Microscopic Anatomy of Bones - Trabeculae - Video Tutorials & Practice Problems
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concept
Trabeculae
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Video transcript
To finish talking about the microscopic anatomy of bone, we're gonna talk about the trabeculae, and trabeculae are something that's found in spongy bone. So we just wanna start by saying, remember, spongy bone is named for its sponge, real original. Right? Sponge like appearance with many open spaces. It has many open spaces like a sponge. It is not soft like a sponge. Alright. The in a spongy bone, the parts that isn't open space, those are the trabeculae, and these are what we said before. They're sort of these small rods or struts in the spongy bone. So before we go on, we wanna look at our diagram here, and we have a diagram of the edge of a bone, and we can see the compact bone on the edge. And on the inside, we see this spongy bone with all these trabeculae connecting. Each one's pretty short and small, but they're connecting in all these different directions, giving bone its strength because they're all going in different ways. And when you look at it kind of close-up, it looks kind of chaotic and random. It's not totally. We'll talk about that in a second. But we're also now just gonna pull out one trabecula and talk about its structure. You'll see here it contains lamellae. Right? There's these layers these layers of the bone matrix. It has osteocytes, and those osteocytes are living in the lacunae. The spaces inside the bone are arranged along the lamellae. It has canaliculi, the tiniest spaces through the bone that those osteocytes reach out through so that they can exchange materials. But what you'll notice is missing is that there is no well organized osteon, and there's no central canal. So a lot of these times, these lamellae, again, they're not in rings. They're just sort of lined up in in a line. Sometimes in bigger ones, they're in a ring. Sometimes in the biggest ones, there might be a blood vessel going through them, but it's not like compact bone where you have these regular osteons with a central canal and everyone's sort of built the same. These are all gonna be different, and usually, there's there's no blood vessel in the middle. They can get away with that because they're so small, and all of these osteocytes are relatively close to the edge of the trabecula. So as long as there's blood supply going through the spongy bone, and here you can see all these blood vessels wrapping through the spongy bone, The blood the bone cells in the lacunae can get the nutrients they need. They can get rid of waste, etcetera. Alright. Now I said when you look at this, it may look kinda chaotic and random, but when you zoom out and you look at a cross section of bone, you'll notice that the trabeculae actually have sort of a pattern to them. They tend to align to the lines of stress in a bone, so I'm gonna write that down, align with the lines of stress. So what I mean by that, if you look at a cross section of bone and you imagine the way that, like, weight would be passing through the bone, the trabeculae are usually, at least a lot of them, aligned in a way that they're gonna take that weight head on right through the strut in the strongest way that the trabecula is built. And then there's gonna be cross pieces that are holding everything together. Now that's a lot like scaffolding, and we liken spongy bone to scaffolding earlier on. Scaffolding has all these cross pieces, but it definitely has those bars that are running straight up and down because that's the way the weight is gonna be applied to the scaffolding. The same thing is gonna happen with these trabeculae. Alright. Before we go on, I just wanna know, we've been calling this spongy bone, and you're probably fine calling it spongy bone in your course, but you'll probably see it with some other names too. You might see it called trabecular bone, and that's obviously just named after the trabeculae, or sometimes you'll see it called cancellous bone. Trabeculae just comes from the Greek meaning a beam or a timbers, so we're talking about the rods or struts in that case, while cancellous comes from I'm sorry, from the Latin meaning lattice. Lattice or latticework being like a, you know, crosswise structure with spaces in between. Alright. With that, we have finished the microscopic anatomy of bones. We just want to say good work, everybody, and I'll see you in the next video.
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example
Microscopic Anatomy of Bones - Trabeculae Example 1
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3m
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Video transcript
Our example wants us to identify which structures and cells are associated with compact bone and which are associated with spongy bone, And we have a table here. We have a list on the left hand column of vocab, not all the vocab we've learned, but fair amount. We have a column for compact bone and a column for spongy bone. I'm gonna go through. I'm just gonna give a check if it's in that type of bone, and I'll leave it blank if it isn't. Now we also over here, we have these diagrams that we've been seen before. We have a diagram showing our structure of compact bone on the top, and we have a diagram showing the structure of spongy bone on the bottom, just to remind us. Alright. So first up, we have the osteoblast. So do you find osteoblast in compact bone or spongy bone? Well, osteoblasts are those bone building cells, and they build the matrix for any bone. So they are gonna be in both compact bone, I'll give the green check there, as well as spongy bone. Alright. Next up, we have the perforating canals. Where do you find them? Well, if we look over at our diagram here of the compact bone, remember, the perforating canals run perpendicular to the central canals. They're connecting the central canals with the blood supply and and supplying them with nerves as well. So that's gonna be in the compact bone, because that's where you find the central canals. The spongy bone has all spaces through it. You don't need canals for blood vessels to go through. There's just space in the spongy bone where the blood vessels can be. Next, we have the endosteum. Alright. Think endosteum in compact bone or spongy bone. Alright. Endosteum, remember, is that very thin layer of osteoprogenitor cells that's on the inside of the bone. Well, it is definitely in spongy bone. So I'm gonna give a check there because every single trabecula, all those trabeculae, are wrapped with that endostium. Now in compact bone, it's gonna just be along the very edge of the compact bone. It will be in the medullary cavity there along the edge. So I am gonna give it a check for compact bone, but I just do wanna stress, maybe I'll put the the check and spongy bone in a circle just because it's definitely more associated with the spongy bone, but it is associated with the inside of that compact bone as well. Alright. Next, we have osteons. Alright. The osteon, the compact bone or spongy bone. Well, we said that the osteon is the functional unit of compact bone. So I'm definitely given the check there. And we said it's like you see the different tree trunks when you look at cross section of compact bone. You see all these different circles on the compact bone. We said in spongy bone, there is no osteon. So we're gonna leave that one blank. Alright. Next, we have the trabeculae. So trabeculae, compact or spongy bone? I remember trabeculae are the struts in spongy bone, so we'll find it in spongy bone. Compact bone doesn't have any struts. It's all solid, so we're gonna leave that one blank. Next, we have the osteocytes. So osteocytes, compact or spongy bone. Well, remember, osteocytes are the mature bone cells, and they are living inside the matrix. They're living inside the matrix of the compact bone and in the trabeculae in the spongy bone. So I'm going to give a green check to both of them. And then finally, we have the canaliculi. Canaliculi, do you find it in the compact bone or spongy bone? Remember, those are the smallest little spaces in the bone that those osteocytes can connect with each other. So because the osteocytes living in their lacunae are in both types of bone, you need the canaliculi in both types of bone as well. Alright. With that, we have practice problems to follow. Give them a try.
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Problem
Problem
Which structure allow osteocytes receive nutrients in spongy bone?
A
Central Canals.
B
Perforating Canals.
C
Canaliculi.
D
Extra Cellular Matrix.
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