HUN3224 Cumulative Final Exam Study Guide Exam I Study Guide I Digestion and Absorption of Carbohydrates Lipids and Proteins A Physiology of the gastrointestinal GI tract 1 List the parts of the GI tract in the proper sequence and the purpose function of each Also list the accessory organs and their purpose function in relation to digestion and absorption GI tract Oral Cavity esophagus stomach collectively upper digestive tract small intestine large intestine lower digestive tract Oral Cavity mouth and pharynx that provides the entry way to the digestive tract On entering the mouth mastication occurs food is chewed by the teeth and jaw muscles to break down food It is made ready for swallowing by mixing with secretions saliva released from the salivary glands which contain the enzymes salivary amylase lingual lipase Salivary glands Parotid water electrolytes Na K Cl and enzymes Does NOT secrete mucus Submandibular Sublingual water electrolytes enzymes and MUCUS Enzymes Salivary amylase responsible for the initial breakdown of carbohydrates Lingual lipase responsible for breaking down fats mainly triglycerides Enzyme decreases with aging really important enzyme for babies to break down triglycerides in the milk 20 of digestion of triglycerides is done by this enzyme Lysozymes Kill bacteria Immunoglobulin A kills microorganisms that you ingest with your food Esophagus From the mouth the food mixed with saliva bolus passes through the pharynx into the esophagus As you swallow the epiglottis shifts upward this closes the glottis preventing food from going into your trachea and then your lungs The movement of the bolus through the esophagus is peristalsis a progressive wave like motion pushing the food down towards the stomach it takes about 10 seconds Upper esophageal sphincter Voluntary contraction because of striated muscles Lower esophageal sphincter gastroesophageal sphincter Smooth muscle non voluntary contraction The pressure in this is higher than the pressure in the stomach The pressure is what holds the sphincter closed so it can impede passage of food from the esophagus into the stomach When you swallow the pressure decreases in the sphincter causing it to relax and let food go into the stomach Gastro Esophageal Reflux Disease When food is in the stomach the pressure in the lower esophageal sphincter is low or the muscle are weak Therefore it relaxes when it is not suppose to and the acid and food can go back to your esophagus and starts eroding the mucosa This can cause irritation or ulcers depending on severity Esophagitus develops from acid erosion later form of GERD Treatments include Taking anti acids basic returns pH Histamine blockers target H2 Pepcid AC Zantac are used H2 blockers bind to the receptors of the parietal cells decreasing HCl secretion Proton pump inhibitors Prilosec Nexium HCl can be released by proton pump these medication inhibit the actions of proton pump therefore H and Cl cannot go into the stomach Aggravating heartburn Lower Pressure in sphincter chocolate high fat foods peppermint alcohol Increase acidity coffee caffeine alcohol calcium tea Irritants spicy foods citrus Also coughing and weight lifting abdominal pressure increases lying down after eating Stomach Responsible for holding food mechanical mixing and breaking down of food gastric secretions and the absorption of alcohol and Aspirin The stomach extends from the Lower esophageal sphincter to the duodenum of the small intestine The stomach contains four main regions cardia fundus body pylorus Cardia receives the swallowed food from the esophagus NO PARIETAL CELLS Fundus lies adjacent and above the cardia Body serves primarily as the reservoir for swallowed food and is the main production site of gastric juice Empty holds 2oz expands and when filled it can hold 50 oz Pyloric consists of the lower 1 3 of the stomach Grinds and mixes food with the gastric juices this is where the breakdown of food happens forming chyme Also provides peristalsis for gastric emptying through pyloric sphincter into the duodenum NO CHIEF CELLS The stomach has three kinds of muscles that begin the mixing of food with gastric juices circular longitudinal oblique This mixing is when the breakdown of food begins in the stomach to make it easier for the enzymes to act upon the nutrients Several cell types that secrete different substances are found in the gastric gland Neck Cells secrete bicarbonate and mucus Parietal Cells secrete HCl and intrinsic factor Intrinsic factor is needed for the absorption of vitamin B12 Have receptors for gastrin acetylcholine histamine Chief Cells secrete pepsinogen inactive form of enzyme also gastric lipase HCl activates it to pepsin active it can also activate itself autocatalytic Gastric lipase breaks down short chain and medium chain lipids Enteroendocrine Cells G cells secrete a variety of hormones Such as gastrin this stimulates HCl and certain enzymes Pyloric Sphincter A circular muscular valve links the stomach to the duodenum of the small intestine Regulates movement of food and acid from stomach to small intestine Small Intestine Represents the main site for nutrient digestion and absorption is composed of the Duodenum Ileum Jejunum The small intestine has many folds which increase the surface area for the contact of the enzymes with the food Duodenum Proximal part of small intestine linked to stomach through the pyloric sphincter Mucus is important to protect mucosa when chyme acid food enters before bicarbonate can be released it is more important than the bicarbonate in neutralizing the chyme Large Intestine The main purpose of this organ is the digestion of water and electrolytes specifically Na Cl Accessory Organs pancreas liver gallbladder Provide or store secretions that ultimately are delivered to the lumen of the digestive tract and aid in the digestion absorption process Pancreas Stimulated when sphincter relaxes and food comes in to the small intestine releasing proteases lipases water bicarbonate neutralize acid pH takes a long time for bicarbonate to be secreted into the small intestine Enzymes secreted in their inactive form so they do not break down the pancreas Liver Site for the synthesis of bile Gallbladder Stores and releases bile 2 Describe how the epithelial lining of the small intestine is structured to enhance surface area to facilitate nutrient absorption Epithelial lining also called the mucosa and is structured to maximize surface area and thus
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