PGY EXAM 4 QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026

PGY EXAM 4 QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026 Primary function of digestive system - Answers To transfer ingested nutrients, electrolytes, & water from external environment to body's internal environment GI tract (alimentary canal) - Answers 30 ft long tube that extends from mouth to anus How long does it take for food to go from mouth -- stomach - Answers 10 s How long does it take for food to go through stomach - Answers 1-3 hrs How long does it take for food to go through small intestine - Answers 7-9 hrs How long does it take for food to go through large intestine - Answers 25-30 hrs Sphincters of GI tract - Answers Upper esophageal sphincter Lower esophageal sphincter Pyloric sphincter Ileocecal sphincter Internal anal sphincter External anal sphincter Accessory organs of GI tract - Answers Salivary glands, liver, gallbladder, (exocrine) pancreas Salivary glands - Answers Secrete a hypotonic, alkaline fluid containing mucus, enzymes, & lysosomes Function of mucus in salivary gland - Answers Lubricate ingested material & facilitate swallowing Function of enzymes in salivary gland - Answers Carbohydrate & lipid digestion (a-amylase & lingual lipase) Function of lysosomes in salivary gland - Answers Antibacterial action Liver - Answers Secretes bile Bile - Answers Secreted by liver. Consists of bicarbonate, cholesterol, phospholipids, & bile salts which is required for fat digestion What is required for fat digestion - Answers Bile salts Gallbladder - Answers Stores & concentrates bile Upon ingestion of a fat-containing meal, it is injected into the duodenum via the common bile duct (Exocrine) pancreas - Answers Pancreatic acinar cells synthesize & secrete enzymes into small intestine that digest carbs, fats, protein, & nucleic acids Pancreatic epithelial cells synthesize & secrete bicarbonate into small intestine to neutralize acidic chyme coming from stomach Pancreatic duct -- common bile duct -- duodenum GI tract processes - Answers Secretion, digestion, absorption, motility, defecation Secretion - Answers Release of substances into lumen of GI tract to facilitate digestion Digestion - Answers Chemical & mechanical breakdown of foods into small units to facilitate absorption Absorption - Answers Transfer of substances from lumen of GI tract into enteric capillary beds surrounding GI tract Motility - Answers Mixing of luminal contents & mvmt of material along GI tract by muscle contraction Defecation - Answers Excretion of feces consisting of ingested material that was not digested/absorbed, bacteria, & some metabolic end-products Lumen of GI tract - Answers Continuous with the external environment Venous drainage of GI tract - Answers Portal vein -- liver -- hepatic vein -- IVC Absorbed materials processed by liver prior to release into general circulation Blood flow to GI & accessory organs - Answers Parallel circuits 4 layers of GI tract - Answers Mucosa, submucosa, muscularis externa, serosa Structure of mucosa - Answers Epithelial cells -- lamina propria (connective tissue) -- muscularis mucosa Submucosa - Answers Connective tissue w blood/lymphatic vessels & submucosal plexus Muscularis externa - Answers Circular & longitudinal smooth muscle; myenteric plexus Serosa - Answers Connective tissue What increases the total area of the luminal surface of the small intestine - Answers Circular folds of mucosa & submucosa Villi Microvilli Villi (& contents of its layers) - Answers Fingerlike projections of mucosa into lumen Outer layer- columnar epithelial cells, goblet cells, enteroendocrine cells Inner layer- capillaries, lacteal (lymphatic vessel), Peyer's patches (lymphatic nodules) Goblet cell - Answers Secretes mucus Function of enteroendocrine cells located in "intestinal glands" - Answers Secrete hormones that regulate GI function Function of capillaries in GI tract - Answers Take up most of materials absorbed from lumen of GI tract Lacteal - Answers A single blind-ended lymphatic vessel. Essential for fat absorption! Peyer's patches - Answers (Lymphatic nodules) monitor gut contents, identify harmful pathogens, initiate appropriate immune response (helps produce IgA) Microvilli - Answers Projections of luminal membrane of villus epithelial cells Motility, secretion, digestion, & absorption of oral cavity & esophagus - Answers Initial breakdown of ingested material via chewing & very limited enzyme activity M: chewing, swallowing