UNIT-3-BIOCHEMISTRY-OF-DIGESTION-PPT-NEW-WITH-VIDEO (1).pdf

UNIT III DIGESTION PRESENTED BY: Fean Joyce A. Colita, RMT, RN  DIGESTION Objectives a. Define the main stages of digestion, mechanisms involved in absorption of nutrients from the digestive tract. b. Identify the role of digestive enzymes for the abs...

UNIT III DIGESTION PRESENTED BY: Fean Joyce A. Colita, RMT, RN  DIGESTION Objectives a. Define the main stages of digestion, mechanisms involved in absorption of nutrients from the digestive tract. b. Identify the role of digestive enzymes for the absorption and metabolism. c. Determine the gastrointestinal organs that are functional. d. Associated and responsible for digestion and absorption of the food. DEFINITION OF DIGESTION  Digestion is the process by which food is broken down into components simple enough to be absorbed in the intestine. Absorption is the uptake of the products of digestion by intestinal cells (enterocytes) and their delivery to blood or lymph. DIGESTION Digestion and absorption of nutrients are closely linked and are regulated by the nervous system, hormones and paracrine factors. The physical presence of food particles in the GI tract also stimulates these processes. MECHANISM OF DIGESTION  MECHANISM Digestion begins in the mouth, where the salivary glands produce α-amylase, which breaks down starch into oligosaccharides DIGESTION and sugars. When the food gets into the stomach, the amylase is deactivated by the low pH. Digestion includes both mechanical and chemical processes. 1. MECHANICAL DIGESTION is a purely physical process that does not change the chemical nature of the food. Instead, it makes the food smaller to increase both surface area and mobility. It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with saliva. MECHANISM OF DIGESTION 1. MECHANICAL DIGESTION it occurs after the food leaves the mouth. The mechanical churning of food in the stomach serves to further break it apart and expose more of its surface area to digestive juices, creating an acidic “soup” called chyme. MECHANISM OF DIGESTION 1. MECHANICAL DIGESTION Segmentation occurs mainly in the small intestine, consists of localized contractions of circular muscle of the muscularis layer of the alimentary canal. These contractions isolate small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents. By moving food back and forth in the intestinal lumen, segmentation mixes food with digestive juices and facilitates absorption. MECHANISM OF DIGESTION 2. CHEMICAL DIGESTION Breakdown of food particles by the action of enzymes to make the food into smaller particles starting in the mouth, digestive secretions break down complex food molecules into their chemical building blocks (for example, proteins into separate amino acids). These secretions vary in composition, but typically contain water, various enzymes, acids, and salts. The process is completed in the small intestine. Food that has been broken down is of no value to the body unless it enters the bloodstream and its nutrients are put to work. MECHANISM OF DIGESTION 2. CHEMICAL DIGESTION This occurs through the process of absorption, which takes place primarily within the small intestine. There, most nutrients are absorbed from the lumen of the alimentary canal into the bloodstream through the epithelial cells that make up the mucosa. Lipids are absorbed into lacteals and are transported via the lymphatic vessels to the bloodstream (the subclavian veins near the heart). MECHANISM OF DIGESTION MECHANISM OF DIGESTION  DIGESTION TAKES PLACE IN FIVE STAGES: 1. Ingestion - Food must be placed into the mouth before it can be acted on 2. Propulsion - To be processed by more than one digestive organ, foods must be propelled from one organ to the next. Peristalsis is involuntary and involves alternating waves of contraction and relaxation of the longitudinal muscles in the organ wall. 3. Food breakdown and digestion – Mechanical breakdown fragments food into smaller particles. Segmentation is a movement back and forth across intestinal wall of organ, mixing it with the digestive juices. It is the large food molecules are chemically broken down to their building blocks of enzymes. 4. Absorption - The small intestine is responsible for absorption. It carries the nutritional substance into the bloodstream. The blood then carries these substances to all parts of the body 5. Excretion/ Defecation - After absorption, the rest of the food passes into the large intestine. The parts of the food that cannot be used by the body are turned into feces. These feces are expelled from the body through the anus. MECHANISM OF DIGESTION  3. DIGESTIVE ENZYMES Enzymes activity is influenced by pH, temperature and the substance concentration of the solution. Depending on the type of enzyme, the pH will have a different impact on the rate of reaction. Major enzymes are: MECHANISM OF DIGESTION  1. CARBOHYDRATES DIGESTION a) Salivary amylase b) Pancreatic amylase Produced in Salivary glands Produced in Pancreas released released from mouth with from small intestine with neutral level of pH level. normal pH level. c) Maltase Produced in Small intestine released from small intestine with normal pH level.  