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= Lesson 77 - Gastrointestinal Diseases =
= Lesson 77 - Gastrointestinal Diseases =
== The Gastrointestinal Tract ==
== The Gastrointestinal Tract ==
77.1.1 The Mouth
77.1.1 The Mouth
The gastrointestinal tract begins with the mouth and ends with the anus. Disease symptoms may arise anywhere along that route if we do not follow the Laws of Life, i.e., if we live unhealthfully. A few of the most common “diseases” will be discussed and the reason for their occurrence. It is not necessary to elaborate upon every disease known, as all diseases stem from a common cause—toxicosis. First of all, it is necessary for you to have a brief review of the function and structure of the normal gastrointestinal tract.
The gastrointestinal tract begins with the mouth and ends with the anus. Disease symptoms may arise anywhere along that route if we do not follow the Laws of Life, i.e., if we live unhealthfully. A few of the most common “diseases” will be discussed and the reason for their occurrence. It is not necessary to elaborate upon every disease known, as all diseases stem from a common cause—toxicosis. First of all, it is necessary for you to have a brief review of the function and structure of the normal gastrointestinal tract.
=== The Mouth ===
The tongue, composed primarily of striated muscles and covered by mucous mem- brane, plays important roles in the mastication of food and in the act of swallowing. The teeth have an important role in the mechanical mastication of food prior to swallowing.
The tongue, composed primarily of striated muscles and covered by mucous mem- brane, plays important roles in the mastication of food and in the act of swallowing. The teeth have an important role in the mechanical mastication of food prior to swallowing.
As digestive enzymes act solely at the surface of food particles, the rate of digestion is related directly to the extent to which food is masticated.
As digestive enzymes act solely at the surface of food particles, the rate of digestion is related directly to the extent to which food is masticated.
=== The Pharynx and Esophagus ===
The pharynx is the portion of the digestive tract serving is a passageway for both the respiratory and digestive systems.
The pharynx is the portion of the digestive tract serving is a passageway for both the respiratory and digestive systems.
bral column. Esophageal glands serve to lubricate food during its passage from the phar- ynx to the stomach.
bral column. Esophageal glands serve to lubricate food during its passage from the phar- ynx to the stomach.
=== The Stomach ===
The stomach is the most widely-dilated portion of the digestive tract. It functions to store and digest food. In the stomach, solid food ultimately is converted into a semifluid mass by contraction of the muscular wall combined with mixture of the food with the glandular secretions of the gastric mucous membrane. Although food in the upper region of the stomach may remain solid for relatively long periods, food becomes transformed into a pulpy fluid mass (chyme) in the lower part of the organ.
The stomach is the most widely-dilated portion of the digestive tract. It functions to store and digest food. In the stomach, solid food ultimately is converted into a semifluid mass by contraction of the muscular wall combined with mixture of the food with the glandular secretions of the gastric mucous membrane. Although food in the upper region of the stomach may remain solid for relatively long periods, food becomes transformed into a pulpy fluid mass (chyme) in the lower part of the organ.
The cardia is the opening between the esophagus and the stomach. The pylorus is the opening between the stomach and the duodenum. The circular muscle layer is thick- ened in the pyloric region to form the pyloric sphincter.
The cardia is the opening between the esophagus and the stomach. The pylorus is the opening between the stomach and the duodenum. The circular muscle layer is thick- ened in the pyloric region to form the pyloric sphincter.
==== Gastric Juice ====
Cells of the gastric glands secrete a total volume ranging between two and three liters per day. This digestive fluid contains a number of substances. In addition, gastric mucous cells and glands secrete a thick alkaline mucus that forms a thin coating on the stomach wall. Thus, it is of great importance in protecting the epithelial lining of the stomach.
Cells of the gastric glands secrete a total volume ranging between two and three liters per day. This digestive fluid contains a number of substances. In addition, gastric mucous cells and glands secrete a thick alkaline mucus that forms a thin coating on the stomach wall. Thus, it is of great importance in protecting the epithelial lining of the stomach.
