7 Esophageal Physiology Flashcards
Organs involved in swallowing
- The organs involved in swallowing
- primary functions
- Deglutition/
- Peristaltic contractions/
- The failure or lack of coordination of peristaltic contractions/
- This leads to the symptoms of/
- The reflux of gastric contents into the esophagus and pharynx is prevented primarily by/
- Their failure to do so may lead to/
- Peristaltic contractions/
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The organs involved in swallowing
- the oral cavity, pharynx and esophagus -
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primary functions:
- to form and then transport a bolus from the oropharynx to esophagus (deglutition),
- to propel this bolus into the stomach,
- to prevent the reflux of gastric contents into the esophagus, pharynx and respiratory tract.
- to protect the esophagus from the potential injury due to reflux of acidic material from the stomach.
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Deglutition is a complex process that involves several striated muscles and cranial nerves, the hard palate and the larynx.
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Peristaltic contractions of the muscular walls of the esophagus propel swallowed materials into the stomach.
- The failure or lack of coordination of peristaltic contractions may disrupt the propulsion of swallowed material along the conduit.
- This leads to the symptoms of dysphagia (difficulty swallowing) or odynophagia (painful swallowing).
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The reflux of gastric contents into the esophagus and pharynx is prevented primarily by specialized, tonically contracted sphincter muscles that impede the retrograde movement of gastric and esophageal contents, respectively.
- Their failure to do so may lead to reflux esophagitis and heartburn or pyrosis (a substernal and epigastric burning sensation).
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Peristaltic contractions of the muscular walls of the esophagus propel swallowed materials into the stomach.
Structure and Function of the Swallowing Organs (p.3-4)
- The esophagus
- ?
- three functionally distinct segments
- The pharynx and esophagus form/
- The pharynx
- ?
- The muscular wall of the pharynx is composed of/
- The most caudal of these muscles/
- The cricopharyngeus/
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The esophagus
- a tubular structure of about 20 - 22 cm in length.
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three functionally distinct segments:
- upper esophageal sphincter (UES)
- high resting tone; relaxes with swallowing
- tubular esophagus
- no resting tone; propagating contractions
- lower esophageal sphincter (LES)
- high resting tone; relaxes with swallowing
- upper esophageal sphincter (UES)
- The pharynx and esophagus form a tubular conduit made up of distinct neuromuscular elements that are functionally integrated to perform the task of swallowing.
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The pharynx
- a tapered hollow cylinder that connects the mouth and nasopharyngeal cavity to the esophagus and trachea.
- The muscular wall of the pharynx is composed of three overlapping sheets of striated muscle, the pharyngeal constrictors.
- The most caudal of these muscles, the inferior pharyngeal constrictor, thickens to give rise to a distinct band of striated muscle, the cricopharyngeus.
- The cricopharyngeus is positioned at the inlet of the esophagus where it functions as the upper esophageal sphincter.
Structure and Function of the Swallowing Organs
- Below the pharyngo-esophageal junction, the esophagus forms/
- The esophageal musculature consists of/
- There is a transition zone/
- what makes up the distal esophagus
- The circular muscle layer thickens/
- At rest,
- the pharyngeal musculature generates/
- The upper esophageal sphincter (cricopharyngeus) generates/
- the tonic contraction of the lower esophageal sphincter/
- The striated and smooth muscle portions of the esophagus between the two sphincters form/
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Below the pharyngo-esophageal junction, the esophagus forms a continuous tube to the stomach.
- The esophageal musculature consists of outer longitudinal and inner circular layers that are named according to the axial orientation of their constituent muscle cells.
- There is a transition zone of several centimeters at about the level of the tracheal bifurcation over which the striated muscle mixes with and is replaced by smooth muscle
- Smooth muscle makes up the distal esophagus.
- The circular muscle layer thickens a little at the esophagogastric junction to form a muscular ring called the lower esophageal sphincter.
