MouthDigestion begins here, where the dog picks up its food. It chews the food, and saliva starts to break it down.
EsophagusA muscular tube that breaks nothing down. Waves of muscle push each swallow along to the stomach.
StomachOne simple bag with no compartments, which is what monogastric means. A dog's is large for its size. Acid and enzymes begin to break down protein here.
LiverA large organ with five main lobes in the dog. It makes bile, which helps to digest fat.
PancreasA long narrow gland, V-shaped in the dog. It makes enzymes that digest food in the small intestine.
Small intestineThree parts in a row: duodenum, jejunum and ileum. Most of the nutrients are taken up here.
CecumA blind pouch where the large intestine starts. Meat eaters have a small one; the dog's is a short twisted tube.
ColonThe main part of the large intestine. It takes water back from what is left of the food. A dog's is short and smooth, with no pouches.
RectumThe end of the large intestine. It holds the waste until it leaves the body.
AnusThe opening at the end of the tract. The waste leaves the body here.
The horse 9
StomachOne simple stomach, small for the size of the horse. So a horse eats small meals through the day. A horse cannot bring its food back up.
Small intestineA long tube of duodenum, jejunum and ileum. Enzymes digest starch, protein and fat here. A horse has no gallbladder, so bile runs in from the liver all the time.
CecumA very large blind sac that works as a fermentation vat. Its microbes break down the fiber of grass and hay.
Large colonThe biggest part of the tract. It has four sections, two ventral and two dorsal, and the fermenting of fiber goes on in it.
Pelvic flexureThe turn where the large colon folds back on itself. It comes between the ventral and dorsal halves. The tube is much narrower here.
Small colonNarrower than the large colon. It takes up water, and the droppings are shaped into balls here.
RectumThe last short length of the tract. The droppings wait here to leave the body.
ForegutMouth, esophagus, stomach and small intestine. Here the horse's own enzymes do the digesting.
HindgutCecum, large colon, small colon and rectum. Microbes ferment fiber here, which is why a horse is called a hindgut fermenter.
How this list was compiled: Every name checked on 2026-09-30 in two sources. The dog: S. Sisson, The Anatomy of the Domestic Animals (1914, public domain), https://archive.org/details/anatomyofdomesti00siss; the Merck Veterinary Manual's page for dog owners on the digestive system, https://www.merckvetmanual.com/dog-owners/digestive-disorders-of-dogs/introduction-to-digestive-disorders-of-dogs; Wikipedia, Monogastric and Cecum, https://en.wikipedia.org/wiki/Monogastric. The horse: Ohio State University Extension, The Gastrointestinal Tract of the Horse, https://ohioline.osu.edu/factsheet/1022; Rutgers Equine Science Center, The Basics of Equine Nutrition, https://esc.rutgers.edu/fact_sheet/the-basics-of-equine-nutrition/; the Merck Veterinary Manual's page for horse owners, https://www.merckvetmanual.com/horse-owners/digestive-disorders-of-horses/introduction-to-digestive-disorders-of-horses; and Sisson (1914), the horse. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
This monogastric digestive system diagram lays two tracts out in order. A monogastric animal has one simple stomach. The dog's tract is short; the horse's has a very large cecum and colon. Both are plans, not to scale.
Read the full guide
The dog
Follow the tract from the left: mouth, esophagus, stomach, small intestine, colon, rectum, anus. The liver and the pancreas lie beside it and send bile and enzymes into the small intestine. The cecum is the small blind pouch where the small intestine meets the colon.
The horse
Switch to Horse. The stomach is small, and the cecum is a very large blind sac where microbes ferment fiber. The large colon folds back on itself at the narrow pelvic flexure. The small colon runs to the rectum. Press Quiz me to name each part yourself.
The brackets split the horse's tract in two: the foregut ends with the small intestine, and the hindgut starts at the cecum.
Questions and answers
What does monogastric mean?
It means one stomach: a single simple chamber, not several. Cats, pigs, horses, rabbits, guinea pigs and people are monogastric. Cattle, sheep, goats and deer are ruminants, whose stomach has four compartments.
Is a horse a monogastric animal?
Yes. A horse has one simple stomach and is not a ruminant. It ferments the fiber of grass in its cecum and large colon instead, so it is called a hindgut fermenter.
Why is a horse's cecum so large?
It is a fermentation vat. Microbes in the cecum and the large colon break down plant fiber. Meat eaters have little fiber to ferment, and their cecum is small.
Does a horse have a gallbladder?
No. A horse has no gallbladder to store bile, so its liver sends bile into the small intestine all the time.