Vasculature is what carries the blood around the body. It's going to be lined with a special type of epithelial tissue we call endothelium, and that's going to line the interior surface of these blood vessels. It actually also lines the interior surface of lymphatic vessels, but we'll talk about those a little later. Now there are basically three types of vasculature you need to know. There are arteries, which are going to transport blood away from the heart. That is what determines an artery. The direction of blood flow is going away from the heart. Veins transport blood to the heart. Now the reason I emphasize the direction is because it's a common oversimplification that people just say, oh, veins transport deoxygenated blood, and arteries transport oxygenated blood. That's true in the case of systemic circulation, but don't forget there's also pulmonary circulation. So in the systemic loop, arteries are carrying oxygenated blood, but in the pulmonary loop, the arteries carry deoxygenated blood. Remember, that's going to be the part where the heart pumps the deoxygenated blood to the lungs. So an artery is transporting that. Now, arteries have these elastic walls, and you know, a lot of smooth muscle, and this allows them to change their diameter, which is going to be important when we talk about blood pressure. And as arteries start to branch and get smaller as they make their way to the tissues, and ultimately become capillaries, we call these branches arterioles. And they have smooth muscle just like arteries, but they have a smaller diameter. So veins, kind of like the opposite scenario here, they are going to carry deoxygenated blood in the systemic loop, but in the pulmonary loop, they are going to bring oxygenated blood from the lungs to the heart. Right? Veins carry blood to the heart. When the blood's coming from the lungs to the heart, it has oxygen, and because the naming of veins and arteries is about the direction of flow, that's why veins are carrying oxygenated blood there. Now, veins are kind of different from arteries. They don't have as much smooth muscle, they have some. But they can compensate for this because they actually will run through skeletal muscles, and we'll talk about the significance of that when we talk about blood pressure. Now, veins also have valves in them. Basically, there's going to be these flaps of tissue, and they'll allow flow in one direction but will prevent backflow. And the reason this is so important is because the pressure in veins is lower than in arteries. Right? Arteries are going to have a lot of pressure coming from the heart to keep the blood moving in the right direction. Veins, not so much, because they are going to be coming after the capillary beds. So in order to ensure that the blood keeps flowing in the right direction, veins have these valves in them. Now, just like arteries branch into arterioles before they become even smaller and are considered capillaries at that point. As capillaries start to converge together, they form what are called venules. So these are going to be little veins that are going to converge together and form veins, like the main big veins. And, of course, venules come from converging capillaries. So what are capillaries? These are the sites where the magic happens, really. This is where gas exchange is going to occur between blood and tissues. And they are really small, they are tiny. They have walls that are only one cell thick, and their diameter is about the size of a red blood cell. So they can basically, as you see here, let through one red blood cell at a time. They are super thin. I am sorry. They have a super small diameter, and they are super thin to allow for easy exchange. Now they are found in tissues as what are called capillary beds. Basically, it is like a very branched network of capillaries that sort of diffuse through a tissue, and this helps maximize the surface area and exchange. Now, because capillaries lack smooth muscle, they can't control blood flow like veins and arteries can. They can't constrict and dilate. However, there are what are called precapillary sphincters. Basically little sphincter muscles that will control blood flow into the capillary beds. So this is a capillary's way of compensating and being able to have some control over blood flow. And again, it is through these precapillary sphincters that the blood moving into the capillary beds is controlled. So looking at our diagram here, tracing our loops again, we have the heart and this here, remember, oops, is an artery because it is going where the blood is going away from the heart. And this is a vein because it is going to the heart. These are arteries, and they are going to branch, as you can see here, and turn into arterioles, or be considered arterioles. And when they get to the tissue they are going to become super branched and diffuse and form a capillary bed. Sounds comfortable, doesn't it? Capillary bed. I could take a nap there. Now capillary beds, the capillaries in a capillary bed are going to converge and form venules, and those will converge and form veins, and those veins will lead back to the heart. So that is the basic rundown of the vasculature. With that, let's flip the page.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
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- Mendel's Experiments26m
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- Punnett Square Probability26m
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- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
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- 27. Protists1h 12m
- 28. Plants1h 22m
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- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
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- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
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- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
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40. Circulatory System
Circulatory and Respiratory Anatomy
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