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Flashcards in Larynx, pharynx, trachea Deck (16):

Anatomy: pharynx

  • Boundaries:
    • Base of tongue
    • Retropharyngeal wall
    • Caudal extent of hard palate and the epiglottis
  • Divided into oropharynx and nasopharynx and separated by soft palate
  • A region; bounded by discrete structures
  • Function--compresses bolus and with the tongue forces the bolus into the esophagus


Anatomy: larynx

  • Cartilages:
    • Esophagus
    • Thyroid
    • Cricoid
    • Arytenoid
  • Hyoid apparatus


Radiographic anatomy: pharynx/larynx views

  • Many structures involving the larynx and pharynx can be identified on well-positioned and properly exposed radiographs
  • Lateral view is most helpful
  • In the VD view most structures are superimposed on the cervical spine (not helpful)


Pharynx/larynx: Mineralization

  • Difficult to discern laryngeal structures in animals 2-3 months old due to lack of mineralization
  • Mineralization of all laryngeal structures is a normal aging change--seen as early as 1-3 years, occurs even earlier in large breeds
  • Cricoid cartilage is 1st to become mineralized


Pharynx/larynx: positioning and patient characteristics

  • Obesity reduces air in the region--less contrast and increased difficulty interpreting lesions
  • In neutral position in a lateral radiograph, the larynx is ventral to and ends at the level of C1 and C2
  • Head position can greatly influence laryngeal position


Pharynx/larynx: Incidental findings

  • The depth and phase of respiration will also effect position of laryngeal structures
  • Basihyoid bone and other hyoid bones (due to rad. positioning) are often mistaken for a foreign body


Clinical manifestations of pharyngeal and laryngeal lesions

  • Dysphagia
  • Inspiratory dyspnea
  • Stridor
  • Change in the voice


Tracheal anatomy

  • Tubular semi-rigid midline structure
  • Attached at larynx and carina
  • Held in position by mediastinum and neck muscles
  • Slightly more moveable in the cranial mediastinum


Radiographic anatomy: trachea

  • Easiest to evaluate on lateral view
  • Use VD to assess displacement
  • Thoracic trachea found on the right of the mediastinum
  • Deviation to right is exaggerated in obese and brachycephalic breeds--do not mistake this for a mediastinal mass
  • Slight divergence of the trachea from the spine in the normal dog
  • Trachea may angle slightly ventrally at the caudal extent and into the carina
  • In normal animals the trachea diameter does not vary significantly during respiration


Trachea: mineralization

  • Mineralization of the tracheal rings is a normal, degenerative or aging process
  • Seen in large breeds, chondrodystrophic breeds, and in young dogs with no clinical sig.
  • May increase with metastatic mineralization


Trachea: radiographic positioning

  • In a lateral view, the neck must remain in a neutral position
  • Extension results in compression and narrowing of trachea at the thoracic inlet
  • Flexion results in a bend in the cranial mediastinum--may result in a false diagnosis of a cranial mediastinal mass


Clinical manifestations and lesions of the trachea

  • Cough--"honking"
  • Dyspnea
  • Common lesions
    • Tracheal displacement
    • Neoplasia
    • Hypoplasia (congenital in English bulldog)
    • Tracheitis--no rad signs
    • Tracheal collapse


Tracheal displacement

  • Reliable sign of a mass lesion
  • In the cervical regions the masses have to be large to result in displacement
  • Larger lesions will result in compression of the trachea
    • Heart enlargement
    • Cranial mediastinal and tracheobronchial lymph nodes
    • May originate within the trachea


Tracheal neoplasia

  • Uncommon
  • Osteochondromas and carcinomas are most frequent in the dog and cat
  • Produce clinical signs of airway obstruction
  • Appear as masses within the lumen
  • Other differential diagnoses include polyp and abscessation 


Tracheal collapse

  • Dynamic in nature
  • Diameter varies with resp. cycle
  • Toy breeds predisposed; weakening in tracheal rings
  • Dynamic narrowing occurs in cervical trachea (thoracic inlet) during inspiration 
  • Dynamic narrowing occurs in thoracic trachea (carina) during expiration
  • To evaluate trachea, films must be taken at inspiration and expiration
  • Often coughing exaggerates the lesion
  • Inducing a cough while performing flouroscopy may be required to demonstrate the lesion


Pitfalls (trachea)

  • Redundant trachealis dorsalis membrane
  • Draping esophagus