Gastrointestinal Flashcards
What is the effect of increased parasympathetic tone on gastrointestinal contractions?
May cause segmental contractions which inhibit progressive motility.
How do you distinguish the small colon on palpation?
Presence of faecal balls and an antimesenteric band that is palpable along the length of this segment if it is impacted.
Which electrolytes are lost in large volumes of gastric reflux or diarrhoea?
Na, K, Ca, Mg and HCO3
What are the potential mechanisms for increased lactate concentration in cases of colic?
- Large colon ischaemia- Reduced perfusion to peripheral tissue due to hypotensive shock- Generalised intestinal ischaemia may result in absorption of lactate from the lumen- Increased blood viscosity reduces perfusion of capillary beds, exacerbating ischaemia and tissue hypoxia.
If oesophageal rupture is suspected or aspiration is a possibility which contrast material should be used for a contrast oesophogram?
Iodinated organic compounds in an aqueous solution should be used instead of barium.
What are the sites for the FLASH U/S examination of the abdomen?
Ventral abdomen, gastric window, spleno-renal window, left middle third of the abdomen, duodenal window, right middle third of the abdomen and thoracic window.
For an oral glucose absorption test, how much glucose is given, at what time point and what level should the peak be in blood glucose be, and what are the different levels of malabsorption cut offs?
1g/kg of d-glucose as a 20% solution in water via NGTPeak at >85% above baseline glucose between 90-120minComplete malabsorption is a peak <15% above resting, partial malabsorption is between 15-85% above resting.
What are the benefits of a xylose absorption test over a glucose absorption test and how is the protocol different?
d-Xylose absorption is not confounded by hormonal effects of mucosal metabolism of glucose as the glucose absorption test is. Protocol is: 0.5g/kg d-xylose as a 10% solution; peak is between 60-90min but is a concentration between 20-25mg/dl.
What effects do the normal diet have on results of an oral glucose absorption test or an oral xylose absorption test?
OGAT: higher peaks in horses eating grass/hay compared with concentrates and from those at pasture compared with stabled. OXAT: higher peaks in horses fed low-energy diet such as alfalfa chaff than those fed high-energy diets such as oat chaff, oats and corn.
List tests for assessing gastric emptying
- Contrast radiography in foals- Nuclear scintigraphy for liquid or solid phase emptying- Acetaminophen absorption and measurement in serum- 13C-octane acid breath test using a labelled test meal and detection of the novel isotope in breath.
List the intestinal barriers against pathological invasion at the varying cellular levels.
Epithelium: tight junctions and mucous layerMacrophages: resident macrophages in the lamina propria, submucosa and intestinal lymphoid organs are among the first to respond to infection.
Describe the events that lead to intestinal inflammation with epithelial breach.
Breach of the mucosal barrier initiates an inflammatory response through synthesis of pro-inflammatory chemokines (IL8) and cytokine (TNFalpha, arachidonic acid metabolites) by epithelial cells which then trigger influx of neutrophils and other leucocytes into the tissue. Mast cells are sentinel cells that sense microbial invasion and release TNFa. Macrophages within the lamina propria, submucosa and intestinal lymphoid tissue activate CD14 TLR4 complex which initiates transcription of TNFa and IL1B which synergise with LPS to amplify the macrophage response. Once initiated, TNFa, IL1B and other proinflammatory products of neutrophils, monocytes, mast cells and eithelial cells amplify the inflammatory response, in part through release of nitric oxide and other nitrogen radicals which are microbicidal but also vasoactive.
List the four important changes that occur in the intestinal vasculature in response to inflammation.
- Alteration of blood flow (initially increased, then decreased due to increased viscosity with fluid loss and oedema, increased leucocyte margination, platelet adhesion etc)2. Increased vascular permeability (due to histamine, leucotrienes, prostaglandins and other inflammatory mediators cause endothelial cell contraction, creating leaky gaps)3. Increased adhesiveness of endothelial cells, leucocytes and platelets (cytokines stimulate endothelial cells to express adhesion molecules that support adhesion of leucocytes and platelets. 4. Exposure of the basement membrane and activation of the complement, contact and coagulation cascades. (adhesion to the exposed basement membrane enables exposure of neutrophils and platelets to mediators of inflammation which activates the cells to release oxidants and proteases that injure the endothelium and can cause irreparable harm to the microvasculature). Marginated neutrophils begin to transmigrate between endothelial cells and this, if not closely regulated can worsen vascular leakage.
Why is neutrophil depletion considered protective in some models of GIT inflammation?
During the acute response neutrophils are activated to release products that are not only lethal to pathogens and proinflammatory but are also damaging to host cells and tissues.
What are the most potent stimuli for neutrophil activation at the site of inflammation?
Complement, cytokines (TNFa and IL1B), platelet activating factor (PAF), immune complexes and bacterial products
What are the main regulators/stimulators of mast cells?
Complement fragments (C3a, C5a and C4a)Neural pathways which respond to enteric pathogen invasion
What are some important roles of mast cells during intestinal inflammation?
- First line defense at epithelial barriers- When activated the release histamine, proteases, heparin and cytokines, as well as inflammatory mediators including prostaglandins, PAF and leucotrienes. - On the vasculature they increase endothelial permeability and cause vasodilation- Mast cell derived mediated enhance epithelial secretion, including the mast cell protease tryptase which regulates GIT physiologic responses during inflammation, including intercellular junction integrity, motility and pain responses. - Mast cell products alter intestinal motility, generally increasing it to enable expulsion of intestinal contents. - Mast cell derived leucotrienes and TNFa have a crucial role in host defence against bacterial pathogens, including neutrophil recruitment, regulating dendritic cells and adaptive immune responses. - Mast cells are phagocytic and can act as antigen presenting cells.
What is the function of complement fragments?
During activation of the complement cascade, soluble fragments of C3, C5 and C4 (C3a, C5a and C4a) are liberated. These anaphylatoxins are chemotactic for neutrophils, and activate neutrophils and mase cell degranulation as well as stimulating ROS.
What is the basic mechanism behind ischaemia-reperfusion injury?
Reperfusion of ischaemic tissue is associated with platelet and neutrophil clumping in the small vessels of the mucosa which can impede blood flow. Platelets are activated and adhere to exposed basement membrane and activated endothelial cells and provide a surface for leucocyte adhesion. The accumulation of platelets and leucocytes reduces vessel diameter and blood flow while potentiating local coagulation and thrombus formation. Various factors (histamine, leucotrienes, prostaglandins, thromboxane etc) from the activated leucocytes have a role in regulating local perfusion during inflammation. In addition, nitric oxide is a potent regulator of blood flow. However, many of the mediators affecting perfusion also affect endothelial permeability, altering osmotic and hydrostatic balance and tissue oedema, so in extreme cases local and systemic coagulopathies initiated by the vascular injury and absorption of microbial products and inflammatory mediats induce a hypercoaguable state and exacerbate thrombus formation and tissue injury/infarction
How does neutrophil migration damage endothelial and epithelial barriers?
To facilitate neutrophil migration to the site of inflammation they release serine proteases and metalloproteinases to liquefy tissue matrix proteins that make up intercellular junctions. These degradative enzymes are particularly damaging to basement membranes and the cellular barriers of the endothelium. However a similar effect occurs with the epithelium - TNFa and IFNy from activated neutrophils increases the permeability of tight junctions of enterocytes. Subepithelial accumulation of neutrophils can lead to deadhesion of the epithelial cells from the basement membrane and mild to severe ulceration. The end result is PLE and absorption of bacterial cell wall constituents.
What factors are thought to affect motility during diarrhoea?
- Invasive bacteria cause rapid bursts of motor activity in the colon that appear to decrease transit time through the large intestine. - Absorption of endotoxin and release of inflammatory mediators such as prostaglandins disrupts the motility patterns of the large intestine, resulting in less coordinated contractions.
What are phagocyte derived reactive oxygen metabolites and what effects do they have on tissue?
Phagocytes produces superoxide radicals as a host defense mechanism to kill invading microorganisms. During inappropriate stimulation, as can occur with inflammation, trauma or ischaemia-reperfusion, increased levels of toxic oxygen species are produced causing marked tissue damage. Activated phagocytes secrete peroxidase enzymes into the extracellular space, which catalyse oxidation of Cl to yield HOCl which is 100-1000 times more toxic than O2- and is a non-specific oxidising and chlorinating agent that reacts with amines to form N-chloramines. The end result is marked tissue damage and altered permeability.
In what conditions is the GIT permeability to endotoxin/bacteria increased?
- Strangulating obstruction and bowel infarction- Inflammation eg enteritis or colitis- Bacterial overgrowth- Intraluminal acidosis (eg grain poisoning/overload)
Which cytokines are of interest in the pathogenesis of endotoxaemia?
TNFa, the interleukins, chemokinse and growth factors such as granulocyte-monocyte colony stimulating factor.
adrenergic neurons are typically __________ to gut?
inhibit or stimulatory? Molecule?
Inhibitory: adrenaline/epinephrine
What is Aldosterone and where is it secreted?
