Hey guys, here that a bit of an article in histology. And this time, we’re going to be going over something that a lot of folks have a hard time wrapping their head around, and that is the epiphyseal growth plate.
So we look at this picture of a long bone.
You can see that we’re zoomed in on that thin band of hyaline cartilage there in the epiphysis of the bones.
Why it’s called an epiphyseal growth plate, and the growth plate is divided? Into five distinct layers.
There’s a zone of Reserve cartilage immediately beneath that, a zone of proliferation, meaning that’s the area where we’re going to make new cartilage tissue, the site of hypertrophy where the cartilage cells themselves, the chondrocytes, are going to enlarge and then die off the area of calcification where the holes left by the dead cartilage cells are going to be infiltrated by osteoblasts which are going to start to calcify the cartilage tissue and then finally deepest down the zone of ossification where they calcified cartilage is a Modeled into the lamellar bone in the area of ossification. So how these zones relate to the direction of bone growth isn’t a lot of people tend to struggle with, so I’ve put together just a little animation that will hopefully make this make just a bit more sense.
Let’s look at just the growth plate all by itself. The zone of proliferation is called the zone of accumulation for a reason. It’s going to be making new tissue. So As Kandra Genesis begins and the zone of expansion, new cartilage tissue will be made.
Hey, Sana proliferation got to increase right now. What’s going to happen next is deep down in the zone of accumulation lower.
Those are the cells that are the oldest.Those increased the most prolonged time ago, and they’re eventually going to begin to undergo hypertrophy.
So the cells are going to experience a morphological change. They’re going to get bigger. They’re going to continue to grow meanwhile underneath these cells down here that were hypertrophied. They’re going to begin to undergo calcification. These recently hypertrophied cells start to calcify and notice that the zone of proliferation is still pushing up. These cells in the zone of accumulation have now differentiated, which has become the zone of hypertrophy.
So the bottom part of the zone of expansion is currently not part of the area of accumulation.
It’s part of the zone of hypertrophy.
Likewise, the zone of hypertrophy has become the zone of calcification and then finally down here. The zone of calcification is going to be remodeled into new bone.
So the calcified cartilage is remodeled into bone.
And now, what was the zone of calcification is the zone of ossification.
So essentially, as the zone of proliferation grows, the Left Behind cells from the previous iteration of growth accumulation become the zone of hypertrophy.
The cells that were zone of hypertrophy become a zone of calcification, and the cells in the area of calcification become ossification.
Let’s kind of wrap this up with a side-by-side.
So here’s our original cartoon of the epiphyseal growth plate.
And here’s the cartoon we ended up with at the end so you can see that it has gotten longer, but it has gained longer by extending up. Upward right toward the zone of proliferation so we can kind of think of the epiphyseal growth plate as like a snail, and as a snail crawls along, it’s going to leave a trail of bone behind it, so that the bones are going to going to pardon me.
The zones are going to once more.The bone is going to grow toward the epiphyses.Meaning the bones are going to rise from the edges outward a lot of people. I think that the bone is growing inward, but that is not the case as cartilage is being produced at the top of the proliferation zone.
Everything beneath. It is being turned into more bone. More cartilage is made at the top everything beneath it becomes bone.
So I hope that helped make some sense of how those layers in the epiphyseal growth plate contribute to bone growth and why the bonus is growing in the direction it’s growing.