GI Function Digestion is the mechanical and chemical breakdown of food in the GI Absorption is the transport if nutrients from the gut to the blood or lymphatic Metabolism is the chemical utilization of nutrients mostly within the liver Excretion is the removal of wastes or the release of toxins

Digestion Alimentary canal includes the oral cavity, pharynx, esophagus, stomach, small intestine, and colon Sphincters are ring muscles that separate segments of the canal and act as control valves The mucosa secretes mucus to lubricate the canal to allow for peristalsis Accessory organs include the liver, gallbladder, and pancreas

Digestion Liver for digestion produces bile which breaks down fat by emulsion, excreted from the hepatic duct The gallbladder stores and excretes bile when stimulates by the small intestines Pancreas secretes enzymes for the breakdown of foods in the small intestines, like lipase and amylase Digestion occurs mechanically, chemically, and passively

Digestion Mechanical, is mastication, peristalsis, and gastric contractions by muscle actions Chemical reactions are hydrolysis, oxidation, or emulsification of food, gastric and pancreatic juices Hydrochloric acid in the stomach breaks down most food, and then bicarbonate is a buffer for alkalinity After 6 hours, CHO are monosaccharides, TGs are FAs and glycerol, and proteins are amino acids

Digestion Hormones trigger secretions such a mucus, electrolytes, water, enzymes Gastrin secretes Hydrochloric acid in the stomach, often controlled by emotions Fats cause the releasable of bile from the gallbladder Certain foods that release excessive amounts of Hydrochloric acid can cause ulcers

Food Pathway In the mouth chewing forms a bolus, which is swallowed into the pharynx From the pharynx food enters the esophagus and propelled down to the duodenum by peristalsis Salivary glands moisten food into chyme, which is then broken down by amylases Before entering the stomach food must pass through the cardiac or esophageal sphincter

Food Pathway A J-shaped pouch which can expand and contract relative to gastric emptying, controlled by CCK Gastrin secretes Hydrochloric acid in the stomach, often controlled by emotions Pepsinogen activates to Pepsin, which breaks peptide bonds in proteins Gastric lipase along with bile acids break to fatty acids from lipids, stimulated by secretin

Food Pathway Gastroparesis is the slowing of digestion which is often caused by neuropathy, DM, opiates Symptoms include nausea, vomiting, bloating, abdominal pain The small intestines make up 20 feet in total, starting at the pyloric sphincter The first 10 inches is the duodenum, the next 8 feet is the jejunum, the last 11 feet is the ileum

Digestion The pancreas secretes 3 kinds of amylases which breaks down carbohydrates Maltase, for maltose into glucose and glucose; Sucrase, for glucose and fructose Lactase, for glucose and galactose; which can cause lactose intolerance Younger and Older populations often secrete less lactase, causing GI distress

Digestion In cheese lactose separates into whey and curd, with most lactose in the whey Who want to consume lactose include, lactaid, lactose- free, or lactase supplements In the intestine trypsin and peptidases breakdown elemental proteins into single amino acids

Absorption Nutrients either enter into the blood stream or the lymphatic system to be utilized The lymphatic system empties into the thoracic duct which merges with the bloodstream From inside the intestines folds of villi with thousands of microvilli collect nutrients Then capillaries called lacteals absorb nutrients into circulation by active transport The end destination for most nutrients is the liver via the hepatic portal circulation

Absorption Fats must be broken down into glycerol and fatty acids to be absorbed and the repackaged to form chylomicrons Chylomicrons or lipoproteins are the circulated in the lymphatic system Microvilla have a shot half life and can begin to atrophy within 1 week, causing gut ischemia The colon extends past the ileum and largely made up of the cecum which houses fluids and micro bacteria for elimination Stool is composed of 75% water, which can be thickened by fiber and probiotics

Malabsorption Typically determined by type and volume of stool with >350gm/d Medication, parasites, surgical procedures, disease states, and medical complications Gut failure typically presents with hypoactive bowl sounds, no flatus, distended and hard abdomen, nausea In pancreatitis or cholecystisis steatorrhea can occur, fat malabsorption typically seen with flow smell and yellow color Food allergies are immune response to particles found in food that can cause harm

Metabolism Chemical reactions of anabolic or catabolic occurring within cells to produce energy from carbs, proteins, and fats Breakdown of catabolism of nutrients yelled carbon dioxide, heat, water, and energy in the form of ATP With excess energy outside metabolic ability to utilize, nutrients are converted to glycogen or lipids and stored as fat Anabolic utilization of proteins helps to build muscle, skin, hair, and organ tissues Any foods not digested, absorbed, or metabolized is excreted through the kidneys or the colon