Digestive System - Biology

No chemical digestion occurs in the esophagus. The esophagus is used in order to move food into the stomach using peristaltic motion.

Amylase is introduced in the mouth and begins breaking down carbohydrates. Pepsin in the stomach helps digest proteins. Lipase, trypsin, and other digestive enzymes are introduced in the small intestine, where the majority of chemical digestion takes place.

The duodenum is the first section of the small intestine. It is the site of the most digestion in the small intestine (and the digestive tract in general) because pancreatic enzymes and bile are released into its lumen. These enzymes break down proteins and carbohydrates, while the bile helps to digest lipids and fats. The jejunum and ileum are primarily involved in absorbing nutrients. The cecum is part of the large intestine.

While the pancreas is responsible for the secretion of the majority of digestive enzymes, the liver is responsible for the creation of bile. The gall bladder is responsible for the storage of bile. When the gall bladder is stimulated, bile is released into the small intestine, where it helps with the emulsification and digestion of fats.

The liver has a variety of functions, including blood detoxification, glycogen formation, and blood filtration. The liver is not responsible for chemical digestion, but is needed to synthesize and store key nutrients and macromolecules. Protein digestion primarily takes place in the small intestine, though the process begins in the stomach.

The large intestine is located near the end of the gastrointestinal tract. Its primary function is to reabsorb water and nutrients prior to elimination of waste. Mechanical digestion of food occurs in the mouth and stomach. Chemical digestion of food occurs in the mouth (saliva has amylase), stomach, and early in the small intestine. Blood glucose levels are maintained by the pancreas.

Bile is a dark greenish brown substance continuously produced by the liver. It is stored and concentrated in the gallbladder, and is released into the small intestine after eating. In the small intestine, bile aids in the digestion of lipids (this is a very important part of the absorption of fat soluble substances such as certain vitamins).

The digestive system begins at the mouth where food is chewed into pieces small enough to be digested. In the mouth, food is already starting to be digested by enzymes, and is lubricated by saliva (saliva starts to be secreted even before you take your first bite). Next the pharynx, also called the throat, receives the food from the mouth. The food is then moved to the esophagus, which carries food to the stomach. From the stomach food is moved to the small intestine, then to the colon, rectum, and anus. During this process there are a number of motility types, hormones, secretions, and accessory digestive organs involved in the digestive process.

The trachea, also known as the windpipe, moves air from the pharynx (shared with the digestive system) to the bronchi and then into the lungs. It plays no role in digestion.

The pancreas is an important organ in digesting fats. The fat soluble vitamins (A, D, E, K) rely on the pancreatic function for their absorption into the body. Without the pancreas, an individual with cystic fibrosis will have fat soluble vitamin deficiencies and steatorrhea (fatty stools).

The stomach contains the enzyme pepsin, which helps sever the peptide bonds between amino acids and breaks protein molecules into smaller fragments. As the contents of the stomach enters the small intestine, more digestive enzymes are added to further digest the proteins; however, the first step occurs in the stomach.

It is important to note that the mouth is the first location at which carbohydrates are digested, due to the protein amylase found in saliva.

This is a fundamental question that checks for clear understanding of the purpose of the digestive system. The digestive system includes the mouth, esophagus, stomach, small intestine, and large intestine. The primary functions of these structures are to break down and absorb nutrients from ingested food.

The respiratory system is responsible for providing a site for gas exchange (namely the alveoli). The circulatory system delivers oxygen to tissues, while the excretory system removes nitrogenous wastes and maintains water balance via kidney function.

It is important to know sites of production and action of the digestive enzymes. In the stomach, the very low pH environment facilitates gastric enzyme function, so we can already assume that an acidic compound is involved in the stomach.

HCl, or hydrochloric acid, is the acidic compound released by parietal cells and functions to kill microorganisms, digest acid labile substances, and activate pepsinogen to create pepsin.

The second main digestive compound of the stomach is pepsin, a protease, which digests amino acids into smaller peptides. It is released as a zymogen, or inactive form, by chief cells before it is activated to pepsin. The inactive form of pepsin is called pepsinogen.

Bile is a substance produced by the liver, stored by the gall bladder, and secreted into the duodenum of the small intestine for emulsification of fat globules. HCO3-, or bicarbonate ion, is a basic substance released by the pancreas into the duodenum to neutralize the entering chyme, reducing acidity to allow for optimal enzyme activity in the duodenum. Neither bile, nor bicarbonate are active in the stomach.

The chemical digestion of food is facilitated by the secretion of the hormone gastrin, which stimulates the secretion of hydrochloric acid. Insulin is secreted by the pancreas in response to high levels of blood glucose. Glucagon is secreted in response to low levels of blood glucose. Aldosterone is secreted by the adrenal cortex and increases reabsorption of salt in the kidney, subsequently increasing water retention and blood volume. Thyroxine is secreted by the thyroid and increases the metabolic rate of most body cells.

Amylase is the enzyme secreted in salvia and into the small intestine by the pancreas that breaks down startch. Insulin is a hormone released from the pancreas that decreases blood glucose levels. Lysozyme is an enzyme present in saliva, tears, and sweat, and functions as a natural antibacterial. Pepsin is an enzyme responsible for the breakdown of proteins. Gastrin is a hormone released by the cells of the gastrointestinal organs which stimulates secretion of from the stomach, ultimately aiding in digestion.

The presence of food in the stomach stimulates the release of gastrin, which stimulates the secretion of gastric acid (). The acid in the stomach aids in digestion, and also functions as a nonspecific line of defense from infection, destroying most pathogens. Cholecystokinin is a hormone produced by the small intestine, and is responsible for stimulating release of digestive enzymes by other gastrointestinal organs. Amylase is an enzyme that breaks down starch. Motilin is a hormone that aids in digestion via pathways other than stimulating production of gastric acid in the stomach.

When food is swallowed and reaches the stomach, the distension of the stomach is the number one stimulator for acid production. Smelling food and chewing food does stimulate acid production, however, the rise in acid produced is not as significant as produced by distention of the stomach.

No chemical digestion occurs in the esophagus. The esophagus is used in order to move food into the stomach using peristaltic motion.

Amylase is introduced in the mouth and begins breaking down carbohydrates. Pepsin in the stomach helps digest proteins. Lipase, trypsin, and other digestive enzymes are introduced in the small intestine, where the majority of chemical digestion takes place.

The duodenum is the first section of the small intestine. It is the site of the most digestion in the small intestine (and the digestive tract in general) because pancreatic enzymes and bile are released into its lumen. These enzymes break down proteins and carbohydrates, while the bile helps to digest lipids and fats. The jejunum and ileum are primarily involved in absorbing nutrients. The cecum is part of the large intestine.

While the pancreas is responsible for the secretion of the majority of digestive enzymes, the liver is responsible for the creation of bile. The gall bladder is responsible for the storage of bile. When the gall bladder is stimulated, bile is released into the small intestine, where it helps with the emulsification and digestion of fats.

The liver has a variety of functions, including blood detoxification, glycogen formation, and blood filtration. The liver is not responsible for chemical digestion, but is needed to synthesize and store key nutrients and macromolecules. Protein digestion primarily takes place in the small intestine, though the process begins in the stomach.