True or False
The stomach serves as a temporary holding chamber for food before it enters the small intestine.

A. Segmentation uses migrating motility complexes to move chyme:Migrating motility complexes are a form of peristalsis that occurs during the post-absorptive state to clear the bowel. Segmentation is characterized by localized, rhythmic contractions of circular muscle. It does not involve migrating complexes.

B. Segmentation mixes and exposes chyme to the mucosa, not for propulsion:Segmentation involve stationary, oscillating contractions that move chyme back and forth. This maximizes contact with the absorptive surface and mixes contents with digestive juices. It is the primary motion during active digestion.

C. Segmentation pushes chyme forward, while peristalsis mixes it:This choice inverts the definitions of the two movements. Peristalsis is the sequential contraction that propels contents anterograde through the tract. Segmentation is specifically designed for mixing rather than forward movement.

D. Segmentation occurs only after the small intestine is emptied:Segmentation is the predominant movement during the presence of food in the small bowel. Once the intestine is empty, the motility pattern shifts to the migrating motor complex. It is an active digestive process.

A. Lysozyme:This enzyme functions as an antimicrobial agent by cleaving the peptidoglycan walls of certain bacteria. It provides a non-specific immune defense within the oral cavity. It possesses no catalytic activity toward carbohydrates or starches.

B. Salivary amylase:Also known as ptyalin, this enzyme initiates the hydrolysis of complex polysaccharides into smaller oligosaccharides like maltose. It operates at an optimal neutral pH within the mouth. This is the first step of chemical carbohydrate digestion.

C. Pepsin:This protease is secreted by gastric chief cells as pepsinogen and is activated by hydrochloric acid in the stomach. It is specialized for the cleavage of peptide bonds in proteins. It does not participate in carbohydrate breakdown.

D. Salivary lipase:This enzyme is secreted by von Ebner’s glands on the tongue to begin the hydrolysis of triglycerides. It targets dietary lipids rather than carbohydrates. Its activity continues within the stomach due to its acid-stable nature.