Is a steroid hormone (mineralocorticoid) secreted by outer zone glomerulosa of adrenal cortex.
Secreted after low-salt diet, angiotensin, adrenocorticotropic hormone, or high potassium levels.
Aldosterone: function
act on distal convoluted tubules and collecting ducts of the kidney causing secretion of K+ and reabsorption of Na+ and H2O.
What is the GI function of Aldosterone?
It stimulates sodium and water reabsorption from the gut and salivary glands in exchange with K+ ions.
Species dependent: water and Na+ reabsorption in proximal colon and decrease absorption in distal colon.
Autocrine definition
secretions of a given cell modify or regulate functions of the same cell
By what process is water absorbed in the small intestine?
Entirely by diffusion
Where are the 2 CCK receptors located?
CCK-1 (CCKA) is primarily found in the GI tract. Its primary fnction is to stimulate bicarb secretion, gall bladder emptying and inhibiting gut motility.
CCK-2 (CCKB) is primarily found on CNS. Its primary function is to regulate nociception, anxiety, memory and hunger.
Cholecystokinin: Action
Stimulates pancreatic enzyme secretion and gallbladder contractions; inhibits food intake and gastric emptying
Cholecystokinin: Production site
Duodenum, jejunum, ileum; endocrine I ("i") cells and enteric neurons of duodenum and jejunum
Cholecystokinin: Release stimulus
Fats and protein
Cholinergic neurons are typically _________ to gut? inhibit or stim? Molecule?
stimulatory, Acetycholine
Describe the basic electrical rhythm of the stomach.
Mixing waves = Slow waves (spontaneous) that result in mixing of the food (chyme), more intense at antrum
Discuss the blood flow in the salivary glands.
The salivary glands make kalikrein - which when secreted splits a-2 globulin into bradykinin = VASODILATION
Discuss the excretion of bilirubin.
1. RBCs are degraded by reticuloendothelial system (heme + globin)2. Via heme oxygenase = Biliverdin3. Unconjugated bilirbin (bound to albumin)4. In liver conguates with glucuronic acid = Bilirubin glucuronide (80%) and bilirbuin sulfate (10%) = Conjugated bilirubin5. Conjugated bilirubin is excreted in bile into intestesines6. In intestines - intestinal bacteria convert it into urobilinogen7. About 90% of urobilinogen is converted to stercobilinogen then converted to stercobilin and is excreted in feces8. About 10% of urobilinogen is absorbed into blood and is either recycled to bile (about 95%) or excreted by kidney (about 5%). When urobilinogen is exposure to air in the urine it is converted to urobilin
Do the slow waves in the GIT cause muscle contraction?
NO! Except in stomach. Provide electrical background to allow AP when excited by intermittent spike potentials (which excites muscle contractions)
Does the large intestinal have villi and Crypts of Lieberkuhn?
No villiYes - Crypts of Lieberkuhn
During fasting what type of gastric contraction periodically occurs?
Migrating myoelectric complexes = mediated by motiliin
Explain enterohepatic circulation of bile salts?
Bile salts are reabsorbed in SI (diffusion and active transport) → Portal blood → Liver venous sinusoids → Hepatocytes → BileAbout 94% of bile salts are recirculated (up to 17x)
Five Functions of the gut
motilitysecretiondigestionabsorptionstorage
Gastric inhibitory polypeptide: action
inhibits gastric secretions and emptying and stimulates insulin secretion. Slows movement of ingesta particularly from stomach to intestine.
Gastric inhibitory polypeptide: Production site
duodenum and jejunum
Gastric inhibitory polypeptide: release stimulus
fat and glucose (glu. in duodenum)
Gastrin & histamine =?
Gastrin increases acid secretion indirectly by stimulation of histamine release from ECL which can activate H2 receptors on acid secreting gastric parietal cells.
Gastrin binds to ____________
CCK-2 receptor, g-protein coupled receptor. Causes stimulation of gastric acid secretion and hyperplasia of enterochromaffin-like cells.
Gastrin forms
G-17 (90%) and G-34 (10%, duodenum)
Gastrin: Action
Stimulates acid secretion and growth of stomach epithelium (cancer marker)
Gastrin: prod. site
stomach (pylorus and antrum) and duodenum G cells
Gastrin: Release stimulus
Protein, increased high gastric acidity, gastric distention
How are bile salts made?
From cholesterol (diet or made in liver) → 1. cholic acid OR 2. Chenodeoxycholic acid → These combine with either 1. Glycine or 2. Taurine → Conjugated bile salts
How are pancreatic enzymes secreted?
Pancreatic enzymes are secreted as zymogens (INACTIVE form) - Such as trypsinogenOnce into the small intestine they are activated = Trypsin
How are the action potentials different in the GIT?
Calcium-sodium channels = Much slower to open/close = Longer duration of AP
How does parasympathetic stimulation affect the ENS?
Increases activity of ENSMainly vagus nn (some through pelvic nn)
How does sympathetic stimulation affect the ENS?
Inhibits GIT activity = From T5-L2 → sympathetic chains → celiac ganglion → mesenteric ganglia (postganglion neuron bodies) → Postganglic fibers to ENTIRE GIT → Secrete norepinephrine (small amounts of epinephrine)Inhibits intestinal smooth muscle, blocks/inhibits neurons in ENS
How dot he enterocytes of the Crypts of Lieberkuhn result in formation of a watery vehicle?
1. Active secretion of Cl-2. Active secretion of HCO3-Drags along Na+ and water
How is gastric secretion inhibited?
Food in SI1. Reverse enterogastric reflex (myeneteric NS, sympathetic NS, vagus n)2. Food in SI stimulates secretion of SECRETIN and 3 other inhibitors (gastric inhibitory peptide, somatostatin, vasoactive intestinal peptide)
How is pepsinogen activated?
Pepsinogen (inactive) is secreted by the peptic/chief cells in the gastric/oxyntic gland. This is converted to pepsin (ACTIVE = highly proteolytic at low pH) when HCl is present
How is urea formed in the urine?
Amino Acid + Keto acid (alpha keto-glutoric acid) gets transminated into keto acid + amino acid (glutamic acid)Via oxiative deamination glutamic acid is converted to keto acid + NH3 (ammonia)The ammonia combined with CO2 and creates urea!
In general what regulates stomach emptying?
Signals from stomach and duodenum (potent)
In the nerve fibers how are AP generated?
By rapid entry of Na into nerve through Na channels
Motilin: Action
induction/regulation of phase III of the MMC (migrating motor complex) during fasting (digestive state). Works on both muscles and nerves. Stimulates gastric emptying between meals and secretion of pepsinogen (protein digesting enzyme)
Motilin: Production site
M cells of duodenum and jejunum (jejunum lesser extent than duod.)
Motilin: Release stimulus
Acetylcholine
Name 1 thing that is stimulated and 2 things that are inhibited by gastric inhibitory peptide (GIP)?
Stimulates:1. Insulin releaseInhibits:1. Gastric motility (mild)2. Gastric Acid Secretion
Name 2 enzymes that aid in starch digestion that are not found in intestinal epithelium.
1. Salivary alpha amylase (Ptyalin)2. Pancreatic amylase
Name 2 mixing movements in the GIT?
1. Peristalsis again sphincter = churning of content2. Local intermittent constrictive contractions within gut wall (chopping and shearing contents)
Name 3 places that protein digestion occurs?
1. Stomach2. Duodenum/Upper jejunum (pancreatic secretions)3. Enterocytes (duodenum and jejunum)
Name 3 stimuli that result in secretion of cholecystokinin?
1. Protein2. Fat3. Acid
Name 3 stimuli that result in secretion of gastrin?
1. Protein2. Distension3. Nerve (gastrin releasing peptide from vagal stimulation)Acid = Inhibits release
Name 3 things that stimulate the secretion of motilin.
1. Fat2. Acid3. Nerve
Name 4 other functions of the liver in metabolism.
1. Stores Vitamins - A, D, B122. Blood coagulation - makes factors (needs Vit K)3. Storage of iron == Ferritin4. Metabolizes drugs, hormones, Ca2+, others
Name 4 things that are stimulated and 1 thing that is inhibited by secretin.
Stimulates:1. Pepsin secretion2. Pancreatic bicarbonate secretion!!! (neutralizes acidic contents)3. Biliary bicarbonate secretion4. Growth of exocrine pancreaseInhibits:1. Gastric Acid secretion
Name 6 roles of cholecytsokinin.
Stimulates:1. Pancreatic enzyme secretion2. Pancreatic bicarbonate secretion3. BG contraction4. Growth of exocrine pancreasInhibits:5. Gastric emptying (moderate - time for digestion)6. Appetite (sensory afferent in duodenum via vagus to appetite centers)
Name the 2 primary bile acids.
Cholic acid and chenodeoxycholic acid
Name the 4 fat soluble vitamins.
Vitamins A, D, E, K
Neurocrine definition
secretion by enteric neurons of neuromodulators or regulatory peptides that affect nearby muscle cells, glands, or blood vessels.
