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 The stomach is a muscular, hollow organ in the upper gastrointestinal tract of Human, humans and many other animals, including several invertebrates. The Ancient Greek name for the stomach is ''gaster'' which is used as ''gastric'' in medical t ...

(one stomach). A monogastric can be classified as an

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

, an

omnivore An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize t ...

(facultative carnivore), or a

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...

(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 The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 milli ...

rabbits Rabbits are small mammals in the family Leporidae (which also includes the hares), which is in the order Lagomorpha (which also includes pikas). They are familiar throughout the world as a small herbivore, a prey animal, a domesticated form ...

, and guinea pigs. Examples of monogastric omnivores include

humans Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

pigs The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus '' Sus''. Some authorities cons ...

, and

hamsters Hamsters are rodents (order Rodentia) belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. The best-known species of hamster is the golden or Syrian ...

. Furthermore, there are monogastric

carnivores A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...

such as

cats The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the ...

and seals. A monogastric digestive tract is slightly different from other types of digestive tracts such as a

ruminant Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microb ...

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 Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

and

chickens The chicken (''Gallus gallus domesticus'') is a domesticated subspecies of the red junglefowl (''Gallus gallus''), originally native to Southeast Asia. It was first domesticated around 8,000 years ago and is now one of the most common and w ...

Digestive System

The digestive system of a monogastric is a one way tract that can be divided into two section: the foregut and the hindgut. The foregut consists of the mouth, esophagus, stomach, and small intestine. The hindgut consists of the large intestine, cecum, colon, and rectum. 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 with 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. Saliva within the mouth helps further break down the food with

enzymes An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as pro ...

and aids the organism in swallowing.

Amylase An amylase () is an enzyme that catalysis, catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large ...

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 (American English), oesophagus (British English), or œsophagus (Œ, archaic spelling) (American and British English spelling differences#ae and oe, see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), c ...

. The esophagus does not participate in any food break down. Its main function is to perform contractions called

peristalsis Peristalsis ( , ) is a type of intestinal motility, characterized by symmetry in biology#Radial symmetry, radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an wikt:anterograde, anterograde dir ...

to push food towards the stomach. Located at the end of the esophagus is the lower esophageal sphincter, which keeps stomach acid from flowing into the esophagus. Animals such as horses and rabbits cannot vomit due to this strong muscle. The

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. Stomach acid is made up of mainly

hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

(HCl), which has a pH of around 1.0 to 2.5. 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 Pepsin is an endopeptidase that breaks down proteins into smaller peptides and amino acids. It is one of the main digestive enzymes in the digestive systems of humans and many other animals, where it helps digest the proteins in food. Pe ...

. The last organ in the foregut is the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

. The small intestine, like the esophagus, uses peristalsis to push food through the tract. It contains three parts: the

duodenum The duodenum is the first section of the small intestine in most vertebrates, including mammals, reptiles, and birds. In mammals, it may be the principal site for iron absorption. The duodenum precedes the jejunum and ileum and is the shortest p ...

jejunum The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been pr ...

ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may ...

. The duodenum takes the partially digested food from the stomach and further breaks it down into digestible nutrients such as carbohydrates, lipids, and vitamins. 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.

Hindgut

The hindgut begins right after the small intestine and begins with the

cecum The cecum ( caecum, ; plural ceca or caeca, ) is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix (a ...

, which is the first part of the large intestine. The cecum within monogastric animals can vary drastically. Carnivores contain a small cecum, while herbivores contain a large one due to their need of fermentation. The function of the cecum in monogastric carnivores and some omnivores is water and salt absorption. The cecum plays a much bigger role in monogastric herbivores that need a way to ferment cellulose for energy. 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. The

large intestine The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the Digestion, digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces befor ...

is responsible for absorbing water into the bloodstream and turning leftover waste into stool. Waste includes large nutrient particles, dead cells, and other fluid. Bacteria in the large intestine break down some of the remaining nutrients in the food, while some vitamin and minerals continue to be absorbed. Peristalsis is used to push the stool into the

rectum The rectum (: rectums or recta) is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. Before expulsion through the anus or cloaca, the rectum stores the feces temporarily. The adult ...

. The colon is similar to the large intestine. Its main function is forming stool and absorbing water. The rectum holds stool until its ready to be released through the

anus In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facil ...

. This is the last organ in the monogastric digestive system.

References

Digestive system Biology terminology {{Biology-stub