Digestion, Absorption, and Transportation (FN1070) PDF

Digestion, Absorption, Transportation FN1070 – WEEK 3 Diges&on  1. Air/Food/Liquid all need to go to the right places. 2. A passageway is needed for food to get from the mouth, through the diaphragm, to reach the stomach below 3. C...

Digestion, Absorption, Transportation FN1070 – WEEK 3 Diges&on  1. Air/Food/Liquid all need to go to the right places. 2. A passageway is needed for food to get from the mouth, through the diaphragm, to reach the stomach below 3. Contents within the GI tract need to keep moving at a precise pace. 7 Facts About 4. Liquid content needs to be kept within narrow limits to prevent the contents from being too runny or thick. Digestion & 5. Liquid is also needed during the process or digestion and Absorption absorption, and then is reabsorbed, leaving just the right amount for waste products to exit the body. 6. The stomach and intestinal cells need to be protected from the digestive juices that break down the food we eat 7. Waste excretion does not happen continuously, but at intervals...this varies between people. Figure 3.1  § Gastrointestinal Tract: § One flexible tube extends from mouth to the anus § Inner space within the GI tract is called the lumen § A nutrient must penetrate through the GI tract wall to enter the body § Many materials pass through the GI tract undigested and are excreted § Mouth The anatomy of § Digestion begins here the diges:ve § Mechanical and chemical digestion begins § Teeth chew large pieces of food into smaller pieces tract (mastication) Taste buds (other senses matter too) Particles mix with fluid to stimulate taste buds Sweet, sour, salty, bitter, umami Tongue moves food around to facilitate chewing and swallowing Swallowed food/fluid passes over the pharynx Epiglottis closes over the airway and food passes through the pharynx to the...  § Esophagus § Esophageal sphincters The anatomy of § Stomach the digestive § Upper/lower portions tract § Addition of digestive juices to form chyme § Pyloric sphincter – opens to release chyme into the small intestine  Small Intestine Three segments: duodenum, jejunum, ilium 3 meters of tubing Digestion and absorption occur throughout the various segments The anatomy of Large Intestine (colon) the diges:ve Ileocecal sphincter tract Water resorption occurs here Ends at the rectum/anus – muscles/sphincters contract to hold contents in, relax to release Gall Bladder and Pancreas also play key roles  Chewing & Swallowing: § Breaks into smaller pieces § Ac1on of the tongue § Saliva The Muscular Action of Peristalsis: § The contrac1on and relaxa1on of circular and Digestion longitudinal muscles along the GI tract § 3 1mes per minute in the stomach / 10 1mes per minutes in the small intes1ne What can interfere with peristalsis?  Stomach Action: § Thickest walls and strongest muscles (3 layers) of the GI tract § Release of gastric juices The Muscular Ac:on of Segmentation: Diges:on § Contractions of the small intestine § Continues to break food down § Promotes close contact with digestive juices  Sphincter Contractions: § Esophageal sphincters § upper – opens with swallowing to let food into the esophagus § Lower- opens to allow movement of food into the The Muscular small intestine and also prevents reflux of stomach Action of contents Digestion § Pyloric sphincter – keeps contents in the stomach, opens ~3x/minute to let small amounts of chyme through into the small intestine § Ileocecal sphincter – allows emptying of contents from the small intestine § Anal sphincter – prevents continuous elimination  § 5 different organs provide secretions to breakdown food into nutrients § Salivary glands § Stomach The Chemical § Pancreas Ac:on of § Liver (via gallbladder) Diges:on § Small intestine § These are provided at different points along the GI tract  § Enzyme § a protein that facilitates a chemical reaction § Is a catalyst that remains unchanged itself § Digestive enzymes facilitate hydrolysis § Remember the ending “ase” The Chemical § Identified by the organ they come from and the compound they work on Action of § Examples: salivary amylase vs pancreatic Digestion amylase § Common