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APHY 201 Exam 4d
Ch. 18 The Digestive System
| Question | Answer |
|---|---|
| Digestion breaks polymers (carbohydrates, fats, and proteins) into monomer building blocks via what kind of reactions? (hint: opposite of dehyration synthesis?) | hydrolysis |
| what process takes takes monomers into the bloodstream to be used by the cells? | absorption |
| true or true, one-way transport allows for specialization of function along the GI tract | true |
| 6 digestive tract functions | motility, secretion, digestion, absorption, storage with elimination, immune barrier |
| motility is movement of food through the tract. what 5 processes does this involve? | ingestion: taking food into the mouth, mastication: chewing and mixing food with saliva, deglutition: swallowing, peristalsis: wave-like, one-way movement through tract, segmentation: churning and mixing back and forth while moving forward |
| secretion (a function of digestion) itself involves what endocrine and exocrine functions? | Exocrine: digestive enzymes, hydrochloric acid, mucus, water, and bicarbonate; endocrine: hormones to regulate digestion |
| digestion vs absorption | digestion: breaking food down into smaller units, both physically and chemically; Absorption: passing broken-down food into blood or lymph |
| how does the digestive tract function as an immune barrier? | Simple columnar epithelium with tight junctions prevents swallowed pathogens from entering body, and Immune cells in connective tissue of the tract promote immune responses |
| the 30-foot GI tract goes from mouth to anus. what are the 7 structures you need to know that this includes? | Oral cavity -> Pharynx -> Esophagus -> Stomach -> Small intestines -> Large intestines -> Anus |
| 6 accessory organs in the digestive system | teeth, tongue, salivary glands, liver, gallbladder, pancreas |
| GI tract layers have 4 layers, or tunics. what are they? be able to describe them. | mucosa, submucosa, muscularis, serosa |
| describe the mucosa (tunic) of the GI tract layers | inner secretory and absorptive layer; may be folded to increase surface area; outermost sublayer is muscularis mucosae that makes the folds |
| describe the submucosa (tunic) of the GI tract layers | very vascular, to pick up nutrients; also has some glands and nerve plexuses; submucosal (Meissner’s) plexus provides nerve supply to muscularis mucosae |
| describe the muscularis externa (tunic) of the GI tract layers | smooth muscle; responsible for peristalsis and segmentation; myenteric (Auerbach’s) plexus between outer longitudinal and inner circular layers provides for control by the ANS |
| describe the serosa (tunic) of the GI tract layers | outer binding and protective layer |
| which tunic has Auerbach's plexus and which tunic has Meissner's plexus? what are these plexuses' other names? | Auerbach's plexus, known as the myenteric plexus, is in the muscularis externa tunic; Meissner's plexus, known as the submucosal plexus, is in the submucosa. |
| the GI tract is regulated extrinsically by both the PSNS and the SNS. how so in the PSNS? (3 bullet points) | PSNS stimulates esophagus, stomach, small intestine, pancreas, gallbladder, and first part of large intestine via vagus nerve; spinal nerves in sacral region stimulate lower lg intestine; preganglionic neurons synapse on submucosal and myenteric plexuses |
| the GI tract is regulated extrinsically by both the PSNS and the SNS. how so in the SNS? (2 bullet points) | inhibits peristalsis and secretion, stimulates contraction of sphincters |
| what 2 ways is the GI tract intrinsically regulated? | hormones from brain or other digestive organs; as well as the entirely separate enteric nervous system where sensory neurons in gut wall help regulate GI tract--including paracrine signals |
| saliva contains what 3 things to start digestion of starch? | contains mucus, an antimicrobial agent, and salivary amylase to start digestion of starch. |
| what is deglutition? (another name for it) | swallowing |
| deglutition involves coordinated contraction of how many pairs of muscles? | 25 pairs |
| what are the 3 parts to deglutition? | oral, pharyngeal, esophageal phases |
| What occurs during the voluntary oral phase of swallowing? | Muscles of the mouth and tongue mix food with saliva to form a bolus. |
| What triggers the involuntary pharyngeal phase of deglutition? | Receptors in the posterior oral cavity and oropharynx initiate it. |
| What prevents food from entering the nasopharynx and vocal cords? | The uvula (soft palate) lifts to cover the nasopharynx, and the epiglottis flips down to cover the vocal cords. |
| How is the bolus moved down the esophagus to the stomach? | It is moved via an automatic process called peristalsis, which is controlled by the swallowing center of the brain stem. |
| How long is the esophagus and how does it pass through the diaphragm? | It is about 10 inches long and passes through the diaphragm via the esophageal hiatus. |
| What type of tissue lines the esophagus? Why? | It is lined with nonkeratinized stratified squamous epithelium to resist abrasion |
| How does muscle control transition along the esophagus? | The upper esophagus contains skeletal muscle with voluntary somatic control, while the lower esophagus has smooth muscle with involuntary autonomic control. |
| Why are humans capable of regurgitating unlike rodents? | Humans do not have a true lower esophageal sphincter muscle, whereas rodents do. |
| What is the condition where the normal stratified squamous epithelium of the esophagus is abnormally replaced by columnar epithelium? | Barrett's esophagus |
