So far, we've talked about the different components of the bone matrix, and we talked about the different bone cells, but now we want to put it all together and think, how is bone really structured at the microscopic level? We're going to start doing that by talking about the osteon. The osteon, well, it's sometimes called the Haversian system, but you're more likely to know it as the osteon. You might see the Haversian system, so you should be familiar with that word at least. This is going to be the structural unit of compact bone, and compact bone has a very regular structure to it.
And we can look at that here. So we're going to look over here at our diagram to start. You're very likely to see a diagram at least very similar to this. And here we see a section of bone, and on the inside, we see some spongy bone, But we're looking at the compact bone here, and what you can see where it's cut in cross-section, you can see all these circles that are sort of packed in tight to each other. Each one of those circles is an osteon.
And the way I think of it when you look at an osteon, it's almost like you're looking at a cross-section of a tree trunk. Right? You see the rings of the tree trunk in a circle, and to make compact bone, you take all these tree trunks and you just sort of push them up tightly together. So you can also see it here in this zoomed-in section. We see one osteon, with those different rings around the center.
So now let's identify those specific parts of the osteon. First up, we have the central canal. The central canal contains the blood vessels and nerves, and we can see that labeled in a diagram here. And we can see these blood vessels and nerves running through the central canal through the center of the osteon. Remember, bone is living dynamic tissue, so it needs a blood supply.
This is how the blood gets to the bone. Now we also said that these central canals are surrounded by these rings. These rings are going to be the lamellae or singularly one lamella. And so these are going to be the concentric rings of matrix, and you can see that a little bit more clearly in another diagram here. We've pulled out the concentric lamellae there to see the different rings surrounding the central canal.
Now, finally, we talked about this a little bit in a previous video. We have the lacunae or the singular lacuna. These are the chambers that contain the osteocytes. Remember, the osteocytes are the mature bone cells that live in the bone. And so you can see these lacunae mostly clearly in another diagram here where we've zoomed in. They run along the lamellae. Sort of in these rings, you see these darker spots where the bone cells live. Those are the chambers that are holding the osteocytes. But remember, this is living dynamic bone.
We need to get a blood supply into it, and we need to get nutrients to the cells. So we have all these little canals and canaliculi that are running through this bone to do that. So we're going to go through each one of those now. Well, first off, we have the central canals, and we already talked about that. We said that's are running through the center of the osteon, but importantly, they are running parallel to the length of the bone, at least through the diaphysis, the shaft of the long bone, And in the around the spongy bone, around the ends of bones or other bones, they're at least running parallel to each other. These are going to supply blood and house those nerve fibers, and they're going to be relatively large. Now they're still microscopic, but they're big enough to hold blood vessels. Now the next one we want to talk about though is the perforating canals, and the perforating canals you can see in another diagram here. And the way I think of the perforating canals, the perforating canals run perpendicular perforating perpendicular to the central canals, and they are there to connect the central canals to other blood vessels and nerves.
Right? If you have central canals that are all running in parallel, they can't run in parallel forever. They need to connect to each other. These perforating canals connect the different central canals to each other, and they also, as you can see here, connect them to the spongy bone or to the medullary cavity where the blood supply for the bone is. These are also going to be relatively large.
Well, because, again, microscopic, but they're big enough to hold those blood vessels. Now, finally, we have these smallest little spaces in the bone. These are going to be the canaliculi, and the canaliculi are labeled in another diagram here, and they're kind of hard to see because they are so small. These are connecting all the different lacunae, and I'm sort of just drawing them in here so that you can see them in a little bit more detail. They are connecting the different lacunae to each other and also to the central canal.
Because lacunae, remember, these are chambers that the osteocytes live in, but those osteocytes need nutrients. And so the canaliculi are the way that nutrients and waste and messages can diffuse through that bone. So these are therefore going to run in all directions, connecting those different lacunae with each other, and they're there for communication and transport between osteocytes. And these are going to be very small. Alright?
They just hold these little extensions from the cells reaching out and connecting with each other. Okay. A picture like this or an actual microscopic image of this is something you are very likely to see, very likely to need to label or at least identify labels on. So we're going to practice that more coming up, and I'll see you there.
