dr orsini....9.18.96 ------ Dyce: chap 3 fig 1,31,32,38,39,42,45,47 (omit 5', 5'', 6,7,8) 49 Chap 4: 18a, 19 chap 13: 3,5 chap 14: 3,8,11,16 --------- Tuesday ams - grand rounds, 8am in B101, Dr.Orsini thinks we might be interested. ---------- So, working down the thoracic limb, looking for various nerves etc. Tomorrow Dr. Dodson will discuss brachial plexus/nerves. Dr.Orsini says we shouldn't worry about what part of spinal cord the main nerves come from - just need to follow nerve from brachial plexus down limb and know what muscles it goes to. Re: vessels - what depth do we need to go into; what about the veins? Veins usually in 95% of cases run parallel to arteries and have the same name. veins are highly variable as well, so don't worry about them unless someone TELLs you to worry about them - eg external jugular. People don't have an external jugular. Don't worry about internal jugular vein which runs along in the carotid sheath. Also know the cephalic vein, which is very superficial on the cranial surface of the forelimb. Often comes off w/skin when skinning the animal. There are some minor arteries and nerves w/it, but don't worry about them. When looking at arteries, we really need to know the main line down to the tip of the toe - how does blood get down there? Dr.Orsini will explain what happens if you can't save the median artery? Dogs and cats might be ok, horse hoof proably would fall off. From heart, subclavian goes to forelimb. When it gets to axilla, it changes to axillary artery, then in the arm is called brachial artery. In forearm, it changes to median artery. It's all the same artery, but has regional names. This is the main arterial stuff to know; most of the rest don't worry about. [diagram - thorax, heart lies between 3rd and 6th ribs, shows ascending aorta which rapidly turns dorsally and becomes descending aorta. Left aorta is main blood supply to the body.] first branch of ascending aorta= brachicephalic trunk, which splits into left common carotid artery and right common carotid artery, main supply to head, and then continues after those branches as the right subclavian artery. Off of this branches the left subclavian artery. The descendig aorta sends off intercostal arteries, which supply blood to the ribs and surrounding tissues. They run between the ribs, and are always just deep to the rib, so you can easily avoid them when putting a needle into the lung. So, right subclavian artery goes right down to bone, and that's the vertebral artery, which runs up the cervical spine through the transverse foramina of the vertebrae. Gives blood to base of brain and face. If both common carotids were cut, vertebral arteries would carry enough blood to head to support life. Collateral circulation: important concept. The circulation of an area is supplied by many arteries, so if function of one vessel is lost, circulation can be maintained. If one artery is damaged, nearby arteries will get bigger and take over function. Costocervical trunk=comes off r.subclavian after the vertebral artery. Supplies blood to neck and first 3-4 ribs. Next branch is superficial cervical artery, gives blood supply to superficial cervical lymph node. courses right by superficial cervical LN which is deep to omotransversarius. Last branch of subclavian=internal thoracic, which courses cranially up the sternum, close to the midline, covered by the transversus thoracis muscle. So, then, the subclavian continues as the axillary artery through the axillary region. The first branch of the axillary artery is the external thoracic, which supplies blood to the superficial and deep pectoral muscles.then, the lateral thoracic artery, supplies lateral thoracic muscles eg latissimus dorsi. Then there's the subscapular artery, which branches into a small artery, the thoracodorsal artery, which supplies the dorsal aspect of the thorax (don't worrya bout it. It also branches into caudal circumflex humeral artery, supplying the triceps et al, and the cranial circumflex humeral, which runs on the cranial side of the humerus. probably won't need to identify these two. now, axillary turns into brachial artery, and as it gets to forearm, it's called median artery. (it's ok to call it axillary, though. it's the same artery...) Main supply to paw is the median. Don't really need to know. In cat, radial artery branches off median, and is main supply to paw, you should think about this. Another difference in the cat - there is a small hole in the distal humerus - the supracondylar foramen - that the brachial artery and median nerve run through. Clinically, w/a fx humerus, you can see arterial and nerve damage in the cat in this area. P 166 small millers - branches of brachial artery. observe comon interosseous, but don't worry about the next three.