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Dysphagia > HC 2 Physiology > Flashcards

HC 2 Physiology Flashcards

1
Q

Explain the “chambers” and “sphincters” in this part of the alimentary tract.

A

Oral cavity + oropharynx + esophagus = a series of expanding and contracting chambers, divided by muscular sphincters: m. orbicularis oris, soft palate & UES

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2
Q

How is the propulsion of the bolus towards the stomach being established?

A

It’s a result of

  • forces or positive pressure developed behind the belous
  • vacuum or negative pressure developed in front of the bolus
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3
Q

Which phases do we see in the act of deglutition?

A
  1. preparatory phase
  2. oral phase
  3. pharyngeal phase
  4. esopagheal phase
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4
Q

Explain the preparatory phase. What is done? Where? Voluntarily or involuntarily?

A
  • Preparation of the bolus:
  • mastication
  • mixing with saliva
  • dividing for transport
  • voluntary, can be interrupted at any time
  • in the first chamber of the swallowing system: the oral cavity, between orbicularis oris (1st sphincter) and soft palate (2nd sphincter)
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5
Q

Which facial muscles, tongue muscles and mastication muscles play a role in the bolus preparation?

A

* facial muscles: maintaining bolus on the the tongue and between the teeth:

  • buccinator: contraction to keep bolus between teeth, to prevent food from pooling in the cheek pockets
  • orbicularis oris: prevent spilling from mouth corner

* tongue muscles: movement & positioning of the bolus

  • intrinsic muscles: alter shape and tone of the tongue
  • extrinsic muscles: movement of the tongue (up, down, left, right,…)
  • sensory function: information about the bolus size/consenstency,…

° mastication muscles: masseter, temporatlis, pterygoideus lateralis, pterygoideus medialis

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6
Q

Explain the position of the tongue and soft palate during preparatory and oral phase. Why?

A

1. preparatory phase: to keep the bolus from escaping prematurely into the pharynx:

  • posterior part tongue up against soft palate
  • soft palate pushes downward

2. oral phase: to close off the nasopharynx and open the pharynx

  • top of the tongue on the superior alveolar ridge behind maxillary central incisors
  • voluntary opening pharynx: posterior part tongue depresses, soft palate elevates
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7
Q

Explain the importance of saliva

A
  • mucous: lubricates the bolus
  • enzyme for digestion
  • dilutes the bolus
  • maintaining healthy oral tissues

=> 1-1.5 liter per day

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8
Q

Explain the oral phase. What is done? Volutary or involuntary?

A
  • propulsion of bolus from oral cavity to pharynx
  • start = voluntary
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9
Q

What muscles are involved in the oral phase and why?

A
  • levator veli palatini: elevation soft palate => close nasopharynx (to avoid bolus going upward into nasopharynx, to avoid escape of air pressure), open pharynx
  • hyoglossus + styloglossus: depression posterior tongue => open pharynx
  • pharyngeus constructor superior: more forceful closure of the nasopharynx
  • orbicularis oris + buccinator: maintain oral air pressure
  • mylohyoid: early hyoid elevation as a preparation to the pharyngeal phase
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10
Q

Explain the pharyngeal phase. What is done? Voluntary or involuntary? Biggest challenge?

A
  • passage of food through the pharynx into the esophagus
  • involuntary and irreversable mechanism
  • challenge: coordination of respiration and swallowing
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11
Q

When does the pharyngeal phase start and end?

A
  • onset:
  • tongue -> bolus into oropharynx
  • mandibular muscles stabilize tongue base
  • mandible closed
  • pharynx elevates + contracts = descending peristaltic wave
  • end:
  • soft palate and hyoid return to original position
  • larynx is reopened for respiration
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12
Q

Explain the mechanism in which the bolus is driven from the oropharynx into the PE segment

A

Oropharynx closed at time of bolus passage

+ pressure of tongue

+ contraction pharyngeal walls

=> tongue driving force that drives the bolus downwards

SIMULTANUOUSLY:

  • suprahyoid muscles pull hyoid and larynx up and forward => hypopharynx expands => pressure decreases in PE segment => bolus is sucked into PE segment
  • gravity
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13
Q

Which mechanisms protect the airway during swallowing? In what phase of the swallowing act?

