Gastric Juice Composition, Function, Mechanism, and Regulation

Vocabulary flashcards covering the components, functions, cell mechanisms, neural/hormonal controls, and three phases of regulation for gastric juice secretion.

Gastric juice

A clear, acidic fluid secreted by gastric glands in the stomach, with a daily secretion volume of about $1.5-2.5\,L$ per day and a pH of $1.0-3.0$.

Hydrochloric acid (HCL)

A component of gastric juice ($0.1-0.5\%$, pH $1-3$) that creates an acidic pH, activates pepsinogen, kills microbes, and denatures proteins.

Pepsinogen

An inactive enzyme component in gastric juice that is converted to active pepsin by HCL.

Pepsin

An active enzyme in gastric juice converted from pepsinogen by HCL that digests proteins by breaking them into peptones and peptides.

Gastric lipase

A component of gastric juice present in small amounts that digests fats, mainly in infants.

Intrinsic factor

A glycoprotein in gastric juice that helps in the absorption of vitamin B12 in the ileum.

Mucus

A component of gastric juice consisting of mucin that protects the stomach mucosa from acid and pepsin.

Electrolytes (Gastric Juice)

Components of gastric juice including Na, K, CL, and HCO3 that maintain osmotic balance and pH.

Parietal cells

Stomach cells that secrete HCL (acid) and intrinsic factor.

Chief cells

Stomach cells that secrete pepsinogen and gastric lipase.

Mucous cells

Stomach cells that secrete mucus.

G cells

Endocrine cells in the stomach that secrete the hormone gastrin to stimulate secretion.

Cephalic phase

The first phase of gastric secretion regulation stimulated by the sight, smell, taste, thought, or chewing of food, triggering parasympathetic vagus nerve activation and ACh release for about $30\%$ of gastric juice secretion.

Gastric phase

The second phase of gastric secretion regulation stimulated by stomach distension and protein in food, triggering stretch receptors (vagal reflex ACh), gastrin from G cells, and histamine from ECL cells for maximum secretion (about $60\%$).

Intestinal phase

The third phase of gastric secretion regulation stimulated by entry of chyme into the duodenum, leading to a small increase in secretion (about $10\%$) via mild stimulation by intestinal gastrin.

Gastrin

A hormone released by G cells that directly and indirectly (via histamine) stimulates parietal cells.

Histamine

A chemical released by ECL cells that directly stimulates parietal cells via H2 receptors.

Acetylcholine (ACh)

A neurotransmitter released from the vagus nerve that stimulates parietal cells, chief cells, and G cells.

Somatostatin

An inhibitory factor released from D cells that inhibits gastrin.

Secretin

An inhibitory factor released from the duodenum that inhibits gastric secretion.

GIP (Gastric inhibitory peptide)

An inhibitory factor that inhibits gastric secretion.

Prostaglandins

Inhibitory factors that reduce acid secretion and increase mucus production.