BSC 216 Ch. 25 Exam 4 Study Guide
BSC 216 Ch. 25 Exam 4 Study Guide 10617
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This 10 page Study Guide was uploaded by Gretchen Pierce on Wednesday April 22, 2015. The Study Guide belongs to 10617 at University of Alabama - Tuscaloosa taught by Jason Pienaar in Spring2015. Since its upload, it has received 239 views.
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Date Created: 04/22/15
Chapter 25 0 Define segmentation How does it work 0 Movement in which stationary ringlike constrictors appear in several place along the intestine 0 Most common 0 Purpose of segmentation is to mix and churn NOT to move material What s the difference between a short and a long reflex 0 Short Reflex Myenteric reflexes act as peristalsis stretching or chemical stimulation of the digestive tract through the myenteric plexus 0 Long Reflex Vagovagal reflexes act through autonomic nerve fibers stimulate nerves in the brainstem and motor commands parasympathetic fibers of the vagus nerves are important in stimulating digestive motility and secretion Which body cavity do all of the digestive organs sit in o Ventral body cavity thoracic and abdominopelvic What is a serous membrane and which kind of serous membrane is associated with digestive organs 0 The digestive organs are housed by the abdominopelvic cavity of the body and these organs are lined with serous membranes These are the same membranes that cover the abdominal cavity 0 Serous membranes are formed by simple squamous epithelium o Serous membranes are responsible for secreting enough fluid lubrication for the digestion What is the difference between the visceral and parietal peritoneums o Parietal Peritoneum is the portion that lines the abdominal and pelvic cavities These cavities are also known as the peritoneal cavities o Visceral Peritoneum covers the external surfaces of most abdominal organs including the intestinal tract What is mesentery Can you name at least 3 functions of the mesentery o Mesentery is connective tissue that loosely suspends the stomach and intestines from the abdominal wall 0 Three functions Ability of the stomach and intestines to undergo extreme contractions Allows freedom of movement in the abdominal cavity Contains many lymph nodes and lymphatic vessels What are the 4 layers that you will find in organs of the alimentary canal o lnnermost Mucosa Submucosa Muscularis Externa and Serosa What is the function of the myenteric nerve plexus The submucosal nerve plexus o The function of the myenteric nerve plexus if the ability to control peristalsis and other contractions of the muscularis externa o The function of the submucosal nerve plexus is the ability to control glandular secretions of the mucosa and movement of the muscularis mucosae What does the epiglottis do 0 The epiglottis covers the trachea when swallowing and preventing foreign objects from entering the lungs What is the tongue s main function in the digestive process 0 The tongue compresses food against the palate to make the bolus Which of the salivary glands is most susceptible to myxovirus mumps o The parotid gland distinguish the salivary glands based on their method of excretion duct no duct 0 Submandibular one duct that empties at the side of the Linguinal frenulum o Sublingual multiple ducts that empty posterior to the papilla of the submandibular duct Where do the parotid submandibular and sublingual glands empty their products 0 The oral cavity What is saliva composed of What are the functions of its components 0 Saliva is composed of 970995 water and a solute comprised of salivary amylase Linguinal lipase mucus lysosomes immuglobin A and electrolytes 0 Their functions include Moistening mouth inhibiting bacteria growth cleansing teeth starting starchcarb digestion dissolving molecules and moistening food to transform into a bolus What are the functions of the upper and lower esophageal sphincters o The lower sohincter prevents stomach acid from entering the esophagus and erosion of the esophageal wall 0 The Upper Sphincter prevents excess air from going down the esophagus Can you describe the 5 steps of swallowing o 1 Tongue compresses food against palate to form a bolus o 2 Bolus passes into the pharynx Misdirection of bolus is prevented by tongue blocking oral cavity soft palate blocking nasal cavity and epiglottis blocking larynx o 3 Upper esophageal sphincter constricts and bolus passes downward o 4 Peristalsis drives bolus down esophagus Esophagus constricts above bolus and dilates and shortens below it Describe the buccal and pharyngealesophageal phases of deglutition swallowing o Buccal Phase voluntary control Tongue collects food presses it against palate forming a polus and pushes it posterior Food accumulates in oropharynx in front of blade of the epiglottis Epiglottis tips posteriorly and food bolus slides around it through the laryngeal opening Bolus enters laryngopharynx and stimulates tactile receptors and activates next phase 0 Pharyngoesophageal Phase involuntary Three actions prevent food and drink from reentering the mouth or entering the nasal cavity or larynx 0 Root of the tongue blocks oral cavity 0 Soft palate rises and blocks the nasopharynx o Infrahyoid muscles pull the larynx up to meet the epiglottis while laryngeal folds close the airway Food bolus is driven downward by constriction of the upper middle and lower pharyngeal constrictors Bolus enters esophagus stretches it and stimulates peristalsis the importance