Paracrine definition
peptides secreted from cells with subsequent diffusion through the interstitial space to contact and affect other cells
Secretin: Action
stimulates HCO3- secretion and inhibits acid secretion (nature's anti-acid). Stimulates exocrine pancreatic and biliary secretions of water, bicarb. gastric mucus and pepsinogen; endocrine pancreatic secretions of insulin, glucagon, and somatostatin; and pancreatic growthInhibits gastric acid secretion, motility of intestine and gastric mucosal growth.
Secretin: production site
duodenum and upper jejunum; S cells
Secretin: Release stimulus
Gastric acid, fat, protein, bile acids, and herbal extractsControlled by action of hormones: CCK, hormonal-neuronal control (CCK-vagal)
What 3 locations do carbohydrate digestion occur?
1. Mouth2. Small intestine (pancreatic secretions)3. Villi (Brush border)
What 3 pancreatic enzymes are responsible for fat digestion?
Pancreatic lipase (fat into FA and monglycerides)Cholesterol esterase (hydrolysis of cholesterol)Phospholipase (FA splits from phospholipids)
What 3 pancreatic enzymes are responsible for protein digestion?
1. Trypsin!!!!2. Chymotrypsin3. Carboxypolypeptide (can release AA)
What 4 components are absorbed via micelles with bile salts?
1. Fatty Acids2. Monglycerides3. Cholesterol4. Other Lipids
What accounts for the huge regenerative capacity of the liver?
HGF (Heptocyte growth factor) produced by mesenchymal cells
What are 2 main things that are lost in diarrhea?
HCO3- and K+ = Hypercholermic metabolic acidosis
What are 2 stimuli for secretion of secretin?
1. Acid2. Fat
What are 3 stimuli for gastric inhibitory peptide (GIP) secretion?
1. Protein2. Fat3. Carbohydrates (less)
What are essential for emulsification of tryglycerides?
Bile salts and lecithin
What are hunger contractions?
When the stomach as been empty for hours - Rhythmic powerful contractions
What are slow waves in the GIT?
Rhythmic contractions - determine by frequency of slow waves (NOT AP but slow undulating changes in resting membrane potential)Varies along GIT
What are spike potentials in GIT?
True AP - Each time peaks of slow waves temporarily more + spike potentials = Peaks
What are the 2 actions of gastrin?
Stimulates:1. Gastric acid secretion2. Growth of gastric mucosa
What are the 2 duodenal factor that control stomach emptying?
Inhibit Emptying1. Enterogastric Relfex (food in duodenum inhibit pyloric pump)2. Hormones = CCK (from jejunal cells that sense fat) = Blocks stomach motility (caused by gastrin)
What are the 2 gastric factors that control stomach emptying?
Promote emptying = increased pyloric pump1. Gastric food volume (stretch)2. Gastrin release
What are the 2 main blood supplies for the liver?
Portal vein and hepatic artery
What are the 2 main glands in the SI that result in secretions?
1. Brunner's glands = Mucus and bicarbonate2. Crypts of Lieberkuhn = Digestive Juices (mucus and watery vehicle)
What are the 2 main stimuli for secretion of pepsinogen from peptic/chief cells?
1. Acetylcholine (vagus n. and gastric enetric plexus)2. Acid in the stomach
What are the 2 main ways that proteins are absorbed in the SI?
Via Na+ co-transporter or less by facilitated diffusion
What are the 2 major movements in the SI?
1. Mixing contractions = segmentation contractions (from SI distension with chyme)2. Propulsive Movements = Perstaltic wavesStretch (chyme in duodenum), gastroenteric reflex, hormones (gastrin, CCK, insulin, motilin, serotonin)
What are the 2 major movements of the colon?
1. Mixing movements - large circular contractions2. Propulsion movements = MASS MOVEMENTS (dt gastrocolic and duodenocolic reflexes = distension)
What are the 2 reflexes that control defecation and which one is "stronger"?
1. Intrinsic Reflex (local ENS - myenteric plexus)2. Parasympathetic Defecation Relfex (via pelvic nn) = VERY POWERFUL peristalsis and inhibits internal anal sphincter?
What are the 2 types of movement in the GIT?
Propulsive movements (food to move to accommodate digestion/absorptive)2. Mixing movements (of contents)
What are the 2 types of peristalsis during the esophageal phase?
1. Primary peristalsis - continuous wave from pharynx
2. Secondary Peristalsis = from distension of esophagus (controlled by myenteric NS)
What are the 2 types of secretions from salivary glands?
1. Serous = Ptyalin (a-amylase) = Digest starch2. Mucus = Mucin = Lubrication
What are the 3 final monosaccharides?
1. Glucose2. Galatose3. Fructose
What are the 3 main actions that can result in depolarization of smooth muscle cells in GIT?
1. Stretching of muscle2. Stimulation by acetylcholine release from parasympathetic nn3. Stimulation by several specific GI hormones
What are the 3 main cell types that make of the gastric/oxyntic gland and what do they secrete?
1. Mucous Neck Cell = Mucus2. Oxyntic/Partiel Cells = HCl, intrinsic factor3. Peptic/Chief Cells = Pepsinogen
What are the 3 main functions of the liver in fat metabolism.
1. High rate of oxidation of fatty acids (fats → glycerol + FFA → Beta oxidation →Acetyl CoA→TCA Cycle or acretoacetic acid2. Synthesis cholesterol (for bile salts), phospholipids (cell membranes), lipoproteins3. Convert carbs and proteins into fat
What are the 3 main motor functions of the stomach?
1. Storage of food until into SI2. Mixing of food with gastroc secretions into chyme3. Slow empyting of chyme from sotmach into SI
What are the 3 main stimulators of H+ secretion on parietal cells and what are their receptors?
1. ACh (From Vagus n, M3 receptor)2. Gastrin (From G cells in antrum, CCKb receptor)3. Histamine (From ECL cells, H2 receptor)
What are the 3 main stimuli for HCl secretion and which cells do these substances stimulate?
1. Acetylcholine = All cells are stimulated2. Gastrin = Only parietal cells are stimulated3. Histamine = Only parietal cells are stimulated
What are the 3 main stimuli for pancreatic secretion?
1. Acetylcholine2. Cholecystokinin (CCK)3. Secretin
What are the 3 phases of gastric secretion and how much do they account for acid secretion?
1. Cephalic Phase = 30% acid production2. Gastric Phase = 60% acid production3. Intestinal Phase = 10% acid production
What are the 3 phases of pancreatic secretion?
Same as gastric secretion1. Cephalic = 20% pancreatic enzymes2. Gastric = 5-10% pancreatic enzymes3. Intestinal: LOTS of pancreatic fluid and bicarbonate (secretin); 70-80% pancreatic enzymes (CCK)
What are the 3 phases of swallowing?
1. Voluntary Stage (bolus into pharynx)2. Pharyngeal Stage (involuntary)3. Esophageal Stage (involuntary)
What are the 3 things in the portal triad?
1. Portal Vein2. Bile Duct3. Hepatic Artery
What are the 4 main functions of the liver in carbohydrate metabolism?
1. Store glycogen (glucose buffer)2. Convert galactose/fructose into glucose3. Gluconeogenesis
What are the 4 main functions of the liver in protein metabolism?
1. Deamination of AA2. Formation of urea3. Formation of plasma proteins (except Ig)4. Interconversion of AA
What are the 4 steps of Vitamin B12 absorption?
1. Dietary B12 released from pepsin (stomach)2. Free B12 binds to R protein (from saliva)3. Duodenum: Pancreatic proteases degrade R protein and Vit B12 transferred to intrinsic factor (prevented from degrading)4. Vit B12-Intrinsic Factor Complex - Ileum it is transported
What are the 6 magic properties of mucus?
1. Adheres tightly to food and spreads thin2. Sufficient body to coat GIT so that food rarely touches mucosa3. Causes formation of fecal balls4. Resistant to digestion by digestive enzymes5. Particles slide along it easily6. Amphoteric properties (can buffer acid or alkali)
What are the areas that lymph is created/filtrated in the liver lobules?
Within the Space of Disse
What are the basic steps in secretion from a glandular cell in the GIT?
1. Diffusion of substance from capillaries into glandular cell2. Secretory substance made in ER3. Formed by ribosomes and Golgi4. Stored Glogi vesicles5. Increased permeability = Increased intracellular Ca2+ = Vesicles fuse to apical membrane = Exocytosis
What are the Brunner's gland stimulated by in the SI?
Result in mucus and bicarbonate secretionStimulated by: food, vagal stimulation, secretinResult in protection of mucosa in duodenum
What are the effects of norepinephrine and epinephrine on GIT nerves (stimulation of smpathetic nn)?
More negative = Hyperpolarized (less excitable)
What are the enzymes in the duodenum/upper jejenum that aid in protein digestion?
Pancreatic enzymes: Trypsin. Chymotrypsin, carboxypolypeptidase, proelastase
What are the final products of carbodyhrate digestion?
Monosaccarides that are absorbed immediately into portal blood
What are the layers of the GI wall?
1. Serosa 2. Longitudinal smooth muscle layer 3. Circular smooth muscle layer 4. Submucosa 5. Mucosa (bundles of smooth muscle fibers)
What are the main villus enzymes?
