Blood Vessels
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With three types of blood vessels that are carrying blood in various forms around the body, the first one we need to consider is the arteries. Now, they have muscular, thick walls, and they can contract much like a muscle would. They push blood around the body and they carry predominantly oxygenated blood, so that's blood that is carrying oxygen. Capillaries branch off from the arteries. They have very thin walls and they're almost one cell thick, so very, very thin walls, and this means that gases and nutrients can diffuse easily through those walls. There are more capillaries in the body than any other blood vessel type.
The other one we need to consider is the veins, represented on this model in blue. The veins carry the deoxygenated blood. The blood isn't blue, but it is a darker colour, a darker, deep red. Veins have smooth muscle inside them and they contract like in a wave motion. They carry blood under low pressure, and so they have a series of one-way valves and gravity to help them get blood back to the heart and then, ultimately, to the lungs. These valves stop blood pooling.
So, we've gone through and I've described to you the different types of blood vessels. If we were to cut an artery, for example, we have a major, major artery in our leg, the femoral artery. If we cut that, the blood is under pressure. It's oxygenated, so it will be bright red. Because it's under pressure from the heart, from the aorta, ultimately, that's pushing that around the body and the muscles in the arteries, a serious cut then, we would get a pumping motion. The blood would spurt out.
A vein, on the other hand, if we cut a vein, as we said previously, it's not under huge pressure. It's under low pressure. The blood, when it comes through, will be a darker colour like a dark, deep red, and rather than spurting out, it would ooze. It's like a steady flow.
Capillaries, again, are different. As I said, there are more, in the way of blood vessel, there are more capillaries in the body than anything else, and capillaries, when they bleed, because they're such small vessels, they bleed like an oozing formation through the skin, quite like when if you fall over, and you graze your knee quite badly to break the skin, and to get the blood oozing through. That is the capillaries that you have damaged. Of these, a capillary is quite easy to deal with. We can clean it up and put a plaster on. A vein might need a little bit more pressure for a little bit, but should be able to be bandaged quite quickly. An artery is a lot more serious and we need to apply pressure. We need to raise that limb if at all possible, to try and get the blood moving back towards the heart.
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