| What is the medical term for the abnormal replacement of cell types seen in Barrett's Esophagus? | The abnormal replacement of tissue is referred to as metaplasia. |
| What causes the injury that leads to Barrett’s Esophagus? | It is caused by injury to the esophageal mucosa from gastroesophageal reflux disease (GERD). |
| What is the primary risk associated with Barrett's Esophagus? | It increases the risk of developing esophageal adenocarcinoma. |
| (recognize for multiple choice) What are the 5 main functions of the stomach? | The stomach stores food, churns it with gastric secretions, begins protein digestion, kills bacteria with acid, and moves chyme into the small intestine. |
| What are the 4 regions of the stomach? | The regions are the cardiac region, the fundus, the body, and the pyloric region. |
| What are the folds in the stomach lining called? | rugae |
| What is the function of mucous neck cells in the gastric pits? | They secrete mucus to help protect the stomach lining from acid. |
| (starred) What 2 important substances do parietal cells secrete?--and one of them is a factor that does what? | Parietal cells secrete hydrochloric acid (HCl) and intrinsic factor, which helps the small intestine absorb vitamin B12. |
| (starred) What do chief (zymogenic) cells secrete? | pepsinogen, the inactive form of the protein-digesting enzyme pepsin. |
| (bolded) Which cells secrete histamine and serotonin as paracrine signals? | Enterochromaffin-like (ECL) cells. |
| (bolded) What do G cells secrete? | gastrin hormone. |
| (bolded) What do D cells secrete? | somatostatin hormone. |
| What is the function of the hormone ghrelin secreted by P/D1 cells? | signals the brain to regulate hunger and body weight. |
| How is H+ transported during the formation of HCl? | H+ is moved into the lumen via primary active transport by H+/K+ ATPase pumps. |
| Which 3 molecules stimulate HCl secretion? | Gastrin, histamine, and acetylcholine from parasympathetic neurons stimulate HCl secretion. |
| How does gastrin indirectly stimulate HCl production? | Gastrin stimulates ECL cells to produce histamine, which then stimulates parietal cells to make HCl. |
| What do medications like Tagamet and Zantac do? | They reduce acid by blocking H2 histamine receptors on parietal cells. |
| What are the main functions of HCl in the stomach? | HCl drops the pH to 2, denatures ingested proteins, and converts inactive pepsinogen into active pepsin. |
| What is the role of pepsin in digestion? | Pepsin is a protease that catalyzes the hydrolysis of peptide bonds in ingested proteins. |
| With what 3 ways does the stomach defend its lining against acid and pepsin? | It utilizes an adherent layer of alkaline mucus, tight junctions between epithelial cells, and rapid cell mitosis that replaces the epithelium every three days. |
| Why does starch digestion stop in the stomach? | Salivary amylase becomes inactive at the highly acidic pH of 2; starch digestion continues later on in the small intestine |
| Which 2 common substances are absorbed directly in the stomach? How can they be absorbed there directly? | Alcohol and NSAIDs like aspirin are absorbed due to their high lipid solubility. |
| What is the most common cause of peptic ulcers? | The bacterium Helicobacter pylori, which reduces mucosal barriers to acid, is the primary cause (rather than stress or spicy foods). |
| How are peptic ulcers typically treated? | They are treated with a combination of K+/H+ pump inhibitors (like omeprazole) and antibiotics. |
| How do NSAIDs contribute to acute gastritis? (hint: what is needed to stimulate alkaline mucus production?) | NSAIDs inhibit prostaglandin activity, which is needed to stimulate protective alkaline mucus production. |
| How is the duodenum naturally protected from acidic chyme? | It is protected by a mucosal layer and bicarbonate secreted by Brunner’s glands and the pancreas. |
| What is the condition where ulcers develop due to excessive amounts of gastrin and HCl produced by a tumor? | Zollinger-Ellison syndrome |
| How does a Roux-en-Y gastric bypass work? | It creates a small pouch in the gastric fundus to which the mid-jejunum is directly attached. |
| What happens during a vertical sleeve gastrectomy? | About 85% of the stomach (specifically the fundus and body) is removed, but the intestinal pathway remains unaltered. |
| Which intestinal hormone is believed to improve insulin secretion following bariatric surgery? | GLP-1. |
| What are 3 common symptoms of Gastroesophageal Reflux Disease (GERD)? | Reflux of acidic gastric chyme produces symptoms like heartburn, a cough, and a sore throat. |
| What are the main risk factors for developing GERD? | Risk factors include obesity, pregnancy, and a hiatal hernia. |
| The small intestine has 3 structures (duodenum, jejunum, ileum) but where does the small intestine start and end? (between what 2 structures?) | It starts at the pyloric sphincter and ends at the ileocecal valve. |
| What structural features greatly increase the surface area for nutrient absorption in the small intestine? | The plicae circulares (folded mucosa and submucosa), villi (folded mucosa), and microvilli (folded epithelial plasma membranes). |
| What are the 2 general functions of the small intestine? | The complete digestion of carbohydrates/proteins/fats, and the absorption of nutrients. |
| Which 5 nutrients are absorbed in the duodenum and jejunum? | Sugars, lipids, amino acids, calcium, and iron are absorbed in the duodenum and jejunum. |
| Which 3 substances are absorbed in the ileum? | Bile salts, vitamin B12, water, and electrolytes are absorbed in the ileum. |
