Larynx Flashcards
Function of the larynx
- Involved in vocalization/phonation
- Protection of lower respiratory tract by closing at swallowing
- Closing the glottis for straining, defecation, parturition
Upper airway, nasopharynx, larynx
- Pharyngeal recess
- Opening of auditory tubes
- Laryngeal entrance
- Epiglottis
- Arytenoid cartilages
- Vocal folds
Parts of the larynx
- Entrance: laryngeal aditus
- Laryngeal vestibule
- Glottis (closes the larynx)
- Infraglottic cavity (in middle of cricoid cartilage)
Cartilage of the larynx
- Epiglottic cartilage
- Arytenoid cartilage
- Cricoid cartilage
- Thyroid cartilage
Epiglottic cartilage
Single, median, leaf-shaped, most rostral, elastic
Arytenoid cartilage
- Paired, pyramidal-shaped, irregular, mainly hyaline (firmer and can become ossified), but corniculate process is elastic
- Corniculate tubercle (covered in mucosa) attached to aryepiglottic folds
- Muscular process is major muscle attachment
- Vocal process is attached to vocal ligament
Dog arytenoid cartilage
Has an additional process called the cuneiform process
Thyroid cartilage
- Single, trough shaped, largest, a body and 2 lateral plates, hyaline (firm, can become ossified)
- Rostral processes connect with thyrohyoid
- Caudal processes connect with cricoid
- Caudal thyroid incisure is covered by ligament
Cricoid cartilage
Single, most caudal, signet ring-shaped, a seal (lamina) and an arch ventrally, hyaline (firm, can become ossified)
Position of larynx
- Larynx remains suspended from cranial base by hyoid apparatus
- Moves as hyoid and tongue move
Articulations of larynx
In dog, there are 2 synovial joints
1. Crico-arytenoid
2. Crico-thyroid
What is the most important joint for regulating glottic opening?
Crico-arytenoid
Ligaments and mucosa of the larynx
- Elastic ligaments hold cartilages together and to other structure
- Vestibular ligaments- less elastic
- Vocal ligaments- less elastic
**Mucosa covers them to make folds
Laryngeal ventricles
Outpouching of mucosa forms a ventricle called a diverticulum
- Present in horse, dogs, and pigs. Not in ox and cats.
Pigs also have median laryngeal recess which causes an issue when intubating pigs
Extrinsic laryngeal muscles
- Sternothyroideus
- Thyrohyoideus
- Pharyngeal muscles (thyropharyngeus & cricopharyngeus)
Intrinsic muscles nerve supply
- mostly by caudal recurrent laryngeal branch of vagus nerve
- only exception is crycothyroideus which is supplied by cranial nerve
Intrinsic muscles
- cricoarytenoideus dorsalis
- cricoarytenoideus lateralis
- arytenoideus transversus
- cricothyroideus
- thyroarytenoideus
Cricoarytenoideus dorsalis
- Abductor of vocal folds
- Only one that opens glottis
- Can result in roaring when opening does not occur properly
Cricoarytenoideus lateralis
o Adductor
o Closes glottis
Arytenoideus transversus
o Adductor
o Closes glottis
Cricothyroideus
o Lengthens/tenses vocal folds (course adjustment)
o Supplied by cranial nerve
Thyroarytenoideus
- Adjusts tension in vocal folds (fine adjustment)
- Is split into ventricularis and vocalis in dogs and horses
Roaring in horses
- damage to the caudal (recurrent) laryngeal nerve
**usually left side - results in flaccid vocal fold (inability to abduct) leading to narrowed airway and noise during exercise
- can be corrected by surgically removing or altering vocal folds so they remain abducted
**similar to debarking of dogs
Purring in cats
Involves fast twitching of laryngeal muscles and diaphragm
- air pressurecaudal to closed glottis increases until pressure exceeds the closure pressure of glottis. Allows a burst of air escaping then temporarily lowers pressure until air pressure builds again. Repeats over and over again
