thumb|This diagram shows the monogastric digestive system of a human and rabbit. Notice the difference in cecum size between the two species.
A monogastric organism defines one of the many types of digestive tracts found among different species of animals. The defining feature of a monogastric is that it has a simple single-chambered stomach (one stomach). A monogastric can be classified as an herbivore, an omnivore (facultative carnivore), or a carnivore (obligate carnivore). Herbivores have a plant-based diet, omnivores have a plant and meat-based diet, and carnivores only eat meat. Examples of monogastric herbivores include horses, rabbits, and guinea pigs. Examples of monogastric omnivores include humans, pigs, and hamsters. Furthermore, there are monogastric carnivores such as cats and seals.
A monogastric digestive tract is slightly different from other types of digestive tracts such as a ruminant and avian. Ruminant organisms have a four-chambered complex stomach and avian organisms have a two-chambered stomach. An example of a ruminant and avian are cattle and chickens. Each organ has its own role in the break down and digestion of food consumed by the animal.
Foregut
The digestive system and foregut start in the mouth. The mouth is in charge of the simplest form of break down of food throughout the digestion process. The mouth masticates, commonly known as chewing, food taken in by the organism. Amylase is an example of an enzyme found within many monogastric omnivore's saliva to help break down starches. Once food is swallowed, food travels down the esophagus. The esophagus does not participate in any food break down. Its main function is to perform contractions called peristalsis to push food towards the stomach.
The stomach follows the esophagus and contains several muscles, acid, and enzymes. Its main function is to further break down food into a substance that is digestible for the small intestine. The lower muscles in the stomach mix the food with stomach acid. The acidity of stomach acid denatures consumed proteins, which helps digestive enzymes break down peptide bonds within the molecules. An example of this enzyme is pepsin.
The last organ in the foregut is the small intestine. The small intestine, like the esophagus, uses peristalsis to push food through the tract. The jejunum and ileum are responsible for absorbing most of the nutrients that pass through the digestive system. These sections contain a large number of villi that increase the surface area of the intestinal lining and help absorb the broken down nutrients. Horses for example ferment their carbohydrates in the cecum and large intestine with the help of microbes, which makes them hindgut fermenters. This is opposed to foregut fermenters, or ruminants.