physiology of pharynx
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Physiology of pharynxDr Manpreet Singh Nanda
Associate Professor ENTMMMC& H Solan
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Functions of PharynxDeglutitionRespirationVocal resonanceSecretion of mucus by mucous memebrane to
lubricate the pharynxProvides drainage to nose, oral cavity, middle
ear
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Functions of NasopharynxAirway for passage of air into larynx, trachea
and lungsHearing – middle ear ventilation, maintains
air pressureResonance for voice productionDrainage for nasal and nasopharyngeal
secrtetionsPrevents aspiration (Nasopharyngeal isthmus
closes during, swallowing, vomiting, speech..
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Functions of OropharynxCommon conduit for air and foodDeglutitionVocal resonanceTaste sensation (tongue base, soft palate,
anterior pillar, posterior pharyngeal wall)Local defence and immunity (Waldeyer’s
ring)
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Functions of tonsils and adenoidsImmunity against bacteria, virus.... By T
Lymphocytes in parafollicular regionBarrier to infection (protective sentinels)Ig A antibody production by B Lymphocytes
in folliclesFirst 5 years life later atrophy
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Functions of LaryngopharynxCommon conduit for air and foodVoice resonanceDeglutition
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DeglutitionProcess of propulsion of bolus of food from oral cavity
into stomach through oropharynx controlled by neuromuscular activity
It also disposes dust and bacteria laden mucusCauses pharyngeal opening of E.T to establish equal
pressure on both sides of T.MPhases – 1. Oral – voluntary – 1 second2. Pharyngeal – both – 1 second3. Oesophageal – involuntary – 8 to 20 second..Swallowing center in Medulla near nucleus of Vagus N
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Oral PhaseFood chewed Lubricated with salivaConverted into bolusHeld between tongue and palateTongue elevated against palate (myelohyoid)Food propelled into oropharynxVOLUNTARY 1 SECOND
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Pharyngeal PhaseReflex actions1. Closure of Nasopharyngeal isthmus (Soft palate raised
against passavants ridge)2. Closure of Oropharyngeal isthmus (Palatoglossus muscle)3. Closure of Laryngeal inlet (contraction of aryepiglottic folds)Contraction of pharyngeal constrictors -> bolus pushed to
cricopharyngeal sphincter Relaxation of cricopharyngeus muscle (Fall in pressure) -> food
passes into oesophagusMIXED PHASE 1 SECONDNOTE – During swallowing rise in pressure of 40 mm Hg
pressure at pharyngo oesophageal junction which falls leading to relaxation of sphincter and it opens.
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Oesophageal PhaseClosure of cricopharyngeal sphincterPrimary peristalsis of oesophagus (contraction of
circular muscles)Food moves downRelaxation of gastro oesophageal sphincter and
opens (X CN)Food enter stomachSphincter closesNote –Secondary peristalsis is due to oesophageal
distension (aeurbachs plexus)INVOLUNTARY 8 – 20 SECONDS
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NEURAL CONTROLCN V and XII – Chewing and tongue
movementCN VII – Taste (chorda tympani), Sensory to
oral cavity (Nervus Intermedius), Motor to Orbicuilaris oris
CN IX – Taste, PharynxCN X – Taste, Larynx, Laryngopharynx
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Sounds during swallowingHeard by auscultation over neck1st Sound – AT COMMENCEMENTDue to fluids acting on post pharyngeal
wall......2nd Sound – bubbling or trickling noiseAfter 4 – 10 seconds and continue 2-3
seconds
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Thirst sensationPHARYNGEAL COMPONENTDehydration -> Decreased salivary secretions
-> Dry pharyngeal mucosa -> stimulation of sensory receptors (IX X CN)
CENTRAL COMPONENT (EXTRAPHARYNGEAL OR THIRST DRIVE)
High intake of salt and low water intakeIV hypertonic salineIntercellular dehydration -> Thirst......
(Hypothalamus)
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DysphagiaDifficulty in swallowing due to obstruction or
interference to food passage Odynophagia – pain during swallowing Causes of odynophagia – infectious oesophagitis
due to bacteria, virus and fungi, corrosive injury, ulcers and inflammation
Symptoms – Throat discomfort, FB sensation, coughing, choking, regurgitation, heart burn, aspiration........
Causes – oral, pharyngeal, laryngeal, oesophageal, neck, CNS, CN, psychosis
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Oral causesDisorder in mastication – trismus, tumour,
TM jointDisorder in lubrication – salivary glandDisorder in tongue mobility – paralysis, ulcer,
tumourTrauma, buccal ulcers, infection
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Pharyngeal causesNeurological – brainstem lesions, multiple
sclerosis, myasthenia gravisMuscular – myopathy, hypothyroidismUES dysfunctionStructural – malignancy, surgeryInflammatorySpasmodic – tetanus, rabiesParalytic – palatal palsy
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Oesophageal causesMechanical obstruction- malignancy , peptic
stricturesLumen obstruction – FB, strictures, tumoursWall lesions – oesophagitisMotility disorders – achalasia, diffuse
oesophageal spasm, scleroderma
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External causesCervical – thyroid, cervical spondylosis,
tumours, lymphadenopathyThoracic – aneurysm of aorta, mediastinal
tumours, dysphagia lusoriaAbdominal – Hepatic enlargementDysphagia lusoria - .. Dysphagia due to
pressure on thoracic oesophagus due to vascular anomalies in chest like right aortic arch, double aorta, abnormal rt subclavian a..
Dignosis is by CT scan or angiography
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EvaluationHistoryAge – child congenital causes, 20 to 40 yrs achalasia, plummer
vinson > 40 yrsSex – plummer vinson – femalesOnset – sudden in FB or food impaction, gradually progressive
in malignancy, peptic strictures, intermittent in spasmsDuration – less in inflammation, more in benignMore for liquids – achalasiaSolids progressing to liquids – malignancy, stricturesIntolerance to acid food and fruit juices – ulcerHoarseness – laryngealRegurgitation and heart burn – hiatus herniaNasal regurgitation – palatal paralysis
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Aspiration into lungs – laryngeal paralysisPast history – diabetes, diptheria, poliomyelitis, FB
ingestion, globusNote – Any elderly > 2 weeks dysphagia – rule out
malignancyPlummer Vinson syndrome – females > 40 yrs,
anaemia, glossitis, koilonychia, splenomegaly, dysphagia more for solids
Achalasia – Males (mc), cardiospasm, regurgitation, more for liquids due to failure of relaxation of LES for passage of food
TO RULE OUT PSYCHIATRIC ILLNESS
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Physical examinationOral cavityOropharynxHypopharynxLarynxNeckChestCranial nervesCNS
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InvestigationsPan endoscopy – oesophagoscopy, laryngoscopy,
bronchoscopy, nasopharyngoscopyBarium swallow – along with fluoroscopy for malignancy,
achalasia, strictures, hiatus herniaX ray Neck – radio opaque FBChest Xray- CVS, pulmonary, mediastinal diseasesCT scan/ MRI – Neck and mediastinum, skull base Blood – haemogram (anaemia)Blood sugar – diabetesManometry and pH monitoring- GERD, acid induced
oesophageal spasmsThyoid scan , angiography
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TreatmentHydration – IV fluids, ryles tube feed, feeding
gastrostomy, jejunostomyTreat the causeMedical treatment for anaemia,
inflammation, trauma, aspiration pneumoniaSurgical treatment- fracture reduction,
resection, dilatation