The key difference between monogastric and polygastric digestive system is based on the characteristics of the stomach. That is; the Monogastric digestive system has a single-chambered stomach while the polygastric digestive system has a four-chambered stomach.
The digestive system is the main factor that differentiates ruminants from non-ruminants. Ruminants are animals that have a four-chambered stomach. In contrast, non-ruminants are animals that have a simple stomach with a single chamber. Ruminants undergo a long repeated digestion process. Therefore, the requirement of a multi-chambered stomach is very important in ruminants.
CONTENTS
1. Overview and Key Difference
2. What is Monogastric Digestive System
3. What is Polygastric Digestive System
4. Similarities Between Monogastric and Polygastric Digestive System
5. Side by Side Comparison – Monogastric vs Polygastric Digestive System in Tabular Form
6. Summary
What is Monogastric Digestive System?
A monogastric digestive system is a system comprising of a single-chambered stomach. Organisms such as horses, rabbits, dogs, pigs as well as humans have a monogastric digestive system. In a monogastric digestive system, secretion of gastric juice and digestive enzymes takes place in a single-chambered stomach. Furthermore, organisms with the monogastric digestive system cannot digest cellulose. However, due to the presence of cellulose-degrading gut bacteria, monogastric organisms can digest cellulose. Thus, microbial fermentation takes place in the monogastric herbivores.
Figure 01: Monogastric Digestive System
A monogastric digestive system starts its operation instantly upon the entry of food into the mouth. The glands secreting digestive fluids are stimulated upon the entry of food. Once the initial mechanical and chemical digestion takes place in the mouth, the food passes into the stomach through the oesophagus. Food digestion takes place in the stomach, and finally, small intestine absorbs nutrients into the bloodstream. Following that, the undigested food matter is removed from the body by egestion. The whole process takes place through the involvement of various digestive enzymes and secretions.
What is Polygastric Digestive System?
A polygastric digestive system is a system comprising of a four-chambered or a multi-chambered stomach. This form of the digestive system is common among ruminants such as cattle, sheep and deer. The four chambers in the stomach are known as the rumen, the reticulum, the omasum and the abomasum. Further, the presence of four chambers also allows the complete digestion of high cellulose-containing food matter ingested by ruminants.
Figure 02: Polygastric Digestive System
Organisms with polygastric digestive systems do not undergo extensive mechanical and chemical digestion in the mouth. Instead, they swallow their food in very large amounts, allowing a minute chewing process. With time, they will ruminate or take back the swallowed food, further chew it and swallow again. The ball of food that is brought up and re-chewed is called the cud.
Moreover, rumen bacteria play a very important role in the digestion of cellulose. They engage in complete digestion of cellulose, converting the cellulose to volatile fatty acids. The omasum and the abomasum are mainly involved in the grinding process of food.
What are the Similarities Between Monogastric and Polygastric Digestive System?
- Both have structures such as mouth, stomach, small intestine, large intestine, rectum and anus.
- They undergo holozoic nutrition pattern.
- Moreover, both systems secrete various enzymes and chemicals for the process of digestion.
- These systems are present in higher-order eukaryotes belonging to the kingdom Animalia.
- Both systems provide energy and nutrients necessary for the growth.
- Moreover, both systems are mediated by both physical and chemical digestion processes.
What is the Difference Between Monogastric and Polygastric Digestive System?
The key difference between monogastric and polygastric digestive system is the number of compartments in the stomach. Monogastric organisms have a single compartment stomach while the polygastric organisms have a multi-compartment stomach. While non-ruminants belong to the monogastric category, ruminants belong to the polygastric category. Due to the variation of their digestive systems, the method in which they undergo digestion process and their digestive products also vary.
The below infographic summarizes the difference between monogastric and polygastric digestive system.
Summary – Monogastric vs Polygastric Digestive System
Monogastric and the polygastric digestive systems are two main categories of digestive systems based on their characteristics of the stomach. Thus, the monogastric digestive system bears a single compartment stomach. In opposition to this, the polygastric digestive system bears a four-compartment stomach. In fact, this is the main distinguishing feature between the ruminants and non-ruminants. Besides, their ability to digest cellulose also differs in the two types of digestive systems. While the monogastric digestive system cannot digest cellulose completely, the polygastric digestive system can digest cellulose completely. So, this summarizes the difference between monogastric and polygastric digestive system.
Reference:
1. Karasov, William H, and Angela E Douglas. “Comparative Digestive Physiology.” Comprehensive Physiology, U.S. National Library of Medicine, Apr. 2013, Available here.
Image Courtesy:
1. “Figure 34 01 05ab” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Anatomy and physiology of animals The rumen” By The original uploader was Sunshineconnelly at English Wikibooks. – Transferred from en.wikibooks to Commons by Adrignola using CommonsHelper (CC BY 3.0) via Commons Wikimedia
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