Equine GI Tract Flashcards
What two structures are specialized in the horse GI system?
Cecum and ascending colon
How many ribs does the horse have? What structure is smaller as a result of their unique rib cage
18 ribs.
The paralumbar fossa is smaller.
What is the consequence of horses having a smaller paralumbar fossa?
It restricts surgical access.
Where is the equine stomach located?
Approx between ribs 9 and 15.
The floor of the abdomen is mainly occupied by…
the ascending colon.
Where does the duodenum become the jejunum?
At the level of the cranial mesenteric artery.
What is the length of the jejunum in meters?
25 meters
Describe the jejunum’s structure and placement in the abdomen.
- Mostly collapsed like a ribbon.
- Most of the jejunum is in the left dorsal part of the abdomen.
- Some parts can be found on the floor of the abdomen as it can fit itself between other structures.
Where can the jejunum enter that can cause problems (rare but can happen)?
The epiploic foramen.
Vessels in which part of the mesentery can be blocked without consequence? Why?
The larger vessels closer to the cranial mesenteric artery can be blocked without causing issues due to anastomoses.
Problems with smaller vessels closer to the small bowel will be more significant.
What does the cecum look like?
Large and comma shaped. It begins quite wide at the base and tapers to the apex.
Where is the cecum located?
It occupies a lot of the right flank and most of the paralumbar fossa on the right side. The apex is located more medially. The apex is located cranially almost at the level of the xiphoid cartilage.
Where does the cecum attach to the roof of the abdomen?
Between rib 15 and L2.
The cecum covers what part of the kidney?
The caudal pole of the right kidney.
Can the cecum be felt during rectal palpation?
Yes
What happens to the gas produced by fermentation?
Gas accumulation from fermentation passes through the rectum. It cannot be released cranially through the mouth so if there is a blockage it will accumulate.
What is the base of the cecum embryologically?
Part of the ascending colon that is dilated and folded back on itself.
Where does fermentation begin in the horse’s GI tract?
In the cecum.
What two structures are open to the cecum? What are the names of their corresponding openings?
Ileum = ileal papilla
Ascending colon = cecocolic ostium
Describe movement of ingesta in the cecum.
There is a fold between the ileal papilla and the cecocolic ostium that directs ingesta from the ileum down the body of the cecum towards the apex. The ingesta is then brought back up and over the fold due to muscle contractions. The ingesta then passes through the cecocolic ostium to the first part of the ascending colon; the right ventral colon.
How meany flexures does the ascending colon have? Name them.
Three flexures.
- Ventral diaphragmatic / sternal flexure
- Pelvic flexure
- Dorsal diaphragmatic flexure
What changes occur at the pelvic flexure?
A significant directional change (180 degrees) and a decrease in diameter.
Which part of the ascending colon does not have attachment to the body wall?
The whole left side.
What are the folds on the cecum and colon called?
Haustra
What are teniae?
A distinct white band of muscle that runs along the cecum and colon. It is made of the outer longitudinal muscle that has organized into strong bands?
What creates the haustrae?
Contraction of the teniae. The haustra are moving structures in the live animal.
What connects the two segments of the ascending colon?
The ascending mesocolon.
How many teniae does the cecum have? How many of them are not readily visible?
The cecum has 4 teniae.
Two of them are camouflaged in attachments: the ileocecal fold and the cecocolic fold.
The cecocolic fold is located on which side of the cecum?
The lateral side.
How many teniae does the right ventral colon have?
4 but 2 are covered by the ascending mesocolon
How many teniae does the left ventral colon have?
4 but 2 are covered by the ascending mesocolon
How many teniae does the left dorsal colon have?
1 (and therefore it has no haustra)
How many teniae does the right dorsal colon have?
3
Which section of the ascending colon has the largest diameter?
The right dorsal colon.
Which section of the ascending colon is the shortest?
The right dorsal colon.
How many teniae does the transverse colon have?
2
How many teniae does the descending colon have?
2
Where are fecal balls formed?
Descending colon
How is the position of the descending colon different in horses when compared to carnivores?
It has a longer mesocolon and is allowed more movement.
What is a common area for blockages in the equine GI tract?
The pelvic flexure.
