10.16.96

there seems to be a GI tract of some kind hanging in the front of the 
room suspended from the ceiling by some kind of twine. odd, that.

tomorrow we're starting ruminant dissection. see DYCE p 53.

the reticulum is pushed RIGHT up against the back of the diaphragm, and 
the heart is just on the other side of the diaphragm. sometimes cows will 
eat weird stuff like nails, wire, sparkplugs, etc. if cow eats, for 
example, wire, it can poke through reticulum, through diaphragm, and then 
can also go easily through heart.

TOPOGRAPHY is important. think 3d.

the SPLEEN is relatively small, and is adhered to left side of rumen, 
dorsal aspect. RUMEN Divided into dorsal sac, vetral sac - both have 
blind extensions caudally- caudodorsal blind sac and caudoventral blind 
sac. This is right out of SMALLWOOD. THere is also a cranial sac cranial 
to the ventral sac.

so food comes into rumenoreticular compartment. heavy stuff falls into 
reticulum, hopefully eventually passes on. soft material passes into back 
of rumen, which is a big fermentation vat. there are certain grooves - 
LEFT LONGITUDINAL GROOVE between the dorsal and ventral sacs. There is a 
CAUDAL GROOVE caudally bet. dorsal and ventral sacs and a CORONARY GROOVE 
separating ventral and caudal ventral sacs, and there's a rumenoreticular 
groove, and a CRANIAL GROOVE

p 77 smallwood- GI tract opened up.

so, the OMASUM about the size of volleyball in cow, softball in goat, 
comes off the side of the reticulum, and the ABOMASUM comes off the 
bottom of the OMASUM and lies ventrally to the rumen. the OMASUM can 
become gas filled and get displaced dorsally - surgical problem.

The DUODENUM comes off the ventral sac of the rumen, and from there on 
the GI tract very similar to the small animal, w/one exception.

other difference in GI system of ruminant is the ascending colon. Dogs 
and cats eat relatively well balanced diets. These herbivores need to be 
able to break down plant stuff for their needs, so they need an extra 
fermentation vat. Horse has cecal development. Recall that in dog 
transverse colon lies just cranial to cranial mesenteric artery. Ruminant 
has same setup for transverse and descending colon, but has first an 
enlarged, caudally directed cecum, and then the ascending colon proceeds 
in a spiral formation - eg, it's much longer than in dog/cat, and it 
coils up and is held together by mesentery (mesocolon). in fact, you 
can't unspiral this part of the colon, because it is held together by the 
mesocolon.