1. Peptidase (peptides → AA)2. Sucrase, maltase, isomaltase, lactase (dissaccharides → monosaccharides)3. Intestinal lipase (fats → glycerol and FA)
What are the net results of gastric parietal cells?
Net secretion of HCl and net absorption of HCO3- (alkalaine tide that is seen after meals)
What are the steps in HCl secretion in a oxyntic/parietal cells?
1. Water dissociates into H+ and OH- in the cytoplasm2. H+/K+ ATPase allows H+ to be secreted into the canaliculi3. Potassium in brought into the cell on the basolateral membrane by a Na+/K+ ATPase pump, this makes low intracellular Na+, which brings Na+ into the cell from the canaliculus4. Pumping out of H+ allows formation of HCO3- since OH- is accumulating in the cell cytoplasm, this is mediated by carbonic anhydrase, this is then secreted in exchange for Cl-, which is sent out into the canaliculus to meet with H+ and make HCl5. Water passes into the canaliculus by osmosis
What are the steps in making bicarbonate in the pancreas?
1. CO2 diffuses into the cell from the blood, combines with water to form carbonic acid (H2CO3), dissociates into H+ and HCO3-2. H+ is traded in the blood for Na+, which is transported out of the cell with HCO3-3. This also pulls water by osmosis
What are the stimuli for propulsive movements = peristalsis in GIT?
Stimulus = Distenstion (stretching) caused by materialSome chemical and physical irritation, strong parasympathetic nervous signals
What are the two imperative steps in emptying the GB and what controls this?
Need contraction of GB and relaxation of Sphincter of Oddi (at exit of common bile duct into duodenum) This is stimulated by CCK that is released in response to a fatty meal in the duodenum
What are the two layers of muscles in the GIT?
1. Circular muscles2. Longitudinal muscles
What are the two main cells types of the Crypts of Lieberkuhn?
1. Goblet Cells = Mucus2. Enterocytes = Absorb and secrete water and electrolytes (PURE ECF, alkaline fluid)
What are the two main functions of pancreatic secretions?
1. Digestive enzymes2. Na bicarbonate
What are the two main roles of bile salts?
1. Emulsifying or detergent function (decrease surface tension, allows GIT to break down fats)2. Absorption of micelles into blood (MAJOR effect! = fatty acids, monoglycerides, cholesterol, other lipids)
What are the two main roles of bile?
1. Fat digestion and absorption (based on bile acids/salts that aid in emulsifying and absorbing fats)2. Excretion of waste (including bilirubin and cholesterol)
What are the two major glands in the stomach and what do each of them secrete?
1. Oxyntic Gland (Gastric Gland) = HCl, Pepsinogen, intrinsic factor, mucus2. Pyloric Gland = Mucus, Gastrin
What are the two major plexus and what do they control?
1. Myenteric Plexus (Auerbach's): Outer plexus twn longitudinal and circular muscle layers - mainly control GI movements2. Submucosal Plexus (Meissner's): Inner plexus - controls mainly GI secretions and local blood flow
What are the two stages of bile secretion?
1. Bile is secreted by hepatocytes into bile canaliculi2. Bile flows through ducts to the hepatic duct → common bile duct → duodenum OR cystic duct to GallbladderAlong the way in the ductules/ducts watery Na+ and HCO3- solution secreted by secretory epithelial cells (stimulated by secretin)
What are tonic contractions in the GIT?
Continuous (not associated with slow waves) - can last mins to hoursThese are in addition or instead of rhythmical contractions
What causes Ca to enter the muscle fiber to result in a contraction?
Slow waves do NOT cause Ca to enter (ONLY Na), thus no muscle contraction aloneDuring a spike potential (generated by slow waves) = Large amount of Ca enters = muscle contraction
What cells are consider the electrical pacemakers for smooth muscle cells?
Interstitial cells of Cajal - Undergo cyclic change in membrane potentialUnique ion channels that periodically open = inward pacemarkers currents
What cells secrete gastric inhibitory peptide (GIP)?
K cells of duodenum and jejunum
What components are in salivary to attack bacteria?
1. Thiocyanate ions2. Lysozyme3. Ig
What controls stomach emptying?
"Pyloric pump" - intense peristaltic wave in the antrum, pyloric sphincter also controls this
What controls the cephalic phase of gastric secretion?
Sight, smell, taste of food → HCl + pepsin releaseControlled by: Cerebral cortex (appetite center amygdala and hypothalamus) → Vagus n. → Stomach via AcetylchoineG cells →Gastrin Releasing peptide = GASTRIN release
What controls the cephalic phase of pancreatic secretion?
Acetylcholine (vagal n.) = 20% pancreatic enzymes (BUT NO fluid)
What controls the gastric phase of gastric secretion?
Food in stomach (stretch) = HCl releaseControlled by:Long vagovagal reflex = acetylcholineLocal enteric reflex Peptides and AA → G cells → GASTRIN
What controls the gastric phase of pancreatic secretion?
Acetylcholine (vagal n.) = 5-10% pancreatic enzymes (BUT NO fluid)
What controls the intestinal phase of gastric secretion?
Food in duodenumControlled by:Enterooxyntic (not gastrin per CVT??)
What controls the intestinal phase of pancreatic secretion?
1. Chyme in SI (acid) → Secretin (from S cells in duodenum) → Lots of pancreatic fluid and bicarbonate2. Food in SI (peptides/fat) → CCK (from I cells in duodenum and upper jejunum) → 70-80% pancreatic enzymes
What determines the rate and action potentials and contractions in various segments of GIT?
The frequency of slow waves which is controlled by pacemaker = Interstital cells of Cajal
What do neural and hormonal input influence in GIT?
Neural input and hormonal input DO NOT influence the frequency of slow waves, they do influence the frequency of action potentials
What do the ECL cells secrete that results in the parietal cells secreting HCl and what controls this process?
Rate and amount of HCL produced is directly related to histamine from ECL cells, which is controlled by GASTRIN
What does ECL cells stand for?
Enterochromaffin-Like cell (ECL cell)
What does lactase do?
Splits Lactose into galactose and glucose
What does maltose and other 3-9 glucose polymers split into?
Glucose by maltase and alpha-dextinase
What does motilin do in GIT?
Stimulates gastric and intestinal motility (cyclic release = waves → interdigestive myoelectrical complexes
What does sucrose do?
Splits sucrose into fructose and glucose
What enzyme is made in pancreatic acini that helps to prevent autodigestions and were is it present?
Trypsin InhibitorPrevents activation of zymogens in pancreas or ducts or intracellular
What enzymes and where are disacchardies hydrolyzed into monosaccharides?
Intestinal Epithelial Enzymes - Within villi in the brush border1. Maltase2. Alpha-Dextrinase3. Lactase4. Sucrase
What happens in the stomach glands between meals?
They make mucus, almost NO acid!
What happens to bile when it is stored in the GB?
The bile is concentrated (Water, Na+, Cl- are absorbed through the wall of the GB) - via active transport of Na+ and passive movement of others = Concentration of bile salts, cholesterol. Lecithin, bilirubin
What is a reflex that comes from the GIT to spinal cord/brain and then back to GIT?
Defecation reflexes = from colon/rectum to spinal cords and back to produce powerful colon, rectal, and abdominal contractions = Defecation
What is a unique feature of the electrical activity of GIT smooth muscle?
Slow waves = Not AP but oscillating depolarization and repolarization
What is another name for gastric inhibitory peptide (GIP)?
Glucose-dependent insulinotrophic peptide
What is another name for pits?
Crypts of Lieberkuhn = Secretory cells in GIT
What is another name for the Na+/glucose cotransporter in the SI?
SGLT 1
What is important about the 3 stimuli that result in pancreatic secretions?
The stimuli potentate each other, meaning that pancreatic secretion is greatest with the combined stimuli as compared to single stimuli
What is mucus made of?
Water, electrolytes, glycoproteins
What is ptyalin?
a-Amylase to digest starches, found in salivary secretions are part of serous secretion
What is renointestinal reflex and vesicointestinal reflex?
Inhibits intestinal activity due to kidney or bladder irritation
What is splanchnic circulation?
• Blood flow in gut, spleen, pancreas → liver (via portal vein) → hepatic sinusoids (reticuloendothelial cells to remove bacteria, carbs and proteins absorbed) → hepatic veins → vena cava
What is the "law" of the gut?
Peristaltic reflex = gut reflexes to result in receptive relaxation (easier propulsion) - Perstaltic waves to the anus
What is the accessory pancreatic duct and which species have it?
Opens into duodenum at minor duodenal papillaDogs = ALWAYS!Cats = Occasionally
What is the action potential in GIT dependent on?
Action potentials in GIT cannot occur unless the slow wave brings the membrane potential to threshold
What is the colonoileal reflex?
Reflexes from colon to inhibit emptying of ileal contents into colon (reflex from gut to prevertebral sympathetic ganglia back to GIT)
What is the driving force behind secretion of HCl from the oxyntic/parietal cells?
H+/K+ ATPase pump on the apical membrane that results in secretion of H+ intot he canaliculus
What is the enterogastric reflex?
