Specialized Connective Tissue: Bone - Video Tutorials & Practice Problems
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concept
Intro to Bones
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So now that we've covered cartilages in our previous lesson videos in this video, we're going to begin talking about the second type of specialized connective tissue in our lesson, which is bone. Now, it's important to note that moving forward in our course in separate chapters and separate videos, we're going to talk a lot more details about bones and the skeletal system. And so here in this video, we're only going to do a brief introduction and a brief overview of some of the basics of bone tissue. And so that's important to keep in mind as we move forward. And so when it comes to bone tissue, it's important to note that it's sometimes referred to as Asus tissue. And so it turns out that in the human body, there are about 206 different bones and each individual bone is its own complex living organ that needs to be able to undergo repair and remodeling in order for the bones to serve their functions. Now, we already know that bones or Asus tissues are going to be tissues with a rocklike hardness to them. We know that our bones are very, very hard. Now what's surprising to a lot of students is that bones or Asus tissues are actually very highly vascularized, which means that yes, our bones have lots of blood vessels. And so when they break our bones can bleed. And so the high vascularization of bones or Asus tissue is actually going to allow for relatively quick and complete healing of bone or Asus tissue upon being injured or damaged. Now, the blood vessels actually travel through these areas known as central canals and bone or Asus tissue is actually going to be extremely durable because bones need to support our entire bodies and they need to be able to handle the compression forces that comes with load bearing the weight of pretty much our entire body and all of the other tissues. Now, in terms of the extracellular matrix of bone or Asus tissue, it can actually be broken up into two parts, an organic part and an inorganic part. The organic part is going to include lots of collagen fibers, which we know is going to give this tissue a lot of strength and some flexibility as well. And then the inorganic part is going to include minerals such as calcium phosphate crystals and the calcium phosphate crystals. This inorganic part is really what gives bones its rock hard hardness and or its rocklike hardness and it's also what's going to give bones its rigidity and give the extracellular matrix its rigidity as well. Now, in terms of the cell types really. There are two main cell types that we identify here that are going to be important for bones. And so it's important to note that the root osteo is a root that means bone. And so you can find this root osteo in the two cell types that we identify including osteoblasts and osteocyte. Now, the osteoblasts are going to be blast cells that are going to be immature cells that are more active and actively build and secrete components of the extracellular matrix, including ground substance and protein fibers. And then the osteocyte are going to be site cells that are more mature, less active and are more about maintaining the extracellular matrix through minor repairs and routine maintenance. And so these more mature osteocyte are actually going to be found in chambers called Laconi, just like we saw cartilage chondrocytes are found in chambers called Laconi as well. And so the Laconi are going to be chambers that house those osteocyte. Now, there is another relevant cell type in bones that we'll talk more about later in our course, called the osteoclast. And the osteoclast is going to break down bone in order to release those calcium and phosphate minerals that the body may need. But again, we'll talk about those later in our course. Now, in terms of the functions, bones actually have surprisingly a lot of different functions, including the obvious function of structural support. It gives our bodies its structure and its shape, but it also allows for protection because bones such as our skull, which we know is really hard, can actually protect the delicate organs that lie underneath such as the brain. For example. Now, bones are actually going to be important for storing calcium and other minerals such as phosphates. And they can also store fats as well inside of the bones as we'll talk about more later in our course. And also bones provide a cavity for a process known as hematopoiesis, which is just a fancy name for the process of blood cell formation. And so yes, blood blood cells are actually formed inside of bones. Again, a process that we'll get to talk more details about later in our course. And so notice over here, what we have is an image of a person and you can see the bones that lie underneath of this person in this image and notice that here we have a micrograph showing you some bone or Asus tissue. And you can see that the osteocyte are these darker spots that you can see uh throughout and they are going to lie within those Laconi. And uh you can also see that the central canal is being labeled as well. And again, the central canal is going to have the blood vessels which make the bone or aus tissue highly vascularized. And so this year concludes our brief introduction to bone and Asus tissue. And again, later in our course, we'll be able to talk a lot more details about bones and Asus tissue and skeletal tissues and the skeleton in its entirety. And so this year concludes this video and we'll be able to apply these concepts as we move forward. So I'll see you all in our next video.
2
example
Specialized Connective Tissue: Bone Example 1
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2m
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So here we have an example problem that says osteoporosis is a condition where the bone mass decreases, making bones brittle and susceptible to fracture. Based on the structure of bone tissue is osteoporosis caused by an issue with the osteoblasts or the osteocyte. And why. And so recall from our previous lesson videos that all connective tissues including bone or Asus tissue is going to be similar and that the cells take up much less space than the extracellular matrix. And so if the bone mass is decreasing, really what we're saying is that there's going to be less extracellular matrix. And so what we can say is that with less bone mass, that means that there's going to be less extracellular matrix or less ECM. And recall that osteoblasts are blast cells and blast cells are more active cells that actively secrete and build components of the extracellular matrix. Whereas osteocyte are site cells and they are more so about maintaining the matrix through minor repairs and routine maintenance. And so the osteocyte are not going to be actively building the extracellular matrix. The osteoblasts are and again with less bone mass because that means less extracellular matrix we can assume that this is going to be some kind of issue with the osteoblasts. And so for that reason, we can put an arrow here and indicate that osteoblast will be our answer. Now, in reality, osteoporosis is actually not caused just by one type of cell. It's actually caused by an imbalance in multiple cells functioning improperly. And so, recall that in addition to osteoblasts and osteocyte, we briefly mentioned that there are also osteoclasts and osteoclasts. We'll get to talk more about later in our course, but they're more about breaking down the bone. Whereas osteoblasts are more about building up the bone. And it's important to have a healthy functioning balance between osteoblast and osteoclasts in order for bones to function properly. However, osteoporosis results when there is an improper balance between osteoblast and osteoclast causing the extracellular matrix to become less, leading to less bone mass and making those bones more susceptible to fracture. But the correct answer to this example, problem is going to be osteoblasts, not the osteocyte. So that concludes this example and I'll see you all in our next video.
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Problem
Problem
How does the ECM of bone differ from the ECM of cartilage?
A
ECM of cartilage is flexible: ECM of bone is rigid.
B
ECM of cartilage is rigid: ECM of bone is flexible.
C
Bone and cartilage have the same ECM.
D
The difference between the ECM can't be determined.
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Problem
Problem
Osteonecrosis is a condition where blood flow to bones is cut off resulting in tissue death. Which of the following would you expect to be most directly affected by the loss of blood flow?
A
The inorganic matrix.
B
Collagen fibers.
C
Osteocytes.
D
A-C are correct.
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