Endocrinology - Calcium and Phosphate Regulation

armando has to design biology and medicine videos please make sure to subscribe join the forum and group for the latest videos please visit Facebook Armando has Erdogan in this video we're going to look at endocrinology calcium and phosphate regulation so the hormones essentially involved in regulating calcium and phosphate levels in the blood and there's three important hormones involved these are vitamin d parathyroid hormone and calcitonin so like all endocrine systems we should look at what glands and what tissues are involved so here I'm drawing the brain where we have the hypothalamus and the pituitary gland but surprisingly enough we won't really look at these in this video we will however look at this gland here called the thyroid gland which is situated on our throat this is a dorsal view of the thyroid gland so it's a view from the back and at the back of the thyroid gland we can find our four glands additional glands which are different called the parathyroid glands and we have four of these on the dorsal side of the thyroid gland other important organs and stuff that we will talk about in this video include the bone because this is where calcium and phosphate can be found the minerals and actually most of the calcium is 99% is stored in the bone and we also will talk about the kidneys the gut the GI T the liver as well as the skin so let us first the hormone that will firstly concentrate on is parathyroid hormone but before that we have to see what the significance of calcium and phosphate is in our body so we have to regulate calcium and phosphate levels because for one calcium is important for a muscle contraction nerve conduction and phosphate is important for other biochemical processes as well as you know energy so now let's look at the first hormone which is parathyroid hormone so parathyroid hormone is released when we have a decrease in plasma calcium levels so a decrease in plasma calcium levels will stimulate the parathyroid gland to release hormone called parathyroid hormone parathyroid hormone targets a few things firstly it targets the bone it stimulates the bone to sort of to break down its minerals so that we so calcium and phosphate can enter the plasma therefore it increases calcium and phosphate levels in the plasma the parathyroid hormone also targets the kidneys it targets the enzyme in the kidneys called one alpha hydroxy lays one alpha hydroxy lasers main function is to activate vitamin D so what it does is it converts a chemical to 25 hydroxy vitamin d3 also known as Cal so dial to one to five dihydroxy vitamin d3 well which is calcitriol so calcitriol is the active form of vitamin D calcium then targets a few things firstly it stimulates the bone as well somehow and it to break it down so that we can increase the minerals calcium and phosphate in the blood calcitriol also has a negative feedback on the parathyroid gland so it inhibited because if we have so much calcitriol we don't need that much parathyroid hormone anymore and then council trial also targets the GI T it stimulates the GI T to increase calcium and phosphate absorption kalsa trial also targets the kidneys itself so if we zoom into the functional units of the kidneys these are the nephrons Here I am drawing one nephron the nephron is made up of the head the proximal convoluted tubules PCT loop of Henle LOH distal convoluted tubule DCT and collecting ducts CD so calso trial actually targets the proximal convoluted tubules here to stimulate the reabsorption of calcium thus increasing plasma calcium levels in this dive in the nephron the parathyroid hormone also has an effect but it has an effect on the distal convoluted tubules it stimulates the cells in the distal convoluted tubules to reabsorb calcium as well thereby increasing plasma calcium levels so now I hope that all made sense now let's go back to kalsa dial and calso trial calcitriol being the active form of vitamin d but where do these things come from well actually it it actually the 25 hydroxy vitamin d3 or calcium comes in the liver but the whole process actually originates in the skin in this skin we have a chemical just there a cholesterol they're known as 70 hydroxy cholesterol and when the Sun the sun's UV rays hits this it actually converts 70 hydroxy cholesterol to vitamin d3 cholecalciferol and this all occurs in the skin cholecalciferol then travels to the liver where it gets converted by the liver enzymes to 25 hydroxy vitamin d3 or kalsa dial and then this calcium is what moves into the kidneys and in the kidneys Calzada as we know gets converted by one alpha hydroxylase so I hope that all made sense so essentially when we look back at the three important hormones vitamin D its main goal is to increase plasma calcium levels parathyroid hormone its main goal is to increase calcium plasma levels as well now whereas calcitonin does the