2. PROTEIN DIGESTION a) Pepsin b) Trypsin Produced in gastric glands Produced in pancreas released released from stomach with high from small intestine with normal or acidic pH level. pH level. c) Peptidases Produced and released from small intestine with normal pH level.  3. FAT DIGESTION a) Lipase Produced in pancreas released from small intestine with normal pH level.  PHASES OF DIGESTION  I. SALIVARY DIGESTION PHASES OF DIGESTION ▪ Once the food has been placed in the mouth, both mechanical and chemical processing begins. ▪ First the food is physically broken down into smaller particles by chewing. ▪ Then, as the food is mixed with saliva, salivary amylase begins the digestion of starch, chemically breaking it down into maltose. ▪ Saliva is normally secreted continuously to keep the mouth moist, but when food enters the mouth, much larger amounts of saliva pour out. Essentially no food absorption occurs in the mouth. (However, some drugs, such as nitroglycerine, are absorbed easily through the  SALIVARY ENZYMES PHASES OF DIGESTION – Salivary amylase is the first step in the chemical digestion of food. This is one of the major reasons that it is so important for people to take time while eating and thoroughly chew their food. This initial step in the digestive process is essential to the proper breakdown of food eaten and the ultimate liberation of the nutrients within to be absorbed later in the digestive process. As the starches, polysaccharides, and complex carbohydrates continue through the digestive tract, they are further broken down from additional amylase released from the pancreas into the proximal small MECHANISM OF DIGESTION  II. GASTRIC DIGESTION Secretion of gastric juice is regulated by both neural and hormonal factors. PHASES OF DIGESTION The sight, smell, and taste of food stimulate parasympathetic nervous system reflexes, which increase the secretion of gastric juice by the gastric (stomach) glands. the presence of food and a rising pH in the stomach stimulate the stomach cells to release the hormone gastrin. Gastrin prods the gastric glands to produce still more of the protein digesting enzymes (such as pepsinogen), mucus, and hydrochloric acid. Under normal conditions, 2 to 3 liters of gastric juice are produced every day. Hydrochloric acid and the protein- digesting enzymes have the ability to digest the stomach itself, causing ulcers. However, as long as enough mucus is made, the stomach is protected. GASTRIC ENZYMES 1. Pepsin - The extremely acidic environment that hydrochloric acid provides is necessary, because it activates pepsinogen to pepsin. The active protein-digesting enzymes. 2. Renin - The second protein-digesting enzyme produced by the stomach, works primarily on milk protein and converts it to a substance that looks like sour milk. Many parents mistakenly think that the curdy substance infants spit up after feeding is milk that has soured in their stomach. Produced in large amounts in infants, is the same enzyme used to make milk curdle into cheese. It is not believed to be produced in adult III. INTESTINAL DIGESTION  PANCREATIC ENZYMES 1. Pancreatic 2. Pancreatic proteinases amylase (Trypsin, chymotrypsin, along with brush border enzymes, caboxypeptidase PANCREAS complete the digestion carry out about half Divided into head, body, and tail. Connected directly to the duodenum by accessory duct, of starch (polypeptides of protein digestion and indirectly by pancreatic duct (which joins the into disaccharides). (digest peptides into common bile duct). amino acids. Serves as both an endocrine (pancreatic islets secrete 3. Pancreatic hormones) and exocrine gland (acini secrete pancreatic 4. Pancreatic fluid and enzymes for chemical digestion in the small intestine). lipase nucleases Pancreatic fluid contains sodium bicarbonate to raise the responsible for fat digest nucleic acids pH of chime in small intestine to 7.1-8.2, stopping pepsin activity and promoting activity of pancreatic enzymes. digestion ( digest into nucleotides. Pancreas also produces hormones Insulin (lower blood triglycerides into sugar level), and glucagon (raises blood sugar level). fatty acids). PANCREATIC JUICE contains a rich supply of bicarbonate ions, which makes it very basic (about pH 8). When pancreatic juice reaches the small intestine, it neutralizes the acidic chyme coming in from the stomach and provides the proper environment for activation and activity of intestinal and pancreatic digestive enzymes. Pancreatic juice contains enzymes. The release of pancreatic juice into the duodenum is stimulated by both the vagus nerve and local hormones. When chyme enters the small intestine, it stimulates the mucosa cells to produce several hormones. III. INTESTINAL DIGESTION PANCREATIC JUICE