| Why is absorption in the small intestine very rapid? (physical functional reason) | It is rapid due to the large surface area provided by the villi and microvilli. |
| What type of tissue and what type of cells make up the villi? (hint: the cells secrete mucus) | The villi are made of columnar epithelium with mucus-secreting goblet cells. |
| What do the capillaries and lacteals inside the villi absorb? | Capillaries absorb monosaccharides and amino acids, while lacteals absorb fats. |
| What do Paneth cells in the Intestinal crypts (Crypts of Lieberkuhn) secrete? (2 molecule types) | They secrete the antibacterial molecules lysozyme and defensin. |
| How often do mitotic stem cells in the intestinal crypts replenish the intestinal cells? | They divide by mitosis to replenish intestinal cells every 4 to 5 days. |
| What are the foldings of the apical surface of each epithelial cell? also called the brush border. | microvilli |
| Where are intestinal brush border enzymes located? | They are attached to the plasma membrane with their active sites exposed to chyme, rather than being released into the lumen like other enzymes. |
| (starred) what structures/enzymes hydrolyze disaccharides, polypeptides, and other substrates into simple nutrient molecules? | brush border enzymes |
| (starred) What does the brush border enzyme sucrase digest, and what does that molecule turn into? | It digests sucrose into glucose and fructose. |
| (starred) What does the brush border enzyme maltase digest, and what does that molecule turn into? | It digests maltose into glucose. |
| (starred) What does the brush border enzyme lactase digest, and what does that molecule turn into? | It digests lactose into glucose and galactose. |
| (starred) which brush border enzyme produces free amino acids, dipeptides, and tripeptides? | aminopeptidase |
| (starred) which brush border enzyme activates trypsin, which indirectly activates other pancreatic juice enzymes? | enterokinase |
| What is the term for the inability to digest the disaccharide lactose into glucose and galactose for absorption by the small intestine? | lactose intolerance |
| When do people with lactose intolerance typically lose the ability to produce the enzyme lactase? | with age, typically by age 4 |
| What causes the symptoms of gas, bloating, and diarrhea in lactose intolerance? | These symptoms are caused by commensal (enteric) bacteria consuming the accumulated lactose in the intestine. |
| How does peristalsis in the small intestine compare to the stomach? | Peristalsis in the small intestine is weaker, resulting in much slower movement of food than in the stomach. |
| What is the purpose of segmentation in the small intestine? is it stronger or weaker than in the stomach? | Segmentation is stronger in the small intestine than in the stomach and serves to mix the chyme in place. |
| Which cells act as pacemakers to produce graded depolarizations (slow waves) in the small intestine? | The interstitial cells of Cajal (ICCs) |
| What causes the action potential "spike" and resulting contraction in intestinal muscle cells? | Depolarization from the interstitial cells of Cajal opens voltage-gated Ca2+ channels in the muscle cells. |
| How does contraction stimulation travel short distances between intestinal cells? | It travels through gap junctions, though it must be regenerated in neighboring pacemaker regions. |
| How do autonomic nerves regulate intestinal contractions? | They influence the enteric nervous system to stimulate or inhibit the interstitial cells of Cajal. |
| How does acetylcholine (ACh) from the parasympathetic nervous system affect intestinal motility? | It interacts with muscarinic ACh receptors to increase the amplitude and duration of slow waves. |
| What is the sequence of 9 regions that food passes through in the large intestine? | It travels from the ileocecal valve into the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, and finally out the anus. |
| What structures are found in the mucosa of the large intestine? (what type of tissue and what else?) importantly, what does it not have? | It contains columnar epithelial cells with goblet cells, crypts, and lymphatic nodules, but it does not have villi. |
| What are the pouches on the outer surface of the large intestine called? | haustra. |
| What are the primary functions of the large intestine? (hint: 4 absorbed molecule types) | Its functions include the absorption of water, electrolytes, vitamin K, and some B vitamins, as well as the production of vitamins via microbes and the storage of feces. |
| What is the general term for the several hundred species of bacteria living in the large intestine? | They are collectively called the microflora or intestinal microbiota. |
| What is the difference between commensal and mutualistic bacteria? | Commensal bacteria benefit without harming or benefiting us, while mutualistic bacteria provide a benefit to both themselves and us. |
| Are most of the bacteria in the large intestine aerobic or anaerobic? | They are mostly anaerobic. |
| Which vitamins do the intestinal microbes produce? | They produce vitamin K and some B vitamins. |
| what is produced by microbes that benefit the digestive system, provide energy for large intestine epithelial cells and help absorb electrolytes like sodium and chloride? | short-chain fatty acids |
| How do normal microflora protect the body from harmful bacteria like E. coli? | by outcompeting the harmful species. |
| What can happen if the normal microflora of the large intestine is disrupted? what disease can it lead to? | It can lead to inflammatory bowel disease (IBS) |
