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Questions and Answers
What are the types of movements in the small intestine?
What are the types of movements in the small intestine?
What is the maximum frequency of segmental contractions in the duodenum and proximal jejunum?
What is the maximum frequency of segmental contractions in the duodenum and proximal jejunum?
12/min
Peristaltic waves in the small intestine move towards the anus at a velocity of 0.5 to 2.0 cm/sec.
Peristaltic waves in the small intestine move towards the anus at a velocity of 0.5 to 2.0 cm/sec.
True
What is the primary function of the migrating motility complex (MMC)?
What is the primary function of the migrating motility complex (MMC)?
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Chyme is propelled through the small intestine by ______ waves.
Chyme is propelled through the small intestine by ______ waves.
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Which phase of the MMC has the longest duration?
Which phase of the MMC has the longest duration?
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Match the following types of intestinal movements with their functions:
Match the following types of intestinal movements with their functions:
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Haustrations are large circular constrictions that occur in the colon.
Haustrations are large circular constrictions that occur in the colon.
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How many times a day do mass movements occur in the colon?
How many times a day do mass movements occur in the colon?
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Study Notes
Overview of Intestinal Movements
- Important for digestion and absorption; includes movements in small intestine and colon.
- Key structures: ileocecal valve and sphincter regulate flow into the colon.
General Principles of Gastrointestinal Tract Functions
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Propulsive:
- Contraction ring and receptive relaxation help in moving content.
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Mixing:
- Involves peristaltic and local constrictive contractions to blend contents.
Movements of the Small Intestine
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Mixing (Segmentation) Contractions:
- Localized contractions induced by stretching; crucial for thorough mixing with digestive juices.
- Frequency:
- Up to 12 contractions per minute in duodenum.
- About 8-9 in ileum.
- Enhances absorption by slowing transit time.
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Propulsive (Peristalsis) Contractions:
- Waves propel chyme through small intestine at 0.5 to 2.0 cm/sec.
- Travels only a few centimeters before weakening; net movement averages about 1 cm/min.
- Takes approximately 3 to 5 hours from pylorus to ileocecal valve.
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Migrating Motility Complex (MMC):
- Functions as “intestinal housekeeper” during fasting; occurs every 1.5 hours.
- Phases of MMC:
- Phase 1: Quiescent period (40 to 60 minutes, few contractions).
- Phase 2: 20 to 30 minutes of some peristaltic activity.
- Phase 3: Lasts 5 to 10 minutes; strong contractions occur, causing growling noises.
Regulation of Intestinal Movement
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Neural Control:
- Initiated by duodenal stretch and gastroenteric/gastroileal reflexes.
- Submucosal plexus controls muscularis mucosa and villi contractions.
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Hormonal Control:
- Increases motility via gastrin, cholecystokinin (CCK), insulin, motilin, and serotonin.
- Decrease in motility through secretin and glucagon.
Movements of the Colon
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Mixing Movements (Haustrations):
- Large circular contractions occur to mix fecal material and promote absorption.
- Areas of unstimulated muscle bulge to form haustra, resulting in slow mixing.
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Propulsive Movements (Mass Movements):
- Characterized by slow, powerful contractions 1 to 3 times a day, notably after meals.
- Strongest during the first hour post-breakfast.
Reflexes Impacting Colonic Activity
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Gastrocolic Reflex:
- Stimulation of the colon in response to gastric distension signals the need to move contents.
-
Duodenocolic Reflex:
- Activation of colonic activity triggered by stretch receptors in the duodenum.
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Description
This quiz explores the various intestinal movements essential for digestion and absorption within the gastrointestinal tract. It covers key concepts such as peristalsis and segmentation contractions, along with their mechanisms and significance in nutrient absorption.
