"Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma."
The study of how the digestive system processes food, absorbs nutrients, and eliminates waste.
Anatomy of the Digestive System: The study of the structure and function of the organs that make up the digestive system, including the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.
The Digestive Process: The sequence of events that occur during the digestion of food in the digestive tract, including ingestion, propulsion, mechanical and chemical digestion, absorption, and elimination.
Gastrointestinal Motility: The muscular contractions that propel food through the digestive tract, including peristalsis, segmentation, and mixing.
Secretions of the Digestive System: The fluids and enzymes that are secreted by the various organs of the digestive system to aid in digestion and absorption.
Digestive Enzymes: The proteins that catalyze the breakdown of food molecules into smaller, more readily absorbable molecules.
Nutrient Absorption: The process by which the digested food molecules are taken up by the cells lining the digestive tract and transported to the rest of the body.
Role of Bacteria in Digestion: The importance of the bacterial populations in the gut for the health and function of the digestive system.
The Enteric Nervous System: The network of neurons in the digestive tract that regulates gastrointestinal motility, secretion, and blood flow.
Hormonal Regulation of Digestion: The role of hormones in coordinating the functions of the different organs of the digestive system and regulating digestion and absorption.
Disorders of the Digestive System: Common diseases and conditions that affect the digestive system, including acid reflux, ulcers, inflammatory bowel disease, and colorectal cancer.
Therapeutic Approaches: The pharmacological and dietary interventions used to treat digestive disorders, as well as surgical interventions when necessary.
Oral Physiology: It involves the mechanical and chemical breakdown of food in the mouth, teeth, salivary glands, and tongue.
Gastric Physiology: It involves the secretion of gastric juices, mixing and churning of food with these juices, and mechanical and chemical breakdown of food in the stomach.
Small Intestine Physiology: It involves the absorption of nutrients, minerals, vitamins, and water, as well as the secretion of digestive enzymes, hormones, and fluids.
Large Intestine Physiology: It involves the absorption of water, electrolytes, and vitamins, as well as the formation and elimination of feces through the rectum and anus.
Liver Physiology: It includes the production, storage, and secretion of bile, which aids in the digestion and absorption of fats.
Pancreatic Physiology: It involves the secretion of digestive enzymes, bicarbonate ions, and hormones, which assist in the breakdown of all types of food molecules.
Gallbladder Physiology: It involves the storage and secretion of bile produced by the liver, which aids in the digestion and absorption of fats.
Enteroendocrine Physiology: It involves the regulation of gastrointestinal hormones, which modulate digestion, absorption, and appetite.
Microbial Physiology: It involves the role of gut microbiota in the fermentation of undigested carbohydrates, production of short-chain fatty acids, and regulation of immune function.
Neuromuscular Physiology: It involves the coordination of smooth muscle contractions and the regulation of gastrointestinal motility by enteric nervous system, autonomic nervous system, and central nervous system.
"Digestion is often divided into two processes based on how food is broken down: mechanical and chemical digestion."
"The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes."
"Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions."
"In chemical digestion, enzymes break down food into the small compounds that the body can use."
"Mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva."
"Saliva, a liquid secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food; the saliva also contains mucus, which lubricates the food, and hydrogen carbonate, which provides the ideal conditions of pH (alkaline) for amylase to work, and electrolytes (Na+, K+, Cl−, HCO−3)."
"About 30% of starch is hydrolyzed into disaccharide in the oral cavity (mouth)."
"It will then travel down the esophagus and into the stomach by the action of peristalsis."
"Gastric juice mainly contains hydrochloric acid and pepsin. In infants and toddlers, gastric juice also contains rennin to digest milk proteins. As the first two chemicals may damage the stomach wall, mucus and bicarbonates are secreted by the stomach."
"The stomach provides a slimy layer that acts as a shield against the damaging effects of chemicals like concentrated hydrochloric acid while also aiding lubrication. Hydrochloric acid provides acidic pH for pepsin."
"At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which is waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes."
"Pepsin breaks down proteins into peptides or proteoses, which is further broken down into dipeptides and amino acids by enzymes in the small intestine."
"When the pyloric sphincter valve opens, partially digested food (chyme) enters the duodenum."
"Digestive enzymes from the pancreas and bile juice from the liver mix with the chyme in the duodenum, and then the digestion process continues in the small intestine."
"95% of nutrient absorption occurs in the small intestine."
"Water and minerals are reabsorbed back into the blood in the colon (large intestine) where the pH is slightly acidic (about 5.6 ~ 6.9)."
"Some vitamins, such as biotin and vitamin K (K2MK7) produced by bacteria in the colon, are also absorbed into the blood in the colon."
"Absorption of water, simple sugar, and alcohol also takes place in the stomach."
"Waste material is eliminated from the rectum during defecation."