| What 3 mechanisms help protect the intestinal tract from bacteria? | Protection is provided by mucus from goblet cells, the secretion of defensin by Paneth cells, and the secretion of IgA antibodies by plasma cells. |
| How does the normal intestinal microbiota help maintain the epithelial barrier? (2 benefits) | good bacteria limit inflammation and promote the repair of damaged epithelium. |
| How do commensal bacteria help reduce food allergies? what WBC do they promote the production of, and what do those do? | They promote the production of regulatory T lymphocytes, which help increase tolerance to antigens from food. |
| Which cells act as antigen-presenting cells to activate T-reg cells against commensal bacteria? | Intestinal dendritic cells. |
| What is the term for the inflammation of the vermiform appendix? | appendicitis |
| What role does the appendix play in the digestive system? | It does not function in digestion, but it contains lymphoid nodules and a population of commensal bacteria to help replenish normal intestinal microbiota when needed. |
| What are the symptoms of appendicitis? (at least 2) | It produces pain in the lower right abdominal quadrant, nausea, and other confusing symptoms. |
| What dangerous condition can result from a burst appendix? (hint: ends in itis) | It can cause peritonitis, an inflammation of the peritoneal membranes that can lead to circulatory shock and death. |
| Where does most fluid and electrolyte absorption occur in the digestive tract? | Most absorption occurs in the small intestine, though some is left for the large intestine. |
| How much water (mL) is typically left unabsorbed to be excreted with feces each day? | About 200 ml of water is left per day. |
| How is water absorbed in the large intestine? actively or passively? --what sets up the mechanism? | Water is absorbed passively by following an osmotic gradient set up by active Na+/K+ pumps. |
| Which hormone stimulates greater salt and water absorption in the large intestine? | Aldosterone. |
| What is the term for the excretion of excessive fluid in the feces? | diarrhea |
| viral gastroenteritis, also known as the stomach flu, usually causes what symptom? | diarrhea |
| How do bacteria like strains of E. coli, V. cholera, and C. difficile cause secretory diarrhea? | They cause it by releasing an enterotoxin. |
| How do bacteria like Salmonella, Campylobacter, and Shigella produce inflammatory diarrhea? | They produce it by invading the mucosa and causing damage and inflammation. |
| what is the difference between secretory diarrhea and inflammatory diarrhea? | Secretory: large, watery stools, often from bacterial toxins or certain hormones. Inflammatory: when the bowel lining is damaged, causing blood, pus, and mucus to leak into the stool; caused by infections or autoimmune diseases |
| What is the primary health concern associated with diarrhea? | dehydration due to excessive fluid loss. |
| What triggers the need to defecate? | As material passes to the rectum, pressure increases, causing the internal anal sphincter to relax and the need to defecate to rise. |
| Which muscle allows for the voluntary control of defecation? | The external anal sphincter. |
| What do the longitudinal rectal muscles do during defecation? | They contract to increase pressure as the anal sphincters relax. |
| What is the term for the contraction of abdominal and pelvic skeletal muscles that aids in defecation? | Valsalva’s maneuver. |
| Which 2 conditions are classified under inflammatory bowel disease (IBD)? | Crohn’s disease and ulcerative colitis. |
| What physiological changes in the intestines increase permeability and lead to ulcerations in IBD? | Decreased mucus secretion by goblet cells and changes in the tight junctions between epithelial cells. |
| What are the characteristic symptoms of Crohn’s disease? | It is characterized by inflammation that causes fibrosis, prolonged diarrhea with abdominal pain, fatigue, and weight loss. |
| What 2 factors may be promoting the rising incidence of IBD in the United States? | It may be promoted by a poor diet and the overuse of antibiotics, which alter the intestinal microbiota and provoke an immune response. |
| What body system's regulation is affected by the complex factors that cause Irritable Bowel Syndrome (IBS)? | It is caused by factors that affect the neural regulation of the GI tract. |
| What are the main symptoms of Irritable Bowel Syndrome (IBS)? | It produces abdominal pain and discomfort alongside diarrhea, constipation, or alternating periods of each. |
| What alteration in the gut is proposed as a root cause of IBS? | Alterations of the intestinal microbiota, specifically defective interactions with the enteric nervous system and the brain, are believed to contribute to IBS. |
| difference between IBD and IBS? | IBD (Inflammatory Bowel Disease) is an autoimmune condition causing visible inflammation, ulcers, and physical damage to the digestive tract, IBS (Irritable Bowel Syndrome) is a functional disorder where the gut looks normal but fails to function properly |
| what is the difference between the enterohepatic circulation and the portal system? what does each accomplish? | HPS is 1-way vein network w/nutrient- & toxin-rich blood from digestive organs to the liver. EC loops & recycles specific substances (like bile acids) between the liver and the intestines. (Circular loop: Liver → Bile Duct → Intestine → Blood → Liver) |
| What is the largest abdominal organ and where is it located? | The liver is the largest abdominal organ, located immediately beneath the diaphragm, mostly on the right side. |
| Why does the liver have amazing regenerative abilities? | It can regenerate due to the high rate of mitosis of hepatocytes. |
