Chyme Definition
Digestion is the process by which food that we eat is digested. The food is acted upon by various enzymes in the digestive system and this helps to break down the food into smaller subunits. These subunits have carbohydrates, fats, starch and proteins and thus they help in providing energy. For 4-5 hours the food is stored in the stomach and after that, it gets mixed with acidic acids of the stomach. The mixing takes place with the help of churning movements of the muscular walls of the stomach and then this food mixed with gastric juices is called chyme. This forms the basic chyme definition and chyme meaning. Chyme in the stomach is known as stomach chyme. To understand more about whats chyme we need to learn about the process of digestion.
Digestion of Food
The digestion of food is accomplished by chemical and mechanical processes. The actual fragmentation of large pieces of food into smaller pieces that digestive enzymes can enter is referred to as mechanical digestion. Enzymes in chemical digestion break down food into small molecules that the body can access.
Digestion in Mouth
Chyme meaning can be understood from the process where the digestion in the human body starts. Mastication of food and facilitation of swallowing is performed by the buccal cavity. The teeth along with tongue and saliva also help in the mixing of food. Mucus helps in lubricating and adhering the masticated food particles into a bolus. The bolus is just a mass of food. The saliva is secreted by salivary glands into the oral cavity and it contains electrolytes like calcium, sodium and potassium ions and enzymes. The enzymes are salivary amylase and lysozyme. Ptyalin is another name for salivary amylase. This enzyme is absent from the saliva of many mammals like cows and buffaloes and carnivores animals like lions and tigers.
Pigs have amylase in their saliva. The oral cavity initiates the process of digestion. It is done by hydrolytic action of the carbohydrate splitting enzyme, the salivary amylase. This enzyme hydrolyses about 30 percent of starch into a disaccharide-maltose. The lysozyme present in the saliva acts as an antibacterial agent that prevents infections. This mass of food(bolus) is then pushed down through the pharynx into the oesophagus. This process is called swallowing or deglutition. Through successive waves of muscular contractions, the bolus is moved down the oesophagus. These muscular contractions are called peristalsis. There is a sphincter between the oesophagus and stomach called the gastro-oesophagal sphincter. It controls the passage of food into the stomach.
Gastric Glands
The gastric glands play an important role in the formation of chyme food. The mucosa of the stomach has gastric glands. They have three major types of cells namely
Mucous neck cells secrete mucus.
Peptic or chief cells that secrete pepsinogen.
Parietal or oxyntic cells that secrete HCl and intrinsic factors.
Digestion in the Stomach
We have a rough idea about chyme from the chyme definition part above. Chyme is formed in the stomach. Stomach stores the food for 5-6 hours. The thorough mixing of food with the gastric enzymes is called the chyme. This is the exact chyme medical definition and chyme definition anatomy. The pepsinogen is activated by hydrochloric acid and then it gets converted into active enzyme pepsin, the proteolytic enzyme of the stomach. Pepsin converts proteins into proteases and peptones. The mucus helps in protecting the stomach wall from concentrated hydrochloric acid. HCl provides the optimal pH for pepsins. Non-secretion of HCl or gastrectomy can lead to iron deficiency anaemia. Therefore, the mixing of the gastric juices along with food particles forms chyme.
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Figure: Chyme formation.
Digestion in the Small Intestine
The pancreatic juice contains enzymes. These are present in an inactive form and are activated later. trypsinogen, chymotrypsinogen, amylases, procarboxypeptidase, lipases and nucleases. Trypsinogen is activated by an enzyme that is enterokinase. This is secreted by the intestinal mucosa. The bile released into the duodenum consists of bile pigments. Bilirubin and biliverdin are bile pigments. Bile salts are sodium bicarbonate, sodium glycolate, sodium taurocholate. The bile also has cholesterol and phospholipids. Bile has no enzyme and it helps in the emulsification of fats. Emulsification means that they help in the breakdown of fats into very small micelles. Micelle is a combination of fatty acids, monoacylglycerols and bile salts. Bile also helps in activating the lipases. Goblet cells secrete mucus and are secreted by mucosal epithelium. The intestinal juice contains a variety of enzymes like disaccharides, maltase, dipeptidases, lipases, nucleosidases, etc. The mucus along with the bicarbonates from the pancreas protects the intestinal mucosa from acid as well as provide an alkaline medium for efficient enzymatic actions. Submucosal glands like Brunner’s glands also help in this process.
