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102 Cards in this Set

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What are the four secretory salivary glands and what is their secretions?

Parotid: serous/watery secretion


Mandibular/submaxillary: serous and mucous


Sublingual: serous and mucous


Buccal: mucous

Where is saliva initially secreted by? And where is it modified?

Secreted by acinar 
 
Modified by the ducts (Na & HCO3 absorption, K secretion)

Secreted by acinar



Modified by the ducts (Na & HCO3 absorption, K secretion)

What is the pathway for saliva excretion?

Acini -> Intercalated ducts -> Striated ducts -> Excretory ducts

Regardless of how much saliva is produced, the saliva is also _______ with the blood in ruminants.

Isotonic

What two components of saliva are unique in Ruminants?

Bicarbonate and Phoshate

What are the four components of saliva?

Na+, Cl-, HCO^3-, PO4^2-

Na+, Cl-, HCO^3-, PO4^2-

The quantity and composition of saliva depends on what two factors?

Species


Level of chewing activity

What is the flow rate of ruminants and non ruminants?

Ruminants - isotonic, with a high flow rate = increasing HCO3 and decreasing HPO4



Non Ruminants - low flow rate = increasing K and high flow rate = increasing HCO3

Secretion levels for cattle, horses, sheep, and birds

Cattle 60-160 L/d


Horse 10-12 L/d


Sheep 6-16 L/d


Birds 0.007-0.03 L/d

Functions of saliva in ruminants?

-fluid for fermentation (no secretory glands in the reticulo-rumen)


-increase alkaline saliva (HCO3-, HPO4-) to buffer rumen pH


-Recycle PO4- and Urea

Functions of salivary secretions in dogs and cats?

-evaporative cooling


-salivary amylase (not cats)


- lipase

Function of saliva in pigs

-increasing salivary amylase: function in proximal stomach but inactivated at low gastric pH


Function of salivary secretions in horses?

-no salivary digestion enzymes


-'latherin' - protein secreted from salivary glands (mastication) and skin (evaporative cooling)

Functions of salivary glands in birds?

-lubricate ingesta (mucous secreting cells)


-salivary amylase


-'pigeon milk' (fat cells from crop) for feeding in young

How is the salivary secretion regulated by the sympathetic?

By the sympathetic


-NE-induced contraction of 'basket' myoepithelial cells


-expel stored saliva rich in protein and mucin


How is the salivary secretion regulated by the parasympathetic?

By the parasympathetic


-Ach excites the acing cells = increased saliva low in protein


-salivary reflexes: coordinated by 'salivary enters' in the hindbrain

Distribution of gastric mucosa in a dog?

Majority proper gastric (oxyntic) and pyloric 


-small cardiac and non glandular 

Majority proper gastric (oxyntic) and pyloric


-small cardiac and non glandular

Gastric mucosa distribution in the pig?

Mostly cardiac and proper gastric


-some non glandular and some pyloric

Distribution of gastric mucosa in horses and rats?

Mostly non glandular and proper gastric


-some pyloric and cardiac



**margo placates between non glandular and gastric

Distribution of gastric mucosa for cow?

Mostly all non glandular


Some proper gastric and pyloric


Little cardiac

What are the 4 gastric glands and their secretions?

Neck cells - secrete mucous, HCO3, trefoil peptides (repair/damage/protective cells)


Parietal/oxyntic cells - secrete HCL, intrinsic factor (vit B12 absorption)


Chief or peptic cells - secrete pepsinogen, gastric lipase


Endocrine cells - secrete gastrin, somatostatin, histamine, and GRP (proventriculous)

What is the Cardiac gland and what does it secrete?

Branched tubular glands - secrete mucous, HCO3

What are the pyloric glands and what do they secrete? (lack parietal cells)

Neck - secrete mucous


Chief cells - secrete pepsinogen (few)


Endocrine cells - secrete gastrin, somatostatin, histamine, and GRP (proventriculous)

Gastric Gland (image)

What are the 2 gastric cell types that are in the proventriculus?

Simple mucous glands = mucous



Compounds submucosal glands = mucous, H=, pepsinogen

What is the function of the following...