| What structure in the liver is separated by highly permeable capillaries called sinusoids, which have fenestrae and lack a basement membrane? | hepatic plates |
| What are the special phagocytes located within the liver sinusoids? | Kupffer cells |
| What can hepatic damage from alcohol or viral hepatitis cause? | liver fibrosis that can eventually lead to cirrhosis of the liver. |
| How are the products of digestion delivered to the liver? where are they absorbed and what vein delivers them? | They are absorbed into intestinal capillaries and delivered to the liver via the hepatic portal vein. |
| Which 7 organs drain venous blood into the hepatic portal vein? | The pancreas, gallbladder, stomach, omentum, and spleen drain into it. [also small and large intestines, though slides didn't include them] |
| What is the pathway of blood in the hepatic portal system? | from capillaries to veins to capillaries and back to veins: blood flows from the capillaries of the GI tract and spleen into the hepatic portal vein, breaks down into the capillaries (sinusoids) of the liver, and exits via the hepatic veins into the IVC |
| What percent of cardiac output is dedicated to total hepatic blood flow? | It is about 25% of cardiac output, which is needed to maintain hepatic clearance. |
| which structures are arranged as hexagonal liver lobules with hepatic arteries, hepatic portal veins, and a central vein? | hepatic plates |
| What 3 structures make up a portal triad? | A bile duct, a hepatic artery, and a hepatic portal vein. |
| What is the process where molecules secreted into the bile by the liver are absorbed again in the small intestine and returned to the liver? | enterohepatic circulation |
| (starred) Which 3 endogenous compounds have a high percentage reabsorbed through enterohepatic circulation? | Bile salts, urobilinogen, and cholesterol. |
| (starred) What is the relative reabsorption rate and circulation status of the endogenous phospholipid lecithin? | A small percentage is reabsorbed and it undergoes enterohepatic circulation. |
| (starred) Does endogenous conjugated bilirubin undergo enterohepatic circulation? | No, it has no enterohepatic circulation. |
| (starred) What is the relative reabsorption rate and circulation status of exogenous drugs like ampicillin, streptomycin, and tetracycline? | A high percentage is reabsorbed and they undergo enterohepatic circulation. |
| (starred) What is the relative reabsorption rate and circulation status of exogenous drugs like sulfonamides and penicillin? | A small percentage is reabsorbed and they undergo enterohepatic circulation. |
| What are the 5 major categories of liver function? | Detoxification of blood, carbohydrate metabolism, lipid metabolism, protein synthesis, and secretion of bile. |
| With what 4 ways does the liver detoxify the blood? | Through phagocytosis by Kupffer cells, chemical alteration of molecules, production of less toxic compounds like urea, and excretion of molecules in bile. |
| What 3 roles does the liver play in carbohydrate metabolism? | It converts blood glucose to glycogen and fat, produces glucose via gluconeogenesis, and secretes glucose into the blood. |
| What 3 roles does the liver play in lipid metabolism? | It synthesizes triglycerides and cholesterol, excretes cholesterol in bile, and produces ketone bodies from fatty acids. |
| Which 3 important protein/groups are synthesized by the liver? | Albumin, plasma transport proteins, and clotting factors like fibrinogen and prothrombin. |
| What is the composition of bile? (5 items) | It is composed of bile pigment (bilirubin), bile salts, phospholipids (lecithin), cholesterol, and inorganic ions. |
| Where is bilirubin produced (3 regions) and what is it derived from? | It is produced in the spleen, liver, and bone marrow, and is derived from the heme group of hemoglobin (minus the iron). |
| How is free bilirubin transported in the blood since it is not water-soluble? | carried attached to the protein albumin. |
| How does the liver make bilirubin water-soluble for excretion? | It conjugates free bilirubin with glucuronic acid. |
| What gives feces its brown color? | Intestinal bacteria convert conjugated bilirubin into urobilinogen, which is then converted into stercobilin, making feces brown. |
| What gives urine its amber color? | Some urobilinogen is filtered by the kidneys into the urine, where it is called urochrome. |
| What is the term for the substances made from bile acids (derived from cholesterol) conjugated with glycine or taurine? | bile salts |
| How do bile salts aid in fat digestion? | They form micelles that emulsify fats into smaller pieces, providing a greater surface area for fat digestion by lipase. |
| How does the liver chemically alter ammonia, porphyrins, and purines for detoxification? what are they converted into? | Ammonia is converted into urea, porphyrins into bilirubin, and purines into uric acid. |
| What is the group of heme-containing enzymes in hepatocytes that degrade drugs... steroids and exogenous environmental toxins? | cytochrome P450 enzymes |
| How can grapefruit interact with cholesterol medications like Lipitor? | Compounds called furanocoumarins (like bergamottin) slow down a P450 enzyme, causing the drug to be metabolized more slowly. |
| What is the rare genetic defect causing a buildup of porphyrin, leading to psychiatric conditions and sunlight-induced photosensitivity? | hepatic porphyria |
| What 4 processes does the liver use to balance blood glucose levels? | It uses glycogenesis and lipogenesis to store glucose, and glycogenolysis and gluconeogenesis to release glucose. |
