In this example, we want to label this image, and this image is quite clearly a cross-section of bone at the microscopic level. So let's go ahead and get labeling. First off, we want to circle one osteon. Remember, the osteon is the functional unit of bone. And when I look at an osteon or when I look at a cross-section of bone, what I see often are these sorts of, like, all these different tree trunks that are kind of packed together.

Each individual tree trunk in a cross-section is going to be the osteon. So in this image, we see two of them. We can see one here that I just circled, and this is the only circled one, but I'll just point out the other one here is the other one that we can see at least most of. Alright. So I've circled my one osteon.

Now we want to draw arrows pointing to at least 3 lacunae. Now remember, the lacunae are where the osteocytes, the mature bone cells, live. The bone matrix is this solid matrix, so you need this little chamber in which the cells can live. And in a cross-section like this, it looks like these sorts of flattened black dots. There are probably 100 of them in this picture.

I only need to label 3. Well, there's 1. There's 1. There's 1. It says at least 3. Here's another one. Right? We could do that all day. Okay. Next up, we're going to label 2 lamellae.

The lamellae, if we think of this osteon as a tree trunk, are the different rings of the tree. And you can see that these lacunae are in those rings. So I just need to put a dotted line on 2 of them. That's kind of about where one is. Hard to hit it exactly, but you get the idea.

Okay. And that leaves us with drawing a star on the central canal. The central canal is the middle of the osteon. It's in the center, and it's the canal that holds the blood vessels and nerves. We can see it as this black circle right there.

Labeling a picture like this is something that, in my experience, does come up on tests relatively often, so you probably want to be able to do it. With that, see you in the next video.