Signals from colon/small intestines to inhibit stomach motility and secretions (reflex from gut to prevertebral sympathetic ganglia back to GIT)
What is the enzyme in the enterocytes that aids in final polypeptide and amino acid digestion?
Peptidases (aminopolypeptidase, dipeptidase)
What is the enzyme in the stomach that aid in protein digestion?
Pepsin
What is the final composition of saliva and where do these changes take place?
Within the salivary ducts = HIGH K+ and HCO3- (little Na and Cl)1. K+ active secretion2. HCO3- secretion3. Na active absorption4. Cl- passive absorption (follows Na)
What is the final product of fat digestion?
Fatty acids and 2-monoglycerides
What is the final product of protein digestion?
Amino Acids
What is the function of the myenteric plexus in peristalsis?
If no myenterix plexus (congenital) peristalsis will NOT occurBlock it with atropine (affecting cholinergic nn in myenteric plexus)
What is the gastrocolic reflex?
Signals from stomach to cause evacuation of colon (reflex from gut to prevertebral sympathetic ganglia back to GIT)
What is the gastroielal reflex?
After a meal = increased peristalsis in ileum = emptying
What is the main difference btwn the myenteric and submucosal plexuese?
Myenteric Plexus = Linear chain of interconnected neurons that run the length of GIT - Control muscle activity along length of gutSubmucosal Plexus = Functions within the inner wall of each segment of intestine, sensory signal from epithelium integrate at submucosal plexus to help control intestinal secretions, local absorption, location contraction of submucosal muscle
What is the main electrolyte that is secreted by enterocytes?
Cl- (based on increased cAMP). Na+ and water follow = secretion
What is the main mechanism of ion absorption in SI?
Active transport of Na+Na+ is actively transported from basolateral membrane into interstitial space Low intracellular conc of Na → electrochemical gradient → therefore more Na moves from chyme into enterocyte
What is the major component of the Crypts of Lieberkuhn in the large intestine?
MUCUS (some bicarbonate) - Lubrication and hold feces together
What is the major site of Na+ absorption in the SI?
Jejunum
What is the MOA of PPI, omeprazole?
Inhibit the H+/K+ ATPase on the apical membrane of the gastric parietal cell
What is the most important enzyme of fat digestion?
Pancreatic lipase (little by enteric lipase)
What is the most important function of pepsin?
Digestion of collagen (to allow digestion of other cellular proteins)
What is the name of gastrin secreting tumors?
Zollinger-Ellison Syndrome within the pancreas
What is the name of the reticuloendothelial cells in the liver?
Kupffer cells
What is the nervous system that is within the wall of the gut?
Enteric Nervous System
What is the neurotransmitters that results in excitation in GIT?
Acetylcholine
What is the neurotransmitters that results in inhibition in GIT?
Norepinephrine
What is the pancreatic duct and which species have it?
Opens within bile duct at major duodenal papillaDogs = Usually (smaller, but can be absent)Cats = ALWAYS!
What is the peritoneointstinal reflex?
irritation of peritonenum = intestinal paralysis
What is the primary nerous control of saliva?
Parasympathetic = 2 salivary nuclei in brainstemStimulated by high centers (appetite) or something on tongue
What is the primary secretion from salivary glands?
Either ptyalin or muscus with same electrolyte composition as ECF
What is the primary secretion in the esophagus?
MUCUS for Lubrication (simple and compound mucous glands)
What occurs in the colonocytes for Na and K?
Na+ absorption (+++aldosterone)K+ secretion
What pancreatic enzyme is responsible for carbohydrate digestion?
Pancreatic amylase (starch into disaccharides and trisaccharides)
What results in relaxation of stomach during the storage function of the stomach?
Distension with food → “vasovagal reflex” to brain stem → relaxes stomach wall (to accommodate more food)
What stimulates the conversion of pepsinogen into pepsin?
HCl
What stimulates the release of acetylcholine that results in pancreatic secretions?
Vagus n. and ENS stimulation
What stimulates the release of cholecytskinin (CCK) that results in pancreatic secretions?
Released from duodenum and upper jejunum from I cells in response to protein or AA in the lumen
What stimulates the release of secretin that results in pancreatic secretions?
Released from duodenum and jejunum in response to acidic content of chyme in the lumen
What type of channels control the depolarization and repolarization of the slow waves in GIT?
Ca 2+ open resulting in Ca2+ entering cell = DepolarizationK+ open resulting in K+ OUT of cell = Repolarization
What would you expect with bilirubin in Cholestasis?
Conjugated bilirubin high
What would you expect with bilirubin in hemolysis?
Unconjugated bilirubin high
What would you expect with bilirubin in total EHBDO?
NO bilirbin in feces (since no stercobilin stool is light), no urobilin in urine
When the G cells in the pyloric glands sense that there is a protein rich meal what occurs?
G cells are stimulated by protein to release GASTRIN into the blood to reach the ECL cells, which when stimulated by gastrin will release HISTAMINE which results in HCL release from the parietal cells
Where is cholecystokinin secreted?
I cells of duodenum, jejunum, and ileum
Where is gastrin produced?
G cells from antrum, duodenum, jejunum
Where is secretin secreted from?
S cells from duodenum, jejunum, ileum
Which anal sphincter is under voluntary control?
External anal sphincter
Which cell type does the parietal cells in the gastric glands work closely with?
ECL cells
Which cell type secretes HCl?
Oxyntic/parietal cells (part of gastric/oxyntic gland)
Which cell type secretes intrinsic factor (dog)?
Oxyntic/parietal cells (part of gastric/oxyntic gland)
Which cell type secretes pepsinogen?
Peptic/Chief cells (part of gastric/oxyntic gland)
Which cells in the pancreas make bicarbonate?
Epithelial cells that line the ductules and ductsRole of bicarbonate is to neutralize acid from stomach chyme
Which cells make gastrin?
G cells in the pyloric glands in the distal end of the stomach
Which cells secrete motilin?
M cells of stomach, duodenum, jejunum
Which enzyme in the brush border in the SI converts trypsinogen into trypsin?
Enterokinase
Which hormones control release of pancreatic digestive enzymes?
Vagal stimulation (acetylcholine)Cholecystokinin (CCK)
Which hormones control release of pancreatic fluid and bicarbonate?
Secretin
Which hormones decreased motility in SI?
Secretin and glucagon
Which hormones increased motility in SI?
gastrin, CCK, insulin, motilin, serotonin
Which hormones results in secretion of watery Na+ and HCO3- solution from secretory epithelial cells during the second stage of bile secretion?
Secretin!! Which is stimulated by presence of acid within the duodenum
Which nerves control the parasympathetic defecation reflex?
Pelvic nn
Which nutrient is NOT carried in portal blood and why?
o Fats absorbed from GIT (not carried in portal blood) into intestinal lymphatics to thoracic duct to systemic circulation
Which pancreatic enzyme can activate all the other pancreatic enzymes?
Trypsin
Which plexus in GIT controls GI movements?
Myenteric Plexus (Auerbach's)
Which plexus in GIT controls GI secretions and local blood flow?
Submucosal Plexus (Meissner's)
Which secretagogue is the most important in gastric acid secretion?
Histamine!
Which transporter is located on the basolateral surface to transport glucose, galactose, and fructose into the blood?
GLUT 2
Which transporter on the apical surface allows for facilitated diffusion of fructose?
GLUT 5
Why are the directional movements of peristalic waves to the anus?
Can occur in either direction, but orad dies out = likely related to polarization of myenteric plexus
Why is neural stimulation of the salivary glands unique?
They are controlled by both parasympathetic and sympathetic NS
Why is saliva hypotonic?
Active net solute absorption and salivary ducts are impermeable to water
Ptyalin in the saliva hydrolyzes starch into which disaccharide?A. FructoseB. GlucoseC. LactoseD. MaltoseE. Sucrose
D. Maltose Ref: Guyton, Ch.66 pg. 834
Which of the following pancreatic enzymes leads to digestion of proteins into individual amino acids?A. TrypsinB. CarboxypolypeptidaseC. ChymotrypsinD. Aminopolypeptidase
B.Ref: Guyton p 835
Which of the following is not a potential stimulus for gastric acid secretion?a. Norepinephrine secretion resulting from stimulation of sympathetic nerves.b. Vagal nerve activity resulting from the sight of food.c. The presence of undigested protein in the pyloric antrum.d. Acetylcholine release stimulated by gastric stretch receptors acting on nerves of the ENS.e. Histamine release from cells in the gastric mucosa.
