In what way is segmentation different from peristalsis in the small intestine?
Segmentation uses migrating motility complexes to move chyme.
Segmentation mixes and exposes chyme to the mucosa, not for propulsion.
Segmentation pushes chyme forward, while peristalsis mixes it.
Segmentation occurs only after the small intestine is emptied.
The Correct Answer is B
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.
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Related Questions
Correct Answer is A
Explanation
A. Brush border:This ultra-structural feature consists of thousands of microscopic, finger-like projections called microvilli. It vastly increases the surface area for membrane-bound enzymes and nutrient transporters. It is the primary site for terminal carbohydrate and protein hydrolysis.
B. Lymphatic plexus:This network of vessels is located within the deeper layers of the mucosa and submucosa. It is responsible for the drainage of lymph and the transport of absorbed dietary fats. It is an internal vascular structure.
C. Submucosal layer:This is a distinct histological layer composed of dense irregular connective tissue containing blood vessels and nerves. It supports the overlying mucosa but does not form the apical surface. It provides structural integrity to the gut.
D. Gastric pit:These are deep pores in the stomach lining that lead to the gastric glands. They are macroscopic or microscopic depressions rather than apical cellular modifications. They serve as conduits for exocrine secretions like hydrochloric acid.
Correct Answer is B
Explanation
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.
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