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it tends to be problematic to put all the foundation work together in 
order to understand the clinical presentation, and that's why we're 
having the clinical correlations. we need to maintain the information and 
be able to make the jumps between anatomy and biochemistry and all the 
rest of it.

case from a few yr ago:

cat belonging to older w philly couple. someone shot the cat. cat came to 
ER w/puffiness and bleeding from neck wound.

what could be involved? what are the consequences? how do we manage the 
case?

well, it was a healthy normal cat until being shot, when it developed 
puffy bleeding neck and shy attitude. they were't SURE it had been 
shot...so what else would be considered? differential list: shooting 
(since owners thought so), bite wound, other obscure ideas of little 
relevance.

watching the cat: it breaths with increased inspiratory effort and 
increased respiratory rate. why? possibilities include airway 
obstruction, edema, pain. when something hurts, you don't want to move 
it, and if you don't move breathe normally, you have to breathe more 
deeply etc. also could be bleeding into the trachea which would prevent 
effective ventilation of affected lung tissue.

you should also find out about this cat how severe is the injury. is the 
cat just a little sore with a minor soft tissue injury, or has the cat 
damaged a main vessel and is it bleeding into the trachea, or whatever? 
we need to check efficiency of respiration. are the mms pale, pink, blue, 
or what? pale=shocky/hypovolemic/hemorrhaging -->possibilities. or, mms 
could be cyanotic, indicating more severe respiratory problem. could be 
pale and cyanotic. one other thing you can do besides check mms is check 
the capillary refill time and peripheral pulses.

it turns out this cat is uncomfortable but has pink mms and good pulses. 
this gives you a frame of references for what is going to happen next. in 
trauma,things can change very rapidly,, so you need to know "what's 
happening now" and then in 10 minutes if there is a major change, it can 
affect what you will do. you always want a baseline.

so, what is injured in this cat? are limbs and general mobility ok? if it 
were lame on LF leg, there could be something going on in the leg, or 
something in the spinal nerve.....a neck injury could cause drastic 
effects on the rest of the body if the cord is compromised....

anatomy of the neck:

the cord is in a dorsal/middle position protected by the vertebral 
column. 
note: there could be trauma to the bone of the column, causing pain and 
swelling, compressing the cord or the spinal nerve.

the diaphragm is innervated by the phrenic nerve which comes from the 
segmental cervical nerves. the ribs are innervated by thoracic spinal 
nerves.

also in the neck is the carotid artery and the jugular vein. the carotids 
are ventral and lateralish to the vertebral column. also in this area are 
the vertebral arteries, in and around the vertebral column. note: in 
dogs/cats: you can ligate both carotids and the vertebrals have 
sufficient collateral circulation to keep brain alive at a minimal level 
until such time as the collateral circulation is enhanced over time. in 
people you can't do that.

in the nose: huge area of bone and respiratory epithelium, and bunches of 
blood vessels in betweeen: blood vessels to warm air flowing in and to 
humidify the air coming in. so if doing nasal sx and there's too much 
bleeding you can ligate the carotids temporarily. 

also in the neck are the jugular veins, superficial to the carotids, in 
very superficial position, at serious risk in fact of damage due to bite 
wounds or what have you. Functionally, that's not as much of a problem as 
it sounds like, because it's a lower pressure system than the carotid 
artery!

if you tear the carotid artery, it is likely to stay within the neck and 
activate the extrinsic pathway and coagulate.

esophagus and trachea in the neck too.
trachea first
trachea is made of cartilaginous rings and connective tissues. why not 
all cartilage? FLEXIBILITY, ability to expand. how does the trachea get 
this ability? contains muscles, and epithelium, and elastic tissue, in 
dorsal segment of trachea. ventrally there are U rings of cartilage. 
tracheal injury could result in collapse of the trachea, if cartilage 
cut, because any swelling/escape of air into tissue, will compress sides 
of trachea, obstructing the lumen.

air gets into the lungs via negative pressure. to get air into the lungs 
you need the stiffness of the cartilage to maintain the lumen in the open 
position.

bulldogs often have problem - pharyngeal tissues are too big. head is too 
short. what happened is that when head was made smaller, internal tissues 
remained the same, but they are in a smaller space, so when you get 
negative pressure in the airway, the tissues get sucked in and they get 
airway obstruction. this means bulldogs tend to swallow a lot of air and 
have considerable flatulence.......

larynx: what goes on there? it remains open during inspiration, that's 
why it's cartilage. two main functions: remaining open, and modulating 
resistance; and preventing aspiration. 

head/neck poorly engineered.  nose should be below the mouth so that the 
airway and the foodway don't have to cross!

so, the larynx was developed with an epiglottis which will put a flap 
over the airway, and the arytenoids also can close the airway opening. 
when you swallow, the larynx is pulled forward by the hyoid apparatus and 
that causes the epiglottis to cover the airway like a trashcan lid. the 
intrinsic muscles of the larynx cause the arytenoids to close the top and 
the vocal fold to close the bottom of the airway by pulling the sides 
together. there are cranial and caudal laryngeal nerves. the caudal or 
recurrent lar. n. has most of the motor responsibility. it travels all 
the way down the neck and back up so is open to injury in the neck. 
laryngeal nerves go down the neck w/the vagosympathetic trunk and is 
right next to the carotid. then it wraps around aortic arch and runs back 
up the neck in proximity to the dorsolateral aspect of the trachea.

if you paralyze the caudal laryngeal nerve you can have exertional 
respiratory distress.

no immediate problem with lacerated esophagus in acute trauma, but next 
time animal eats or drinks there will be a major problem. you won't know 
that problem exists unless there is material leaking out of the 
esophagus.

so in our cat what is causing the neck swelling? lacerated trachea, subq 
emphysema, air in the tissues causing compression on lacerated trachea 
could also happen. if a BDLD interaction (bigdoglittledog) a huge hole in 
trachea could cause air to leak out and leak into the tissue of the 
mediastinum. then instead of staying in mediastinum, if dog coughs or 
something, it could leak into the lateral pleural space, and then you end 
up compressing the lungs even more. PNEUMOTHORAX.

if the cat came in in severe respiratory distress with air in the neck, 
first thing to do is chest tap to look for free air in there. this cat 
wasn't that bad off though

bottom line: this cat did develop problems. the injury involved the 
vagosympathetic trunk. vague GI signs ensued. Vagosymp trunk supples GI 
tract. unwillingness to eat, frequent regurgitation, etc. 

so think of the neck as a conduit, with things travelling through it. 
there are very few things totally unique to the neck. one of them is the 
thyroid/parathyroid glands. that could also be damaged in a neck injury. 
then you would a have a hypothyroid or hypoparathyroid pet.




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