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Questions and Answers
Which contraction type first appears on an empty stomach?
What is the interval duration between Type I contractions?
What pressure is produced by Type II contractions?
How do the tone of muscles change during Type I contractions?
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When do Type III contractions appear?
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Which of the following organs is NOT classified as a retroperitoneal organ?
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Which mechanism is NOT involved in the digestive and absorptive functions of the GI system?
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Which of the following is an example of propulsive movement in the GIT?
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Which sphincter is located at the entrance from the intestine to the ileocaecal part?
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What initiates the reflex response of peristalsis in the GIT?
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Study Notes
Types of Gastric Contractions
- Type I Contractions: First contractions occurring on an empty stomach; last for about 20 seconds, with intervals of 3-4 seconds; pressure produced is around 5 cm of Hâ‚‚O.
- Type II Contractions: Arise when gastric muscle tone is stronger; last 20 seconds with reduced pauses; pressure produced ranges from 10-15 cm of Hâ‚‚O.
- Type III Contractions: Occur under severe hunger; marked increase in muscle tone.
Gastrointestinal Tract (GIT) Functions
- Mechanisms for Digestion: Include softening food, propelling it through the GIT, and mixing it with bile and digestive enzymes.
- Intrinsic Smooth Muscle Properties: Play a vital role in motility, influenced by intrinsic and extrinsic reflexes, paracrine messengers, and GIT hormones.
GIT Motility Activities
- Chewing (Mastication): Occurs in the mouth.
- Swallowing (Deglutition): Involves mouth and esophagus.
- Gastric Motility: Movement within the stomach.
- Small Intestine Motility: Propulsion and mixing occur here.
- Colon Motility: Movement and absorption happen in this section.
- Defecation: Passage of feces from the body.
GIT Sphincters
- Seven major sphincters regulate passage within the GIT:
- Upper esophageal
- Lower esophageal
- Pyloric
- Ileocecal valve
- Houston's valves
- Internal anal sphincter
- External anal sphincter
Types of GIT Movements
- Propulsive Movements: Move food along the GIT (Peristalsis).
- Mixing Movements: Include churning and local contractions to ensure intestinal contents remain mixed.
Peristalsis
- Reflex initiated by stretching of the gut wall, occurring throughout the GIT from esophagus to rectum.
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Esophageal Stages:
- Primary Peristaltic Contraction: Triggered by bolus reaching the upper esophagus; pressure enables propulsion towards the stomach.
- Secondary Peristaltic Contraction: Activated if primary contraction fails, induced by bolus distension.
Deglutition Reflex
- Involves both voluntary and involuntary actions centered in the medulla oblongata.
- Stimulus: Bolus presence in the oropharyngeal region triggers receptor activation.
- Afferent Pathway: Impulse travels via glossopharyngeal nerve to deglutition center.
- Efferent Pathway: Signals to the soft palate, pharynx, and esophagus trigger muscle contractions to facilitate swallowing.
Gastric Motility & Emptying
- Food is stored and mixed in the stomach for about 3-4 hours to form chyme before entering the duodenum.
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Types of Movements in the Stomach:
- Hunger contractions (Type I, II, III)
- Receptive relaxation
- Peristalsis
- Filling the Stomach: Food layers arranged from greater to lesser curvature, with liquids flowing towards the pyloric end.
Gastric Emptying Process
- Swallowed food is gradually released into the intestine.
- Regulated by peristaltic waves and pyloric sphincter relaxation.
- Antrum and Pylorus: Work together to control solid and liquid food passage; more liquid contents squirt into the intestine at regulated intervals.
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Description
This quiz explores Type I contractions and their characteristics in the gastric muscles. Learn about their occurrence, duration, and frequency while understanding their physiological significance. Perfect for students studying gastroenterology or related fields.