ACunningham Ch. 29
Which gastrointestinal hormone is released in response to digestive products in the intestines and causes gallbladder contraction and release of bile, inhibits stomach contraction, and inhibits appetite?a. Gastric inhibitory peptideb. Cholecystokininc. Gastrind. Secretin
b. Cholecystokinin
Which of the following is true regarding hydrochloric acid secretion in the parietal cells?a. H+ is secreted from the apical membrane of the parietal cell via facilitated diffusionb. H+-K+ ATPase works at the basolateral membrane to load the parietal cell with hydrogen ionsc. Bicarbonate is formed by carbonic anhydrase and transported out of the parietal cell by the bicarbonate chloride cotransporterd. H+ is pumped into the lumen by active transport from a H+-K+ ATPase at the apical membrane of the parietal cell
d. H+ is pumped into the lumen by active transport from a H+-K+ ATPase at the apical membrane of the parietal cell
Saliva contains high concentrations of which two ions?a. bicarbonate and sodium b. sodium and chloride c. chloride and bicarbonate d. bicarbonate and potassium
d. bicarbonate and potassium
The extrinsic innervation of the gut consists of:a. The enteric nervous system.b. The myenteric and submucosal plexuses.c. Sympathetic (splanchnic) and parasympathetic (vagus) nerves.d. Sympathetic (vagus) and parasympathetic (splanchnic) nerves.e. The pelvic nerve
CCunningham Ch. 27
What are the anatomical differences between the esophagus of dogs, cats and horses?
Dogs, cattle and sheep, its entire length is striated muscleCats, horses and humans, the proximal esophagus has striated muscle and the distal esophagus smooth muscle.
Which of the following hormones stimulates insulin release?A. GastrinB. CCKC. Gastric Inhibitory PeptideD. Motilin
C. Now known as glucose dependent insulinotrophic peptideRef. Guyton 802
Which of the following are effects of the gastric hormone secretin?a. Stimulation of mucosal endothelial growthb. Promotion of insulin secretionc. Promotion of bicarbonate secretiond. Stimulate gastric acid secretion
c. Promotion of bicarbonate secretion
Intrinsic factor must be present in gastric secretions to allow for adequate absorption of vitamin ____ in the ileum. Without intrinsic factor, pernicious anemia can occur. A. B6B. B12C. CD. DE. E
B. B12Ref: Guyton, Ch. 67 pg. 844
Inhibition of the enzyme carbonic anhydrase is likely to have what effect on gastric pH?a. Decrease gastric pHb. Increase gastric pHc. Have no effect on gastric pH
BCunningham Ch. 29
3. The term slow waves as applied to the gut refers to:a. Slowly moving fronts of electrical activity that are propagated down the enteric nervous system.b. Slowly moving fronts of electrical activity that result from coordinated changes in cell membrane potential occurring throughout the smooth muscle of the intestinal wall.c. Slowly moving fronts of ingesta that proceed down the intestine in response to peristaltic movement.d. Slowly moving fronts of action potentials that are constantly passing over the gut smooth muscle.e. Slowly moving fronts of peristaltic contractions that pass uniformly over the entire small intestine during the digestiveperiod.
BCunningham Ch. 28
The ____________ reflex occurs as a result of distension of the stomach and duodenum after a meal and is transmitted by way of the autonomic nervous system. a. Defecationb. Enterogastricc. Gastrocolicd. Gastroileal
c. Gastrocolic
What factor does not contribute to depolarization of intestinal smooth muscle?a. Stretching of the muscleb. Sympathetic stimulation by norepinephrine releasec. Stimulation by several gastrointestinal hormonesd. Parasympathetic stimulation by acetylcholine
b. Sympathetic stimulation by norepinephrine release
Which of the following causes decreased blood flow to the gastrointestinal tract? A. CCKB. BradykininC. AdenosineD. Sympathetic stimulation
D. sympathetic stimulationRef. 805
Which of the following hormones inhibits small intestinal peristalsis? A. GastrinB. CCKC. InsulinD. SecretinE. Motilin F. Serotonin
D. Secretin Glucagon can also inhibit motility in small intestineGuyton 13th ed Ch. 64
Irritation of the peritoneum results in which of the following neurologic reflexes?a. peritoneointestinal reflex – the strong inhibition of excitatory enteric nerves resulting in intestinal paralysisb. peritoneoenteritis reflex - the strong inhibition of excitatory enteric nerves resulting in intestinal paralysisc. peritoneointestinal reflex – the strong excitation of the enteric nervous system inducing hypermotilityd. renointestinal reflex - the moderate inhibition of excitatory enteric nerves resulting in intestinal paralysis
a. peritoneointestinal reflex – the strong inhibition of excitatory enteric nerves resulting in intestinal paralysis
The enteric nervous system is composed mainly of two plexuses. Which one controls mainly gastrointestinal secretion and local blood flow ?a. Myenteric plexusb. Mucosal plexusc. Submucosal plexusd. Parasympathetic plexus
Answer : cGuyton (12th ed.) p. 755
List the steps in HCL production by the parietal cell
1. H2O + CO2 + carbonic anhydrase = H2CO3 (carbonic acid)2. Carbonic acid dissociates into: a. H+ - active transport in the apical membrane into the lumen b. Bicarb - exchanged with Cl in the basolateral membrane 3. Cl diffuses through the apical membrane into the lumen 4. In the lumen H+ + Cl- = HCl
Which of the following hormones stimulates gastric acid secretion?A. GastrinB. CCKC. SecretinD. Motilin
A. GastrinRef. Guyton 802
An animal is presented to you with aspiration pneumonia (the result of food material entering the lower respiratory tract). Which of the following lesions would be a likely cause?a. Loss of myenteric plexus function in the pharynx and upper esophagusb. Loss of slow-wave activity in the pharynx and upper esophagusc. A lesion in the brainstemd. A lesion in the tracheae. None of the above
CCunningham Ch. 28
What is the source of the most important signal that regulates gastric emptying?A. StomachB. DuodenumC. IleumD. Colon
B. Duodenum Guyton 13th ed p. 811
Which of the following is required for normal absorption of cobalamin in the ilium?a) enterokinaseb) glucose-dependent insulinotropic peptidec) intrinsic factord) pepsinogen
Answer CGuyton pg. 844
Damage to which of these neurologic structures can result in paralysis of the swallowing mechanism?A. CN V, IX, X, & swallowing center of the brainstemB. CN V, IX, & XC. CN V, VII, & XIID. CN V, IX, X, XII, & swallowing center of the brainstem
Answer DV - trigeminal - sensory to face and motor to m of masticationIX - glossopharyngeal - muscles of swallowing X - vagus - efferentXII - hypoglossal - motor to tongue efferent nerve fibers from swallowing center in the brainstem travel in the facial, vagus, hypoglossal and glossopharyngeal nerves and motor branch of trigeminalCunningham p 276
Which of the following is the most important enzyme for starch digestion? a) Ptyalinb) Pancreatic Amylasec) a-dextrinased) maltase
B. pancreatic amylase Ptyalin - (also an amylase but just in saliva)Alpha dextrinase - disaccharides Maltase - maltose Guyton pg. 834
The myenteric plexus is inhibited by which of the following hormones? A. GastrinB. CCKC. SecretinD. VIP - vasoactive inhibitory peptide
D. VIP (thought to be but not for sure)Ref. Guyton 800
Which cell in the pyloric glands is responsible for secreting histamine in response to stimulation by gastrin?a. Parietal cellsb. Chief cellsc. Enterochromaffin-like cellsd. Goblet cells
c. Enterochromaffin-like cells
Which of the following aspects of colon physiology is common to many species, irrespective of interspecies anatomicaldifferences in colon structure?a. Rapid flow of ingestab. Adaptive relaxationc. Retropulsion, or antiperistalsisd. Haustra formation
CCunningham Ch. 28
Which of the following is characteristic of the inter digestive phase of small intestinal motility?a. Migrating motility complexes consisting of waves of peristaltic contractions that pass over the entire length of the small intestineb. Rhythmic segmentationc. Short waves of peristalsis that die out after a few centimetersd. Complete relaxation of small intestinal smooth muscle
ACunningham Ch. 28
This reflex results when food stretches the stomach allowing for the stomach reducing the tone of the muscular walla. Vasovagal reflexb. Gastrocolic reflexc. Gastroenteric reflexd. Gastroesophageal reflex
a. Vasovagal reflex
Most proteins are absorbed through intestinal epithelial cells in the form of dipeptides, tripeptides, and a few free amino acids. By what mechanism are most absorbed?A. Co-transportB. Facilitated diffusionC. Simple diffusionD. Primary active transport
Answer A. Co-transportGuyton Pg 841
Action potentials in the GI smooth muscle are potentiated by the influx of which ion? A. Cl- B. NaC. CaD. K
C. Ref. 799
Parietal cells within the gastric glands release __________, which is needed for absorption of vitamin B12 in the ileum.a. Intrinsic factorb. Hydrochloric acidc. Cortisold. Histamine
a. Intrinsic factor
Which of the following best describes the motility of the proximal region of the monogastric stomach?a. Rhythmic segmentationb. Peristalsisc. Retropulsiond. Adaptive relaxation
DCunningham Ch. 28
Which of the following ions has higher concentrations in saliva compared to plasma?a. Calciumb. Chloridec. Potassiumd. Sodium
c. Potassium
What factor within the duodenum cannot initiate enterogastric inhibitory reflexes?a. Distension of the duodenumb. Irritation in the duodenal mucosac. Alkalitity of the duodenal chymed. Osmolality of the chyme
c. Alkalitity of the duodenal chyme
Which one of the following hormones is secreted by K cells?a. Cholecystokininb. Secretinc. Motilind. Gastric inhibitory peptide
d. Gastric inhibitory peptide
Which nerve controls the external anal sphincter?a. Pelvic nervesb. Pudendal nervec. Myenteric plexusd. Obturator nerve
b. Pudendal nerve
Which of the following accurately describes forward movement of a food bolus through the gastrointestinal tract?A. The swallowing center is located in the medulla and pons of the CNS.B. The movement of a food bolus through the esophagus is passive and only performed by smooth muscle.C. The stomach processes food and has no storage capacity. D. Having hunger pangs (I.e. being "hangry") does not exist, and the stomach does not contract strongly with prolonged emptying.