S: saliva, lipase D: carbs, fats (minimal) A: N/A Motility, secretion, digestion, & absorption of stomach - Answers Reduce ingestion material into chyme M: peristaltic mixing & propulsion S: HCl, pepsinogen & gastric lipase, mucus, bicarbonate, gastrin, histamine D: proteins, fats A: lipid-soluble substances (alcohol, aspirin, etc) Divisions, motility, secretion, digestion, & absorption of small intestine - Answers Primary site of absorption (duodenum & jejunum) D: duodenum, jejunum, ileum M: mixing & propulsion via segmentation S: enzymes, bicarbonate, bile, mucus, hormones (CCK, secretin, GIP, etc) D: carbs, fats, proteins, nucleic acids A: peptides, amino acids, glucose/fructose, fats, water, vitamins & minerals Motility, secretion, digestion, & absorption of large intestine - Answers Undigested material temporarily stored in large intestine prior to defecation. Partial metabolism/digestion of material by intestinal bacteria M: segmental mixing, mass mvmt for propulsion S: mucus D: N/A (except for bacteria) A: ions, water, vitamins & minerals Methods of absorption across intestinal epithelia - Answers Transcellular & paracellular Transcellular vs paracellular transport - Answers Transcellular- through cells across 2 membranes (luminal & basolateral) Paracellular- between cells (across tight junctions via simple diffusion) By which method does most absorption occur - Answers Transcellular. Requires transport proteins on both membranes (luminal & basolateral) What parts of the cell use primary active transport - Answers Plasma membrane & intracellular organelle membranes (lysosomes, smooth ER, etc) Why must ingested carbohydrates be digested - Answers Only monosaccharides can be absorbed by intestinal epithelial cells (ingested carbs are primarily polysaccharides or disaccharides), so they need to be broken down. What substance digests polysaccharides into mono & disaccharides - Answers Pancreatic amylase Membrane transport proteins for glucose/galactose - Answers Luminal- Na+ glucose symporter Basolateral- GLUT2 uniporter Membrane transport proteins for fructose - Answers Luminal- GLUT5 uniporter Basolateral- GLUT5 uniporter Why must ingested proteins be digested - Answers Only amino acids & di/tripeptides can be absorbed by intestinal epithelial cells (must be broken down) Process of protein digestion - Answers 1) HCl & pepsin (secreted by stomach) digest proteins down to peptide fragments 2) Pancreatic proteases digest peptide fragments to di/tripeptides 3) Peptidases (luminal membrane small intestine epithelia) digest most of the di/tripeptides to amino acids Membrane transport proteins for amino acids - Answers Luminal- Na+ amino acid symporter Basolateral- amino acid uniporter Membrane transport proteins for di/tripeptides - Answers Luminal- H+ peptide symporter (Peptides broken down to amino acids by cytoplasmic peptidases) Basolateral- amino acid uniporter Why must ingested fats be digested - Answers Only monoglycerides & fatty acids can be absorped by intestinal epithelial cells, so ingested triglycerides must be digested Fat digestion - Answers Pancreatic lipase digests triglycerides in lumen of small intestine Triglyceride -- monoglyceride + 2 fatty acids Problem: ingested lipids exist as large water-insoluble droplets. Lipase action would be restricted to the droplet surface where rate of digestion would be slow. What is the solution? - Answers Large droplets divided into smaller droplets by emulsification, which increases the rate of digestion Emulsification - Answers Physical process of breaking up large fat droplets into smaller droplets, thereby increasing the surface area that enzymes can use to digest the fat (increasing rate of digestion) Emulsifying agents - Answers Liver bile salts, ingested phospholipids Substances that coat small droplets to prevent them from recombining Substances that are soluble in both fat and water and enable fat to be uniformly dispersed in water as an emulsion. Problem: emulsifying agent coating could impair lipase accessibility to the lipid. What is the solution? - Answers The pancreas secretes colipase (protein) which attaches to the droplet & binds lipase. As a result, the lipase can efficiently digest triglyceride How do fats cross the luminal membrane - Answers By diffusion; there are no fat transporters Problem: Monoglycerides & fatty acids are water-insoluble. Movement from the emulsion droplet to the membrane would be slow. What is the solution? - Answers Bile salts