exocrine

level l1-l3
retroperitoneal
enclosed on r by duodenal loop
overlies IVC, extends left to hilus of kidney, anteriorly on l w spleen
anteriorly overlied by stomach
head, body and tail drained by main pancreatic duct

fusion of embryonic ventral and dorsal ducts
enters duodenum through ampulla
joined with bile duct in 60%
proximal part of dorsal duct empties into intestine through minor papilla

failure of ducts to fuse
5% population

acinar and duct
80%
groups of acini form primary lobules
separated by interlobular ct

islets of langerhans

RER: extensive, studded w ribosomes; at basal end
at RER-golgi junction, no ribosomes
golgi: smooth surfaced stacks, centrally in supranuclear or juxtanuclear region
condensing vacuoles: at trans golgi, immature
secretory/zymogen granules: protein storage, restricted to apical cytoplasm; # varies w stage of development and stimulation
plasma membrane: separated by tight, adhering, desmosomes, and gap junctions
tight junction is leaky

cell-cell communication, junctions, site of hormone receptors, intracellular second messenger systems, ion pumps, channels, nutrient transporters

proteases, amylases, lipases, nucleases
zymogens: proenzymes, inactive

converted from trypsinogen by enterokinase (enzyme of intestinal brush border)
trypsin cleaves remaining zymogens to active form

activation by CCK, cholinergic agonists, and bombesin/GRP
activation causes IP breakdown, ca++ mobilization, PKC activation, then secretion

VIP and secretin
increased cAMP, activation of cAMP protein kinase, secretion

wall of initial segment of duct
continuous w duct cells that form intercalated duct
these form intralobular, then interlobular ducts
primary and accessory pancreatic ducts to duodenum

flat, low cuboidal cells
penetrate acinar unit
centroacinar cells at center of acinus

within acinar lobule
many mitochondria
minimal RER
many ribosomes
few golgi
hco3 secretion

in interlobular ct with vessels and nerves
pyramidal
many apical secretory granules
secrete mucin

convergence of interlobular ducts
obstruction causes rapid destruction of acinar tissue, slower destruction of ducts and islets, permanent and irreversible fibrosis

electrolytes and fluid secretion
viscosity control critical for flow
hormonally regulated: secretin increases hco3 secretion
pancreatic enzymes function at neutral pH

transient obstruction of terminal biliopancreatic ductal system (gallstones) and alcohol

increased viscosity of secretions
pancreatic insufficiency is brought on by fibrosis due to blockage in intralobular ducts

fatal

major: parotid, submandibular, sublingual; complex gland drained by single excretory duct
minor: in mucosa/submucosa, drained by multiple ducts; labial, palatine, buccal, anterior and posterior lingual
salivary gland: secretory acini and branching duct system; parenchyma arranged in lobules separated by interlobular ct

myoepithelial cells: support acini
serous cells: produce watery enzyme secretion, pyramidal shape, polar
mucus cells: thick viscous secretion, mucin, cuboidal to columnar, polarity, secretory tubules

cell arrangement of mucus cells capped by serous cells in mixed system

short narrow tubes connect acinus to striated duct
simple cuboidal epithelial cells, less differentiation
cytoplasm has mitos, few small secretory vesicles, organelles for protein synthesis
multipotential precursor cell

within lobule
extensive folding of basolateral membrane
cytoplasm has abundance of mitochondria
drain into extralobular or excretory ducts
terminate into main excretory duct

electrolyte fluid resembles plasma ultrafiltrate
acinar secretion sole source of fluid in final saliva
composition is modified during passage along intralobular/striated and extralobular/excretory ducts