Phases of Digestion – Key Vocabulary

Vocabulary flashcards that cover the major terms and concepts involved in the cephalic, gastric, and gastrointestinal phases of digestion.

Cephalic Phase

Initial phase of digestion triggered by the sight, smell, taste, or thought of food; brain (via the vagus nerve) stimulates gastric secretions and motility before food reaches the stomach.

Gastric Phase

Second digestive phase that begins when food enters the stomach; stomach distension activates stretch receptors and increases vagus-mediated secretions and segmentation contractions.

Gastrointestinal (Intestinal) Phase

Final phase that starts when acidic chyme reaches the duodenum; the intestine uses neural and hormonal signals to regulate how quickly the stomach empties.

Vagus Nerve

Cranial nerve X carrying parasympathetic fibers to and from digestive organs; stimulates gastric secretions and muscle activity.

Gastrin

Hormone released by stomach endocrine cells during cephalic and gastric phases; reinforces gastric acid secretion and motility.

Segmentation

Rhythmic mixing contractions of the stomach (and intestines) that churn contents without propelling them forward.

Peristalsis

Wave-like muscular contractions that propel chyme toward the duodenum.

Chyme

Liquefied mixture of partially digested food and gastric juice produced in the stomach.

Duodenum

First section of the small intestine; receives chyme and initiates acid neutralization and intestinal phase feedback to the stomach.

Secretin

Duodenal hormone released when acidic chyme enters; inhibits gastric activity and stimulates bicarbonate secretion elsewhere to neutralize acid.

Cholecystokinin (CCK)

Duodenal hormone released by acidic or fatty chyme; slows gastric emptying and stimulates gallbladder and pancreatic enzyme release.

pH Receptors

Chemoreceptors in the duodenal wall that monitor lumen acidity and trigger responses when pH drops.

Stretch Receptors

Mechanoreceptors in the stomach wall that detect distension, initiating and sustaining the gastric phase of digestion.

Extrinsic Neural Pathway

Gut-to-brain communication via the vagus nerve that alters stomach activity based on signals from the intestine.

Intrinsic Neural Pathway (Local Reflex)

Direct communication between enteric nerve plexuses of neighboring gut segments, functioning independently of the central nervous system.

Parasympathetic Stimulation

Branch of the autonomic nervous system that generally enhances digestive secretions and motility.

Sympathetic Stimulation

Branch of the autonomic nervous system that generally suppresses digestive activity.

Medulla Oblongata

Brainstem control center that adjusts vagus nerve activity to regulate digestive phases.

Distension

Stretching of an organ wall—especially the stomach when food enters—detected by stretch receptors.

Autonomic Nervous System (ANS)

Involuntary motor system comprising sympathetic and parasympathetic divisions that regulate digestive organs.

Acid Neutralization

Process in the duodenum that raises chyme pH to protect intestinal lining and allow efficient digestion.

Hormonal Reinforcement

Use of hormones (e.g., gastrin, secretin, CCK) to amplify or inhibit neural signals during the digestive phases.