Structure of the Circulatory System (Nursing)

00:01 Now let's talk about the cardiovascular system.

00:05 There's a lot to cover.

00:07 But specifically, we're going to talk about blood vessels, the basic differences, for example, between an artery and a vein.

00:14 We're going to talk about great vessels, which are the ones that attach directly to the heart, such as the aorta, the inferior and superior vena cava, and the pulmonary arteries and veins.

00:26 We're going to talk about the heart.

00:29 We're going to talk about its structure externally and internally.

00:32 We're going to talk about cardiac circulation.

00:35 And then finally, we're going to talk about the conduction system that keeps everything flowing in order.

00:41 We're going to start with the basics, blood vessels.

00:45 They generally come in two flavors, artery and vein.

00:48 But they don't probably mean what you think they do.

00:51 You're used to hearing arteries and veins, meaning probably oxygenated blood and deoxygenated blood.

00:57 But that's not how they're defined.

00:59 Arteries are defined as blood vessels going away from the heart, whereas veins are those coming towards the heart.

01:06 So how do they connect up? Well, we start off with an artery.

01:10 Generally, the aorta is the first one.

01:12 And then it's going to range into smaller ones called arterioles.

01:16 And then eventually, the thinnest smallest ones possible capillaries.

01:21 And that's where gas and nutrient exchange is going to take place across their membrane with the surrounding tissues.

01:27 And then those are going to merge into small veins called venules.

01:32 And eventually up to larger veins.

01:35 When we talk about blood vessels, the middle part, the empty part is the lumen.

01:41 And that's where blood is flowing.

01:43 And one of the key differences between arteries and veins, is the fact that arteries are a lot closer to the heart.

01:50 And they feel that pressure and pumping action a lot more than the veins.

01:54 So that blood can go through the lumen just from the force of the heart itself.

01:58 But by the time you've done all this branching, you've gone through the capillaries, and you've reached the venous system, there's not a lot of pressure, and the blood can kind of stagnate, which is why veins, unlike arteries have valves.

02:13 So how to valves help? Well, the key thing with valves is that any sort of movement in the vein will be unidirectional, because of the valve.

02:24 Meaning of valve will closed prevent blood going backwards.

02:29 So here's the vein. And here's an artery that's nearby.

02:33 And arteries have a pulsatile action, so they kind of expand and contract a little bit with each heartbeat.

02:39 And that means will kind of push on the nearby vein.

02:43 And by doing that, they give a little bit of a squeeze to these veins.

02:47 And that's where the valves come into play.

02:49 So if these valves are here, when they're squeezed, it can make sure that it can't go backwards, blood can only go forward toward the heart.

02:58 In fact, you have more valves the further away from the heart you are.

03:01 So by the time you get down into your toes, you have valves like every couple centimeters.

03:08 Those open venous valves are always going to point back towards eventually the right atrium.

03:14 Another thing that helps when it comes to getting venous blood all the way back to the heart are irregular skeletal muscles.

03:22 So skeletal muscles, every time we move are going to create a little bit of force on the veins around them.

03:29 And that's going to kind of create an artificial pump, if you will, on to the venous system.

03:36 And because they're opened in such a way that it can only flow towards the heart, any sort of skeletal movement is actually going to be beneficial with directing venous flow back to the right heart.

03:48 That's why you sometimes hear if you're on a really long plane flight, you should get up and stand around, that's one of the things that you get from doing that is your skeletal muscle pump, allowing the veins to free up and move that blood so they don't stagnate or clot.

04:04 If the veins have valves that don't work so well, you might get something called varicose veins.

04:11 So when those veins become deformed in some way, and they can't prevent blood from flowing backwards back away from the heart, now it's going to start to pool and expand and it's going to cause these veins to dilate.

04:25 Because essentially what varicose veins are where they're superficially visible and large and dilated because these valves just don't work.

04:35 So, when we talk about circulation, we're putting together all the blood vessels that are involved in generally what we call systemic circulation and then a smaller one for pulmonary circulation.

04:48 The story of systemic circulation really begins with the main pump the left ventricle.

04:55 That's what's going to pump out all of our oxygenated blood out the aorta, out to all the various arteries, for example of the head and neck and elsewhere, all the way down to smaller branches and capillary networks to deliver their oxygen.

05:09 And they they're going to come back through the venous system, eventually to reach the right atrium.

05:16 And then we have a shorter smaller pulmonary circulation.

05:20 And that begins with the pumping from the right ventricle, which is going to pump through the pulmonary arteries.

05:28 And here's a good example.

05:29 It's an artery, because it's going away from the heart, but it's carrying deoxygenated blood, kind of the opposite of what you probably always thought.

05:37 And they're going to go to the lungs so they can get oxygenated and come back to the heart as pulmonary veins, Again, an example where a vein is actually carrying oxygenated blood.

05:48 And it will end up in the left atrium, getting arteries away veins or toward.