Surface cells


Neck cells


Simple mucous glands (proventriculus)


Parietal Cells


Chief Cells


Compounds submucosal glands (proventriculus)


Endocrine cells

Surface cells/Neck cells - Lubrication, Protection


Simple mucous glands (proventriculus) - Lubrication (birds mucous)


Parietal Cells - Protein digestion, binding of B12


Chief Cells - Digestion protein and fats


Compounds submucosal glands (proventriculus) - Protein digestion


Endocrine cells - Regulation of acid secretion

What are the 3 phases of gastric acid secretion?

1. Cephalic 


2. Gastric


3. Intestinal 

1. Cephalic


2. Gastric


3. Intestinal

What is the cephalic phase of gastric acid secretion?

-part of the response due to the anticipation, sight, smell, auditory, taste sensations


-mechanism = VAGAL!


10-15% of acid

What is the Gastric phase of gastric acid secretion?

-part of the response is due to stimulation from meal in the stomach


-mechanism = VAGAL, LOCAL, GASTRIN


50-60% of acid


What is the Intestinal phase of gastric acid secretion?

part of the response due to stimulation from chyme in intestines


-Mechanisms = VAGAL, HORMONAL


<5% acid

How does a parietal cell secrete acid? 

How does a parietal cell secrete acid?

1. Carbonic anhydrase catalyzes the conversion of CO2 + H20 to make carbonic acid


2. Carbonic acid dissociates to H+ + HCO3-


3. Proton (H+) pump: H-K ATPase (lumen) pumps H against gradient into lumen, exchange K+


4. HCO3- is secreted into blood in exchange for CL- (Alkaline tide)


5.Cl- digress from cell via Cl- conductance pathway on lumen membrane

What is an alkaline tide?

Alkaline tide happens during intense acid secretion


-increased HCO3- secreted into blood


(normally reversed when HCO3- is secreted via pancreatic juice to neutralize acid in the intestine)

Regulation of the Parietal Cell Secretion - what controls it?

-Neurocrine


-paracrine


-humoral (endocrine)

Regulation of the Parietal Cell Secretion - what is the neuronal release and what does it stimulate?

-Releases gastrin releasing peptide



-Stimulates gastrin from G-cells

Regulation of the Parietal Cell Secretion - What does gastrin do?

Endocrine


-it activates the parietal cell


-stimulates the release of histamine form the enterochromaffin-like cell (ECL)

Regulation of the Parietal Cell Secretion - what does the neuronal release of Ach do?

-directly activates the parietal cell


-stimulates histamine release from the ECL cells

Regulation of the Parietal Cell Secretion - what does histamine do?

activates the parietal cell via a paracrine pathway

Regulation of the Parietal Cell Secretion - accumulation of HCL (low pH=2) stimulates what?

-the secretion of somatostatin from the D-cell

Regulation of the Parietal Cell Secretion - what does the D-cell secretion of somatostatin do?

-inhibits gastrin and histamine (turns off)



**if this doesn't happen might have ulcers

What are the 3 major secretagogues (agonists) of parietal cell HACL secretion (synergism)?

1.Gastrin acting though a CCL2 receptor


2. Histamine acting through a histamine H2 - receptor


3. Acetylcholine acting though a muscarinic 2 (M2) receptor

Regulation of Parietal Cell Secretion (image)

Acid secretion is influenced by what 3 factors?

pH, good buffering and gastric emptying

Regulation of Gastric secretions - what is the gastric phase of acid and pepsinogen secretion stimulated by?

-intraluminal oligopeptides


-distention of stomach

Regulation of Gastric secretions - pepsinogen secreted by chief cells is activated to form what and by what?

-to pepsin


-by HCl secreted from parietal cells

Regulation of Gastric secretions - pepsin breaks down the protein to release what? Which then stimulate what?

-oligopeptides


-stimulate gastrin release form G-cell in antrum

Regulation of Gastric secretions - what does gastrin do?

Acts as a endocrine transmitter to further stimulate...


