Osteogenesis (Bone Formation): Endochondral Ossification (Nursing)

by Jasmine Clark

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    00:00 In the second kind of ossification, we have endorchondral ossification.

    00:05 This is different from intramembranous ossification.

    00:09 In that we are going to go through a cartilage intermediate, instead of going straight from our mesenchymal cells to bone cells.

    00:19 In the first step of endochondral ossification, we're going to develop a cartilage model.

    00:26 This happens when the mesenchymal cells develop into chondroblasts instead of osteoblasts like they did in intramembranous ossification.

    00:36 These chondroblasts will form a cartilage model, which will look like the bones of the body.

    00:45 In the second step, what happens are these chondroblasts are going to secrete extracellular matrix.

    00:53 This extracellular matrix is going to surround the chondroblasts.

    00:58 After this happens and they become completely surrounded or in caged by the extracellular matrix, they are going to mature into chondrocytes.

    01:08 As well, the extracellular matrix begins to calcify or harden a little bit.

    01:17 After this, a nutrient artery is going to penetrate the middle or the center of what will soon be the diaphysis.

    01:26 This is called the development of a primary ossification center.

    01:32 At this point, we are now going to start modeling or creating the shape of the actual bone.

    01:38 And we're going to replace the cartilage with bone tissue.

    01:43 We do this by replacing the chondrocytes with osteoblasts and eventually osteocytes.

    01:52 This occurs from the outside toward the inside of the bone.

    01:58 The type of bone that we are creating in this step is spongy bone.

    02:06 In the next step, we start to develop our medullary cavity.

    02:12 So as we are building bones from the outside in osteoclasts or those immune cells that are able to break down bone begin to break down the bone from the inside.

    02:24 So now we are starting to hollow out the diaphysis of the bone.

    02:32 And the next step, we are also going to be doing the same thing that we did in the diaphysis in the epiphysis.

    02:40 In this step we are going to create a secondary ossification center at both ends of the bone.

    02:47 Just like with the primary ossification center, this is triggered by the introduction of an artery into the epiphysis of the bone.

    02:58 This artery is referred to as the epiphyseal artery.

    03:04 Finally, we are going to create the bone in the epiphysis.

    03:10 The bone is going to replace the chondrocytes that were formed during the secondary ossification.

    03:17 This kind of bone is going to be spongy bone.

    03:21 Unlike in primary ossification, where we created a medullary cavity, we do not create a medullary cavity in the epiphysis.

    03:30 So the spongy bone will be throughout the epiphysis and will not be hollow.

    03:36 At the ends of the bone, we also have the articular cartilage.

    03:42 These are the remnants of the cartilage model.

    03:46 The type of cartilage found here is hyaline cartilage just like the cartilage that we began with.

    03:53 As well on the other side on the side closest to the diaphysis.

    03:57 We also create an epiphyseal plate.

    04:01 It is at this point that we allow for interstitial growth or the lengthening of the bone.

    About the Lecture

    The lecture Osteogenesis (Bone Formation): Endochondral Ossification (Nursing) by Jasmine Clark is from the course Musculoskeletal System – Physiology (Nursing).

    Included Quiz Questions

    1. Chondroblasts
    2. Osteoblasts
    3. Osteoclasts
    4. Osteoprogenitor cells
    1. Endochondral ossification involves the development of a cartilage intermediate.
    2. In endochondral ossification, mesenchymal cells develop straight into bone cells.
    3. Endochondral ossification is associated with the formation of flat bones.
    4. Endochondral ossification does not involve the development of an ossification center.
    5. Endochondral ossification is associated with the formation of long bones.

    Author of lecture Osteogenesis (Bone Formation): Endochondral Ossification (Nursing)

     Jasmine Clark

    Jasmine Clark

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