| Which common plasma proteins are NOT produced by the liver? | Immunoglobulins (antibodies) are not produced by the liver. |
| Which important protein provides colloid osmotic pressure and acts as the principal transport protein? | albumin |
| What happens to liver tissue during cirrhosis? | Liver portal lobules are destroyed and replaced by fibrotic scar tissue and regenerative nodules that lack normal structure. |
| in patients with cirrhosis, disrupted blood flow through the scarred liver sinusoids causes high pressure in the portal vein, a condition called what? | portal hypertension |
| What are the most common causes of cirrhosis? (4 of them) | Hepatitis B virus, hep C virus, alcoholism, and nonalcoholic steatohepatitis (NASH). |
| What 3 conditions are associated with nonalcoholic fatty liver disease? | It is associated with obesity, the insulin resistance of prediabetes and type 2 diabetes, and diets high in saturated fat and fructose. |
| What enzyme metabolizes alcohol into acetaldehyde in the liver? | Alcohol dehydrogenase. |
| What is jaundice (hyperbilirubinemia)? | It is a yellow staining of the eyes, mucous membranes, and skin caused by elevated levels of blood bilirubin. |
| What causes pre-hepatic jaundice? | An increase in free bilirubin due to the increased hemolysis (breakdown) of red blood cells. |
| Hepatic jaundice, caused by hepatitis and cirrhosis, can raise either free or conjugated bilirubin. hepatic jaundice may also be known as what? | mixed jaundice |
| What causes post-hepatic (obstructive) jaundice? | A blockage in the drainage of bile, often resulting from a gallstone, pancreatic disease, or stricture of the bile duct. |
| What structure stores and concentrates bile that is produced by the liver? | gallbladder |
| What is the major component of most gallstones? | Cholesterol. |
| How are gallstones made? | Gallstones are produced when the liver secretes enough cholesterol to create a supersaturated solution, and cholesterol crystals, together with mucus secreted by the gallbladder, can form a sludge that may be visible in an ultrasound. |
| What is the term for what causes the pain and nausea when sizable gallstones block the hepatic, cystic, or common bile ducts? | biliary colic |
| What are the endocrine and exocrine functions of the pancreas? | The endocrine Islets of Langerhans make insulin (beta cells) and glucagon (alpha cells), while the exocrine acinar cells make pancreatic juice. |
| What substance is made up of bicarbonate and about 20 digestive enzymes? | pancreatic juice |
| Which brush border enzyme activates the pancreatic zymogen trypsinogen into trypsin? | Enterokinase. |
| Which 4 pancreatic enzymes are activated by trypsin? | Chymotrypsin, elastase, carboxypeptidase, and phospholipase. |
| Which 5 pancreatic enzymes do not have a zymogen form and require no activator? | Lipase, amylase, cholesterolesterase, ribonuclease, and deoxyribonuclease. |
| How is bicarbonate secreted into the pancreatic juice? | It is countertransported with chloride (Cl-) across the membrane. |
| Why can cystic fibrosis lead to the destruction of the pancreas? | Defective chloride carriers prevent the proper secretion of bicarbonate into the pancreatic juice. |
| Why are most pancreatic proteases secreted as inactive zymogens? | To prevent them from digesting the pancreatic tissue before they reach the small intestine. |
| What are the typical causes of acute and chronic pancreatitis? | Acute pancreatitis is usually caused by gallstones or drug reactions, while chronic pancreatitis is usually due to chronic alcohol abuse. |
| The sight, smell, taste, or thought of food can stimulate salivation and gastric secretions. this is associated with what phase of gastric secretion and what nuclei are stimulated in the brain? | cephalic phase--vagus nuclei are stimulated |
| Which nerve carries the conditioned reflex stimulation from the brain to the digestive organs? | The vagus nerve. |
| What are short reflexes in the digestive system? | They are neural reflexes that do not involve the brain. |
| (starred) What is the function of gastrin secreted by the stomach? | It stimulates parietal cells to secrete HCl and chief cells to secrete pepsinogen. |
| (starred) What is the function of ghrelin secreted by the stomach? | It stimulates appetite and eating. |
| (starred) What is the function of secretin secreted by the small intestine? | It stimulates water and bicarbonate secretion in pancreatic juice and potentiates the actions of CCK on the pancreas. |
| (starred) What are the functions of cholecystokinin (CCK) secreted by the small intestine? | It stimulates gallbladder contraction and pancreatic juice enzyme secretion, inhibits gastric motility and secretion, and maintains the structure of the exocrine pancreas. |
| (starred) What is the function of Gastric inhibitory peptide (GIP) secreted by the small intestine? | It inhibits gastric motility and secretion and stimulates the secretion of insulin from pancreatic islets. |
| (starred) What is the function of PYY (polypeptide YY) secreted by the small intestine? | It decreases hunger and food intake. |
| (starred) What is the function of Glucagon-like peptide-I (GLP-I) secreted by the ileum and colon? | It inhibits gastric motility and secretion and stimulates the secretion of insulin from pancreatic islets. |
| (starred) What is the function of guanylin secreted by the ileum and colon? | It stimulates intestinal secretion of Cl−, causing the elimination of NaCl and water in the feces. |
| How are stomach contractions intrinsically regulated? | They are stimulated spontaneously by pacesetter cells in the greater curvature of the stomach. |
| What triggers the secretion of HCl and pepsinogen in the stomach? | The entry of proteins into the stomach. |
