Microscopic Anatomy of Bones - Bone Matrix - Video Tutorials & Practice Problems
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Bone Matrix
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Bone is a connective tissue, but it's unique among connective tissues and that it's not only very strong but it's also hard. What gives bone those properties, hardness and strength is the bone matrix. So we're gonna talk about the bone matrix in more detail. Here, we're gonna start off just by saying, the extracellular matrix of bone has two basic components. And those two basic components are gonna contribute separately to that strength and the hardness. We're gonna start out by talking about the inorganic matrix. The inorganic matrix is going to be made of mineral crystals and the mineral we're really talking about here is hydroxy appetite. Hydroxy appetite is a crystal that's made of calcium, which I'm just gonna write as C A plus two and phosphate. And you probably know to have strong bones, you're supposed to eat a lot of calcium. Well, that's where that calcium is going. It's going into this hydroxy appetite crystal and you need a lot of it because that ca uh that hydroxy appetite, those inorganic crystals are going to make up two thirds of your bone mass. Now, crystal is pretty heavy, but that's still a lot of bone that, that calcium and phosphate is making up what that hydroxy appetite crystal is doing. It's making your bones hard. Now, when you think about hardness though, I want you to think about something like plaster, something that's hard but fragile or maybe think of something like a dinner plate. Right. Your dinner plates really hard. But if you're to drop it on the floor, it's just gonna smash. You don't want your bones to do that. So to keep your bones from smashing like that, you want organic matrix in there or what we call the osteoid, the osteoid is going to be mostly collagen fibers and also some ground substance. So that ground substance, uh it's just a couple proteins that aren't gonna, we, we don't really need to worry those about those nearly as much as we need to worry about the collagen. Remember collagen is this protein fiber that's really strong, but it's flexible like a rope. Now, there's a lot of collagen fiber in that organic matrix in there. It's the remaining one third of your bone mass and this is what's going to make bones strong. So when I say strong here, I want you to think of rope or something here, I say think of gauze, gauze. You know, you wanna wrap a wound with gauze, it's really flexible, you can wrap it around your arm, you can ball it up whatever, but go ahead and try and rip gauze. It's really difficult to rip because it's really tough. It has all those fibers woven together and each one is really difficult to break. Now, if you take gauze and you put it inside plaster, you end up with something like a cast and a cast is both rigid and tough. And to show this, we have a picture of a, someone with a broken arm with a cast on it. Now, this cast here is actually probably not uh plaster and gauze. It's probably fiberglass, but that uses the same technology, right? Fiber, there's fiber in fiberglass, same technology in carbon fiber. In the olden days, they used to make walls by putting horse hair, plaster, horse hair in the plaster. So all these technologies take a fiber that's strong but flexible and put it in something that's hard but fragile and you get something really tough out. I don't know if you've ever broken a bone but in college, I broke my arm and I had a cast on. I used to landscape in college. I used that cast a hammer in fence post. It was really tough. It's probably not advisable but it worked. All right. So that idea that we have these two different things that contribute separately to make bones both hard and strong. We're gonna talk about a lot more going forward and I'll see you there.
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example
Microscopic Anatomy of Bones - Bone Matrix Example 1
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2m
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This example tells me that there's two bones, one was treated with an acid while one was treated with bleach based on the properties of each bone. After the treatment, predict what component of bone bleach breaks down and what component of bone is dissolved by acid? All right. Instead of just looking the picture, I went ahead and did this. So let's take a look. All right. I have three bones on the counter here. The first one is a normal bone. The second one is treated with an acid. The third one is bleach. OK. This first bone I'm gonna try and break. It's hard to break. Bones are hard to break. Now, it's a chicken bone. I can do it. But if I try to break it more than this, it'd be really hard without something like pliers or a hammer. All right, let's check this one treated with an acid. All right, pretty hard to break. That bone became really flexible. It's just a floppy bendy bone. So think what did the acid dissolve to make the bone like that? All right. Now, the bleach, the bleach breaks pretty easily. It doesn't just crumble, but I can easily, just keep breaking it up with my fingers. If I push it down into the counter, it just makes all these little bone shards. So, therefore, if it's able to break up easily, it doesn't bend. What did the bleach break down in the protein? Ok. Now that we're thinking about that, let's go back to our paper here. So we have our normal bone and when we treat it with bleach, the bone is brittle and it's shattered easily. So, what do you think it is that the bleach breaks down? Well, I'm gonna say that the bleach breaks down collagen. Remember collagen is that protein that fiber that gives bone its strength, its toughness. Collagen is really flexible, but it's also really hard to break. So when you take it out, you're just left with that hydroxy appetite crystal, those calcium crystals, those are hard, but they're really fragile and the bones just shatter pretty easily. You don't want your bones to do that. All right. So now let's think with the acid with the acid. When you treat it with acid, I just used vinegar to do that. So it's pretty easy to do. Uh After soaking it in vinegar, the bone became very flexible and it bent easily. So therefore, what did the acid dissolve do you think? Well, I'm gonna say that the acid dissolved that hydroxy appetite Crystal. I'm gonna just write that in shorthand. As the calcium plus two, the calcium crystals, remember, calcium is hard. So when you take it out, you're just left with a collagen. Collagen does not break easily, but it's really flexible. And so you're left with this floppy bone again, you don't want your bones to do that. You want both these properties. So you want both those things in your bones. All right. Like always we have practice problems to follow. Give them a try.
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Problem
Problem
At her annual checkup, the doctor tells Pilar that she should add leafy greens like spinach and collard greens to her diet to help keep her bones strong. What vitamin or mineral in the vegetables would contribute to bone strength?
A
Iron
B
Calcium
C
Collagen
D
Vitamin D
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Problem
Problem
If the hydroxyapatites were replaced with more typical gel-like extracellular matrix, how would you expect the bones to be affected?
A
The inorganic matrix would lack the hardness necessary for bones to bear weight.
B
The organic matrix would lack the hardness necessary for bones to bear weight.
C
The inorganic matrix would be unable to provide tensile strength.
D
The organic matrix would be unable to provide tensile strength.
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