-HCl secretion from parietal cells


-Pepsinogen from chief cells

Regulation of Gastric secretions - How does gastric distention activate the vago-vagal reflex?

1. Vagal afferent input activates dorsal vagal complex



2. vagal efferent outflow stimulates HCl and pepsinogen secretion



3. vagal efferents (via Ach) activate enteric neutrons and ECL cells (histamine) to stimulate pepsinogen and acid secretion



4. Vagal efferents stimulate secretomotor neurons to release GRP (gastrin releasing peptide) -> realeases gastrin

Regulation of Gastric secretions (image)

Why doesn't the stomach autosuggest?

-Parietal and chief cells: apical barriers are impermeable to NH3, NH4, CO2, HCO3-


-Presence of gastric mucosal barrier

What are the layers of the gastric mucosal barrier? 

What are the layers of the gastric mucosal barrier?

1. Unstirred layer


2. Surface epithelial cells


3. Cell renewal (restitution)


4. Alkaline tide


5. Microcirculation


6. Sensory nerves


7. Prostaglandins (PGE2, PGl2) and NO

Gastric Mucosal Barrier - unstirred layer?

- mucous and HCO3 (physical barrier)

Gastric Mucosal Barrier - surface epithelial cells

-secrete mucous, HCO3, PGs, HSP, trefoil peptides, antimibrobials

Gastric Mucosal Barrier - Cell Renewal (restitution) from what and stimulated by?

-from the mucosal progenitor cells


-stimulated by growth factors

Gastric Mucosal Barrier - Alkaline tide

-exchange H+ out for HCO3- in

Gastric Mucosal Barrier - Microcirculation - maintained by? and do what?

-maintained by PG, NO, H2S


-Protect endothelial cells form injury and prevent platelet and leukocyte aggregation

Gastric Mucosal Barrier - Sensory nerves go where?

-blood


-lamina propria


-mucosa

Gastric Mucosal Barrier - Prostaglandins and NO do what?

maintain/enhance all mucosal defines mechanisms

What region of the Equine stomach is most prone to gastric ulcers? Why?

Non glandular region = 80%


-lacks mucous and bicarbonate layers



Glandular region = 20%


-highly vascular and rapid restitution and mucous bicarbonate protection (heals rapidly)


What is the ontogeny of the stomach of a calf?

Birth - 3ws = pre-ruminant phase (80% abomasum)


3-8 wks = Transition phase (50% abo)


2-4 months = pre/post weaning (25% abo)


Mature = <10% abomasum

GI ontogeny: Functional adaptations of cow stomach = 0-24 hrs

-Colostrum (Ig, Vit A,D,E, lactose, Ca, Mg)


-No acid/pepsinogen in abomasum


-No gastric digestion (Ig protected and absorbed)



**Joint/naval ill, scours, hypothermia, hypoglycaemia, insulin sensitive


GI ontogeny: Functional adaptations of cow stomach = 1d to 3wks (pre-ruminant)

-Milk based = salivary esterase (lipid hydrolysis)


-Reflex closure of reticular groove (by sucking)


-Rennin and milk = curd + whey (curdles in stomach)


-No maltase = starch is indigestible



**scours, steatorrhea

GI ontogeny: Functional adaptations of cow stomach = 3-8wks (transitional)

- Milk and Grain and roughage


-Grain -> VFA -> butyrate = stimulates RR papillae development


-Less insulin sensitive

GI ontogeny: Functional adaptations of cow stomach = 2-4 months and adult (pre/post weaning)

-pepsinogen in ABOMASUM


-RR motility, eructation, alkaline saliva


- METABOLISM - VFA based and less insulin sensitive

What are the 4 types of abomasa ulcers in calves?



**typically in the pylorus

Type-1: non perforating


Type-2: non perforating and blood loss


Type-3: Perforating and local peritonitis


Type-4: Perforating and diffuse pertonitis

What are the 3 common etiologies of abomasa ulcers in calves?

1. Alkalization of the pyloric antrum by bile reflux and duodenum


2. Mechanical trauma - hair balls (trichobenxoars) = abrasive action on mucosa


3. Stress: cortisone and corticotrophin = decreased gastric mucous secretion and cell renewal

What are the 5 gastric ulcer therapies?