of oblique smooth muscle located only in the stomach o o What are the 5 main secretions of the stomach o 1 Hydrochloric Acid HCI o Gastric juice has a high concentration of HCI 0 As low as 08 pH 0 Parietal cells produce HCI and contain carbonic anhydrase CAH 0 CO2 H2O I H2C03 I HCOS H o H is pumped into gastric gland lumen by HK ATPase pump Antiporter uses ATP to pump H out and K in 0 HCO exchanged for CI chloride shift from blood plasma I Cl chloride ion pumped into the lumen of gastric gland to join H forming HCI Elevated HC03 bicarbonate ion in blood causes alkaline tide increasing blood pH 0 Functions of HCI o Activates pepsin and Linguinal lipase o Breaks up CT and plant cell walls Helps liquefy food to form chyme o Converts iniects ferric ions Fe3 to ferrous ions Fe2 Fe2 absorbed and used for hemoglobin synthesis 0 Contributes to nonspecific disease resistance by destroying most ingested pathogens 0 2 Pepsin o Zymogens digestive enzymes secreted as inactive proteins Converted to active enzymes by removing some of their amino acids 0 Pepsinogen zymogen secreted by the chief cells HCI removes some of its amino acids and forms pepsin active form tat digests protein Autocatalytic effect as some pepsin is formed it converts more pepsinogen into more pepsin o Pepsin digests dietary proteins into shorter peptide chains Protein digestion is completed in the small intestine o Acidic environment needed to change pepsinogen to pepsin o 3 Gastric Lipase o Gastric lipase produced by chief cells 0 Gastric lipase and Linguinal lipase play a minor role in digesting dietary fats Digests 1015 of dietary fats in the stomach Rest digested in the small intestine o 4 Intrinsic Factor 0 Intrinsic Factor a glycoprotein secreted by parietal cells 0 Essential to absorption of Vitamin B12 by the small intestine Binds vitamin B12 and then intestinal cells absorb this complex by receptormediated endocvtosis 0 Vitamin B12 is needed to svnthesize hemoqlobin Prevents pernicious anemia o Secretion of intrinsic factor is the only indispensable function of the stomach Digestion can continue if stomach is removed gastrectomy but B12 supplements will be needed 0 5 Chemical Messengers o Gastric and pyloric glands have various kinds of enteroendocrine G cells that produce as many as 20 chemical messengers Most are hormones that enter blood and stimulate distant cells Others are paracrine secretions that stimulate neighboring cells Several are peptides produced in both the digestive tract and the CNS gutbrain peptides Within the gastric glands what is the function of the mucous neck cells parietal cells chief cells and enteroendocrine G cells 0 Mucous neck cells are located within the gastric glands between parietal cells Line the gastric mucosa and gastric pits Parietal cells produce HCI and contain carbonic anhydrase CAH 0 Chief cells are most numerous o Secrete gastric lipase and pepsinogen o Dominate lower half of gastric glands 0 Absent in pyloric and cardiac glands O o How is HCI made what are its functions 0 HCI is made when H is pumped into gastric gland lumen by HK ATPase pump 0 HCI functions include Activates pepsin and Linguinal lipase Breaks up CT and planet cell walls liquefy food to form chyme Converts ingested ferric ions Fe3 to ferrous ions Fe2 Contributes to nonspecific disease resistance by destroying most ingested pathogens How is pepsin made Functions 0 Pepsin is made when HCI removes some of its amino acids and forms pepsin which digests proteins 0 Functions include Digests dietary proteins into shorter peptide chains Completed in the small intestine What is a zymogen o Digestive enzynes secreted as inactive proteins they are converted to active enzymes by removing some of their amino acids Understand the general function of gastric lipase intrinsic factor and chemical messengers o Gastric lipase is produced by chief cells and plays a minor role in digesting dietary fats o Intrinsic factor is a glycoprotein secreted by parietal cells and is essential to absorption of vitamin B12 by the small intestine 0 Chemical messengers are hormones that stimulate distant cells paracrine secretions that stimulate neighbor cells and are peptides that are produced inn the digestive tract and CNS What are 3 mechanisms that the stomach uses to prevent corrosion of itself due to the very acidic environment 0 Mucous coat thick highly alkaline mucus resists action of acid and enzyme 0 Tight junctions between epithelial cells prevent gastric juice from seeping between them and digesting the CT of the lamina propria and beyond 0 Epithelial cell replacement stomach epithelial cells live only 36 days Sloughed off into the chyme and digested with the food Replaced by cell division in the gastric pits h nerve stimulates stomach activity Where in the brain does this nerve originate o The vagus nerve in the Cephalic phase stimulates stomach activity 0 Originates in the medulla oblongata Does the sympathetic nervous system inhibit or stimulate gastric secretion o Sympathetic nervous system inhibits gastric secretion Which hormone produced by enteroendocrine cells stimulates enzyme and HCI secretion 0 Histamine Can you distinguish between the cephalic gastric and intestinal phases of the digestive process 0 Cephalic Phase stomach being controlled by the brain 0 Stomach responds to sight smell taste or thought of food 0 Sensory and mental inputs converge on the hypothalamus Relays signals to medulla obongata o Vagus nerve fibers from medulla obongata stimulate the enteric