----start 11.20.96----

tomorrow we'll hear dr dodson discuss the horse eye.
tomorrow on the schedule we're doing age determination but we're actually 
going to do that on friday. tomorrow and fri early we'll do the eye.

good landmark on these animals is the jugular vein, maxillary vein, 
linguofacial vein.

salivary glands: three major ones: parotid, mandibular, sublingual. the 
sublingual has two parts: the monostomatic and the polystomatic.

the parotid is somewhat triangular in shape and lies ventral to the ear 
in all of these animals. in the horse, goat and cow the parotid is VERY 
large. these animals may produce 10 gallons of saliva a day!

in the dog there is an egg shapped mandibular gland ventral and sl 
cranial to the parotid.

in the goat and horse the mandibular gland is more crescent shaped. the 
parotid may overlie the mandibular gland in these animals as well.
the duct of the mandibular gland courses cranially along the line of the 
mandible toward the mouth, opening in the sublingual caruncle.

the sublingual gland in the dog lies just rostral to the mandibular 
gland, closely associated with it, and it has a duct going along with the 
duct of the mandibular gland. that's the monostomatic part of the 
sublingual. the polystomatic part actually lies under the tongue and has 
multiple openings.

the goat has a monostomatic part and a polystomatic part as well

the horse really only has a polystomatic part.

the goat and horse have extra salivary glands, called the buccal glands. 
they are dispersed around the buccinator glands and look like muscle. 
there are several of them dispersed around the mouth and you should not 
try to distinguish between them and the sublingual monostomatic part in 
the goat.

don't place extra importance on these things. dr orsini remarked that 
perhaps we spent too much time discussing them, didn't mean to make them 
seem more important than they are.

digastricus muscle in the dog went from the paracondylar process of the 
occipital bone to the caudal part of the mandible. it has a caudal and 
cranial belly - caudally its innervated by VII (facial) and cranially by 
V(trigeminal). this is the only muscle that opens the mouth. masseter, 
temporalis, and pterygoids close the mouth.

in the horse you can really see the different bellies, and they are 
joined by a tendon - much more distinct separation than in the dog. also 
in the horse there is an additional part of the digastricus coming off 
the caudal edge of the mandible, and this is the occipitomandibular part 
of the digastricus. this part is also innervated by VII.

diagram- horse head showing hard/soft palate, trachea, 
esophagus...pharyngeal regiion.

in the dog we saw a small slit: opening of auditory canal/eustachian 
tube. in the horse the auditory tube (which goes from nasopharynx to the 
middle ear)(and which equalizes pressure within the middle ear) is 
actually quite large. 

think about it. swallowing, chewing, opens this tube, and helps to 
equalize the pressure.

in the horse is a specialization called the guttural pouch. this is a 
diverticulum off the ventral aspect of the auditory tube.

recall sternomandibularis comes up from the chest and inserts on the 
caudal portion of the mandible. also the lingualfacial vein is in this 
region. recall Viborgs triangle bounded by lingualfacial vein, mandible, 
and sternomandibularis. if you go in surgically within the triangle, you 
will get into the ventral aspect of the guttural pouch, and you can drain 
it if infected. coursing dorsally to the guttural pouch is the internal 
carotid artery. if fungal infection gets rampant in the pouch,  (guttural 
pouch mycosis) it can eat through the membrane and then eat the wall of 
the carotid artery causing the horse to exsanguinate into the pouch and 
out through the nose.

now, why does the horse have this big huge pouch? see smallwood. the 
medial aspect of the pouch is thin membrane opposing the medial aspect of 
the other pouch, so you could open both pouches from one side. there are 
many important structures that go dorsal to the pouch as well. note the 
lateral part and the medial part.

tonight: think about: the bony structure separating the lateral aspect 
and medial aspect of guttural pouch.

make sure to spend about half an hour each lab looking at other 
species...

diagram of nasal cavity in cross section with conchae. in horse and goat 
these are more distinct than in the dog. they fill the nasal cavity so 
that air must flow around them. so you can describe a dorsal, ventral, 
and middle meatus (opening) to the nasal cavity (meatus also means 
passageway.)
but all three communicate with the COMMON meatus (up against the septum) 
and therefore with eachother.

think about this: NG tube commonly used in horse/goat/cow, and it's 
passed down through the (hopefully) very ventral part of the common 
meatus. so this is a large space. now, sometimes it will go through the 
middle meatus, and it makes a bloody mess.

LARYNX: cranial laryngeal nerve and caudal (recurrent) laryngeal nerve - 
both of those are branches of the vagus.

CRICOTHYROIDEUS is the only muscle innervated by cranial laryngeal nerve. 
all the other muscles are innervated by caudal laryngeal.

only diff between ruminant and dog...dog had lateral ventricles...horse 
has beautiful ventricles. goats don't have ventricles. the ventricle 
separates the vocal fold from vestibular fold in horse and dog, but goat 
only has vocal fold since no ventricle.

EAR: don't learn those structures. just know the auricular cartilage and 
the annular (sp> cartilage.



----end----