A. The swallowing center is located in the medulla and pons of the CNS.
Which of the following gasses are formed from bacteria in the large intestine?A. Methane, nitrogen, carbon dioxideB. Oxygen, carbon monoxide, methaneC. Hydrogen, methane, and carbon dioxideD. Carbon monoxide, methane, hydrogen
Answer C. Hydrogen, methane, and carbon dioxideGuyton Pg 849
Which one of the following electrolytes has the highest concentration in bile secreted from the gallbladder?a. Nab. Kc. Cad. Cl
a. Na
The main driving force for hydrochloric acid secretion by the parietal cells is…a. H-K ATPaseb. Cl-HCO3 antiporterc. Na-K ATPased. Cl diffusion
a. H-K ATPase
Which of the following is most responsible for creating an action potential in gastrointestinal smooth muscle and accounts for the long duration of action potential seen? a. Chloride channels b. Calcium-sodium channels c. Fast sodium channels d. Potassium channels
b. Calcium-sodium channels
Which of the following is not a natural ligand for receptors in the pancreas?a. Cholecystokininb. Acetylcholinec. Gastrind. Secretin
CCunningham Ch. 29
Chloride is absorbed in which primary locations in the gastrointestinal tract?A. proximal small intestine & ileumB. duodenumC. ileumD. colon
Answer Apg. 839
Which of the following cells are considered the pacemakers of the GIT?A. G cells B. Cells of Cajal C. I cells D. K cells
B. Ref. 798
Which of the following hormones inhibits gastric acid secretion?A. GastrinB. CCKC. SecretinD. Motilin
C. Ref. Guyton 802
Which of the following causes the GI smooth muscle hyperpolarization? A. StretchB. Acetylcholine C. Hormones D. Norepinephrine
D. NorepiRef. Guyton 799
The rectosphincteric reflex is integrated in the:a. Brainstem.b. ENS.c. Lumbar spinal cord.d. Sacral spinal cord
DCunningham Ch. 28
Pepsin becomes inactivated and has no proteolytic activity above:a. pH 3b. pH 5c. pH 7d. pH 9
b. pH 5
Bile salts have two primary actions, what are they?a. (1) act as a detergent or emulsifying agent to decrease surface tension and (2) facilitate absorption from the intestinal tractb. (1) act as a detergent to increase surface tension and (2) facilitate absorption from the intestinal tractc. (1) induce absorption of food from the gastrointestinal tract and (2) induce digestion of chylomicrons within the lymphatic systemd. (1) regulate electrolyte absorption and secretion within the intestinal tract and (2) digest fatty acids
a. (1) act as a detergent or emulsifying agent to decrease surface tension and (2) facilitate absorption from the intestinal tract
Glucose is transported into the cell via: A. Facilitated diffusionB. Primary active transport C. Secondary active co - transport D. Secondary active counter transport
C. Secondary active co transport occurs more commonly in GI and renal cells, in all other cells glucose enters the cell via facilitated diffusion. Ref: Guyton p 840
Which factor(s) stimulate pepsinogen secretion by the peptic cells ?a. Acetycholine onlyb. Acetylcholine and gastrinc. Acetylcholine and secretind. Cholecystokinin only
Answer : aGuyton (12th ed.) p. 779
The normal resting membrane potential of gastrointestinal smooth muscle cells is:a. -80 to -90 mV b. -105 to -110 mV c. -50 to -60 mV d. -30 to -40 mV
c. -50 to -60 mV
Which of the following can occur as complications to chronic gastritis?I. AchlorhydriaII. Ulcerative colitisIII. Peptic ulcerIV. Pernicious anemiaa) III, IVb) I, IVc) I, III, IVd) I-IV
Answer: c Source: Guyton ed 13, Ch 67, page 844
The control of glandular secretion is mostly due to local stimulation in which of the following locations?a. Jejunumb. Salivaryc. Rectumd. Pancreas
a. Jejunum
1. A unique feature of gastrointestinal (GI) smooth muscle cells is that:a. Their resting transcellular electrical potential has the positive pole on the outside surface of the cell membrane.b. Action potentials, or spikes of membrane depolarization, are not associated with muscle contractions.c. Muscle contractions are stimulated by partial depolarization of the membrane.d. There are spontaneous, rhythmical undulations in the electrical potential across the cell membrane.e. Contraction of the muscles is never influenced by nervous activity.
DCunningham Ch. 28
Which hormone is released from the G cells, stimulating mucosal growth? a. Gastrinb. CCKc. Secretind. GIP
a. Gastrin
Conditions in the duodenum, such as low pH or high fat concentration, can reflexively inhibit gastric emptying. Which reflex arc is involved in this inhibition?a. Parasympathetic nervous systemb. GI enteric nervous systemc. GI endocrine systemd. All the above
DCunningham Ch. 28
The neurotransmitters in the gut are:a. NO and Ach as excitatory, and substance P and VIP as inhibitory.b. NO and Ach as inhibitory, and VIP and substance P as inhibitory.c. NO and VIP as excitatory, and Ach and substance P as inhibitory.d. NO and VIP as inhibitory, and Ach and substance P as excitatory.e. NO and substance P as inhibitory, and Ach and VIP as excitatory.
DCunningham Ch. 27
Which of the following hormones stimulates gastric motility?A. GastrinB. CCKC. SecretinD. Motilin
D. MotilinRef. Guyton 802
Secretion of gastric inhibitory peptide from the K cells of the duodenum and jejunum is stimulated by protein, fat, and carbohydrates. What does secretion of gastric inhibitory peptide stimulate?a. Insulin releaseb. Gastric acid secretionc. Pepsin secretiond. Biliary bicarbonate secretion
a. Insulin release
Which of the following is secreted by activated salivary cells and is important in enzymatic formation of bradykinin?a. cAMPb. Kallikreinc. Secretind. Pepsin
b. Kallikrein
In what specific location in the gastrointestinal tract is the intestinal phase of gastric secretion initiated? a. Stomachb. Duodenumc. Ileumd. Jejunum
b. Duodenum
Cholecystokinin and gastrin:a. Share all of the same receptors.b. Share CCK1 receptors.c. Share CCK2 receptors.d. Share gastrin I receptors.e. Share gastrin II receptors
CCunningham Ch. 27
Which of the following correctly describes the secretion or action of secretin?a. Secretion is mainly stimulated by the presence of carbohydrates in the duodenumb. Secreted from the stomachc. Decreases stomach acid production d. Secretin’s main effect is increasing intestinal motility
c. Decreases stomach acid production
Which of the following hormones stimulates insulin release?a. Cholecystokininb. Gastrinc. Gastric Inhibitory Peptide d. Motilin
c. Gastric Inhibitory Peptide
2. The interstitial cells of Cajal are:a. Modified neurons capable of generating contraction.b. Modified neurons capable of generating only action potentials.c. Modified neurons capable of generating only slow waves.d. Modified smooth muscle cells capable of generating only slow waves.e. Modified smooth muscle cells capable of generating only action potentials.
DCunningham Ch. 28
Colonic “pacemakers”:a. Are anatomically distinct structures composed of specialized smooth muscle cells.b. Shift in their sites under the influence of the ENS.c. Are involved in segmentation, but not peristalsis.d. Control defecation.
BCunningham Ch. 28
The cholera toxin specifically targets which area of the gastrointestinal tract?a. duodenum b. duodenum, jejunum, and ileum c. distal ileum and colon d. colon only
C. Distal Ileum and Colon (location of crypts of liberkun)The enterocytes in these crypts are responsible for water secretion toxin --> increase cAMP --> Cl channels open --> Cl loss activates Na pump--> Na into lumen --> H2O follows Na --> excess water loss --> diarrheaGuyton p. 846
Which of the following hormones stimulates gallbladder contraction?A. GastrinB. CCKC. SecretinD. Motilin
B. CCKRef. Guyton 802
Which of the following reflexes occurs as a result of chyme entering the duodenum?a. gastroileal reflex b. gastroenteric reflex c. mienteric reflexd. viscointestinal reflex
b. gastroenteric reflex
Which enzyme is most active at a pH of 2.0 to 3.0 and plays an important role in digesting collagen? a. Alpha dextrinase b. Amylase c. Pepsin d. Elastase
Answer: C.Reference: Guyton Ch. 66 Pg. 835
3. Which of the following reactions in the liver could be expected to occur during both the digestive phase and a prolonged fast?a. Glycogen synthesisb. Fatty acid synthesisc. Ketone body synthesisd. Ketone body oxidatione. Triglyceride synthesis from fatty acids
ECunningham Ch 32
Lower esophageal achalasia is secondary to damage of:A. Myenteric plexus B. Lower esophageal sphincterC. Cranial nerve X D. Meissner’s plexus
A. The myenteric plexus aka auerbach's plexus is located in between the longitudinal and circular muscle layers and control movement through the entire GIT. The submucosal aka meissner's plexus controls local secretion and blood flowRef: Guyton p 843
Which cell type acts as the electrical pacemaker for the smooth muscle of the gastrointestinal tract?a. Epithelial cells of Cajalb. Enteric nervous plexusc. Enteric purkinje fibersd. Interstitial cells of Cajal
d. Interstitial cells of Cajal
The functions of the GI tract are mainly controlled by:a. The central nervous system.b. The enteric nervous system.c. The endocrine system.d. The enterochromaffin system.e. The hormonal and central nervous systems.