| Which cells initiate and regulate the secretion of HCl and pepsinogen? | G cells (gastrin), D cells (somatostatin), and ECL cells (histamine). |
| What is the cephalic phase of gastric regulation? | It is the control by the brain via the vagus nerves that lasts for the first 30 minutes of a meal and mainly stimulates ECL, chief, and parietal cells. |
| What triggers the gastric phase of regulation? | It is triggered by the arrival of food into the stomach, specifically stomach distension and the chemical nature of the chyme. |
| How does positive feedback work during the gastric phase? | As more proteins are broken down, more secretions are released to continue breaking them down. |
| How does negative feedback work during the gastric phase? | As the pH drops below 2.5 due to more HCl, somatostatin is released, which inhibits gastrin secretion. |
| How do proteins and polypeptides affect the pH of the stomach? | Large amounts of proteins and polypeptides buffer the pH, allowing secretion to match protein concentration. |
| What triggers the intestinal phase of gastric regulation? | The arrival of chyme into the duodenum, causing distension and an increase in osmotic pressure. |
| What is the purpose of the intestinal phase? | It slows the movement of chyme into the duodenum to allow enough time for digestion and absorption. |
| How does stretch in the duodenum affect gastric stimulation? | It activates a neural reflex that inhibits gastric activity via the vagus nerve. |
| What does the presence of fats in the duodenum stimulate? | It stimulates the secretion of enterogastrone hormones that inhibit gastric motility and secretion. |
| What are four enterogastrone hormones that inhibit gastric motility and secretion? | GIP, somatostatin, CCK, and GLP-1. |
| What is the enteric nervous system (ENS)? | It consists of neurons and glial cells (including the myenteric and submucosal plexuses) that innervate the intestines and act independently from the CNS. |
| Which structures does the ENS innervate to intrinsically regulate peristalsis? | It innervates the interstitial cells of Cajal and smooth muscle. |
| How does the enteric nervous system coordinate peristalsis? | It causes the muscle to contract behind the bolus and relax in front of the bolus. |
| What do enterochromaffin-like cells in the intestinal mucosa secrete in response to pressure and food chemicals? | They secrete serotonin and motilin to stimulate muscle contractions. |
| How does guanylin function in the intestines? | It activates guanylate cyclase to produce cGMP, which stimulates the secretion of water and Cl- and inhibits the absorption of Na+, leading to more water and salt lost in feces. |
| What is the gastroileal reflex? | It is when increased gastric activity leads to increased ileum activity and the movement of food through the ileocecal valve. |
| What is the ileogastric reflex? | It is when distension of the ileum causes a decrease in gastric motility. |
| What is the intestino-intestinal reflex? | It is when over-distension of one portion of the intestine causes the relaxation of other portions. |
| What triggers the production of secretin in the duodenum? | A drop in pH triggers its production, causing duct cells to secrete bicarbonate ion to neutralize the acid. |
| What triggers the production of cholecystokinin (CCK) in the duodenum? | The presence of partially digested proteins and fats in the chyme. |
| What stimulates the production of the pancreatic enzymes trypsin, lipase, and amylase? | Acetylcholine (ACh) from the vagus nerve, CCK, and secretin. |
| Which second messengers are used by ACh, CCK, and secretin in the pancreas? | ACh and CCK use Ca2+ as a second messenger, while secretin uses cAMP. |
| What stimulates bicarbonate production in the pancreas? | Secretin. |
| When does the liver increase its continuous production of bile? | When food arrives in the duodenum and when bile acids are returned to the liver via enterohepatic circulation. |
| What do secretin and CCK stimulate regarding bile? | They stimulate increased bicarbonate secretion into the bile. |
| How does CCK affect the gallbladder? | In response to fat in the chyme, CCK stimulates gallbladder contraction to deliver bile to the duodenum. |
| What trophic effect do GI hormones have? | They help maintain the structure of their target organs. |
| Which hormone is responsible for maintaining the structure of the gastric mucosa? | Gastrin. |
| Which hormone is responsible for maintaining the structure of the acinar cells of the pancreas? | CCK. |
| Three Phases of Extrinsic Gastric Regulation | cephalic, gastric, intestinal phases |
| true or false, as HCl levels and pH drops, the acid inhibits G cells directly, shutting down gastrin secretion, which in turn slows down histamine release and brings HCl production back to a safe baseline | true |
| In what forms are most carbohydrates ingested? | Most carbohydrates are ingested as starch or sugars such as sucrose and lactose. |
| Where does starch digestion begin and what enzyme is involved? | It begins in the mouth with salivary amylase, which breaks polysaccharides into shorter chains. |
| Why is there no carbohydrate digestion in the stomach? | The stomach environment is too acidic for salivary amylase to function. |
| Which enzyme continues the digestion of carbohydrates in the intestines? | Pancreatic amylase continues the breakdown of short chains into disaccharides and maltriose. |
| What finishes the breakdown of disaccharides into simple sugars like glucose? | Brush border enzymes in the small intestine finish this process. |