form micelles which package the monoglyceride/fatty acid. Release -- diffusion across membrane What happens after monoglycerides & fatty acids diffuse across the luminal membrane - Answers They are resynthesized into triglyceride by the smooth ER How do triglycerides exit the cell/cross the basolateral membrane & how do they enter bloodstream - Answers TG contained in vesicles; exocytosis These extracellular fat droplets (vesicles) are called chylomicrons, and they're too big to enter capillaries. Instead, they are taken up by villus lacteals (lymphatic ducts) which drain into bloodstream Absorption of fat-soluble vitamins vs water-soluble vitamins - Answers Fat-soluble are absorbed by passive diffusion Water-soluble are absorbed by diffusion & carrier-mediated transport Which vitamins are fat-soluble - Answers A, D, E, K Which vitamins are water-soluble - Answers B & C One exception for absorption of water-soluble vitamins - Answers Vitamin B12 is too big-- cannot diffuse or bind to carriers. Instead, B12 binds to intrinsic factor (protein) which is synthesized & secreted by parietal cells of the stomach. B12-intrinsic factor complex binds to receptors in lower ileum Complex crosses luminal membrane via receptor-mediated endocytosis Loss of intrinsic factor leads to pernicious anemia 2 sources of iron in lumen - Answers Free lumen iron complexes with transferrin TF (secreted by enterocytes). TF-iron complex binds to luminal membrane receptors & is endocytosed. Some iron is stored bound to ferritin (intracellular iron storage site) Heme - Answers (Derived from meat) Important source of dietary iron. Heme absorbed across luminal membrane by endocytosis How can absorption of iron into ECF be regulated - Answers (Example) Let's say there's an increase in plasma iron concentration (intracellular fluid, inside cell). If you decrease transferrin receptor expression, iron uptake will decrease If you increase ferritin transcription (which binds to iron), free iron will decrease, leading to a decreased plasma iron concentration Hemochromatosis - Answers Excess plasma iron (intracellular free iron) Absorption of calcium - Answers Occurs in small intestine Ca2+ crosses luminal membrane via Ca2+ selective ion channel In the cell, Ca2+ binds to Ca2+ binding proteins, which prevents an increase in cytosolic Ca2+. The binding protein transports Ca2+ to the basolateral membrane Ca2+ transported across basolateral membrane by Ca2+ ATPase & Na+-Ca2+ antiporter How does vitamin D regulated the absorption of calcium - Answers ... Hydroxylations of vitamin D - Answers 1st occurs in liver 2nd occurs in kidney (catalyzed by 1a-hydroxylase, which is activated by PTH) Where does majority of water absorption occur - Answers Small intestine Steps of water absorption - Answers 1) Primary solute transport creates small transepithelial osmotic gradient. 2) Water moves from lumen to interstitium down osmotic gradient. (High aquaporin expression -- high permeability) 1) Solute goes in 2) Water goes in What regulates GI tract control mechanisms - Answers Volume & composition of luminal contents NOT nutritional state of body Digestive system designed for max absorption not to maintain homeostasis What initiates GI tract reflexes - Answers Stimuli from mechanoreceptors, osmoreceptors, & chemoreceptors What do mechanoreceptors, osmoreceptors, and chemoreceptors do in GI tract - Answers Mechanoreceptors- detect distension of GI tract wall Osmoreceptors- detect changes in osmolarity of chyme (total solute concentration) Chemoreceptors- detect changes in pH of chyme & detect changes in digestion product concentration in chyme (monosaccharides, amino acids, fatty acids, etc) Primary effectors of GI tract reflexes - Answers GI tract muscle & accessory organs Parasympathetic vs sympathetic stimulation in ENS - Answers Parasympathetic is stimulatory Sympathetic is inhibitory Enteric nervous system (ENS) - Answers Submucosal plexus (in submucosa) + myenteric plexus (in muscularis externa) Submucosal plexus vs myenteric plexus - Answers Submucosal plexus (in submucosa)- influences exocrine gland activity Myenteric plexus (in muscularis externa)- influences smooth muscle activity Short reflex vs long reflex - Answers Short- within ENS only Long- goes to CNS What are external factors that can also affect GI tract via CNS - Answers Emotional state, hunger, sight/smell of food What GI hormones does the stomach vs small intestine secrete - Answers Stomach- gastrin Small