hormones, secretin (se-kre′tin) and cholecystokinin (ko″le- sis″to-kin′in) (CCK), influence the release of pancreatic juice and bile. The hormones enter the blood and circulate to their target organs, the pancreas, liver, and gallbladder. Both hormones work together to stimulate the pancreas to release its enzyme- and bicarbonate-rich product. In addition, secretin causes the liver to increase its output of bile, and cholecystokinin causes the gallbladder to contract and release stored bile into the bile duct so that bile and pancreatic juice enter the small intestine together. bile is not an enzyme. It acts like a detergent to emulsify, or mechanically separate, large fat globules into thousands of tiny ones, providing a much greater surface area for the pancreatic lipases to work on. III. INTESTINAL DIGESTION  BILE necessary for absorption of fats—and the fat-soluble vitamins (K, D, E, and A) that are absorbed along with them—from the intestinal tract. If either bile or pancreatic juice is absent, essentially no fat digestion or absorption goes on, and fatty, bulky stools are the result. In such cases, blood-clotting problems also occur because the liver needs fat-soluble vitamin K to make prothrombin, an important clotting factor. Bile Pigmentation derived from the degradation of HEMOGLOBIN: Biliverdin and Bilirubin Bile Acids 1. Cholic acid: 26 - 60% 2. Chenodeoxycholic acid: 30 - 50% 3. Deoxycholic: 5 - 25% If conjugated with glycine or taurine-glycocholic or taurocholic acid III. INTESTINAL DIGESTION  BILE Functions: Activate steapsin – enzyme lipase Emulsification Choleretics Neutralization of acid (pH >7) Aid in absorption of fat and fat-soluble substances (Hydrotropic effect) Maintain cholesterol in solution III. INTESTINAL DIGESTION  The bile duct, delivering bile from the liver, and the main pancreatic duct, carrying pancreatic juice from the pancreas, unite in the well of duodenum in a bulblike structure called the hepatopancreatic ampulla. The ampulla opens into the duodenum via the major duodenal papilla. The entry of bile and pancreatic juice is controlled by a muscular valve called the hepatopancreatic sphincter or sphincter of oddi. Liver The largest gland in the human body. Divided into 4 lobes (left, right, quadrate, and caudate lobes) held together by falciform ligament. Coronary ligament binds the liver to diaphragm. Each lobe of the liver consists of functional units called hepatic lobules which contain hepatic cells and blood vessels. Nutrients from the small intestine are transported to the liver via the hepatic portal vein for detoxification and metabolism purposes, after Gallbladder A small sac located on the inferior, visceral surface of the liver. Stores and concentrates bile secreted by the liver. Ejects bile into the cystic duct which joins the hepatic duct from the liver, together they form the common bile duct, which in turn joins the pancreatic duct of the pancreas, and ultimately attaches to the duodenum. Bile is a yellowish liquid that is used to emulsify lipids, so that lipases can break down fat easily.  SMALL INTESTINE is composed of Chyme reaching the small intestine is only partially digested. Carbohydrate and protein digestion has begun, but virtually no fats or nucleic acids have been digested up to this point. Here the process of chemical digestion is accelerated as the food now takes a rather wild 3- to 6-hour journey through the looping coils and twists of the small intestine. By the time the food reaches the end of the small intestine, digestion will be complete, and nearly all food absorption will have occurred the duodenum, jejunum, and ileum. It averages approximately 6m (about 19-20 feet) in length, extending from the pyloric sphincter of the stomach to the ileocecal valve separating the ileum from the cecum. The small intestine is compressed into numerous folds and occupies a large proportion of the abdominal cavity. III. INTESTINAL DIGESTION INTESTINAL JUICE Produced by the intestinal glands and mucus cells in the small intestines it is relatively enzyme poor and protective mucus is probably the most important intestinal gland secretion. However, foods entering the small intestine are literally deluged with enzyme-rich pancreatic juice delivered via a duct from the pancreas, as well as bile from the liver. III. INTESTINAL DIGESTION  LARGE INTESTINE Finally the food delivered to the large intestine contains few nutrients, but that residue still has 12 to 24 hours more to spend there. The colon itself produces no digestive enzymes. However, the “resident” bacteria that live in its lumen metabolize some of the remaining nutrients, releasing gases (methane and hydrogen sulfide) that contribute to flatulence and the odor of feces. About 500 ml of gas (flatus) is produced each day, much more when certain carbohydrate-rich foods (such as beans) are eaten. Bacteria residing in the large intestine also make some vitamins (vitamin K and some B vitamins). Absorption by the large