1. Mucosal protectants


2. Proton pump inhibitors


3. H2 receptor antagonists


4. synthetic hormones - Prostaglandin analogues (increase mucosal flow) & somatostatin analogues (decrease gastrin secretion)


5. prokinetics (small animals and horses)

General anatomy of the pancreas....

General anatomy of the pancreas....

-Common bile duct


-Accessory pancreatic duct


-Duct openings


-Body, head, tail


-Sphincter of oddi (common bile duct into duodenum)


-Ampulla of vater (duct opening)

What are the main endocrine cells in the pancreas?

Islet of Langerhans (1-2% of the total mass of the pancreas)


What do the Islet of longerhans cells secrete?

-Glugagon (a-cell; 10%)


-Insulin (B-cell; 75%)


-Somatostatin (δ-cell; 5%)


-Pancreatic polypeptide (F or PP-cell)


-Amylin (Amylin cell)

What are the 3 functions of the exocrine secretions in the pancreas?

1. Neutralization of duodenal pH


2. Optimize environment for bile action


3. Optimize fermentation in cecum and colon (horses)

Explain 'neutralization of the duodenal pH'

1. Inactivate pepsin - prevent acid-pepsin damage to duodenal mucosa


2. Optimize pH for pancreatic and brush border enzyme activity (pancreatic juice pH ~8.2-9.6)

Explain 'optimize environment for bile action'

Increase fatty acid and bile acid solubility

Explain 'optimize fermentation in cecum and colon'

continuous flow of juice in HCO3- buffer (low in enzymes)

What are the two exocrine secretions of the pancreas?

1. Enzymes - Trypsinogen, chymotrypsinogen, procarboxypeptidase, pancreatic amylase, pancreatic lipase, deoxyribonucleases and ribonucleases



2. Electrolytes- alkaline solution of electrolyse to neutralize stomach acid for optimum function of digestive enzymes (H2O, HCO3-, Cl-, Na+, K+, Mg2+, Ca2+)

What are these 3 components? 

What are these 3 components?

Top to bottom


-Acinar cells (enzymes)


-Centro-acinar cells (HCO3-)


-Duct Cells (HCO3-/Cl- exchange)

What are the 4 exocrine secretory proenzymes and enzymes secreted by the acing cells?

1. Peptidases (90%)


2. Amylases (7%)


3. Lipases (2%)


4. Nucleases (<1%)

What is secreted from the centro-acinar cells?

Water and electrolytes (bicarb)

How does the acinar cell secrete enzymes? 

How does the acinar cell secrete enzymes?

-Buds coming from the Zymogen Granules (ZG) from golgi coalesce to form vacuoles that


-Exocytosis of ZG restricted to apical membrane (Basolateral exit blocked) to enter into the lumen


-Tight Junction complex restricts paracellular movement of proteins/ions

How does the acinar cell secrete enzymes with acute pancreatitis? 

How does the acinar cell secrete enzymes with acute pancreatitis?

-excytosis of zymogen granules at basolateral membrane (which is usually blocked) and the apical exit decreased


-INCREASED paracellular permeability


-DECREASED secretion and autophagy (AV; activation of digestive enzymes within cell)



**this causes damage to the pancreas = decrease in digestion and absorption

What is the zymogen Activation Cascade?

What is the zymogen Activation Cascade?

Trypsinogen's are converted to trypsin by ENTEROKINASE (brush border)


-trypsin causes a cascade and changes other zymogens to their active form


(including trypsinogen)

Trypsin


-Zymogen


-Activator


-Action

Trypsinogen


Enterokinase


Endopeptidase: cleaves internal bonds

Chymotrypsin


-Zymogen


-Activator


-Action

Chymotrypsinogen


Trypsin


Endopeptidase

Elastase


-Zymogen


-Activator


-Action

Proelastase


Trypsin


Endopeptidase


Carboxypeptidase


-Zymogen


-Activator


-Action

Procarboxypeptidase


Trypsin


Exopeptidase: cleaves last AA from the c-terminal polypeptide


Phospholipase


-Zymogen


-Activator


-Action

Prophospholipase


Trypsin


Cleaves FA from phospholipids (lecthin)

