swallowing mechanism

8/13/2019 swallowing mechanism

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Mechanism Of Swallowing

Learning Objectives:

At the end of the lecture, the student should be able to:

•

Define Swallowing.• Describe the anatomy of the swallowing mechanism.

• Explain the deglutition process.• Stages of swallowing.

• Coordination of swallowing and respiration.• Mechanism of swallowing.

• Swallowing reflex.

igestive S!stem:

Organ s!stem that processes food extracts nutrients from it and eliminates the residue.

igestive "rocesses:

• #ngestion.

• "ropulsion.

• igestion.

– Mechanical digestion.

– $hemical digestion.

• Absorption.

• efecation.



Swallowing:

• The term swallowing refers to:

– Entire act of deglutition from placement of foodin mouth,

–

Manipulation of food in oral caity, – oral, pharyngeal and esophageal stages of

swallowing until food enters stomach.

Anatom! of the swallowing mechanism:

• %he anatomic area of swallowing mechanismconsists of the oral cavit!, phar!nx, lar!nx andesophagus.

Mechanism Of Swallowing:

• A complicated mechanism, principall!because phar!nx subserves respiration as

well as swallowing.• "har!nx is converted for onl! a few

seconds at a time into a tract forpropulsion of food.

• &espiration not to be compromisedbecause of swallowing.

"h!siolog! of swallowing mechanism:

Swallowing is composed of four distinct phases:

'( Oral preparator! phase,) ( Oral phase,* ( "har!ngeal phase+ ( sophageal phase.



• uration and characteristics of these phases are highlydependent on: – -olume and t!pe of the food – -oluntar! control on swallowed bolus.

• Some types of swallow do not involve all phases,

– /or example swallowing salia in pharynx does not includeoral preparatory and oral phases of swallow.

"h!siolog! of eglutition 0Swallowing1:

• Moving bolus from mouth to stomach:

– !acilitated by salia, mucous secretions.

– "noles mouth, pharynx, and esophagus.

• 2uccal phase:

– #oluntary. – Moes bolus to oropharynx.



Oral "reparator! "hase:

• !ood is prepared for swallowing and then transported to the pharynx.

• $ preparatory phase in which the food is held within the mouth whilethe base of the tongue and the soft palate close the oral caity posteriorly to

preent food spilling into the open larynx and trachea.

%he oral phase:

• $ bolus is formed in the central portion of the tongue and then pushed

posteriorly toward the pharynx with an anterior%to%posterior tongue eleation.

• $s the bolus enters the pharynx the actual swallow or phar!ngeal reflexis triggered.

"har!ngeal phase:

• A reflex action.

• 2olus passes through phar!nx 3uic4l! and then enters esophagus.

•

%his ta4es place in less than a second.

• #nitiation of this process starts when the bolus passes the anteriorfaucial arch and reaches the posterior phar!ngeal wall.

• levation of soft palate prevents material from enteringnasal cavit!.

• %his stage is followed b! phar!ngeal constrictor musclespushing bolus further into the phar!nx, toward cricophar!ngealsphincter.

• Lar!nx prevents material from entering trachea b!respectivel! closing the true vocal cords, false vocal folds, andar!epiglottic folds.

• $ontraction of lower phar!ngeal constrictor is followed b!relaxation of the cricophar!ngeal muscle, allowing the bolus topass into the esophagus.



*.sophageal stage

&pper esophageal sphincter closes

'astroesopaheal sphincter opens

Esophagus controls inoluntary peristaltic moement

Epiglottis reopens

(olus moes from esophagus to stomach.

• This phase begins when the bolus enters the

esophagus at &ES. Then, peristaltic waes of esophagus pushthe bolus se)uentially downward until it reaches the *ES andenters the stomach.

• This phase lasts from + to - seconds. "n the

esophageal phase, the epiglottis returns to its rest positionand the airway opens while the esophageal peristalsismoement continues.

$oordination of swallowing and respiration:

• Swallowing and respiration are reciprocal functions, i.e., respiration halts apnea

periods/ during the pharyngeal phase of a swallow.

• During oral preparatory, oral and

esophageal phases, airway is entirely open.

• Coordination of respiration and

swallowing is crucial for a normal swallow andany mismatch results to aspiration.

• "n the predominant pattern ofcoordination, swallow interrupts exhalation andsub0ect returns to exhalation at end of theswallow.

• Exhalation at the end of the swallow

clears the larynx and pharynx form smallresidues of materials and preent them fromentering the airways.

/lowchart showing 5ormal 2reath Swallow "attern.

Mechanism of swallowing:

• Multiple sensory and motor systems must function to assure asmooth swallowing process.

• li)uid or food has to be perceied in the mouth.

• tongue directs contents into bac1 of the mouth pharynx/.

http://www.latrobe.edu.au/hcs/resources/copdsp/long_descriptions.html#normal_swallow_pattern

http://www.latrobe.edu.au/hcs/resources/copdsp/long_descriptions.html#normal_swallow_pattern



• $t this point, simultaneously, breath must be held, the wind pipe%%which is in front ofthe food pipe%%has to close off to preent aspiration, and muscles of pharynx hae tocontract to propel the food into the esophagus.

• as food is in esophagus, the windpipe has to open up again and breathing has toresume.

• This delicate interplay between the

respiratory systems and thedigestie system re)uires perfecttiming and synchrony of eents topreent cho1ing, regurgitation,aspiration, asphyxia, omiting .

• Soft palate and uula raise.• 2yoid bone and larynx eleate.• Epiglottis closes off top of trachea.• *ongitudinal muscles of pharynxcontract.• "nferior constrictor muscles relaxand esophagus opens.• 3eristaltic waes push foodthrough pharynx.

Mechanism of swallowing:

• Central nerous system controls for both mechanisms are in thebrain stem.

• modulated by higher centers scattered throughout the midbrainand the cortex of the brain.

• Smooth operation of the process re)uires at least a relatielyhealthy brainstem.

Swallowing disorders 0Dysphagia 1

Dysphagia:

• Difficulty in swallowing.• May also experience pain while swallowing.• Some people may be completely unable to swallow or mayhae trouble swallowing li)uids, foods, or salia.

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swallowing mechanism