intestine- secretin, cholecystokinin CCK, motilin, glucose-dependent insulinotropic peptide GIP, glucagon-like peptide 1 GLP-1 Phases of GI control - Answers Cephalic, gastric, intestinal Cephalic phase control - Answers Sight, smell, taste, & chewing of food increases vagal nerve parasympathetic activity. Vagal efferent fibers synapse w ENS, resulting in altered secretory/contractile activity Stimulates parietal cell HCl secretion (ACh as neurotransmitter), gastrin secretion by G cells, & histamine secretion by ECL cells Gastric phase control - Answers Reflexes initiated by stomach distension, acidity, amino acid, & peptide content. Effects mediated by short & long neural reflexes & hormonally by gastrin Stimulate HCl secretion via vagovagal reflex (mechanoreceptors detect stretch/distension) & increased ENS activity (increased ACh, gastrin, histamine) Luminal contents also directly stimulate gastrin release Gastric phase control 2 - Answers Reflexes initiated by stomach distension, acidity, amino acid, & peptide content. Effects mediated by short & long neural reflexes & hormonally by gastrin Stimulate HCl secretion via neural, endocrine, & paracrine factors! Neural- direct stimulation of parietal cell w ACh as neurotransmitter Endocrine- gastrin secretion by G cells stimulated by increased ENS activity w gastrin releasing peptide GRP as neurotransmitter & increased peptide concentration in lumen of stomach Paracrine- histamine secretion by ECL cells stimulated by increased ENS activity & gastrin Intestinal phase control - Answers Reflexes initiated by small intestine distension, acidity, osmolarity, & solute content. Effects mediated by short & long neural reflexes & hormonally by secretin & CCK Antrum of the stomach - Answers Thick smooth muscle Sphincters of the stomach - Answers Lower esophageal sphincter- controls input from esophagus Pyloric sphincter- controls transfer of chyme to small intestine Tubular gland - Answers Stomach epithelial layer invaginates into mucosa Cell types (& their secretions) of tubular gland - Answers Mucous cells Parietal cells: HCl & intrinsic factor Enterochromaffin-like ECL cells: histamine Chief cells: Pepsinogen Antral enteroendocrine G cells: gastrin D cells: somatostatin HCl production - Answers (In parietal cells) HCl produced intracellularly from CO2 & H2O; rxn catalyzed by carbonic anhydrase. H+ & Cl- secreted into lumen What determines HCl secretion rate - Answers # of H+K+-ATPase pumps in luminal membrane (pumps H+ into lumen) To increase HCl secretion, cytosolic ATPase-containing vesicles fuse w luminal membrane; inserts more ATP-ases Hormones that increase HCl secretion vs decrease - Answers Stimulatory: ACh, gastrin, histamine Inhibitory: somatostatin (H+K+-ATPase-containing vesicle trafficking & fusion w luminal membrane) Effect of low luminal pH (acidic) on HCl secretion - Answers Luminal pH 3.0 will decrease further HCl secretion pH 3 directly inhibits gastrin secretion by G cells (decrease HCl) & directly stimulate somatostatin secretion by D cells (suppress HCl secretion & inhibit release of gastrin & histamine) Small intestine in acidic environment - Answers Digestive activity of enzymes in small intestine is reduced by acidic solutions; small intestine works best @ neutral pH. High acidity in duodenum suppresses parietal cell HCl secretion via short/long loop neural reflexes & secretion of secretin & CCK Pepsin secretion - Answers Pepsinogen secreted by chief cells HCl converts pepsinogen to pepsin which digest proteins (Then released pepsin can help cleave pepsinogen) (Most of the factors that regulate HCl secretion also regulate pepsinogen secretion) Functional unit of salivary duct - Answers Salvion 4 primary elements of salvion - Answers Terminal acinus: epithelial cells that secrete initial saliva Myoepithelial cells: surround acinar cells; contractile Intercalcated duct: channels saliva to striated duct Striated duct: saliva composition changes Ion concentrations salivary gland vs plasma - Answers Salivary HCO3- & K+ higher than plasma Salivary Na+ & Cl- less than plasma Sympathetic & parasympathetic effects of saliva secretion - Answers Both stimulate but parasympathetic has much greater effect Parasympathetic effects on salivary glands - Answers Increased secretion, vasodilation, myoepithelial cell contraction, metabolism, growth Factors that suppress parasympathetics/saliva secretion - Answers Fatigue, fear HCl production in stomach - Answers (In parietal cells)