| How are monosaccharides initially absorbed across the intestinal epithelium? | They are absorbed via secondary active transport with sodium, followed by chloride. |
| How do monosaccharides move into the interstitial fluid and capillary blood? | They move by facilitated diffusion through GLUT carriers. |
| How is water absorbed along with glucose and NaCl? | Water follows the NaCl through a paracellular route via osmosis. |
| Where does protein digestion begin and what substances are involved? | It begins in the stomach with pepsin and hydrochloric acid to produce short-chain polypeptides. |
| (starred) Which pancreatic enzymes finish protein digestion in the duodenum and jejunum? | Pancreatic trypsin, chymotrypsin, elastase, and carboxypeptidase. |
| (starred) Which brush border enzyme assists in the final digestion of proteins? | Aminopeptidase. |
| (starred) What are the 3 final products of protein digestion? | The final products are free amino acids, some dipeptides, and tripeptides. |
| How are free amino acids absorbed into the epithelial cells? | They are cotransported with sodium (Na+). |
| How do dipeptides and tripeptides cross into the epithelial cells? | They cross via secondary active transport using a hydrogen (H+) gradient. |
| What happens to dipeptides and tripeptides once inside the cytoplasm of the epithelial cells? | They are hydrolyzed into free amino acids. |
| How do free amino acids move into the blood capillaries of the villi? | They move by facilitated diffusion into the interstitial fluid and then to the blood capillaries. |
| Where does fat digestion begin and what emulsifies it? | It begins in the duodenum when bile emulsifies the fat. |
| Which enzymes break down fats into fatty acids and glycerol? | The pancreatic enzyme lipase, aided by colipase. |
| What enzyme digests phospholipids like lecithin into fatty acids and lysolecithin? | Phospholipase A from the pancreas. |
| (starred) How are fatty acids, monoglycerides, and lysolecithin transported to the brush border? | They move into bile micelles and are transported to the brush border. |
| (starred) What happens to fat molecules after they reach the brush border? | They leave the micelles and diffuse into the epithelial cells of the villi. |
| (starred) What are fat molecules regenerated into inside the epithelial cells? | They are regenerated into triglycerides, cholesterol, and phospholipids, and combined with proteins to form chylomicrons. |
| (starred) How do chylomicrons enter the lymphatic system? | They are secreted by exocytosis into the central lacteal of the villus. |
| (starred) How do chylomicrons enter the bloodstream? | The lymphatic system drops them into the bloodstream from the thoracic duct into the subclavian veins. |
| (starred) What allows chylomicrons to bind to receptors on the capillary endothelium in muscles and adipose tissue? | They pick up an apolipoprotein called ApoE. |
| (starred) Which enzyme digests chylomicrons to release free fatty acids for muscle use or fat storage? | Lipoprotein lipase. |
| Where does the remnant particle containing cholesterol travel after leaving the muscles and adipose tissue? | It travels in the blood to the liver. |
| What do Very-Low-Density Lipoproteins (VLDLs) do? | They are formed in the liver and deliver endogenously produced triglycerides to body cells. |
| What do Low-Density Lipoproteins (LDLs) do? | After triglycerides are removed from VLDLs, they become LDLs, which transport endogenous cholesterol to various organs and are known as "bad cholesterol." |
| What do High-Density Lipoproteins (HDLs) do? | They remove and degrade cholesterol from blood vessels and return it to the liver, and are known as "good cholesterol." |
| Why is a high ratio of HDL cholesterol to total cholesterol beneficial? | It protects against atherosclerosis. |
| What is the optimal pH and product of salivary amylase working on starch in the mouth? | The optimal pH is 6.7 and it produces maltose. |
| What is the optimal pH for pepsin working on proteins in the stomach? | The optimal pH is 1.6 to 2.4. |
| What are the products of pancreatic amylase working on starch in the duodenum? | It produces maltose, maltriose, and oligosaccharides. |
| What is the optimal pH for trypsin, chymotrypsin, and carboxypeptidase in the small intestine? | The optimal pH is 8.0 (more alkaline/neutral). |
| What is the optimal pH and product of pancreatic lipase working on triglycerides in the small intestine? | The optimal pH is 8.0 and it produces fatty acids and monoglycerides. |
| What does the brush border enzyme maltase produce? | It works on maltose to produce glucose. |
| What does the brush border enzyme sucrase produce? | It works on sucrose to produce glucose and fructose. |
| What does the brush border enzyme lactase produce? | It works on lactose to produce glucose and galactose. |
| What does the brush border enzyme aminopeptidase do? | It works on polypeptides at an optimal pH of 8.0 to produce amino acids, dipeptides, and tripeptides. |
| at what points is the pH of the small intestine more alkaline or more neutral and what enzymes work when? | Duodenum 6.0 to mix with stomach acid: Pancreatic amylase, trypsin (proteins), and lipase. Jejunum 7.0-7.4: walls release lactase, maltase, and peptidases. Ileum 7.4 to finish digestion: continued activity of lipase and final sugar-digesting enzymes |
| (starred) what brush border enzyme category is needed for absorption of dietary calcium--an enzyme that is regulated by vitamin D? | Phosphatases--includes Ca2+,Mg2+-ATPase and alkaline phosphatase (the latter of which removes phosphate groups from organic molecules) |
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