Lipase


-Zymogen


-Activator


-Action

None


None


Cleaves FA from glycerol


Amylase


-Zymogen


-Activator


-Action

None


None


Digest starch to maltose and glucose


Cholesterolesterase


-Zymogen


-Activator


-Action

none


none


Releases cholesterol from other molecules


Ribonuclease


-Zymogen


-Activator


-Action

None


None


Cleaves RNA


Deoxyribonuclease


-Zymogen


-Activator


-Action

None


none


cleaves DNA

What are the 4 reasons why the pancreas doesn't auto-digest?

1. Synthesis of enzymes as inactive zymogens


2. Segregation of enzymes in membrane bound components (vacuoles)


3. Trypsin inhibitor packaged in zymogen granules


4. enterokinases on the intestine

How does the Pancreas secrete HCO3-?


(sorry for the length) 

How does the Pancreas secrete HCO3-?


(sorry for the length)

1. Carbonic anhydrase catalyzes the conversion of CO2+H2O to form carbonic acid


2. Carbonic acid dissociate to H+ + HCO3-


3. Na+ H+ exchanger at basolateral membrane extrudes H+


4. HCO3- Cl- exchanger (apical) secretes HCO3- in exchange for Cl-


5. Cl- efflux leads to K efflux (basolateral) to maintain neutrality and Na+ transport (Na,K ATPase replenishes K and maintains Na)


6. HCO3- and Na+ ions into lumen causes osmotic gradient and water moves from blood to pancreas!


What is the HCO3- Cl- exchanger controlled and regulated by?

Cl- efflux though the Cl-s channel that is regulated by SECRETIN!

What are the 3 phases of pancreatic secretion?

Cephalic


Gastric


Intestinal

Cephalic phase


-Stimulant?


-Regulatory pathway ?


-Enzyme Secretion (%max) ?

-Anticipation, sight, smell, mastication, taste


-Vagal


-25%

Gastric phase...


-Stimulant?


-Regulatory pathway ?


-Enzyme Secretion (%max) ?

Distension


Vagal


10-20%

Intestinal Phase...


-Stimulant?


-Regulatory pathway ?


-Enzyme Secretion (%max) ?

-Oligopeptides, essential AA, FA, gastric acid


-Vagal, enteropancreatic reflexes, CCK, Enzyme secretion


-50-80%

Regulation of Pancreatic secretion.... (steps)

1. Intestinal phase (major contributor) stimulated by intraluminal acidity, oligopeptides, AA, & FA


2. S cells release Secretin & I cells release CCK


3. CCK and Secretin mediate pancreatic secretion


How does CCK and Secretin mediate pancreatic secretions?

1. Vago-Vagal reflex


-vagal afferent activates dorsal vagal complex


-vagal efferents (Ach) activate enteric neutrons releasing Ach, VIP, GRP = pancreatic exocrine secretion of CCK (acinar cells) & secretin (ducts)


2. Endocrine (hormonal) : blood to brain then vagal efferents to pancreas


3. Endocrine (hormonal) : blood to pancreas

Mechanisms regulating pancreatic secretions... (steps) 

Mechanisms regulating pancreatic secretions... (steps)

1. Food product activates secretion of CCK by I cells (FA, peptides) and Secretin by S cells (H+)


2. CCK and Secretin act on...


-neuro roots to stimulate release of Ach, VIP, GRP


-go through blood to brain then vagus


-go though blood straight to pancreas (ENS)


to release pancreatic enzymes


What are the clinical signs for Exocrine pancreatic Insufficiency?



**common in german shepherds and rough coated collies

-Yellowish/grey, loose feces


-increased fecal volume and frequency


-weight loss


-flatulence


- increase appetite


-occasional coprophagia

What are the pancreatic function tests?

-Serum trypsin like immunoreactivity


-Decrease fecal proteolytic activity


-Decreased elastase activity