Energy for hydrocholoric acid secretion is provided by aerobic glycolysis. That is, the conversion of glycogen into glucose. Energy is needed for the transport of hydrogen ions across the membrane of the parietal cell1. Chloride ion also is secreted actively by the parietal cells.
Energy for hydrocholoric acid secretion is provided by aerobic glycolysis. That is, the conversion of glycogen into glucose. Energy is needed for the transport of hydrogen ions across the membrane of the parietal cell1. Chloride ion also is secreted actively by the parietal cells.
==== Histamine and Gastric Acid Secretion ====
Histamine is a powerful stimulant to gastric acid secretion, and the action of hista- mine is mediated by cyclic adenosine monophosphate. As the gastric mucosa normally has a high concentration of histamine, liberation of this compound has been implicated as the chemical mediator in stimulation of acid secretions.
Histamine is a powerful stimulant to gastric acid secretion, and the action of hista- mine is mediated by cyclic adenosine monophosphate. As the gastric mucosa normally has a high concentration of histamine, liberation of this compound has been implicated as the chemical mediator in stimulation of acid secretions.
Chemical agents in addition to histamine also appear to have a role in acid secretion by the stomach, for example, gastrin.
Chemical agents in addition to histamine also appear to have a role in acid secretion by the stomach, for example, gastrin.
=== The Small Intestine ===
The small intestine extends from the pyloric sphincter to the cecum, the first portion of the large intestine. It is approximately 18 feet in length and is divided into three por- tions: the duodenum, jejunum and ileum. The duodenum is the shortest, widest and most fixed portion of the small intestine. It receives secretions of the liver and pancreas.
The small intestine extends from the pyloric sphincter to the cecum, the first portion of the large intestine. It is approximately 18 feet in length and is divided into three por- tions: the duodenum, jejunum and ileum. The duodenum is the shortest, widest and most fixed portion of the small intestine. It receives secretions of the liver and pancreas.
Intestinal Villi. Intestinal villi are minute flattened (in the duodenum) or fingerlike (in the ileum) projections of the mucous membrane that cover the entire surface of the intestinal mucosa.
Intestinal Villi. Intestinal villi are minute flattened (in the duodenum) or fingerlike (in the ileum) projections of the mucous membrane that cover the entire surface of the intestinal mucosa.
==== Enzymes of the Small Intestine ====
Many enzymes are found in the small intestine:
Many enzymes are found in the small intestine:
# Asmallquantityofintestinalamylaseispresent.Thisenzymeconvertspolysaccharides into disaccharides.
# Asmallquantityofintestinalamylaseispresent.Thisenzymeconvertspolysaccharides into disaccharides.
# Four enzymes are present in the intestinal fluids that split disaccharides into monosac- charides. These include sucrose, maltase, isomaltase and lactose (in children).
# Four enzymes are present in the intestinal fluids that split disaccharides into monosac- charides. These include sucrose, maltase, isomaltase and lactose (in children).
# Anintestinallipaseisalsopresent,andthisenzymedegradesneutralfatsintofattyacids and glycerol. 77.1.4.2 Accessory Digestion Secretions Pancreatic Secretion Pancreatic secretion The pancreas secretes between 1,200 and 2,000 ml/day of digestive fluid rich in bi- carbonate and a number of enzymes. The pH of pancreatic juice is about 8.0. This al- kalinity, together with the neutrality or slight alkalinity of the bile and intestinal juices, neutralizes acidity of the gastric chyme as it enters the duodenum. The pH of duodenal chyme is raised to between 6.0 and 7.0. Therefore, when chyme reaches the jejunum it is approximately neutral. Consequently, the intestinal contents almost never exhibit an acidic reaction. Pancreatic juice contains a number of potent enzymes for digestion of proteins, car- bohydrates, fats and other compounds. The proteolytic enzymes secreted by the pancreas include trypsin and two chymotrypsins. These enzymes cleave whole and partially-di- gested proteins. Carboxypeptidase is a pancreatic enzyme that attacks peptide chains at their ends, thereby liberating the terminal amino acid with its free carboxyl group. In ad- dition, a ribonuclease and deoxyribonuclease are present in pancreatic juice. These en- zymes split ribonucleic acid and deoxyribonucleic acid, respectively. Pancreatic a-amy- lase hydrolyzes starches, glycogen and many other carbohydrates into disaccharides. However, this enzyme does not hydrolyze cellulose, an important polysaccharide found in plant material. Pancreatic lipase hydrolyzes neutral fats into glycerol and fatty acids.
