What phase involves the backward movement of partially digested food to mix it more thoroughly in the stomach?
Propulsion
Retropulsion
Segmentation
Peristalsis
The Correct Answer is B
A. Propulsion: This movement pushes the gastric contents toward the pyloric sphincter through peristaltic waves. While it is a necessary part of the gastric cycle, its primary direction is forward. It does not describe the mixing reflux.
B. Retropulsion: When a peristaltic wave reaches the closed pyloric sphincter, most of the chyme is forced backward into the stomach body. This high-velocity reverse flow facilitates intense mechanical mixing and further reduction of particle size. It is critical for chyme homogenization.
C. Segmentation: This is the primary mixing movement of the small intestine, characterized by localized rhythmic contractions of the circular muscle. It does not occur in the stomach and does not involve the same retrograde propulsion. It is an oscillating motion.
D. Peristalsis: In the stomach, peristalsis refers to the rhythmic waves of contraction moving from the fundus toward the antrum. While it drives the process of mixing, it is a general term for propulsive movement. Retropulsion is the specific mixing consequence.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
True:CCK is secreted by I cells in the duodenum in response to fatty acids and amino acids. It triggers gallbladder contraction and relaxes the sphincter of Oddi. It also stimulates pancreatic acinar cells to release digestive enzymes.
Correct Answer is C
Explanation
A. Secretion of digestive enzymes:The large intestine does not produce endogenous digestive enzymes. Any remaining chemical digestion in the colon is performed by the resident microbiota. The colonic mucosa is specialized for reclamation rather than catalytic secretion.
B. Breakdown of food particles:Mechanical and chemical breakdown is largely completed by the time chyme reaches the cecum. The large intestine focuses on consolidating waste rather than further degradation. Digestion is a function of the upper gastrointestinal tract.
C. Absorption of water, salts, and vitamins:Colonic enterocytes possess specialized ion transporters and water channels to desiccate fecal matter. They also absorb electrolytes and vitamins, such as Vitamin K, synthesized by bacterial flora. This maintains systemic fluid and electrolyte homeostasis.
D. Production of mucus:Mucus is synthesized and secreted by goblet cells, which are distinct from the absorptive enterocytes. While mucus is abundant in the colon to lubricate feces, it is not the product of the enterocytes. These two cell types have different roles.
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