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At rest,
- the pharyngeal musculature generates a weak tonic contraction that stiffens the pharyngeal wall without occluding the lumen.
- The upper esophageal sphincter (cricopharyngeus) generates a powerful, tonic contraction at rest which occludes the lumen at the junction between the pharynx and esophagus.
- the tonic contraction of the lower esophageal sphincter completely occludes the lumen at the gastro-esophageal junction.
- The striated and smooth muscle portions of the esophagus between the two sphincters form a flaccid tube without tone at rest.
Swallowing (p.6)
- Swallowing starts as a phase of/
- The tongue
- As the swallow is initiated, the tongue/
- As the bolus is propelled into the pharynx, the soft palate/
- At about the same time
- the larynx/
- the arytaenoids/
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Swallowing starts as a phase of preparation including mastication of the food and the formation of the bolus to be swallowed.
- The tongue assumes a cup shape to hold the bolus in the oral cavity.
- As the swallow is initiated, the tongue elevates against the palate in a sequential manner from anterior to posterior to squeeze the bolus into the pharynx.
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As the bolus is propelled into the pharynx, the soft palate elevates to make contact with the posterior pharyngeal wall.
- This seals the oropharynx from the nasopharynx so that nasopharyngeal reflux does not occur.
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At about the same time
- the larynx is elevated, moved anteriorly
- the arytaenoids are displaced anterior to make contact with the epiglottis, thereby closing the laryngeal opening.
Swallowing (p.6)
- Two types of pharyngeal contraction facilitate/
- Early in the swallow
- the pharynx/
- this also/
- A peristaltic contraction of the pharyngeal musculature behind the bolus/
- The tonically contracted upper esophageal sphincter/
- The peristaltic contraction/
- The tonically contracted lower esophageal sphincter/
- Arrival of the peristaltic contraction at the lower esophageal sphincter/
- Two types of pharyngeal contraction facilitate the movement of the bolus towards the esophagus.
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Early in the swallow
- the pharynx shortens in its long axis, decreasing the distance the bolus must travel in transit through the pharynx.
- Pharyngeal shortening also obliterates the laryngeal vestibule and the pyriform sinuses so that none of the bolus is caught in these recesses.
- A peristaltic contraction of the pharyngeal musculature behind the bolus occludes the pharyngeal lumen as it sweeps caudal to force the bolus towards the esophagus.
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The tonically contracted upper esophageal sphincter
- relaxes as the pharyngeal peristaltic contraction advances towards the esophagus
- is actively pulled open as the larynx is elevated and moved anteriorly.
- contracts powerfully as the pharyngeal peristaltic sequence occurs and then rapidly reestablishes its basal tone.
- This facilitates the transfer of the bolus from the oropharynx to the esophagus.
- The peristaltic contraction sweeps without interruption from the upper esophageal sphincter, along the esophageal body, to the stomach.
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The tonically contracted lower esophageal sphincter
- relaxes long before the peristaltic contraction reaches the gastroesophageal junction.
- remains relaxed until the peristaltic contraction arrives to strip the bolus into the gastric cavity.
- Arrival of the peristaltic contraction at the lower esophageal sphincter closes the sphincter with a transient, forceful contraction which soon subsides to the tonic contraction of the resting state.
Neuromuscular Control of Swallowing (p.7-16)
- the swallowing organs composed of striated muscle
- The contractile behavior of these organs is controlled by/
- Axons from nerve cell bodies in these nuclei project/
- The continuous discharge of these nerves is responsible for/
- Relaxation of these muscles results from/
- The peristaltic contraction that sweeps along these organs represents/
- The contraction is peristaltic because/
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the swallowing organs composed of striated muscle
- the pharynx, upper esophageal sphincter, and proximal esophageal body
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The contractile behavior of these organs is controlled by somatic nerves that originate in the nuclei of the glossopharyngeal (IX) and vagus (X) nerves.
- Axons from nerve cell bodies in these nuclei project via cranial nerves, without synaptic interruption, to end in motor end plates on the striated muscle cells.