nervous system of stomach In turn stimulates gastric secretion 0 Gastric Phase controlling itself 0 Period in which swallowed food and semidigested protein activate gastric activity Twothirds of gastric secretion occurs in this phase 0 Ingested food stimulates gastric activity in two ways By stretching the stomach Activates short reflex mediated through myenteric nerve plexus Activates long reflex mediated through the vagus nerves and the brainstem By increasing the pH of its contents 0 Gastric secretion is stimulated by three chemicals Acetylcholine ACh secreted by parasympathetic nerve fibers of both reflexes Histamine a paracrine secretion from enteroendocrine cells in the gastric glands Gastrin a hormone produced by the enteroendocrine G cells in pyloric glands o Intestinal Phase stomach being controlled by small intestine 0 Stage in which the duodenum responds to arriving chyme and moderates gastric activity through hormones and nervous re exes o Duodenum initiallv enhances gastric secretion but soon inhibits it Enhancing mechanisms Stretching of the duodenum accentuates vagovagal reflex that stimulates the stomach Peptides and amino acids in chyme stimulate G cells of the duodenum to secrete more gastrin which further stimulates the stomach o Inhibitory mechanisms 0 Enterogastric reflex duodenum sends inhibitory signals to the stomach by way of the enteric nervous system and signals to the medulla oblongata triggered by acid and semidigested fats in the duodenum Inhibits vagal nuclei reducing vagal stimulation of the stomach Stimulate sympathetic neurons send inhibitory signals to the stomach o Chyme also stimulates duodenal enteroendocrine G cells to release secretin and cholecystokinin They stimulate the pancreas and gallbladder important in digestion in the small intestine Also suppress gastric secretion What are the 3 divisions of the small intestine o Duodenum 25 cm 10 in o Begins at the pyloric valve Receives major and minor pancreatic ducts respectively Receives stomach contents pancreatic juice and bile Stomach acid is neutralized here Fats are physically broken up emulsified by the bile acids Pepsin is inactivated by increased pH Pancreatic enzymes take over the job of chemical digestion Duodenal glands in submucosa of duodenum Secrete an abundance of bicarbonaterich mucus Neutralize stomach acid and shield the mucosa from its erosive effects 0 Jejunum first 40 of small intestine beyond duodenum o Roughly 10 to 17 m in a living person 0 Especially rich blood supply which gives it a red color 0 Most digestion and nutrient absorption occurs here 0 lleum forms the last 60 of the postduodenal small intestine 0 About 16 to 27 m o Thinner less muscular less vascular and paler pink color 0 Peyer patches prominent lymphatic nodules in clusters on the side opposite the mesenteric attachment Immune surveillance of pathogens in the small intestine OOOOOO Which sphincter controls the flow of bile and pancreatic juice into the duodenum o Hepatopancreatic sphincter What are adaptations of the small intestine for purposes of enhancing absorption of nutrients o Mixing chyme with intestinal juice bile and pancreatic juice 0 Churn chyme and bring it in contact with mucousa for contact digestion and nutrient absorption 0 To move residue toward large intestine Based on the flow charts in the power point notes Chapter 25 section 256 can you describe which digestive enzymes breaking down carbs proteins fats and nucleic acids where the breakdown happens in the digestive system and where nutrients are absorbed o Carbs o Salivary amylase in the mouth and pancreatic amylase in the small intestine break down carbs 0 Brush border enzymes dextrinase glucoamylase lactase maltase and sucrose in the small intestine break down carbs 0 They are absorbed through sodium ions and then transported through the hepatic portal vein 0 Proteins o Pepsin in HCI in the stomach Pancreatic enzymes trypsin chymotrypsin and carboxypeptidase in the small intestine and brush border enzymes aminopeptidase carboxypeptidase and dipeptidase in the small intestine break down proteins 0 Amino acids are absorbed via sodium ions they are later transported by the hepatic portal vein 0 Fats o Emulsified by the detergent action of bile salts ducted in from the liver in the small intestine and pancreatic lipase in the small intestine break down fats 0 Fatty acids enter intestines by diffusion they are combined with proteins and they are transported via lymph in the thoracic duct 0 Nucleic Acids o Pancreatic Ribonuclease and deozyrhibonuclease along with brush border enzymes nucleosides and phosphatases both in the small intestine break down nucleic acids 0 Active transport via membrane carriers and then absorbed and transported to the liver o What is the primary function of the large intestine o Eliminates feces by defecation 0 can you identify the large intestine 3 characteristics that distinguish it from other organs in your digestive system 0 Caecum o Colon o Rectum What is the role of commensal bacteria in our large intestine 0 Bacterial Flora populate the large intestine 0 About 800 species of bacteria 0 Digest cellulose and other undigested carbohydrates Body absorbs resulting sugars 0 Help in synthesis of vitamins B and K o How does the defecation reflex work 0 1 Filling of the rectum o 2 Reflex contraction of rectum and relaxation of internal anal sphincter o 3 Voluntary relaxation of the external sphincter
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