pancreatic and salivary glands

secretory glands of the GI tract do what

secrete mucous

secrete digestive enzymes usually produced by zymogens

secretory glands are stimulated by

direct contact stimulation by food

enteric nervous system of gut wall activation

• tactile stimulation

• chemical irritation

• distension of gut wall

what type of glands are pancreas and major salivary glands

compound exocrine glands

lubricates and initiates breakdown of starch

what saliva does

neutralizes acid and completes intraluminal digestion of carbohydrates fats and proteins

pancreatic juice

pancreatic juice is rich in

bicarb

pancreatic exocrine digestive main enzymes and what they do

proteases digest protein

amylases digest carbs

lipases digest fat

secretory units of exocrine pancreas located where

within lobules, acinus and small intercalated duct

what cells synthesize and secrete proteins into lumen of pancreas

acinar cells

epithelial cells do what to secretions as they move along the duct

modify fluid and electrolyte composition

pancreatic juice is a composite of what two things

1. enzymes in isotonic solution from acinar cells

2. bicarb rich solution from pancreatic duct cells

secretagogues of pancreatic acinar cells

CCK and ACh

also secretin (bicarb), vip, GRP

Both CCK and ACh stimulate the secretion of what in acinar cells

NaCl (via Cl- secretion)

NaK pump basal surface does what

creates inwardly directed Na gradient across basolateral membrane

NaKCl cotransporter on basolateral surface does what

produces net Cl- uptake which is driven by the Na gradient which is driven by the NaK pump

intracellular accumulation of Cl- due to NaK and NaKCl leads to what

electrochemical gradient driving Cl- secretion into lumen through apical membrane Cl- channels

this is stimulated by CCK and ACh

lumen becoming more negative because of Cl does what

drives Na into the lumen via the tight junctions, H2O follows

what cells secrete HCO rich fluid that alkalizes and hydrates protein rich primary secretions

pancreatic duct cells

what is responsible for recucling Cl back to the lumen

CFTR, cystic fibrosis transmembrane regulator

acinar cells made the lumen very Cl- which then the pancreatic duct cells are able to use the

Cl-/HCO3 exchanger which secretes HCO into lumen, but Cl MUST be present in the lumen for it to work

(so if there was a problem with acinar cells, or CFTR which sends the cl back, then the bicarb exchange wouldnt work)

what is the most important humoral regulator of ductal bicarb secretion

Secretin

how does secretin do its thang

activates adenyl cyclase

→ raises cAMP

→ protein kinase A

→ phosphorylates CFTR

loss of CFTR expression at plasma membrane

disrupts apical transport

decreased secretion of bicarb and water by ducts

→ thick protein ricj primary acinar secretions → block ducts and cause tissue destruction

maldigestion, fat in stool

how much pancreatic juice is produced every day

1.5 liters

during fasting, enzyme secretion does what

varies cyclically with MMC

ACh regulation of pancreatic secretion

from parasympathetic nerve endings

stimulates acinar cells to increase enzyme production and secretion

CCK regulation of pancreatic secretion

from I cells

acts on pancreatic acinar cells in fed state to increase secretion

stimulated by lipid and CCK releasing factors

secretin regulatino of pancreatic secretion

from s cells

stimulates bicarb

acts in concert with CCK ACh and others

three phases of pancreatic secretion

cephalic

gastric

intestinal

sight smell and taste of food does what

activates cephalic phase of pancreatic secretion

vagus nerve → Ach → digestive enzymes

presence of food in stomach does what

activates the gastric phase of pancreatic secretion

stomach distension → vagovagal gastropancreatic reflex → low levels of pancreatic secretion

chyme entering small intestine does what

stimulates the intestinal phase of pancreatic secretions

1. stim duodenal S cell by gastric acid bile acid and lipids

2. stim CCK release from duodenal cells by lipids

3. vagovagal enteropancreatic reflex, ACh stimulaiton

presence of what reduces pancreatic secretions

fat in distal end of the small intestine

peptide yy mediated most likely

what hormones may play a role in decreasing pancreatic secretions

somatostatin released from d cells

also likely glucagon from alpha cells

pancreatic secretions retained within the organ bc inflammation or obstruction

acute pacnreatitis

what is hyperstimulation pancreatitis

if acinar trypsin (protease) prematurely process to active form and retained in cell

symptoms of acute pancreatitis

severe abdominal pain, nausea and vomiting

may have fever, tachycardia, hypoxemia and hypotension

factors that cause acute pancreatitis

alcohol and gallstones

lipid metabolism disorders (hyperglyceridemia) → pancreatitis

principal salivary glands

parotid

submandibular

sublingual

tell me about the acinar cell populations of the salivary glands

two distinct populations

parotid: alpha amylase (ptylain)

sublingual/submandibular gland: mucin glycoproteins

what controls the salivary gland secretion

ANS

Ach for PNS and NE for SNS

acini secrete a primary secretion in saliva that contains what and is like what

it contains alpha amylase and or mucin

solution much like typical extracellular fluid

how is hypotonic salivar produced

salt reabsorption without water reabsorption in ducts

during max salivation, ionic reabosprtion is _____ due to ________

lower, high flow rate

sodium ions are _________ in from salivary ducts

reabsorbed (reduces concentration in saliva)

potassium ions are _________ into duct

secreted (increases concentration in saliva)

how is bicarb secreted in saliva

Cl-HCO3 exchanger (and CFTR recycles Cl to lumen)

role of saliva

prevent dehydration of oral mucosa and lubrication for chewing and swallowing food

oral hygiene

how is saliva important for oral hygiene

salivary flow washes away pathogenic bacteria

proteolytic enzymes in saliva attack bacteria

what is xerostomia

dry mouth

nervous regulation of salivary secretion

controlled mainly by the PNS

what nuclei are involved in PNS control of salivary secretion

superior and inferior salivatory nuclei in brainstem

taste stimuli activate nucleus and it acts on the glands

sympathetic can slight stimulate what

salivation

chronic progressive autoimmune disease that affects salivary secretion and eye duct secretion

sjogren syndrome

how does sjogren syndrome lead to its dry symptoms

it has antibodies that react with salivary glands that cause inflammation and net decrease in secretion function

(might involve SLC26A6, bicarb cl exchanger)

→ dry mouth and eyes

→ hard to taste, chew, swallow, speak, and have enlarged parotid gland