Hydrochloric acid

Hydrochloric acid and living organisms

Physiology

Hydrochloric acid constitutes the majority of gastric acid, the human digestive fluid. In a complex process and at a large energetic burden, it is secreted by parietal cells (also known as oxyntic cells). These cells contain an extensive secretory network (called canaliculi) from which the HCl is secreted into the lumen of the stomach. They are part of the epithelial fundic glands (also known as oxyntic glands) in the stomach.

Related Topics:
Gastric acid - Digestive fluid - Parietal cell - Lumen - Epithelial - Fundic gland - Stomach

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Pathophysiology and pathology

Safety mechanisms that prevent the damage of the epithelium of digestive tract by hydrochloric acid are the following:

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• negative regulators of its release
• a thick mucus layer covering the epithelium
• sodium bicarbonate secreted by gastric epithelial cells and pancreas
• the structure of epithelium (tight junctions)
• adequate blood supply
• prostaglandins (many different effects: they stimulate of mucus and bicarbonate secretion, maintenance of epithelial barrier integrity, enable adequate blood supply, stimulate the healing of the damaged mucous membrane)

When due to different reasons these mechanisms fail, heartburn or peptic ulcers can develop. Drugs called proton pump inhibitors prevent the body from making excess acid in the stomach, while antacids neutralize existing acid.

Related Topics:
Heartburn - Peptic ulcer - Proton pump inhibitor - Antacid

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In some instances, not enough of hydrochloric acid gets produced in the stomach. These pathologic states are denoted by the terms hypochlorhydria and achlorhydria. Potentially they can lead to gastroenteritis.

Related Topics:
Hypochlorhydria - Achlorhydria - Gastroenteritis

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Chemical weapons

Phosgene (COCl2) was a common chemical warfare agent used in World War I. The main effect of phosgene results from the dissolution of the gas in the mucous membranes deep in the lung, where it is converted by hydrolysis into carbonic acid and the corrosive hydrochloric acid. The latter disrupts the alveolar-capillary membranes so that the lung becomes filled with fluid (pulmonary edema).

Related Topics:
Phosgene - Chemical warfare - World War I - Lung - Hydrolysis - Carbonic acid - Alveolar - Capillary - Membrane - Pulmonary edema

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Hydrochloric acid is also partly responsible for the harmful or blistering effects of mustard gas. In the presence of water, such as on the moist surface of the eyes or lungs, mustard gas breaks down forming hydrochloric acid.

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