 we have seen in some of the video the glands present in gastric mucosa that is of zintic glands and pylid glands and the cells lining these glands now in this video we'll discuss about parietal cells and how these cells secrete HCL. Now if you see these cells the lumen of the gland continues as intracellular canaliculi of the parietal cell so if we magnify the cell we'll see that this is the intracellular canaliculi. So top portion is showing the lumen of the gland and the bottom portion is showing the basolateral membrane and the interstitial space. Along the basolateral membrane there is blood flow going on. Now here two diagrams are shown where in diagram A parietal cell is in resting state and in diagram B parietal cell is in stimulated state. If you see the resting state inside the cells are present some stored membranes known as tubulo vesicles so these are tubulo vesicles. All these tubulo vesicles are present lot of hydrogen potassium 80-paste pump also known as proton pumps. When stimulus for secretion of acid is present these tubulo vesicles go and fuse with the intracellular canaliculus. Now this stimulated cell is showing that state when tubulo vesicles have fused with the membrane and this has increased the surface area of cells exposed to the lumen of auxintic gland. Also it increases number of hydrogen potassium 80 bases present on this membrane. Since secretion of HCl is important for activation of pepsinogen and also for protection we need to know the mechanism of how HCl is secreted by parietal cells. Also HCl secretion can be damaging so knowledge of mechanisms of secretion and the factors which affect secretion can help us in treating the condition. So let us see how parietal cells secret HCl. Inside the parietal cells carbon dioxide combines with water in presence of an enzyme carbonic anhydrase to form H2CO3 which dissociates into H plus ions and bicarbonate ions. The hydrogen potassium 80 base which is present on the luminal membrane throws out this hydrogen into the lumen and brings in potassium from the lumen inside the cell. The bicarbonate ion moves to the interstitial side and ultimately enters the blood vessels in exchange of chloride ions. So hydrogen goes into the lumen by hydrogen potassium 80 base and bicarbonate goes into the blood vessel by bicarbonate chloride exchange. This chloride now enters into the lumen by our chloride channel. This is how hydrogen ions and chloride ions enter into the lumen and thus form hydrochloric acid. If you see these concepts together you can understand that as HCl secretion increases in the lumen more and more bicarbonate is entering into the blood. Now this entering of bicarbonate into the blood increases the pH in the blood. The increase in pH whenever there is a stimulation of HCl secretion is known as alkaline tight. Now have a look at another ion potassium. If you remember sodium potassium 80 base is also present on every cell which also brings in to potassium in exchange of sodium. So there is high interest in the concentration of potassium. Potassium thus also leaks back into the lumen by potassium channels. So actually hydrogen potassium 80 base is recycling the same potassium whatever is entering by means of hydrogen potassium 80 base it leaks back into the lumen. So apart from hydrogen ions chloride ions in the lumen there is also presence of a lot of potassium ions in the secretions. So in cases of vomiting where there is loss of gastric fluid along with loss of acid there is also loss of lot of potassium outside the body. So when there is dehydration due to vomiting it not only leads to loss of body fluids but also these ions causing hypo-kalimid alkalosis. Hypo-kalimid because potassium is being lost and alkalosis because HCl is being lost.