41. Physiology - GI Motility

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Questions and Answers

What is the primary role of the upper esophageal sphincter during swallowing?

To prevent the bolus from entering the pharynx (correct)

To regulate pressure between the thorax and the esophagus

To facilitate the entry of air into the esophagus

To open and close during the entire digestive process

How does gravity influence the movement of the food bolus in the esophagus?

It primarily affects the lower esophageal sphincter

It accelerates the movement if the person is sitting or standing (correct)

It slows down peristaltic contractions significantly

It has no impact since pressure remains constant

What neurotransmitter is released by peptidergic fibers in the vagus nerve that relaxes the lower esophageal sphincter?

Acetylcholine

Dopamine

VIP (vasoactive intestinal peptide) (correct)

Serotonin

What is the effect of intrathoracic pressure on the esophagus?

It equals thoracic pressure, which is lower than atmospheric pressure Signup and view all the answers

What type of contraction is primarily responsible for moving the bolus down the esophagus?

Primary peristaltic contraction Signup and view all the answers

What anatomical structure is specifically involved in preventing gastric acid from entering the esophagus?

Lower esophageal sphincter Signup and view all the answers

During a swallowing reflex, what occurs immediately after the bolus enters the esophagus?

The upper esophageal sphincter closes Signup and view all the answers

In cases of hiatal hernia, what happens to the lower esophageal sphincter?

It becomes less capable of preventing regurgitation Signup and view all the answers

What characterizes the orad region of the stomach in terms of motor activity?

It has both relaxation and tonic contractions without slow wave activity. Signup and view all the answers

Which neurotransmitters are associated with the vagovagal reflex during receptive relaxation?

Non-cholinergic and non-adrenergic neurotransmitters. Signup and view all the answers

What is the primary role of peristaltic contractions in the distal, caudad region of the stomach?

To mix food with gastric secretions and aid digestion. Signup and view all the answers

What is the frequency of slow waves in the duodenum?

12 slow waves/min Signup and view all the answers

Which statement correctly explains adaptive relaxation in the proximal stomach?

It is triggered by mechanoreceptors detecting stomach distension. Signup and view all the answers

Which part of swallowing is under voluntary control?

Oral phase Signup and view all the answers

In terms of motor activity types, which component is not associated with the orad region?

Peristaltic contractions. Signup and view all the answers

Where is the swallowing center located in the brain?

Medulla Signup and view all the answers

What type of information do sensory receptors near the pharynx detect during swallowing?

Somatosensory information Signup and view all the answers

Which nerves carry sensory information to the swallowing center?

Vagus and glossopharyngeal nerves Signup and view all the answers

Which phase of swallowing is controlled by reflexes?

Both pharyngeal and esophageal phases Signup and view all the answers

What initiates the involuntary swallowing reflex?

Activation of somatosensory receptors in the pharynx Signup and view all the answers

What is the primary role of chewing in the digestive process?

To facilitate swallowing and begin digestion Signup and view all the answers

What characterizes the oral phase of swallowing?

It is initiated by the tongue pushing the bolus back. Signup and view all the answers

Which of the following statements is true regarding the esophageal phase of swallowing?

It occurs after the pharyngeal phase. Signup and view all the answers

What is the primary function of slow waves in the alimentary canal?

Facilitate the initiation of peristalsis Signup and view all the answers

Which component is responsible for the differences in motor activity between the proximal and distal regions of the stomach?

Differential innervation of smooth muscle Signup and view all the answers

What characterizes peristaltic contractions in the small intestine?

Circular muscle contraction followed by relaxation Signup and view all the answers

Which phase of gastric motility is primarily responsible for the mixing of gastric contents?

Caudad region motor activity Signup and view all the answers

What is the main purpose of segmentation contractions in the small intestine?

Increase nutrient absorption by mixing contents Signup and view all the answers

What is most likely to occur during the gastrocolic reflex?

Stimulation of colonic contractions Signup and view all the answers

Hirschsprung’s disease primarily affects which part of gastrointestinal motility?

Colonic motility Signup and view all the answers

What is a common characteristic of contractions in the rectum and anal canal related to defecation?

Coordination with abdominal pressure Signup and view all the answers

Which of the following is NOT a function of the processes involved in gastrointestinal motility?

Storage of toxic substances Signup and view all the answers

What primarily triggers the vomiting reflex?

Activation of chemoreceptor trigger zone Signup and view all the answers

What is the primary function of the pharyngeal phase in swallowing?

To propel the food bolus into the esophagus Signup and view all the answers

During the pharyngeal phase, what action does the epiglottis perform?

Covering the opening to the larynx Signup and view all the answers

What initiates the peristaltic wave of contraction during the pharyngeal phase?

