The Skeletal System (Part 2.1): Endochondral Ossification

This video series covers part 2 of the skeletal system. It discusses endochondral and intramembranous ossification and the calcification of bone. It covers bone growth (both lengthening and appositional growth) and bone maintenance. Finally, it discusses calcium homeostasis (including the hormones involved) and the effects of aging on the bone.

[@teachmeaandp335]

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[@anastaciamahoff1869]

do you have part one of this lecture series?

[@teachmeaandp335]

Hello... Unfortunately there were some glitches last semester when I recorded the A and P 1 lectures so some of them are missing. I can email you the powerpoint presentation if you would like. It has a typed script on each slide. [e-mail]

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Do you have lecture part one .thanks

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She is incredibly awesome with her talent of teaching. I said talent because so many people will know the material but they can’t impact on others learning the materials. Thank you for making out time to share your talent I don’t mind getting the part1 PowerPoint thanks

[@almakhald9538]

At what embryonic stage does step 4 occur?

[@teachmeaandp335]

It isn't happening only at one stage. In fact, it's not only in the embryo. When it's happening depends on which bone and what part of that bone we are looking at. The process starts at week 6-7, but it continues as the bones grow and continue to develop. Some bones aren't fully ossified until early adulthood. That means all of the steps are continuing in an outward fashion throughout childhood.

[@almakhald9538]

@@teachmeaandp335
I mean at what week of fetal life does it reach the fourth figure

[@teachmeaandp335]

Different bones ossify at different times, but in general most of the bones have started becoming hard, calcified bones by 11 weeks. This development continues rapidly because by around 20 weeks the fetus has functioning bone marrow (which is in the bones).
So... There's a primary ossification center and cartilage begins to turn to bone starting at 6-7 weeks (keep in mind the embryo is the size of a sesame seed and the we aren't talking about the final human shape yet). By 11 weeks the process has continued to where most bones have been ossified a good amount and the form is more humanoid. By 20 weeks, bones are pretty much in the form that they will be at birth, just smaller. They continue to grow at the epiphyses as the fetus grows.
Again, there are some bones that develop later than others. The small bones of the hand for example develope secondary ossification centers later.