pancreas Flashcards
pancreas anatomy: describe the anatomical regions and functional acini of the pancreas
what type of organ is the pancreas
secretory
4 superior anterior portions of pancreas (right to left )
head, neck, body, tail
inferior anterior portion of pancreas connected to head
uncinate process (hook-like)
what do smaller pancreatic ducts all converge into
larger pancreatic ducts
what do larger pancreatic ducts combine with and where
common bile duct at the ampulla of Vater
what does the ampulla of Vater drain into and where
duodenum at sphincter of oddi
bifurcation of common bile duct
left to cystic duct (gall bladder), right to hepatic ducts (left and right lobes of liver)
where does head of pancreas sit
C-shaped part of duodenum
where does tail of pancreas sit
hylem of spleen
where does perfusion of pancreas come from
branches of superior mesenteric artery and celiac trunk
where does drainage of pancreas go to
hepatic portal vein to liver then systemic circulation
how much of pancreas is exocrine acini cells and supporting cells (duct cells)
98%
what are ducts lined with
columnar epithelia
3 features of islets of endocrine tissue
not connected to ducts, highly vascularised, secrete hormones into blood
function of connective tissue
provides structural support
what do zymogen-secreting acinar cells cells contain and where
zymogen granules towards apical membrane
what is zymogen
inactive enzymes (mainly protease to prevent degradation of cells, as well as lipase and amylase) and enzyme inhibitors
where do secreted enzymes go from acini
into smaller ducts then into larger ducts
function of bicarbonate-secreting duct cells
dilute enzymes and carry into pancreatic duct and duodenum
most abundant cells in islets of Langerhans
insulin-secreting B-cells (70%)
second most abundant cells in islets of Langerhans
glucagon-secreting a-cells (20%)
third most abundant cells in islets of Langerhans
somatostatin-secreting d-cells (10%)
what is atop of all cells in islet of Langerhans
pancreatic capillaries
function of pancreatic capillaries
recieve hormones from surrounding cells and releasing into bloodstream for local and systemic effects
2 types of exocrine cell
acinar, duct
components of acinar cells to produce enzymes
high in Goligu apparatus; rough ER and nucleus towards larger basolateral membrane; zymogen granules towards apical membrane
arrangement of functional subunit of exocrine pancreas
acinar cells towards terminal end of duct to allow secretion of enzyme-rich, viscous, low-volume fluid into terminal duct from acinar cells via exocytosis, using calcium as a second messenger; duct cells line terminal duct
what do duct cells do to fluid secreted by acinar cells
modify it by secreting bicarbonate-rich (via carbonic anhydrase), high-volume, watery fluid via membrane channels, relying on ion gradients
significance of centroacinar cells found between duct cell and acinar cell
internal cellular characteristics of both duct cells and acinar cells, but act more like duct cell
purposes of bicarbonate secretion from duct cells
helps mobilise enzyme-rich component of pancreatic juice so it moves into duodenum, able to neutralise acid chyme
innervation of duct cells
hormonal only
innervation of acinar cells
hormones and CNS
when does pancreas begin to develop
day 35-39
what 2 sites does the pancreas develop from
ventral pancreatic bud, larger dorsal pancreatic bud
where can the duodenum be differentiated from
stomach
where does the ventral pancreatic bud sprout from
liver bud
where does dorsal pancreatic bud sprout from
duodenum
what does the endoderm now start to develop into at day 40-55
branched tubules, which later develop into ducts
what are the ducts connected to
acini (exocrine portion of pancreas)
where do islets of langerhans arise from
duct branchpoints
fate of islets of langerhans
disconnect from ducts to form discrete islands of highly vascularised endocrine tissue amongst parnechyma of exocrine glandular tissue
what happens at the 6 week mark
gut tube undergoes primary rotation
what is the outcome of the duodenum twisting on the pancreas
ventral pancreas and biliary system moves towards dorsal pancreas (allows duodenum to form C-shape also)
what happens on day 56
dorsal and ventral pancreas fuse together
what does the dorsal pancreatic duct normally fuse with, but what can it also be connected to
common bile duct, but can be connected to gut as accessory pancreatic duct
what does the ventral pancreatic duct become
uncinate process of mature pancreas; major route of drainage into small intestine
what is the ventral pancreatic duct already connected to
biliary tree via common bile duct (gall bladder via cystic duct, liver via hepatic duct), become the major pancreatic duct