intestine is limited to the absorption of these vitamins, some ions, and most of the remaining water. Feces, the more or less solid product delivered to the rectum, contains undigested food residues, mucus, millions of bacteria, and just enough water to allow its smooth passage III. INTESTINAL DIGESTION  CHEMICAL CHANGES IN THE LARGE INTESTINES The semi- liquid residue which has escaped digestion and absorption are passed into the large intestine. Intestinal microorganisms disintegrate these organic residues into simpler fragments: III. INTESTINAL DIGESTION CHEMICAL CHANGES IN THE LARGE INTESTINES 1. Fermentation - bacterial degradation of carbohydrates under anaerobic condition Products: Organic acids (e. g. lactic acid, acetic acid, formic acid, propionic acid and succinic acid), Gases (methane, CO2, H2) 2. Putrefaction – bacterial decomposition of proteins under anaerobic condition Example: tryptophan Indole + Skatole 3. Deamination ¬removal of amine group from simple amino acids to form short-chain organic acids 4. Decarboxylation- removal of carboxyl group forming amines III. INTESTINAL DIGESTION CHEMICAL CHANGES IN THE LARGE INTESTINES 5. Detoxification - Reactions involved: A. Oxidation - one of the most important means of detoxification I.) CH3 CH2OH + O2 CO2 + H2O B. Reduction--minor role in the detoxification C. Hydrolysis - some drugs used for therapy are hydrolyzed in the body Acetylsalicylic acid Salicylic acid + Acetic acid D. Conjugation- combination of the toxic substance or its metabolite with a compound occurring normally in the body (whenever oxidation becomes ineffective) Occurs mainly in the liver Conjugating agents: acetic acid, Cysteine, Glucuronic acid, Glutamine, Glycine, Methyl group, Sulfuric acid, Thiosulfate III. INTESTINAL DIGESTION ABSORPTION AND FECES FORMATION about 94% of the total amount of water passing through the alimentary canal is absorbed by the SMALL INTESTINE. Large intestine absorbs MOST of the remaining 6% of water. III. INTESTINAL DIGESTION  FECES Feces consist of undigested foodstuffs, inorganic materials, water, and bacteria. Fecal matter is about 75% fluid and 25% solid material. The composition is relatively unaffected by alterations in diet because a large portion of the fecal mass is of non-dietary origin, derived from the secretions of the GI tract. The brown color of the feces results from the breakdown of bile by the intestinal bacteria. Chemicals formed by intestinal bacteria are responsible in large part for the fecal odor. Gases formed contain methane, hydrogen sulfide, and ammonia, among others. The GI tract normally contains approximately 150 mL of these gases, which are either absorbed into the portal circulation and detoxified by the liver or expelled from the rectum as flatus. III. INTESTINAL DIGESTION  FECES Elimination of stool begins with distention of the rectum, which initiates reflex contractions of the rectal musculature and relaxes the normally closed internal anal sphincter. The internal sphincter is controlled by the autonomic nervous system; the external sphincter is under the conscious control of the cerebral cortex. During defecation, the external anal sphincter voluntarily relaxes to allow colonic contents to be expelled. Normally, the external anal sphincter is maintained in a state of tonic contraction. defecation is seen to be a spinal reflex (involving the parasympathetic nerve fibers) that can be inhibited voluntarily by keeping the external anal sphincter closed. Contracting the abdominal muscles (straining) facilitates emptying of the colon. The average frequency of defecation in humans is once daily. When the diet lacks bulk, the colon narrows and its circular muscles contract more powerfully, increasing the pressure on its walls. This encourages the formation of diverticula, in which the mucosa protrudes through the colon walls, a condition called diverticulosis. Diverticulitis, a condition in which the diverticula become inflamed, can be life-threatening if ruptures occur III. INTESTINAL DIGESTION Clinical Terms 1. Dysphagia - difficulty swallowing due to obstruction or trauma to esophagus. 2. Cholecystitis - inflammation of the gallbladder. 3. Cholelithiasis- stones in the gallbladder. 4. Peptic ulcer - term referring to gastric and duodenal ulcers. 5. Endoscopy - visual examination of the ventral body cavity or the interior of the organs (tubular) with an endoscope which contains a light source and a lens. 6. Colonoscopy - endoscopy of the colon. 7. Sigmoidoscopy - endoscopy of the sigmoid colon. 8. pyloric stenosis - congenital narrowing of the pyloric sphincter. Problems begin when baby begins to take solid food. Corrected surgically.  TIME FOR QUESTIONS!  THANK YOU FOR LISTENING QUIZ BUKAS :> FREE RESOURCE PAGE You can use these gorgeous elements to customize the slides. FREE RESOURCE PAGE You can use these gorgeous elements to customize the slides. FREE RESOURCE PAGE You can use these gorgeous elements to customize the slides.