BCunningham Ch.27
In the small intestine, sodium is mainly reabsorbed in the APICAL border of epithelial cells by which protein?a) Na+/K+ ATPase pumpb) Na+ and substrate co-transportersc) Na+ leak channeld) Na+/Cl- antiporter
B. Na and substrate co-transporters ie. aa, glucose vs the basolateral membranes in which Na/K pump regulates Na transport. Source: Guyton ed 13, Ch 66, page 838
How long does it take for aldosterone to take effect and increase sodium absorption in the intestine?A. 1-3 hoursB. 3-6 hoursC. 6-9 hoursD. 9-12 hours
Answer A. 1-3 hoursCl and H2O follow Na Guyton Pg 839
At the level of the salivary gland, what happens with the following ions?A. Sodium is passively absorbed, chloride is actively absorbed, potassium is actively secreted, and bicarbonate is secreted.B. Sodium is actively secreted, chloride is passively secreted, potassium is actively absorbed, and bicarbonate is secreted.C. Sodium is actively absorbed, chloride is passively absorbed, potassium is actively secreted, and bicarbonate is secreted.D. Sodium is actively secreted, chloride is passively secreted, potassium is passively secreted, and bicarbonate is absorbed.
C. Sodium is actively absorbed, chloride is passively absorbed, potassium is actively secreted, and bicarbonate is secreted.
The term cephalic phase is used in reference to a number of activities occurring in the GI tract. In general, the term means:a. The early phases of digestion, when food is nearest the head.b. Any actions stimulated directly by the presence of food in the stomach.c. Any actions stimulated directly by the presence of food in the mouth.d. Digestive events stimulated by the presence of food in the GI tract, but requiring reflexes integrated in the CNSe. Digestive events that occur before the ingestion of food and in response to central nervous system stimulation that is brought on by the anticipation of eating.
ECunningham Ch. 28
Which of the following does not play a role in regulating pancreatic secretions? A. SecretinB. CCKC. AchD. Pepsinogen
D. Pepsinogen (stimulates acid secretion in the stomach)Secretin - stimulates bicarb secretion by pancreas in response to acid in SI CCK - stimulate bicarb and pancreatic enzyme in response to food in SI Ach - excitatory neurotransmitter Guyton 13th ed. p 826
At which site in the gastrointestinal tract do peptic ulcers most commonly occur? a. Lesser curvature b. Greater curvature c. Gastric cardia d. Pylorus
Answer: D.Reference: Guyton Ch. 67 Pg. 844; Fig 67-1
Which of the following is an important action of cholecystokinin? a. Inhibit gastric acid secretionb. Mucosal growthc. Intestinal motilityd. Stimulate pancreatic enzyme secretion
d. Stimulate pancreatic enzyme secretion
In monogastric animals, saliva produced during periods of rapid secretion has a higher electrolyte concentration than saliva produced during periods of slow salivary secretion. From your understanding of salivary gland physiology, which appears to be the most likely explanation?a. During periods of slow salivary secretion, the acinar cells are inactive, and low-electrolyte saliva is secreted by the duct cells.b. Parasympathetic stimulation of the acinar cells results in the elaboration of a more electrolyte-rich saliva.c. Gastrin stimulation increases the electrolyte concentration of saliva.d. During rapid secretion, fluid produced by the acinar cells is exposed to the actions of the duct cells for a shorter time than during slow rates of secretion.e. Different cell types within the acinus are responsible for salivary production, depending on the type of stimulus.
D Cunningham Ch. 29
Which of the following factors inhibit gastric emptying by initiating enterogastric inhibitory reflexes ? a. Increased pH of the chymeb. Irritation of the duodenal mucosac. Stretching of the stomach walld. Decreased filling of the duodenum
Answer : bGuyton (12th ed.) p. 767
The arrangement of smooth muscle fibers in the muscular layer of the intestinal wall is best described as:a. inner longitudinal and outer circular smooth muscle layers b. inner circular and outer longitudinal smooth muscle layers c. single layer of circular smooth muscle d. two layers of circular smooth muscle, separated by a nerve plexus
b. inner circular and outer longitudinal smooth muscle layers
Small intestinal motility is inhibited by which hormone?a. Secretinb. Motilinc. CCKd. Serotonin
a. Secretin
The pathophysiologic basis of which of the following conditions is associated with damage to the myenteric plexus?A. Pancreatitis B. Achlasia C. AchlorydiaD. Gastritis
B. Achalasia is a condition in which the lower esophageal sphincter fails to relax during swallowing. Pathophysiological studies have shown damage in the neural network of the myenteric plexus of the lower two thirds of the esophagus, which causes spasticity of the musculature of the lower esophagus. As a result, the lower portion of the esophagus fails to undergo receptive relaxation as the bolus of food approaches this area after swallowing. pp. 845-846
In achalasia, damage to which structure in the lower esophagus results in failure of the gastroesophageal sphincter to relax during swallowing ?A. Myenteric plexus B. Submucosal plexus C. Esophageal mucosaD. Esophageal musculature
Answer AGuyton (12th ed.) p. 799
During sodium absorption by glucose co-transport:a. Chloride is absorbed by the paracellular route.b. Chloride absorption is not affected.c. Chloride is absorbed in exchange for bicarbonate.d. Chloride absorption is coupled with potassium absorption.e. Chloride is absorbed in exchange for hydrogen ion
ACunningham Ch 30
Entry of food into the small intestine leads to secretion of which of the following substances important for stimulating pancreatic secretion?a. Cholecystokininb. Vasoactive intestinal peptidec. Acetylcholined. Secretin
a. Cholecystokinin
Rate of digestion is dependent upon which one of the following?a. Total surface area available to digestive enzymesb. Increased sympathetic nervous system stimulationc. Total volume of bile secreted into the proximal duodenumd. Diameter of the pyloric sphincter
a. Total surface area available to digestive enzymes
From luminal to serosal layers, which of the following is the appropriate order in which the layers of the gastointestinal tract occur?A. Epithelium --> mucosa --> mucosal muscle --> sub mucosa --> longitudinal muscle -> circular muscle -> serosaB. Mucosa --> epithelium --> mucosal muscle --> sub mucosa --> circular muscle -> longitudinal muscle -> serosa C. Epithelium --> mucosa --> submucosa --> mucosal muscle --> circular muscle -> longitudinal muscle -> serosa D. Epithelium --> mucosa --> mucosal muscle --> sub mucosa --> circular muscle -> longitudinal muscle -> serosa
D. Epithelium --> mucosa --> mucosal muscle --> sub mucosa --> circular muscle -> longitudinal muscle -> serosa
Which coagulation factor is stimulated by endotoxin to trigger intravascular coagulation by the intrinsic pathway?
- Heparin
- Factor II
- Factor X
- Factor XII
d. Factor XII
Factor XII (Hageman’s factor) is triggered by endotoxin, producing bradykinin and triggering intravascular coagulation
APTT (best for DIC) is specific for intrinsic pathway, very sensitive to collection. Independent of platelet function.
Which drug is the best to enhance gastric emptying in foals with ulcerative duodenitis?
a. Lidocaine
b. Escopolamine
c. Erytromycin
d. Bethanecol
d. Bethanecol
You are treating peritonitis in a 15 year old QH gelding with broad spectrum ABX therapy and choose a beta lactam (penicillin) + a gram negative drug (either aminoglycoside (gent) or enro), but you leave out metronidazole due to concerns about destroying GI flora- what important and frequently cultured anaerobe does this combination not cover?
a. Clostridium
b. Bacteroides fragilis
c. Actinobacillus
d. Rhodococcus
b. Bacteroides fragilis
Bacteroides fragilis is most commonly ID'ed anaerobe cultured from peritonitis in horses.
A is an anaerobe but should be covered by penicillin.
C + D are aerobic bugs- Actinobacillus should respond to pen/gen, and rhodococcus is unlikely in an older horse.
Which one is NOT a risk factor for shedding of salmonella in hospitalized horses?
a. Horses admitted for colic
b. Diarrhea and antibiotic use
c. Presence of reflux
d. Severe GI disease
b. Diarrhea and antibiotic use