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BONE – PART 6 | BONE REMODELING | Regulation of Blood calcium by Parathormone & Calcitriol

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At cnbc a one step solution for all medical studies now friends let’s talk about the bone remodeling so it is a process in which old or injured bone tissue is replaced by a new or healthy bone tissue as this is a bone and this is the cross section of the bone taken like this and let’s suppose this part of the bone is either old or damaged so this part of the bone

Needs to be replaced by new or healthy bone tissue now friends i’m showing the enlarged view of this part here for better understanding as you all know born either it is old or new has cross-linked osteocytes so these are osteocytes and these blue lines are halogen fibers and in-between collagen fibers these are what these are crystals of hydroxyl apatite okay

It means friends these hydroxyl apatite collagen fibers and osteocytes are now become old that is why they needs to be replaced by new bone tissue as you all know all the things are very weak that is why if they will represent in the body for longer duration then they may cause fracture of the bone fracture of the bone so friends to prevent this fracture the

Old bone tissue must be replaced by this new bone tissue now friends let’s see how this whole process of remodeling takes place in the bone as you all know friends the osteocytes play a very important role of monitoring okay so these osteocytes since that the bone tissue which is surrounding these osteocytes has become older has become old that is why it needs

To be replaced by new bone tissue okay so for it these osteocytes give signals to the osteo progenitor cells these are osteoprogenitor cells which are present in the periosteal inner layer of the periosteum and endosteal layer to produce more and more osteoblast cells and these are what osteoblast cells and now the functions of these osteoblasts sailes starts

And the osteoblast sales secretes roots proteins so roots are the proteins so from this are it is rank ligand protein and for this rank ligand we use rank l as short form from oh it is osteo protein protein and for this opg is used and from this oh t and s these are osteopontin clo protein and the thrombo spawned in proteins now friends we will see what are the

Functions of all these proteins now as you all know this giant multinucleated sale having ruffled border is with cells this is osteoclasts l and this osteoclast sale is formed from approximately two to 50 monocytes and macrophages but my dear friends this fusion is not spontaneous this fusion depends on a protein and that protein is called rank ligand so for the

Attachment of these monocytes with these rank ligand these monocytes must have a receptor for these rank ligand and that receptor is called rank so these monocytes without a rank ligand are called undifferentiated or inactive monocyte but after attachment of this rank ligand to this receptor there are some changes occurs in these monocytes and these monocytes are

Now differentiated or they are active monocyte and friends only and only these differentiated or active monocytes are now able to fuse with each other to form a giant cell that is called osteoclasts ale so these are newly formed osteoclasts ale and these cells reaches at a place where bone degradation is needed as bone degradation is a long process that is why

These osteoclast cells must be firmly attached with the surfaces of the old bone and this function of firmly attachment is done by these proteins osteo contains yellow protein and thrombus bonding which formerly at is osteoclast with the extracellular tricks and after formally attachment these osteoclast sales start to secret bone degrading substances or agents

Through these a ruffled border okay and the breakdown agents like protons which creates acidic environment which catalyzes the inorganic salts of calcium and phosphorus and collagen eases polygenesis plus cathepsin k cause a breakdown of organic matrix like collagen fibers so these are pieces of old bone having organic and inorganic material and these break down

Pieces are reused by the body so for it these break down pieces are taken up by the osteoclast sales through their ruffled border by the process of endocytosis and by the process of exocytosis through these cells or face opposite to this ruffled border is sent into the blood and these collagen proteins calcium phosphorus and many more nutrients substances are again

Reused by the body as this part of the bone has broken completely now it’s the time to break this part and 4/8 these osteoclast sales moves forward and for newborn synthesis at this place now askew blast sales osteoblast sales will come at this place and for the synthesis of new bone at this place these osteoblast cells are now ready and this is the newly formed

Bone and similar to this the remaining part of the old bone is first degraded then new bone is synthesized edie degraded places now again what is bone remodeling from rhe in this remodeling it is a resorption of bone and from modeling it is bone formation so here is bone formation so remodeling is actually a combination of bone resorption and bone formation and

If there is only bone formation without bone resorption then it is called only modelling so up till now in the process of bone remodeling we have seen the functions of ds rank ligand and these proteins and now we will discuss the importance of these osteo protege in protein so with the help of these osteoclasts ales this old part of the bone has degraded and in

Place of it new bone is synthesized now to prevent the further activity of these osteoclasts cells as if their activity will not be stopped at right now then they may cause degradation of normal tissue also so to prevent the further activity of ds osteoclast cells a protein that is called osteo protege rain is needed as these osteo protege in proteins binds with

These rank ligand and prevent the attachment of rank ligand with this rank which is present on the undifferentiated or inactive monocytes and because of this these undifferentiated or inactive monocytes will now not be able to convert into the differentiated or active monocytes and because of these osteoclast cells will not be produced and these osteo protein also

Decreases the activity of persistent osteoclast cells in this reference because of these osteo protege lean proteins production of osteoclast sales as well as activity of the osteoclast sales is decreased now how will you remember that this osteo protege ring is related to prevention of rank ligand activity it is very simple friends has this p r in the protege ring

Will remind you that it is related to prevention it is related to prevention and prevention of this rain this ring in the osteo protege ring ring means a rank ligand rank ligand so osteo protein prevents activity of rank ligand now let’s talk about the factors which are affecting the bone as in modeling so first one is exercise if somebody is doing heavy exercise

Like running or bed lifting then it may cause a spread or stress on these processes of the osteo site sales and because of this persistent stretch or stress these osteocytes sales give signals to the osteoblast cells and osteoblasts sales start to synthesize new bone and as you all know in the adult that is at around 20 to 25 years of age the bone cannot increase

In the length cannot increase in the length but because of this extra deposition of bone tissue bone increases in the width and this is a bone after increase in thickness and now this thick bone is able to bear heavy exercise so during heavy exercise only bone formation takes place that is only modeling modeling takes place in the bone and opposite of exercise is

Rest if somebody is doing a rest then osteoclast ik activity increases and because of this thickness of bone decreases so this is a bone in a person who is bed resting for a long duration so during his rest condition only resorption activity takes place in the bone and if somebody is taking vitamin a in a high amount then it causes increase in the thickness of the

Bone my friends let’s talk about how parathormone and calcitriol that is also called vitamin d3 regulates calcium level in the blood this is osteoblasts cell and these are receptors for the para thermal and these are receptors for the vitamin t3 when in the blood calcium level falls then either vitamin d3 or parathormone binds to their receptors on the osteoblast

Cells and after binding they give signals to the osteoblast cells to produce more rank ligand proteins and to decrease the synthesis of these osteo protein proteins as you all know these osteo protein proteins prevents the activity of rank ligand that is why these osteo protein proteins are also called decoy decoy agent for the rancor like and and now as you all

Know what this rank ligand will do so here is surface rank ligand protein as these are undifferentiated or inactive monocytes and this is a rank that is a receptor for the rank ligand so this cell surface rank ligand binds with the cell surface rank and activates monocyte and the monocyte is now differentiated or active as in this differentiation first a one cell

Contacts with the other cell so it is cell to cell contact differentiation and now as you all know what these differentiated or active monocytes will do they will form with self osteo class cell and as you know osteo cluster will do what it will cause degradation of bone tissue and in the bone what is present calcium phosphorus and collagen protein and this calcium

From the degraded bone is sent into the bloodstream and in this way level of calcium increases in the blood so this is how calcium is regulated in the blood by these two hormones

Transcribed from video
BONE – PART 6 | BONE REMODELING | Regulation of Blood calcium by Parathormone & Calcitriol By OxyMBBS