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Dr Bill Rosenblatt DVM from tufts is here doing a residency in dentistry 
and will be available to help us in lab.

the hyoid apparatus is integral to the support of the larynx and the 
tongue. the tongue is suspended by the basihyoid bone.
the hyoid apparatus is connected to the mastoid process of the skull.

when we look at our sectioned heads we'll see the cut edge of the 
basihyoid bone. then we should be able to palpate the thyrohyoid bone 
going back to the larynx. 

laryngeal paralysis: in horses: roaring. the larynx isn't working 
normally.
we used to have a whole lecture on the larynx and we don't anymore and so 
now we'll try to cover it here. 

COMMON PHARYNX: region where nasal passage and oral cavity passageways 
"cross over".

nasopharynx
oropharyx

the EPIGLOTTIS covers the opening from the oral cavity to the pharynx so 
food can't get into the airway. when the animal swallows, the food bolus 
pushes the epiglottis back to simply cover the trachea

larynx
aka voicebox

the larynx is made of a bunch of specialized cartilages that have 
developed from tracheal type cartilage. there is a thyroid cartilage, and 
epiglottic cartilage, a cricoid cartilage. there are synovial joints 
where cricoid cart touches thyroid cartilage but those are not 
functonally important. there is a more important synovial joint where the 
arytenoid cartilages articulate with the cricoid cartilage. so if you 
look down the airway you see the thyroid cartilage as a U with the 
cricoid cartilage and the arytenoids in front of it - the GLOTTIS. the 
arytenoids open and close along with the epiglottis as a backup mechanism 
to keep food out of the trachea.

from the tips of the arytenoids is a membrane that connects them to the 
thyroid cartilage

there is a paired muscle dorsal to the cricoid which inserts on the 
arytenoids which pulls the dorsal ends of the arytenoids together, which 
separates the ventral ends and opens the airways. this is the 
cricoarytenoideus dorsalis muscle. the antagonistic muscle is the 
cricoarytenoideus lateralis. it pulls the top of the arytenoids apart and 
the bottom together and closes the airway. this is important in the 
swallowing mechanism. the dorsalis muscle is important to the breathing 
process. this muscle is sometimes paralyzed secondary to a nerve problem, 
often of unknown origin.

two LARYNGEAL NERVES. a cranial laryngeal and a caudal laryngeal nerve. 
the caudal laryngeal is also called the recurrent laryngeal nerve. the 
recurrent laryngeal nerve travelled with the carotid sheath as you may 
(or may not) recall.

the caudal innervates the dorsalis, and the cranial innervates the 
lateralis. the caudal one is more exposed to possible damage, because it 
goes all up the neck. and in fact this is the nerve that has the most 
problems.

look at p 279 fig 98 of small miller
p 278 don't bother dissecting out the muscles of the first paragraph.
realize this is a complex region. 

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