- The continuous discharge of these nerves is responsible for the maintenance of tone in the striated muscle of the oropharynx and upper esophageal sphincter.
- Relaxation of these muscles results from the inhibition of this tonic somatic neural discharge.
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The peristaltic contraction that sweeps along these organs represents a vigorous discharge of their somatic innervation.
- The contraction is peristaltic because the motor units, single motor neurons and striated muscle cells that they supply, are activated in a fixed craniocaudal sequence.
Neuromuscular Control of Swallowing (p.7-16)
- The neuromuscular control of the smooth muscle esophagus
- The central innervation of the smooth muscle portion of the esophagus arises from/
- Axons from these preganglionic parasympathetic neurons travel/
- The terminal motor innervation of the smooth muscle of the esophagus, the postganglionic neurons, comes from/
- The neural systems seem to be inactive/
- The resting contraction of the lower esophageal sphincter reflects/
- however, some fluctuations in baseline tone may represent/
- The first swallow-induced event in the smooth muscle esophagus/
- This results from/
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The neuromuscular control of the smooth muscle esophagus
- The central innervation of the smooth muscle portion of the esophagus arises from nerve cell bodies in the dorsal motor nucleus of the vagus.
- Axons from these preganglionic parasympathetic neurons travel with the vagus nerve to synapse with neurons in the myenteric plexus.
- The terminal motor innervation of the smooth muscle of the esophagus, the postganglionic neurons, comes from these nerve cell bodies in the myenteric plexus.
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The neural systems seem to be inactive at rest in the smooth muscle segment of the esophagus.
- The resting contraction of the lower esophageal sphincter reflects, mainly, the myogenic tone of the sphincter muscle rather than a strong tonic discharge of nerves;
- however, some fluctuations in baseline tone may represent neural activity.
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The first swallow-induced event in the smooth muscle esophagus is relaxation of the lower esophageal sphincter.
- This relaxation results from the vagal activation of inhibitory myenteric nerves that release nitric oxide.
Neuromuscular Control of Swallowing (p.7-17)
- The progressive nature of the peristaltic contraction in the smooth muscle esophageal segment
- not programmed in/
- controlled by/
- Nitric oxide-releasing myenteric nerves supply/
- Swallowing activates/
- The duration of the inhibition is progressively longer at/
- Excitation that follows the period of inhibition is responsible for/
- _The progressive nature of the peristaltic contraction in the smooth muscle esophageal segment _
- not programmed in the brainstem.
- controlled by neuromuscular mechanisms that are intrinsic to the esophagus.
- Nitric oxide-releasing myenteric nerves supply the circular muscle of the smooth muscle esophagus.
- Swallowing activates these inhibitory nerves simultaneously throughout the esophageal body, to cause a nearly simultaneous inhibition along the length of the smooth muscle esophagus.
- The duration of the inhibition is progressively longer at the more distal sites in the smooth muscle esophagus.
- Excitation that follows the period of inhibition is responsible for the progressive nature of the peristaltic contraction.
Heartburn (Pyrosis) and Gastroesophageal Reflux (p.23-25)
- Heartburn
- frequency
- may indicate/
- If associated with objective signs of mucosal damage (most often erosions)
- The inflammatory process is usually initiated and maintained by/
- Gastroesophageal reflux most often occurs either because/
- This situation is exacerbated if/
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Heartburn
- common symptom in the general population
- may indicate the presence of mucosal inflammation in the distal esophagus.
- If associated with objective signs of mucosal damage (most often erosions), the diagnosis of gastroesophageal reflux disease (GERD) is established.
- The inflammatory process is usually initiated and maintained by the reflux of gastric contents (acid and/or bile) into the esophagus.
