Bone Development: Intramembranous vs. Endochondral Ossification

0:00we're covering bone development or

0:02oics as we learn how we get to

0:05understand our Matrix of bone and we

0:08develop bone there's two types of oifc

0:11which is a bone development intress and

0:14endochondral we're just going to

0:16describe the difference between the two

0:18and then we'll have more videos talking

0:20about them independently but when bone

0:23forms that's called

0:25osteogenesis which is bone formation and

0:28then once it forms it can start to grow

0:30we grow bones in two ways in width which

0:33is a positional growth and then in

0:36length which is interstital growth but

0:38we can't grow until we have the

0:40materials to develop it so it can grow

0:43to me bone development is this process

0:45of OIC we bring in the right materials

0:48which means the right cells to then

0:50create the right Matrix to give us what

0:52we need to develop bone cuz remember

0:54bone is only sometimes 2 to 3% of cells

0:58it's what they develop in make to form

1:00the bone that creates the actual product

1:02that you see as a bone so two types of

1:05oifc intress and endochondral embrus is

1:10referring to within a membrane and we

1:12refer this for dermal bones we say

1:15dermal like closer to the skin so it's

1:17bones that I can when I think about Inus

1:20it's what I can feel so I can feel my

1:22mandible I can feel my frontal bone my

1:24parial bone those are bones that I can

1:26actually touch and feel my clavicle the

1:29right at the SK skin dermal bones and we

1:31call intramembranous alific within

1:34membranes and we'll talk about those

1:36membranes but it's referring to these

1:38types of dermal bones more of a simple

1:40process of bone development versus

1:43endochondral is within cartilage and

1:46specifically it's high and cartilage

1:48that we use it as a model and what

1:50happens is when we talk about ocation

1:53the actual definition is taking one

1:55tissue and replacing it with another in

1:58intrus we take mezen chyal tissue and

2:02turn it into bone and we use the cells

2:04to make bone osteoblast and then our

2:07osteocytes to maintain it when we look

2:09at endochondral we're taking first

2:12mesenchimal tissue and then turn it into

2:14highin cartilage to create a building

2:17block to then turn that into bone and

2:19this can take years in many cases

2:22depending on the bone some words up to

2:2425 years for endochondral usually

2:27referring to long bones so as we look at

2:30this let's just talk about what we talk

2:31about

2:32intress this the picture here is

2:35matching the microscope slide down here

2:37but we're basically saying is I have a

2:39top sheet of mezen kimal tissue and then

2:42a bottom sheet so it's in between two

2:44sheets of tissue remember mesenchimal

2:47tissue is our stem cells or embryonic

2:50tissue for which all connected tissue

2:53arises so mesal tissue is that basic

2:56tissue that then it differentiates and

2:58turns to other types of cells to give me

3:01the final product in this case we're

3:03talking about bone so we'll see two

3:06sheets one here and one here of mezen

3:09chimal tissue that'll gradually migrate

3:12and change with the blood supply to give

3:14me the actual structure of bone how do

3:18we do that well the mesenchimal cells

3:20turn into osto blasts some books will

3:22say well you also see ostero progenitor

3:25cells which we'll talk about that in the

3:26next video but it turns it into bone

3:29because the cells change and because the

3:31cells change their function changes and

3:34what are they doing they're secreting

3:36The Matrix which is that osteoid to

3:38where you're getting the

3:39calcification calcification is creating

3:42the mineralization of the bone

3:44specifically using calcium calcium

3:46phosphate calcium carbonate so I look

3:49down below here this dark purple is

3:51trying to show you the formation of bone

3:53and you could start to see that it's

3:54looking more like spongy bone so we're

3:57turning this into spongy bone and then

3:59on the top I have a membrane sheet of

4:03tissue that mesical tissue and then also

4:05here on the bottom so in between two

4:08membrane sheets I'm creating this type

4:10of bone and it occurs in dermal bones

4:13versus when we look at endochondral this

4:16is showing you a long bone so a lot of

4:18our long bones go through this process

4:20to where they're using now highy and

4:22cartilage to where we occur at the

4:25epipal plate so this section here at the

4:29epip is and then the diaphysis there's a

4:32section in between that region called

4:34the

4:35metaphysis and this is where I have

4:37Highland cartilage this is matching on

4:40this side to where there's different

4:41zones on how it develops but basically

4:44you're going to have hypertrophy or

4:46dying off of cartilage cells and where

4:48did those cells come from we start with

4:50mezen kyl then it turns into Highland

4:53cartilage so we're using condr blast and

4:55condra sites to use this as stacking

4:58cell so they call it AIP AAL plate

5:01because it's literally like we're

5:02stacking plates of cartilage that will

5:04then be replaced by bone we're taking

5:06one tissue turning into another that's

5:08an

5:09OIC so once we're done growing depending

5:13on the bone like I said this could take

5:15years it turns into a pipal line so a

5:18pipal plate and line is at the point in

5:20development a plate is when it's growing

5:22a line is when it's F finally done so

5:25for example some bones take couple

5:27decades for them to actually finish

5:28their product so what we see is a

5:31difference here is that Highland

5:34cartilage model that we're using and

5:36then it starts to turn into bone so when

5:37I look at the dark purple over here for

5:39spongy bone that's forming these dark

5:42little purple sections here so it's very

5:44baby spongy bone that we're looking at

5:46so intramembranous and endoc condal

5:49oics is understanding how do we get to

5:51the final product of bone we use our

5:53cells to create the Matrix but we can't

5:56do that without a foundation we both

5:58start with mezan kimal tissue and then

6:00it just depends on where we're at which

6:02bone are we just using mezen kyal turn

6:05that into osteoblast osteocytes or we

6:07using highin cartilage as a model this

6:09is intramembranous and endoc condro

6:11alific in the next couple videos we'll

6:14break down the two and just go to the

6:15order the steps of the cells and how

6:17they differentiate