Chyme
Chyme is a thick, semi-fluid mixture formed in the stomach during the digestion of food. After swallowing, food is broken down by gastric juices and muscular contractions, resulting in chyme, which is then gradually introduced into the duodenum through the pyloric sphincter. The chyme is highly acidic due to stomach acid, prompting the pancreas to release bicarbonate to neutralize this acidity before further digestion occurs. In the duodenum, bile from the liver emulsifies fats while pancreatic enzymes break down fats, proteins, and carbohydrates, allowing for nutrient absorption in the small intestine.
The digestive process takes several hours, with peristalsis moving chyme through the small intestine into the colon, where bacteria aid in synthesizing vitamins and managing waste. Various disorders can arise from issues related to chyme, often linked to excessive food or fluid intake, leading to discomfort or conditions like acid reflux and dyspepsia. Additionally, imbalances in bile and bicarbonate can result in malabsorption or digestive complications. Understanding chyme's role in digestion is crucial for addressing food-related health issues, particularly in diverse and developing contexts.
Subject Terms
Chyme
Biology
Also known as: Chymus
Anatomy or system affected: Gallbladder, gastrointestinal system, intestines, liver, pancreas, stomach
Definition: The slurry-like mixture of food and digestive juices produced in the digestive tract
Structure and Functions
Chewing and swallowing produce a bolus of food that descends through the esophagus into the stomach. There, the stomach walls secrete hydrochloric acid while waves of muscular contraction called peristalsis mix the stomach contents. The gastric juices break the bolus into small food particles, producing a thick fluid called chyme. Peristalsis causes the chyme to collect in the antrum, the lowest section of the stomach. The pyloric sphincter passes small portions of chyme into the duodenum at regular intervals.
Chyme is highly acidic because of stomach acid. To protect the membrane lining the duodenum, the pancreas releases bicarbonate to neutralize the acid. In the duodenum, digestion continues. Bile produced in the liver is added to the chyme to emulsify fats into small globules. The pancreas contributes enzymes that break down fats, proteins, and carbohydrates so that nutrients, minerals, and salts can be absorbed through the membrane of the small intestine and into the bloodstream.
Over a period of three to five hours, peristalsis pushes the chyme through the small intestine and into the colon. There, bacteria convert some ingredients of the chyme into vitamin K and vitamin B, which the colon extracts along with excess water. Bacteria also produce various gases. These gases are mixed with the remaining waste matter or feces.
Disorders and Diseases
Most disorders relating to chyme come from excessive food or water intake. When too much is eaten, the stomach distends and presses on the diaphragm. Peristalsis and the sheer bulk of the chyme can make breathing difficult and uncomfortable. When food contains a high proportion of fat, spices, or fibers and is eaten too quickly, the stomach can be overburdened. The churning of peristalsis may force some of the chyme back up the esophagus, causing a burning sensation there known as acid reflux or heartburn. This indigestion of the chyme, or dyspepsia, can make the stomach feel sour and achy and can lead to stomach ulcers. The stomach also may react to psychological stress by producing too much acid.
When the pancreas fails to produce enough bicarbonate to neutralize the acid in chyme after it enters the duodenum, the acid may burn through the mucosa in its wall and into tissue, producing a duodenal ulcer. Too much bile added to the chyme, if not reabsorbed in the distal small intestine, can lead to diarrhea, whereas too little bile can contribute to the malabsorption of nutrients. Similarly, excessive water intake may leach sodium from the body or cause the intestine to process the chyme too quickly for all the nutrients to be removed from it.
Researchers are studying the role chyme and its viscosity play in the effects of food-related illnesses, especially in developing nations worldwide, in an effort better understand the role of digestion in health.
Bibliography
Corcoran, Mary K., and Jef Czekaj. The Quest to Digest. Watertown, Mass.: Charlesbridge, 2006.
Lipski, Elizabeth. Digestive Wellness. 4th ed. New York: McGraw-Hill, 2012.
Moxon, Thomas E. et al. “Effect of Chyme Viscosity and Nutrient Feedback Mechanism on Gastric Emptying.” Chemical Engineering Science, vol. 171 (2017): 318-330. doi:10.1016/j.ces.2017.05.048
Parker, Steve. The Human Body Book. New York: DK Adult, 2001.
Seymour, Simon. Guts: Our Digestive System. New York: HarperCollins, 2005.