opposite it will aim to decrease plasma calcium levels so we can say that if there is for example an increase in plasma calcium levels this will stimulate the thyroid gland and it will stimulate the thyroid gland to produce calcitonin calcitonin essentially has the opposite effect of parathyroid hormone so calcitonin goal is to decrease plasma calcium levels when we have an increase of it but I think calcitonin does not have that big of a role much of a role in the human body as compared it does have a role but not as significant as parathyroid hormone so I hope you understood the main goal the main roles of the three important hormones and calcium and phosphate regulation but it's now it is important to look into a bit more detail at how parathyroid hormone elicits its effects on the bone because the bone as we as I mentioned earlier is the main reservoir for calcium the minerals so the boat are made up of two main cells that we will talk about these are osteoblasts which build bone and these are osteoclasts which break down bone however this osteoclast is not activated yet it's so we call it a pre osteoclast and it is the active osteoclast that will resorb bone so it will break down bone which will allow calcium and phosphate to be released in the blood so here I'm drawing a bone again a simplified diagram and on the outside we have the hard bone also known as a compact bone where we where contain you know where we can find collagen as well as minerals and this is what bone is made up of essentially and then on the inner part we have soft bone but in this case I think it's just just good to know that it's just bone okay so now let's go back to the osteoblasts and because osteoblasts II have the main role in activating these osteoclast even though they have opposite roles so on osteoblasts we have a receptor the parathyroid hormone receptor so when parathyroid hormone comes along it will bind onto this receptor and it will cause and we'll have three effects on the osteoblasts firstly it will cause osteoblasts to proliferate second it will it will stimulate the expression of rank ligand on the osteoblast thirdly the parathyroid hormone will cause osteoblasts to stop making arm osteo protege n' now austria protege also known as OPG normally inhibits basically the activity of rank ligand binding on to another receptor so basically parathyroid hormone inhibits this process so it doesn't want OPG to have a effect now on pre osteoclast the pre osteoclast expresses a receptor called the rank receptor so essentially what happens is the rank ligand being expressed on osteoblasts will bind onto the rank on the pre osteoclast and when this occurs and when it's not inhibited by OPG the rank ligand rank complex will cause the osteoclast to proliferate and differentiate there's another chemical which has a sort of stimulates this whole process as well we're on the osteoclast we have a receptors CF mas and a the chemical that I'm talking about is macrophage colony colony stimulating factor or M CSF and when M CSF binds on to this receptor it will stimulate the osteoclast to proliferate and to differentiate so if either of these things occur the pre osteoclasts will then become an active osteoclast and it will become multinucleated the osteoclasts are actually big things it's a much bigger than osteoblasts and it is a type of macrophage that's why macrophage colony stimulating factor so here we have osteoclasts which will release some form of acid and when it releases acid it will basically eat away on the bone and this will cause bone resorption so it will allow the minerals to leave out of the bone and these minerals that I'm talking about our calcium and phosphate so it's essentially parathyroid hormone stimulates this whole process thereby allowing osteoclasts to become activated and to basically release calcium and phosphate from the bone by eating it up and just to recap osteoblasts have the opposite effect in that they their main goal is to build bone so they are the ones that release collagen as well as some minerals so I hope you enjoyed this video on endocrinology calcium and phosphate regulation we looked at three main hormones vitamin D active form calcitriol parathyroid hormone as well as calcitonin thank you for watching

Channel: Armando Hasudungan

Views: 797,802

Rating: 4.9340806 out of 5

Keywords: Calcium (Chemical Element), Phosphate (Chemical Compound), Calcium Phosphate (Chemical Compound), bone, Vitamin D (Nutrient), Cholecalciferol, Parathyroid Hormone (Hormone), Endocrinology (Medical Specialty), Parathyroid Gland (Anatomical Structure), Thyroid-stimulating Hormone (Hormone), Thyroid Disease (Disease Or Medical Condition), bone homeostasis, osteocytes, osteoblasts, plasma calcium, homeostasis, PTH, calcitonin, hormone of bones, calcitriol, Physiology (Field Of Study)

Id: EEM0iRJNhU8

Length: 11min 20sec (680 seconds)

Published: Tue May 19 2015