Look, we saw some delicious food, imagined it or we just smelled some tasty food. Our vagus nerve starts sending signals to our stomach, to make acid, or whatever food we eat and the food that stretches in the wall of the stomach, they stimulate the stretch receptor, our stomach. To make the acid in…
There are some folds present on the inner lining of our stomach, which are called rugae, are present on these rugae, the gastric pit on which are many gastric glands. Which release chemicals that help in the digestion of food. As the vagus nerve signals to our stomach, to make HCl i.e. acid, also known as gastric acid. These gastric glands present on our rugae get activated.
See, as soon as the cells of this gastric gland are activated on our gastric pit, first of all our g cell starts releasing gastrin. G cell is an endocrine gland, which releases its secretion into the blood. See, as soon as gastrin is released, this gastrin stimulates this ECL cell, the enterochromaffin cell, to release histamine…. And as soon as histamine is released, it starts from here, the story of acid production in our body.
Histamine is actually the histamine receptor on our parietal cell, with this receptor histamine binds, and this parietal cell is activated as soon as histamine binds.
See, immediately after activation, carbon dioxide and h2o from our blood enter this parietal cell, and as soon as this h2o and h2o enter the parietal cell, it converts carbonic acid into carbonic acid, with the help of an enzyme carbonic anhydrase. it changes. The organic acid formed inside the parietal cell further dissociates into hydrogen ions and bicarbonate ions.
Now look at the hydrogen ions, also called protons, and the bicarbonate ions that are formed. These are now exited from our cell by exchange of one other ion. First of all, this is our hydrogen ion, it gets out of this parietal cell by exchange with potassium ion. Meaning the hydrogen ion moves out of the parietal cell, and in return, the potassium ion enters our parietal cell, through this proton-potassium atpase channel. The same bicarbonate ion moves into the blood with the exchange of chloride ions, and chloride ions from the blood, through the bicarbonate chloride exchange channel, enter the parietal cell.
Now it happens that this chloride ion also comes out from this parietal cell. And as I just told you that the hydrogen ion already comes out of our parietal cell and comes to the stomach. So both these hydrogen ions and chloride ions combine to form HCl, the hydrochloric acid which we need in the digestion of food, it is also called gastric acid.
And this hcl now kills the bacteria virus coming in our stomach, and breaks down the food we eat, converting them into small absorbable form.