# Anintestinallipaseisalsopresent,andthisenzymedegradesneutralfatsintofattyacids and glycerol.
==== Accessory Digestion Secretions Pancreatic Secretion ====
===== Pancreatic secretion =====
The pancreas secretes between 1,200 and 2,000 ml/day of digestive fluid rich in bi- carbonate and a number of enzymes. The pH of pancreatic juice is about 8.0. This al- kalinity, together with the neutrality or slight alkalinity of the bile and intestinal juices, neutralizes acidity of the gastric chyme as it enters the duodenum. The pH of duodenal chyme is raised to between 6.0 and 7.0. Therefore, when chyme reaches the jejunum it is approximately neutral. Consequently, the intestinal contents almost never exhibit an acidic reaction. Pancreatic juice contains a number of potent enzymes for digestion of proteins, car- bohydrates, fats and other compounds. The proteolytic enzymes secreted by the pancreas include trypsin and two chymotrypsins. These enzymes cleave whole and partially-di- gested proteins. Carboxypeptidase is a pancreatic enzyme that attacks peptide chains at their ends, thereby liberating the terminal amino acid with its free carboxyl group. In ad- dition, a ribonuclease and deoxyribonuclease are present in pancreatic juice. These en- zymes split ribonucleic acid and deoxyribonucleic acid, respectively. Pancreatic a-amy- lase hydrolyzes starches, glycogen and many other carbohydrates into disaccharides. However, this enzyme does not hydrolyze cellulose, an important polysaccharide found in plant material. Pancreatic lipase hydrolyzes neutral fats into glycerol and fatty acids.
===== Bile =====
Bile is secreted continuously by hepatic cells and excreted via a system of ducts into the bile duct and eventually passes into the duodenum.
Bile is secreted continuously by hepatic cells and excreted via a system of ducts into the bile duct and eventually passes into the duodenum.
Bile is a complex fluid containing a number of components. It contains no digestive enzymes, but is of importance in digestion because of the bile salts it contains. Bile salts perform the important task of emulsifying fats in the intestine, thereby increasing enor- mously the total surface area of these substances exposed to the action of pancreatic and intestinal lipases. Exclusion of bile from the intestine results in a loss of up to 25 percent of ingested fat in the feces.
Bile is a complex fluid containing a number of components. It contains no digestive enzymes, but is of importance in digestion because of the bile salts it contains. Bile salts perform the important task of emulsifying fats in the intestine, thereby increasing enor- mously the total surface area of these substances exposed to the action of pancreatic and intestinal lipases. Exclusion of bile from the intestine results in a loss of up to 25 percent of ingested fat in the feces.
=== The Large Intestine ===
The large intestine differs from the small intestine in several ways, including its greater width and the following characteristics:
The large intestine differs from the small intestine in several ways, including its greater width and the following characteristics:
# Theglandsareofgreaterdepth,aremorecloselypacked,andcontainmanygobletcells.
# Theglandsareofgreaterdepth,aremorecloselypacked,andcontainmanygobletcells.
# Thelongitudinalmusclelayerofthececumandcolonislimitedtothreebands,visible on the surface, called teniae coli.
# Thelongitudinalmusclelayerofthececumandcolonislimitedtothreebands,visible on the surface, called teniae coli.
# Manyextensionsoffat-filledperitoneumareapparentalongthefreeborderofthecolon. The cecum, or first portion of the large intestine, is an elongated pouch situated in the right lower portion of the abdomen. Attached to its base is a slender tube, the appendix. The ascending colon extends upward from the cecum on the right posterior abdomi- nal wall to the undersurface of the liver just anterior to the right kidney. The transverse colon overlies the coils of the small intestine and crosses the abdominal cavity from right to left below the stomach. The descending colon begins near the spleen, passing downward on the left side of the abdomen to the iliac crest to become the pelvic colon. The descending colon is six inches in length and does not possess a mesentery. The pelvic, or sigmoid, colon is so called because of its S-shaped course within the pelvic cavity. 77.1.5.1 Large Intestine Secretions Mucus The large intestine is provided with enormous numbers of goblet cells both in the glands as well as on the mucosal surface. These cells secrete quantities of a viscous mu- cus having a pH around 8.0. This is the only major secretion of the large intestine. The mucus serves not only to protect and lubricate the intestinal wall, but to bind fecal mate- rial together. The mucus also serves to protect the colon from acids formed by the enor- mous amount of bacterial activity that takes place in the fecal matter itself. 77.1.5.2 Water and Electrolytes Irritation of the intestinal mucosa (e.g., when a drug is taken such as a cathartic) re- sults in secretion of large quantities of water and electrolytes in addition to mucus. This water and electrolyte secretion serves not only to dilute the irritant, but the colonic dis- tension also stimulates rapid movement of the watery feces to the anus, causing diarrhea. Water and electrolyte loss from a patient can result in dehydration of the body tissues and a severe electrolyte imbalance that can have rapidly fatal consequences, especially in infants.
# Manyextensionsoffat-filledperitoneumareapparentalongthefreeborderofthecolon.
The cecum, or first portion of the large intestine, is an elongated pouch situated in the right lower portion of the abdomen. Attached to its base is a slender tube, the appendix.
The ascending colon extends upward from the cecum on the right posterior abdomi- nal wall to the undersurface of the liver just anterior to the right kidney. The transverse colon overlies the coils of the small intestine and crosses the abdominal cavity from right to left below the stomach.
The descending colon begins near the spleen, passing downward on the left side of the abdomen to the iliac crest to become the pelvic colon. The descending colon is six inches in length and does not possess a mesentery. The pelvic, or sigmoid, colon is so called because of its S-shaped course within the pelvic cavity.
==== Large Intestine Secretions ====
===== Mucus =====
The large intestine is provided with enormous numbers of goblet cells both in the glands as well as on the mucosal surface. These cells secrete quantities of a viscous mu- cus having a pH around 8.0. This is the only major secretion of the large intestine. The mucus serves not only to protect and lubricate the intestinal wall, but to bind fecal mate- rial together. The mucus also serves to protect the colon from acids formed by the enor- mous amount of bacterial activity that takes place in the fecal matter itself.
==== Water and Electrolytes ====
Irritation of the intestinal mucosa (e.g., when a drug is taken such as a cathartic) re- sults in secretion of large quantities of water and electrolytes in addition to mucus. This water and electrolyte secretion serves not only to dilute the irritant, but the colonic dis- tension also stimulates rapid movement of the watery feces to the anus, causing diarrhea. Water and electrolyte loss from a patient can result in dehydration of the body tissues and a severe electrolyte imbalance that can have rapidly fatal consequences, especially in infants.
== Digestive System Disorders ==
=== Nausea and Vomiting ===
=== Nausea and Vomiting ===
Nausea and vomiting may occur for several reasons but basically, they are the body’s way of telling you that it wants to “close down shop for repairs.” When hunger is not present and you are experiencing some nausea, you should not eat. The body must redi- rect all of its energies for the healing crisis that is going on within you. If food is taken at this time, it most likely will be vomited. Fast until hunger returns and health will be restored at the same time.
Nausea and vomiting may occur for several reasons but basically, they are the body’s way of telling you that it wants to “close down shop for repairs.” When hunger is not present and you are experiencing some nausea, you should not eat. The body must redi- rect all of its energies for the healing crisis that is going on within you. If food is taken at this time, it most likely will be vomited. Fast until hunger returns and health will be restored at the same time.