The Hyoid, Larynx And Swallowing Flashcards
What is the role of the hyoid apparatus
The hyoid apparatus suspends
the tongue and larynx from the
base of the skull.
Articulation of the hyoid apparatus
Dorsally it articulates with the petrous
temporal bone just caudal to the
tympanic bulla, and ventrally it
articulates with the larynx.
Muscles of hyoid apparatus
Sternohyoideus - draws hyoid caudally– cervical nerves
Thyrohyoideus – draws hyoid caudally - cervical nerves
Mylohyoideus – draws hyoid rostrally – trigeminal
Geniohyoideus – draws hyoid rostrally – hypoglossal
What is the larynx
The larynx is a cartilaginous and muscular tube suspended from the skull by the hyoid apparatus. Some of the cartilages are mobile and so the shape and calibre of the passage may be altered.
Roles of the larynx
The primary role of the larynx is to protect the lower respiratory tract from foreign bodies.
The secondary role is phonation – voice production
Airway components
1.The vestibule;
The rostral funnel shaped part. The entrance to the vestibule(from the
common pharynx) is called is called the laryngeal aditus. It is roughly circular in shape.
The ventral floor of the opening is the epiglottis, the roof the arytenoid
cartilages and the lateral aspects the aryepiglottic fold (that joins the epiglottis to the arytenoids.
- The Glottis ;
this forms a narrow vertical slit. Strictly speaking the glottis forms the wall of
the slit – the actual airway is called the rima glottidus. The walls are formed by ventrally,
the paired vocal folds, and dorsally the arytenoid cartilages - The infraglottic cavity;
This is relatively wide and runs from the glottis to the trachea
Cartilages of the larynx
4 main cartilages
1.Thyroid – unpaired – verylarge, articulates with the cricoid
2.Epiglottis – unpaired – forms spout like entrance to the larynx
3.Arytenoid – paired – can widen or narrow glottis
4.Cricoid – unpaired – shaped like a signet ring
THE DIFFERENT MUCOSAL FOLDS IN THE LARYNX
Vestibular fold – marks caudal end of vestibule
Vocal fold – vocal cord – responsible for
vocalisation
Aryepiglottic fold - - from epiglottis to arytenoid.
Laryngeal muscles
8 pairs :
•7 pairs - close the glottis
• 1 pair – opens glottis
•Vary the tension on the vocal cords
Of importance;
Cricoarytenoideus dorsalis – abducts the arytenoids and opens the
glottis. This is the only muscle to do this.
Cricoarytenoideus lateralis – one of several muscles that close the glottis
Laryngeal muscles innervation
-recurrent laryngeal nerve except cricothyroid muscle innervated by the cranial laryngeal nerve
Nerve supply to the larynx
The vagus accessory complex X-XI.
-cranial laryngeal nerve-contains autonomic afferents, visceral efferent and special visceral efferents
-recurrent laryngeal nerve-autonomic efferent, left recurrent laryngeal, right recurrent laryngeal
How does the swallowing reflex work
Afferents-glossopharyngeal and vagus nerves are responsible for the part of the afferent innervation which initiates swallowing
Efferents-vagus-accessory complex, via the pharyngeal nerve of the vagus, supplies the motor pathways to all the pharyngeal muscles except the styolopharyngeus which is supplied by glossopharyngeal nerve
BOAS
-stenotic nares (narrow nares)
-abnormal shape or position of nasal turbinates
-extra long soft palate
-tracheal collapse
-hypoplastic (narrow) trachea
-everted laryngeal saccules (deep blind ending pockets)
Dorsal displacement of soft palate in horses
-should lie ventral to the epiglottis
-when it sits above the epiglottis, it is inhaled into the larynx causing coughing/gurgling and effecting performance
-tie forward, induction of palatal fibrosis, staphylectomy
Recurrent laryngeal neuropathy
Unilateral paralysis of the LEFT arytenoid
cartilage, caused by failure of the left cricoarytenoideus dorsalis muscle to
contract (and therefore fail to abduct the left arytenoid cartilage).
