Nervy

I learned some interesting things about nerves in my ruminant anatomy class yesterday morning.

Have you ever hit your funny bone? If you have, the sensory input comes from branches of the ulnar nerve, which travels towards the ulna bone, the caudal bone in the distal limb. However, I can't tell you how common it is for ruminants to hit their funny bone. Who knows what life is like when you walk on four legs?

I also learned something more clinical that I had not touched on since vet tech school. The radial nerve, which travels from medial to lateral, traveling over the lateral brachialis muscle distal to the teres major to supply extensors of the elbow, carpus and digits gives off a large sensory branch, the superficial branch. The superficial branch of the radial nerve gives off the lateral cutaneous antebrachial nerve and then continues in the distal limb associated with the cephalic and accessory cephalic veins.

This means that there are sensory nerves on either side of the cephalic vein since the cutaneous branch parallels the cephalic vein. When doing a blood draw on the cephalic vein of an animal (which is common), you may accidentally hit one of these sensory branches and the animal will yelp and jump. Uneducated assistants and some techs even don't know enough anatomy to know they just poked a nerve and will try to keep going, assuming the animal is just being recalcitrant. I've seen this happen. I've also hit this cutaneous nerve by accident myself on patients. Personally, it gives me the jitters and I try to avoid drawing blood from the cephalic vein, preferring femoral or saphenous in the back leg. However, this is the most common site for peripheral catheters so I still use it quite a bit. Luckily, for catheters you get to shave/clip the hair and so the vein is usually much more obvious.

Another thing we learned in ruminant anatomy class related to the distal limb was naming the distal most arteries. I quote my fabulous and funny professor on this subject: "That's why these names are about 3 feet long, because they are being very specific about where these arteries are."

The two most distal arteries in the ruminant thoracic limb are the palmar common digital artery III, which is a continuation of the median artery and which gives off the axial palmar proper digital arteries of digits III and IV.

In case you are wondering what these names refer to--

• Over the digit, the vessel is described as palmar or dorsal, indicating the surface it runs along
• It is 'common' if it is supplying more than one digit (i.e. digits III and IV which are the two digits of the ruminant)
• It is axial (close to the midline) or abaxial (farther from the midline, more lateral) if supplying a single digit
  

The things one learns in vet school are often very detailed. Like I've said before, it's a whole new language.