10.9.96

p. 38 of smallwood, diagrams p 39 --don't even think about those 
diagrams. look at the "major branches of aortic arch" paragraph. 

today: limb removal. Rich mentioned the dorsal scapular ligament 
yesterday - lateral fascial sheet from supraspinous ligament to scapula.

also today we open chests (instructors to do.)

HEART

DOG.

the heart is a four chambered muscular double pump. function is to move 
blood throughout the body. chambers: right atrium and ventricle, left 
atrium and ventricle. 

   RA |  LA
   ---|-----
   RV |  LV

the vertical division is a septum. There are valves between the atria and 
ventricles (AV valves.) blood flows through vena cava into RA, into RV 
out of RV through pulmonary artery into lungs, through pulmonary vein 
into LA, into LV, out of LV through aorta into body. L side = systemic 
circulation, R side = pulmonary circulation.

heart sits roughly between ribs 3 and 6. about 45 degree angle inside 
body, slightly oblique. you have two flaps sitting on top of the heart, 
those are the atria. the "bottom" of the heart where it meets the sternum 
is the apex, and the part the great vessels come out of is called the 
base. viewed from the right side of the chest, you see mostly the right 
side of the heart. viewed from the left, you can see both ventricles. 
because the heart lies obliquely in the chest.

the atria and ventricles are separated from one another by some fat and 
the coronary groove, through which the coronary artery runs. 
the R and L ventricles are separated by the interventricular grooves, 
also fat filled.

the left coronary artery runs between the r and L ventricles. at the top 
of the L ventricle, it branches and runs around the toop of the ventricle 
as the circumflex coronary artery. it coninues down between the 
ventricles, in the paraconal interventricular groove, as the paraconal 
interventricular br of the l coronary artery. on the oher side of the 
heart, the circumflex branch has come around, and runs down the other 
side of the heart, between the ventricles, and runs to the apex as the 
subsinosal branch of the L coronary artery. it sits in the subsinuosal 
interventricular groove. The right coronary artery just runs around the 
top of the R ventricle. the subsinuosal come off the R coronary artery in 
horses. 

there's venous return of course. the coronary arteries have veins near 
them. the cardiac veins run near the arteries, and the coronary sinus is 
near the circumflex branch of l coronary artery.

dissecting the heart.

Find the cranial and caudal vena cava, and make a longitudinal incision 
through it.  find the right atrium, and extend your incision into the 
auricle (dead end pouch of atrium) There's a little thing in the v.c 
called the intervenous tubercle which directs blood. There's also a fetal 
remnant called the fossa ovalis, bet the vc vc and atrium. There's also a 
coronary sinus. and there's an AV valve bet the R atrium and R ventricle.


when you cut vertically through the heart, don't cut exactly in the 
groove, cut kind of to the side of it s you can see in the chambers. 
another thing to know is that there are pulmonary and aortic valves as 
well as the AV valves, and these all are made of flaps known as cusps, 
two or three depending on the valve. the cusps are held to the walls of 
the heart by muscular attachments called papillary muscles, and there are 
fibrous connections between the muscles and the cusps called chordae 
tendinae.

any questions?

if you look at the heart from a dorsal view, it can be observed that the 
R ventricle is relatively thin walled, while the L ventricle is very 
THICK walled because it must pump blood into a higher pressure system and 
over more distance.