Digestive Enzymes § Carbohydrase § Lipase § Protease  Saliva § From salivary glands § Contains water, salts, mucus and enzymes The Secre:ons § Salivary amylase starts the digestion of CHO of Diges:on § Moistens food § Protects the teeth and linings of the mouth, esophagus, and stomach  Gastric Juice § Mixture of water, enzymes, and hydrochloric acid (HCl) § Hydrochloric acid: The Secretions § Works on protein digestion of Digestion § Reflux into the esophagus may cause sensation of heartburn § Protects stomach from bacterial growth § Cells that line the stomach, and gastric wall, secrete mucus to protect from the acidity of HCl.  Pancreatic Juice and Intestinal Enzymes § Pancreatic digestives juices are secreted into the first portion of the small intestine Secre:ons of § These contain enzymes that work on all three macronutrients Diges:on § Crypt glands secrete intestinal enzymes on the surface of the cells lining the intestinal wall § Contain sodium bicarbonate § Neutralizes the acidity of the acidic chyme coming from the stomach  Bile § Made in the liver § Stored in the gallbladder Secretions of § Emulsifying agent for fat (not an enzyme) Digestion *Refer to Table 3-1 in your text for a summary of digestive secretions and their actions  § Carbohydrates, fat, and protein are ready to be absorbed § Some fibres and other undigested residue are not absorbed and are excreted § Water and any salts that the body can use are reabsorbed The Final Stage § In the colon, intestinal bacteria ferment some fibers in the colon producing water, gas, and energy for the colon cells § Stool is formed from the rest which is deemed waste/not useful for the body § What happens when we have diarrhea or constipation? Absorption  § Most absorption takes place in the…. Absorption Small Intestine § 3meters in length (about the surface area of a tennis court) § Looks smooth, but is actually wrinkly § Villi: Finger-like projections; constantly moving ready to trap nutrients § Microvilli: absorptive area on the villi § Crypt Glands: between the villi; secrete intestinal juices(enzymes) www.reference.com § Goblet Cells: secrete mucous  Folds with villi on them Anatomy of the Absorp:ve System Figure 3-10  Specialized cells: § Certain nutrients are absorbed in the upper GI tract, and certain ones in the lower When might this impact someone’s nutritional Anatomy of the status the most? Absorptive System Food combining: § Means consuming certain foods in combination with one another § This is a myth, as the intestinal tract is capable of handling this  Simple Diffusion, Facilitated Diffusion, Active Transport Video Link  Preparing nutrients for transport once absorbed: § After nutrients have crossed the villi it enters the bloodstream or lymphatic system Anatomy of the § Water-soluble nutrients are released into the Absorptive bloodstream where they move to the liver System § Larger fats and fat-soluble vitamins cluster together into chylomicrons to be transported in the lymphatic system Transporta)on Vascular and Lymphatic Systems  The Vascular (blood circulatory) System: § Closed system of vessels § Continuous flow of blood Vascular System § Pump = heart  Nutrient transport Waste and carbon dioxide Body Blood Tissues Nutrients and oxygen  Heart Veins Arteries Capillaries  Heart Transport through the Digestive Hepatic Vein Arteries System Capillaries Capillaries in Liver (in intestines) Hepatic Portal Vein  The Liver: § First to receive water-soluble nutrients absorbed from the GI tract § Most metabolically active organ in the body Vascular System § Network of capillaries branch throughout the liver making nutrients and oxygen available to the cells § Samples the blood to detoxify harmful substances § Prepares waste products for excretion  § No pump § Fluid is collected in lymph vessels from tissues and direct this toward the heart The Lymphatic § Nutrients (large products of fat digestion and fat- soluble vitamins) absorbed in the lymphatic System system ultimately end up in the bloodstream § Nutrients then circulate through arteries, capillaries and veins, however, they by-pass the liver at first Health and Regula&on of the GI Tract  § Homeostatic regulation § Helps to maintain ”stable” condition § Hormonal (endocrine) and nervous system § Coordinate the digestive and absorptive GI Hormones processes and Nerve § Messages via hormones and nerve pathways indicate whether to secrete or inhibit Pathways digestive secretions § Feedback mechanism § A condition demands a response § Response changes condition § Change cuts off response  Maintenance of Stomach pH Negative Feedback Loop Example: Gastrin  Secretin: § Relaxation of pyloric sphincter allows acidic chyme into the duodenum § Cells on duodenal side react to the acidity and cause the sphincter to close GI Hormones § Pancreatic bicarbonate is secreted to neutralize acidic chyme – this causes pyloric sphincter to relax again § Process allows for protection of intestinal lining § Chyme à duodenal cells release secretin in the blood à signals pancreas to release bicarbonate to neutralize à chyme neutralized à stop secreting secretin à no further release of bicarb  Cholecystokinin (CCK): § Presence of fat stimulate intestinal wall cells to release CCK § CCK travels (in blood) to the: § Gallbladder to release bile into the intestine GI Hormones § Pancreas to secrete its juices, releasing enzymes and bicarbonate in the small intestine § Emulsified fat molecules no longer signal CCK and bile secretion stops § CCK slows digestion in response to fat and protein present in the intestine § Gallbladder removal??  How does the pancreas know how much of an enzyme needs to be secreted? § GI hormones secreted in response to macronutrients that are consumed inform the pancreas which enzymes to secrete § Changes in diet can have a lag as the body GI Hormones adjusts to the changes and signals the appropriate amount of enzymes to be released § Pancreas produces inactive form of enzymes àactivated once in small intestine § Pancreatitis  § Impact of lifestyle factors § Sleep § Physical activity § Stress GI Health § Diet § Characteristics of meals as discussed last week (balance, variety, moderation, adequacy) § Probiotics/prebiotics  § 100 trillion microbes…400+ different species of bacteria § Affected by pH, peristalsis, diet, antibiotic use, and other microorganisms that may enter the GI tract § Very few in stomach due to low pH § Neutral pH and slow peristalsis in lower small or Gut Bacteria large intestine is ideal for growth § Most are “good” bacteria that support immunity and overall health...if in abundance, harmful bacteria have a hard time settling in and thriving § Benefits: alleviate inflammation; IBS and IBD symptoms; ulcers; infant colic; reflux; allergies; overall immunity; lactose intolerance  Probiotics: living microorganisms found in food and supplements that when consumed are beneficial to health § yogurt, fermented foods § A variety of different strains (Lactobacillus and Bifidobacterium) § Role in diarrhea (saccharomyces boulardii) Prebiotics: non-digestible carbohydrates, act as food for Gut Bacteria probiotics § Common types include: § Fructo-oligosaccarides (FOS) - inulin § Barley, whole grains, bananas, garlic, onion, leeks, tomatoes, asparagus § Galacto-oligosaccardes (GOS) § Fermented dairy products Unlockfood.ca Synbiotics: contain both pre and pro biotics  § Choking § Universal sign for choking (Figure H3.2) § Heimlich maneuver § Who’s at risk? § Prevention Gastrointestinal § Belching Conditions § Carbonated beverages, poor fitting dentures, chewing gum § Prevention § Intestinal Gas § Role of undigested carbohydrates § Prevention  § Gastroesophageal reflux (GER) § Lower esophageal sphincter § Prevention § Ulcers § Causes Gastrointes:nal § Prevention Condi:ons § Vomiting § Causes § Fluid and electrolyte disturbances § Interventions § Diarrhea § Causes § Interventions  § Irritable bowel syndrome § One of the most common GI disorders § Various symptoms § Interventions (Low FODMAP) § Celiac disease Gastrointes:nal § Autoimmune disorder Condi:ons § Gluten free diet § Irritable bowel disease § Crohn’s, Ulcerative Colitis § Constipation § Contributing factors § Prevention  Cleansing Diets: § What is their claim? § Do they work? Discussion: § Are they safe? Food Cleanse *See PEN Handout on Brightspace