Conclusion
We can conclude that chyme means the mixing of gastric juices with the food. This process takes place in the stomach. Further, this chyme is transferred to the small intestines for further digestion to take place. The process of digestion in the human body helps in breaking down food into smaller particles and then extract energy from it.
FAQs on Chyme
1. What is chyme in the digestive system?
Chyme is a thick, semi-fluid mass of partially digested food and digestive secretions, formed in the stomach. It is created when the food you eat (the bolus) is mechanically churned and chemically mixed with hydrochloric acid (HCl), mucus, and digestive enzymes like pepsin. This acidic mixture is then gradually released into the small intestine for further digestion and nutrient absorption.
2. What is the difference between a bolus and chyme?
A bolus and chyme represent two distinct stages of food processing in the upper digestive tract.
- Bolus: This is a soft, rounded mass of chewed food mixed with saliva. It is formed in the mouth, is typically alkaline or neutral, and travels down the oesophagus to the stomach.
- Chyme: This is formed in the stomach when the bolus mixes with highly acidic gastric juices. It is a pulpy, acidic fluid that is passed into the small intestine for the next phase of digestion.
3. Why is chyme so acidic?
Chyme is highly acidic because it is thoroughly mixed with hydrochloric acid (HCl) secreted by the parietal cells in the stomach lining. This strong acid serves crucial functions: it sterilises the food by killing most harmful bacteria and pathogens, and it provides the optimal low pH environment required to activate the enzyme pepsinogen into its active form, pepsin, which begins protein digestion.
4. How does the small intestine handle the acidic chyme without getting damaged?
The small intestine is protected from the acidic chyme through a rapid neutralisation process. As chyme enters the duodenum (the first part of the small intestine), it triggers the release of hormones. These hormones stimulate the pancreas to secrete pancreatic juice, which is rich in bicarbonate ions. This alkaline secretion neutralises the stomach acid, raising the pH and creating a safe, slightly alkaline environment necessary for the digestive enzymes in the small intestine to function effectively.
5. How is the release of chyme from the stomach into the duodenum regulated?
The release of chyme is a tightly controlled process managed by the pyloric sphincter, a muscular valve between the stomach and small intestine. This regulation prevents the duodenum from being overwhelmed. When fatty or acidic chyme enters the duodenum, it triggers the enterogastric reflex and the release of hormones like Secretin and Cholecystokinin (CCK). These signals inhibit stomach contractions and constrict the pyloric sphincter, slowing down gastric emptying to a manageable rate.
6. What is the difference between chyme and chyle?
While both are fluids in the digestive system, chyme and chyle are distinct in composition and location.
- Chyme: This is the acidic, partially digested food paste found in the stomach and small intestine. It contains partially broken-down carbohydrates, proteins, and fats.
- Chyle: This is a milky, alkaline fluid found in the lymphatic vessels (lacteals) of the small intestine. It is formed after fats from the chyme are digested and absorbed, consisting of lymph and emulsified fat droplets called chylomicrons.
7. What happens to the key nutrients in chyme once it is neutralised in the small intestine?
Once neutralised, the nutrients within the chyme are subjected to final digestion by a host of enzymes. The pancreas releases powerful enzymes to break down the macromolecules: pancreatic amylase for carbohydrates, trypsin for proteins, and lipase for fats. The intestinal wall also secretes enzymes to complete this process. The resulting simple molecules, such as glucose, amino acids, and fatty acids, are then absorbed through the intestinal lining into the bloodstream or lymphatic system to nourish the body.
