This example tells me that calcium homeostasis is important for muscle contraction and nerve functioning. Bone cells help maintain blood calcium levels between 8.6 and 10.3 milligrams per deciliter. If the blood calcium level drops to 8 milligrams per deciliter, which type of bone cell would become more active and which type of bone cell would become less active? Alright. Then it shows me a picture of 4 different bone cells, so I just want to identify these real quickly.
First up, we have this sort of flattened bone cell. Those flattened bone cells are the bone stem cells. We call those osteoprogenitor cells. Next, we have this sort of cube-shaped one here, an osteoprogenitor cell that bone stem cell may go on to become an osteoblast. And remember that B, B stands for build.
Osteoblasts build new bone. Some osteoblasts, once they've built new bone, will go on to become this spidery shaped bone cell here. This is a mature bone cell. The mature bone cells are osteocytes. And then finally, we have this giant bone cell down here.
In reality, it would be much bigger than these other ones, it has this real ruffled border and multiple nuclei. This is going to be the osteoclast. And remember, clast, C is for cut. Osteoclasts cut into the bone and they remove bone when that's necessary. So in this case, our blood calcium levels have dropped, and we need to raise blood calcium levels.
To do that, we need to remove some bone. To remove bone, what type of bone cell do you want to use? An osteoclast. Osteoclasts with that ruffle border are going to release acids and enzymes that are going to break down the bone. They're going to take that calcium.
It's going to go into the blood and raise that blood calcium level. So what's going to become more active? The osteoclast. Now, what's going to become less active? Well, if you're trying to take calcium out of the bone, you don't want to be building new bone.
Blast B stands for build, osteoblasts will become less active. Alright. With that, remember that bone is not just there for structure, but also for calcium homeostasis, and I'll see you in the next video.