Question

1. A certain cell type produces acid within the stomach. Name the cell and explain why these cells are not destroyed by acid they make.

2. You went to your favorite eatery and ordered the most expensive steak. While eating the delicious steak, a piece accidentally entered into your trachea instead of the esophagus. Explain how this event would affect your blood pH?

Answer 1

1) Parietal cells or oxyntic cells are epithelial cells of the stomach that secrete hydrochloric acid.

The parietal cells are not destroyed because, they secrete H+ and Cl- into the lumen of the stomach, and  both accumulates only in the lumen and not in the parietal cell.

HCl in the lumen of stomach doesnt destroy the mucosal lining because goblet cells secrete protective mucus that acts as a barrier. Also, bases like HCO3- are trapped inside the mucus which neutralizes any HCl that penetrates the mucus.

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2) The blood pH will decrease causing acidosis.

Obstruction of trachea will interfere with the alveolar gas exchange. So, the oxygen is not reaching the blood and CO2 from the blood is not removed. i.e, pO2 decreases and pCO2 increases.

The normal reference range for PaCO2 is 35-45 mm Hg. When the concentration of CO2 increases, more CO2 combines with water to form carbonic acid [H2CO3] which then dissociates into H+.

CO2 + H2O ------------------> H2CO3 --------------------> H+ + HCO3-

So, the H+ concentration increases, which means the blood pH decreses causing acidosis. This type of acidosis caused by hypoventillation is called Respiratory acidosis.