What is the Difference Between Bolus and Chyme

The main difference between bolus and chyme is that bolus is the food mashed up inside the mouth, subsequently converted into chyme, whereas chyme is the food digested inside the stomach. Furthermore, the bolus is more alkaline while the chyme is more acidic. In addition to these, bolus passes into the stomach through the esophagus, while chyme enters into the small intestine. 

Bolus and chyme are two states of the food ingested into the gastrointestinal tract of animals. 

Key Areas Covered 

1. What is Bolus
     – Definition, Composition, Texture, Importance
2. What is Chyme
     – Definition, Composition, Texture, Importance
3. What are the Similarities Between Bolus and Chyme
     – Outline of Common Features
4. What is the Difference Between Bolus and Chyme
     – Comparison of Key Differences

Key Terms 

Bolus, Chyme, Digestion, Gastric Juice, Mouth, Stomach

What is Bolus 

The bolus is the ball-like combination of food and saliva produced as a result of the chewing process inside the mouth. Generally, saliva is a combination of secretions of salivary glands and serous glands, which open into the oral cavity. The three main pairs of salivary glands in the mouth include the parotid glands, submandibular glands, and sublingual glands. Also, the two main types of digestive enzymes present in the saliva are amylase and lingual lipase. Basically, amylase converts the starch in the food into maltose while lipase catalyzes the hydrolysis of lipids. Meanwhile, the serous fluid and mucus inside the mouth are responsible for the lubrication of food.

Figure 1: Bolus

Furthermore, with the help of tongue and teeth, this combination of food and saliva is made into a bolus, which passes into the stomach through the esophagus. Significantly, this ball-like nature is important for facilitating swallowing. 

What is Chyme 

Chyme is the creamy paste containing a mixture of partially digested food and gastric juice. Generally, gastric juice mainly contains hydrochloric acid and sodium chloride. Therefore, it is strongly acidic with a pH between 1 to 3. Basically, this acidic pH causes the denaturation of proteins in the food. Moreover, the enzymes in the gastric juice are mainly responsible for the digestion of proteins. Here, pepsinogen is the main enzyme in the gastric juice, digesting proteins. Gastric juice also contains gastric lipase, hydrolyzing lipids. Furthermore, rennin is a gastric enzyme present in infants.

Figure 2: Three Phases of Digestion in the Stomach

Moreover, churning, which occurs through the peristalsis, is the process of mechanical digestion inside the stomach. Here, waves of muscular contractions, which occur along the wall of the stomach result in the mechanical breakdown of food particles while mixing gastric juice well with food. 

Similarities Between Bolus and Chyme  

• Bolus and chyme are two states of the food ingested into the gastrointestinal tract.  
• Both mix with different secretions of the gastrointestinal tract.  
• They undergo both mechanical and chemical digestion. 

Difference Between Bolus and Chyme 

Definition 

Bolus refers to a soft, round ball of food that has been chewed and is then swallowed to make its way to the stomach while chyme refers to the liquified part of what passes through the stomach and into the small intestine.  

Correspondence 

Moreover, the bolus is the food mashed up inside the mouth, subsequently converted into chyme, while the chyme is the food digested inside the stomach. 

Composition 

While bolus is the food mixed with saliva, chyme is the food mixed with gastric juice. 

Mechanical Digestion 

The bolus is the result of the chewing process of food and saliva inside the mouth while the chyme is the result of churning the food and gastric juice inside the stomach. 

pH 

Moreover, the bolus is more alkaline while the chyme is more acidic. 

Texture 

While bolus is a ball-like food, chyme is a semi liquefied creamy paste. 

Color 

The color of the bolus is similar to that of the food, while chyme still has the tone of the natural color of food. 

Degree of Digestion 

The bolus is at the beginning of the digestion while the chyme is partly finished with digestion. 

Conclusion 

In brief, the bolus is the result of the chewing process of a mixture of food and saliva. Moreover, it is ball-like and passes into the stomach through the esophagus. In contrast, chyme is the result of the churning process of bolus and gastric juice. However, it is a creamy paste, which passes into the small intestine. Therefore, the main difference between bolus and chyme is the type of digestion of food. 

References:

1. The Digestive Process, NutriWatch, 23 May 2000, Available Here.

Image Courtesy:

1. “Swallow food” By Boumphreyfr – Own work (CC BY-SA 3.0) via Commons Wikimedia   
2. “2416 Three Phases Gastric Secretion” By OpenStax College – Anatomy & Physiology, Connexions Web site.  (CC BY 3.0) via Commons Wikimedia