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Gastroesophageal reflux most often occurs either because
- the lower esophageal sphincter does not maintain adequate tone at rest
- the lower esophageal sphincter relaxes inappropriately, at other times besides swallowing, to allow the retrograde movement of gastric contents into the esophagus
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This situation is exacerbated if
- esophageal peristalsis is disordered so that gastric contents are not cleared from the esophagus
- the motor function of the stomach is impaired so that it does not empty in a timely fashion
- there is a decrease in saliva production
Heartburn (Pyrosis) and Gastroesophageal Reflux (p.26-29)
- Hiatal hernias
- link between these herniations and reflux
- Not every patient with heartburn/
- 60-70 % of patients with typical reflux symptoms/
- symptoms are still caused by/
- Causes of heartburn
- pyrosis does not always mean/
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Hiatal hernias
- often equated with gastroesophageal reflux disease
- often asymptomatic
-
link between these herniations and reflux
- recurrent reflux is the main mechanism leading to formation of the hernia.
- mucosal injury results in contractions of the muscularis mucosae, which has a longitudinal orientation.
- Over time, such contractions may disrupt the diaphragmatic attachments of the esophagus, allowing shortening and formation of a hiatal hernia.
- The hernia, in turn, creates a small reservoir of gastric acid above the diaphragm that facilitates reflux.
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Not every patient with heartburn has reflux disease.
- 60-70 % of patients with typical reflux symptoms will not have mucosal disease.
- symptoms are still caused by reflux, but it is not really GERD as there are no mucosal lesions, leading to non-erosive reflux disease (NERD).
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Causes of heartburn
- most commonly caused by reflux
- other illnesses that are clearly less frequently, such as infections like Candida albicans, CMV or Herpes virus.
- patients who do not take pills with adequate amounts of fluids will have them lodge in the distal esophagus to cause inflammation and heartburn.
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pyrosis does not always mean injury or inflammation of the mucosa
- up to one third of healthy volunteers experience esophageal distension as heartburn
- the availability of effective acid-lowering medications has changed the landscape of reflux disease.
Evaluation of the Patient with Heartburn:
Historical Features
- evaluation of the patient with heartburn
- most frequently described as/Some patients describe heartburn as/
- The symptom is almost never described as/
- The severity of the heartburn/
- The typical patient with heartburn has the symptom/
- exacerbations
- Heartburn is often relieved by/
-
evaluation of the patient with heartburn
- most frequently described as a burning or hot sensation that is located in the midepigastrium near the xyphoid process or over the lower half of the sternum.
- Some patients describe heartburn as a “sour stomach” or “indigestion”.
- The symptom is almost never described as a sharp, crampy or squeezing pain.
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The severity of the heartburn does not predict the severity of the underlying pathological process.
- The typical patient with heartburn has the symptom intermittently.
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exacerbations
- Most are related to practices by the patient that intensify esophageal inflammation or promote gastroesophageal reflux.
- Smoking cigarettes or drinking alcohol promotes reflux by decreasing the force of closure of the lower esophageal sphincter.
- Eating large, fatty meals increases reflux by multiple mechanisms.
- First, overeating increases the pressure gradient from the stomach to the esophagus.
- The result is increased reflux across the lower esophageal sphincter.
- Second, fats entering the duodenum decrease the force of closure of the lower esophageal sphincter and decrease the rate of gastric emptying.
- Finally, gastric distension increases the spontaneous relaxations of the lower esopahgeal sphincter.
- First, overeating increases the pressure gradient from the stomach to the esophagus.
- Coffee and spicy foods and citrus juices also increase heartburn.
- When the patient is recumbent, reflux episodes may increase because gravity no longer counteracts the retrograde flow of intragastric contents across the lower esophageal sphincter.
- vomiting
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Heartburn is often relieved by
- avoiding aggravating factors
- buffering agents like milk or antacids
- drinking water which presumably works by diluting and clearing acid from the distal esophagus.
Evaluation of the Patient with Heartburn:
Associated Symptoms and Illnesses
-
Dysphagia
- indicative of a complication arising from gastroesophageal reflux.
- may have mechanical lesions of the esophagus like esophageal cancer, peptic stricture or Schatzki’s ring.
