have smooth muscle and the smooth muscle is going to contract and relax when it needs to dilate or constrict so the arterioles are going to control blood flow to certain parts of the body for example if you have a drop in blood flow or a drop in cardiac output meaning that your heart is not pumping out as much blood as it should for example when you're sleeping the cardiac output is typically reduced at that point the arterioles the smooth muscle in the arterials is going to relax so it's going to dilate and when it dilates they get bigger which increases blood flow it reduces the resistance and it increases blood flow so for example in parts of the body like the brain and other vital organs you have to sustain blood pressure and blood volume the same so even when you're when you're exercising or when you're sleeping your brain is going to receive the same amount of blood no matter what activity you're doing because if it doesn't then you're typically going to faint if it receives less and it also cannot receive more as that it increases more problems so the important thing to note here is the arterioles are responsible for slowing down the blood from the arteries because arteries are going to have crazy pressure remember the arteries come right out of the heart and they're going to sustain crazy amount of blood pressure so they're going to have lots of blood flowing at very high speed now you cannot even have gas exchange when the blood is just zipping by so you need another structure which is the arterial that are just smaller arteries that do not have the as much elastic fibers or don't have any elastic fibers and they also don't have much fibrous tissue so this is fibrous tissue however they have these smooth muscle that is responsible for slowing down blood pressure from the artery so that it can then reach the capillary at very slow pace and then gas exchange could occur now note that the capillary is the only blood vessel that only has endothelium because the venules that come off right from the capillaries these venules also have some fibrous tissue around however the capillaries are very fragile as they're one cell thick making up the endothelium and of course venules then quickly transform and combine into larger veins that are then going to carry the blood over and and back to the heart so now we are going to discuss blood volume and blood content so first let's begin with with blood volume and take a look at how much blood we have in our bodies so for males we'll start off with males here we have five to six liters of blood depending on the male size of course now females on average are going to have four to five liters of blood so just a liter less and blood typically makes up about six to eight percent of the total body mass so the entire mass of the body just the six to eight percent makes up volume of the blood and it makes up about 20 percent of the extra cellular fluid so the fluid that is around the cells it makes up about 20 of that and we are going to discuss this specific statistic in greater detail when we talk about the immune system so now let's discuss the composition of the blood so here we'll discuss composition and and the content of the blood so first this this yellow part we have something called blood plasma so this is the blood plasma and blood plasma makes up the majority of the blood which is going to be about 55 of the blood as you can see here this has more than than the red part and blood plasma is is this yellowish structure it's non-cellular so it doesn't contain any cells but the major function of the blood plasma is basically just a filler so it it provides the patient with blood volume which can prevent shock and it also has plays a factor in blood clotting now looking at the other elements that make up about 45 percent of the blood which is going to be the rest that is not part of blood plasma these are called formed elements this is formed elements which is 45 of the blood and that's going to include this white layer and the red part now this this white layer is called the buffy coat so i'm going to label it here it's going to be called buffy coat puffy coat because it's kind of if you spin the blood in the centrifuge this is kind of what you get you get this buffy coat and it's basically made up of platelets which are responsible for blood clotting platelet plate let's and they've they're part of the white blood cells and they make up a very small amount i would say about one percent of the formed elements now the rest the 44 of the formed elements make up red blood cells so the red blood cells are the the red part right here and platelets are also called thrombocytes and white blood cells are called leukocytes so leuco glucosites and red blood cells are called erythrocytes very throw sites so sometimes when we're gonna discuss things about the red blood cells which we will i may refer to them as erythrocytes and they make up 99 of the formed elements and that's this part right here so that's the general depiction of of the composition of the blood so this concludes our first lecture on the circulatory unit from the anatomy and the physiology of humans in the next video we're going to finish off this circulatory unit with functions and anatomy of the heart [Music] you