A

In the pharyngeal phase:

  • hyoid and larynx rise + pulled forward
  • closure of vocal folds
  • epiglottis folds down (because of 1. elevation hyoid and larynx and 2. contraction of thyrohyoid muscles)
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14
Q

How does the larynx protect the airway?

A

From below upward:

  1. true vocal folds
  2. vestibular folds
  3. lower vestibule
  4. upper vestibule
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15
Q

What systems are needed to open the PES?

A
  1. laryngeal elevation (elevate cricoid and thyroid cartilages)
  2. bolus driving forces
  3. cricopharyngeal relaxation (inhibition of tonic contraction of PE segment) by brainstem
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16
Q

The oropharyngeal phase is a complex sequence of ….? How is it triggered and controlled?

A

… excitatory and inhibitory events, less then 1 sec.

Triggered and controlled by a group of neurons in the reticular formation of the brainstem = “central pattern generator” = drives a sequence of complex and repetitive movements

17
Q

In which systems is the central pattern generator divided?

A
  1. afferent input system: sensory signals from receptors in the muscles and mucosa of the pharynx to the generator
  2. efferent system corresponding to the motor outputs: excitatory and inhibitory signals to the muscles of the oropharynx
  3. organizing system
18
Q

Explain the afferent input to the central pattern generator

A

= 3 cranial nerves provide peripheral sensory feedback: trigeminal, glossopharyngeal, vagus (SLN superior laryngeal nerve)

  • stimulation of sensory receptors in pharynx by the posterior movement of the bolus initiates the involuntary pharyngeal phase
  • this afferent input modulates the central network activity: the swallowing muscle sequence is the same, but is adapted to bolus constistency and size
19
Q

What is thought to initiate the involuntary pharyngeal phase?

A

Stimulation of sensory receptors in the pharynx by the posterior movement of the bolus

20
Q

What is the nucleus tractus solitarius?

A
  • in brainstem
  • all afferent fibers involved in initiating or facilitating swallowing converge here
  • fibers of glossopharyngeus (IX) and SLN (X)
21
Q

Why do scientist think that also higher cortical input influences the coordination of swallowing by the central pattern generator?

A
  • many of the neurological disorders do not involve the brainstem
  • swallowing can be initiated voluntarily (dry swallow) without stimulation of the pharynx by a bolus

=> a widespread network of brain regions (cortex, subcortex, insula, cerebellum) participate in the control of swallowing

22
Q

Which cranial nerves contain the main motor nuclei of the brainstem?

A
  • hypoglossal (XII) -> tongue muscles
  • ambiguus (X) -> larynx, pharynx, esophagus
23
Q

What are brainstem interneurons?

A
  • Connect sensoric input and motoric output (programming and coordination)
  • Connect multiple areas of the brainstem and other areas in CNS => integration of swallow and airway-protective reflexes
24
Q

Explain the esophageal phase. What is done? Voluntary or involuntary? How is it modified?

A
  • bolus transported down the esophagus into the stomach
  • involuntary
  • peristaltic wave of contraction: variable speed and strength based on sensory feedback (bolus characteristics)
25
Q

What’s the difference between primary and secondary wave?

A
  • primary = normal starting wave, starting from top
  • secondary = peristalsis without a preceding oropharyngeal phase, in response to stimulation of esophageal sensory receptors (e.g. due to bolus size)
26
Q

Explain the neural control of the esophagus

A
  • smooth muscle contraction controlled by autonomic nervous system
  • striated muscle contraction controlled by the motonuclei of the brainstem (nucleus ambiguus, n. X)
  • excitatory and inhibitory input to the muscles
27
Q

Which cranial nerves are involved in sensory/motor input/output during swallowing?

A

zie ‘nerves swallowing act’

Dysphagia (10 decks)

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