- Chronic gastroesophageal reflux may also give rise to esophageal motor abnormalities that are known to produce dysphagia.
- odynophagia (painful swallowing) most often indicates severe focal inflammation in the form of erosions or ulcers of the esophagus.
- The coexistence of heartburn and respiratory symptoms, like chronic cough, hoarseness, laryngitis, asthma or recurrent pneumonias, should alert the clinician to the possibility that these symptoms are caused by gastroesophageal reflux.
- patients may describe cardiac problems as heartburn
Evaluation of the Patient with Heartburn:
The Therapeutic Trial as a Diagnostic Test
- therapeutic trial with one of the proton pump inhibitors
- ?
- These agents/
- Failure of the therapeutic trial suggests/
- This approach should only be employed/
- Concurrent symptoms/
- Diagnosis of GERD
-
therapeutic trial with one of the proton pump inhibitors
- simplest, safest and most cost effective way to determine if heartburn is caused by gastroesophageal reflux
- These agents significantly inhibit acid production in the stomach.
- Failure of the therapeutic trial suggests that the symptoms do not arise from acid reflux
- This approach should only be employed if the patient presents with simple heartburn only.
- Concurrent symptoms like dysphagia, odynophagia or chest pain are indicative of more serious problems
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Diagnosis of GERD
- Typical symptoms (pattern recognition).
- Diagnostic trial with proton pump inhibitor in patients with uncomplicated GERD.
Evaluation of the Patient with Heartburn:
Endoscopy in the Evaluation of the Patient With Heartburn (p.31)
- Endoscopy
- the best way to determine/
- able to identify/
- a visually normal appearance to the esophageal mucosa does not rule out/
- the diagnosis of gastroesophageal reflux should be based on/
- tests are primarily indicated in individuals with/
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Endoscopy
- the best way to determine if heartburn is due to reflux and complicated by mucosal injury (esophagitis).
-
able to identify
- obvious signs of esophageal inflammation, like esophageal ulcers or erosions,
- subtle inflammatory changes of the esophageal mucosa that are not seen with other methods like the barium swallow.
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a visually normal appearance to the esophageal mucosa does not rule out gastroesophageal reflux as the etiology for heartburn, as patients may experience symptoms due to acid reflux but do not have mucosal injury,
- a scenario that accounts for 60-70 % of patients with typical reflux symptoms (NERD).
- the diagnosis of gastroesophageal reflux should be based on symptoms rather than testing
- tests are primarily indicated in individuals with atypical symptoms or potential complications.
Evaluation of the Patient with Heartburn
- Ambulatory Intraesophageal pH Monitoring (p.33)
- ?
- performed by/
- identifies patients with/
- does not prove that/
- The diagnosis of esophagitis requires/
- symptom severity/
- ambulatory pH monitoring should not be considered/
- Barium Swallow (p.32)
- provides information about/
- usefullness / sensitivity
- documents/
- Ambulatory Intraesophageal pH Monitoring
- a simple method that quantifies esophageal acid exposure.
-
performed by placing the probe into the distal esophageal lumen.
- The pH electrode is attached via a nasal tube to a recording device or transmits information via radio waves to records intraesophageal pH values for 24 – 48 hours.
- Standard analytical methods display the intraesophageal pH over the recording time and allow to correlate acid exposure to symptoms or precipitating factors.
- identifies patients with abnormal gastroesophageal reflux,
- does not prove that these patient have esophagitis.
- The diagnosis of esophagitis requires demonstrating the presence of inflammation of the esophageal mucosa.
- symptom severity does not necessarily correlate with the amount of esophageal acid exposure.
- ambulatory pH monitoring should not be considered a first line test for the evaluation of heartburn.
- Barium Swallow
- provides information about significant structural changes within the esophagus.
- useful, but lower sensitivity than endoscopy in the recognition of mucosal lesions.
- documents the presence and extent of a hiatal hernia.