The swallowing reflex Signup and view all the answers

What role does the enteric nervous system play in the esophageal phase of swallowing?

It is primarily responsible for the coordination of peristalsis Signup and view all the answers

What prevents reflux of food into the pharynx once the bolus has passed through the upper esophageal sphincter?

The swallowing reflex Signup and view all the answers

What is the consequence of an unsuccessful primary peristaltic wave in the esophagus?

A secondary peristaltic wave is initiated Signup and view all the answers

During the swallowing process, when does breathing get inhibited?

During the pharyngeal phase Signup and view all the answers

Which structure pulls upward to create a narrow passage for food to move into the pharynx?

The soft palate Signup and view all the answers

What physiological process occurs immediately after food passes through the upper esophageal sphincter in the esophageal phase?

Initiation of a primary peristaltic wave Signup and view all the answers

Study Notes

Esophageal Motility

The esophagus transports food from the mouth to the stomach, assisted by sphincters at each end.
The upper esophageal sphincter blocks air entry, while the lower esophageal sphincter prevents acid from entering the esophagus.
Intraesophageal pressure mirrors the thoracic pressure, which is lower than atmospheric pressure.
This difference in pressure can be measured with a balloon catheter in the esophagus, particularly relevant for hiatal hernias.
Hiatal hernias can lead to regurgitation due to the negative pressure surrounding the esophagus and a displaced lower esophageal sphincter.

Swallowing

Initiated voluntarily in the mouth, but transitions to an involuntary reflex controlled by the swallowing center in the medulla.
Sensory information about food in the mouth is detected by somatosensory receptors in the pharynx, initiating the swallowing reflex through the glossopharyngeal nerve.
This information is conveyed to the medulla, which coordinates sensory input and directs motor output to muscles in the pharynx and upper esophagus.
Swallowing comprises three phases: oral, pharyngeal, and esophageal.

Oral Phase

The tongue pushes a bolus of food back towards the pharynx, activating somatosensory receptors that trigger the involuntary swallowing reflex in the medulla.

Pharyngeal Phase

This phase propels food from the mouth, through the pharynx, to the esophagus, in the following steps:
The soft palate elevates, creating a tight passageway to prevent food from entering the nasopharynx.
The epiglottis closes the opening to the larynx, and the larynx rises against the epiglottis, preventing food from entering the trachea.
The upper esophageal sphincter relaxes, allowing food to move from the pharynx to the esophagus.
Peristaltic contractions begin in the pharynx, propelling food through the open sphincter.
Breathing is inhibited during the pharyngeal phase.

Esophageal Phase

Controlled in part by the swallowing reflex and the enteric nervous system.
Food moves through the esophagus to the stomach.
After the bolus passes through the upper esophageal sphincter in the pharyngeal phase, the sphincter closes to prevent reflux into the pharynx.
A primary peristaltic wave, initiated by the swallowing reflex, moves down the esophagus propelling the food forward.
If the primary wave doesn't clear the esophagus, a secondary peristaltic wave is triggered by continued distension in the esophagus.

Gastric Motility

The stomach is divided into two functional regions: proximal/orad and distal/caudad.

Proximal Stomach

The proximal stomach includes the fundus and proximal body, containing oxyntic (fundic or gastric) glands, and is responsible for receiving ingested meals.

Distal Stomach

The distal stomach comprises the antrum and distal body, responsible for mixing food and propelling it into the duodenum.

Receptive Relaxation

The ability of the orad stomach to accommodate large volume increases with minimal pressure changes.
A vagovagal reflex triggered by gastric distension, this relaxation is abolished by vagotomy.
CCK (cholecystokinin) also contributes to receptive relaxation by increasing the orad stomach's distensibility.
Non-cholinergic and non-adrenergic neurotransmitters, specifically NO and VIP (vasoactive intestinal peptide), are implicated in the vagal pathway.

Adaptive Relaxation

Mechanoreceptors in the stomach are stimulated as it fills with food, eliciting another vagovagal reflex.
CCK activation also triggers a vagovagal reflex.
Low amplitude, tonic contractions in the proximal stomach gently move chyme towards the distal stomach.
These contractions are not mediated by slow waves.

Caudad Region

The distal, caudad stomach exhibits two types of motor activity:
Peristaltic contractions for mixing and digestion.
Migrating motor complex (MMC) and slow wave activity

Peristaltic Contractions

The caudad stomach contracts to mix food with gastric secretions and initiate the digestive process.

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Description

This quiz explores the mechanisms of esophageal motility and the process of swallowing. It covers the role of sphincters, pressure dynamics, and the neural control of swallowing. Test your understanding of these physiological processes and their relevance in conditions like hiatal hernias.