Lecture #36: Digestive Glands and Liver I Flashcards
Describe the general histological organization of the pancreas.
lobulated, compound, tubulo-alveolar gland with both as exocrine and an endocrine secretory function
What type of gland is the pancreas? Also, does it have endocrine or exocrine secretory function?
- Gland -> lobulated, compound, tubulo-alveolar gland
- Has both exocrine and endocrine secretory function
What does the delicate connective tissue of the pancreas contain ?
- The delicated CT contains:
- blood vessels
- lymphatics
- nerves
- excretory ducts
What is the main excretory duct of the pancreas known as?
Duct of Wirsung
What is the name of the smaller accessory duct of the pancreas?
Duct of Santorini
What kind of epithelium are interlobular ducts of the pancreas lined with ?
simple columnar epithelium and goblet cells
What type of epithelium are intercalated ducts of the pancreas lined with?
low cuboidal cells
What do the cells of the intercalated ducts of the pancreas secrete ?
- water
- bicarbonate ion
What receptor for which hormone is found in cells of the intercalated duct of the pancreas?
cells with receptors for SECRETIN
Acinus Structure
- Acini are serous
- Acinar cells are pyramidal serous cells
- Centroacinar cells
- NO striated ducts
- NO myoepithelial cells
- Release of digestive enzymes from serous acinar cells is stimulated by CCK
- Bicarbonate-rich, alkaline fluid is released by ductal epithelial cells in response to secretin
What is the function of acinar cells?
- Acinar Cells are Pyramidal Serous Cells:
- basal zone which is basophilic and contains nucleus and RER
- apical zone with zymogen granules
- precursors of the enzymes in pancreatic juice
- trypsin, chymotrypsin, amylase, and lipase
- specific receptors for cholecystokinin
What is the function of centroacinar cells?
- form a truncated cuboidal epithelium within the lumen of acini
- continuous with the epithelium of the intercalated duct
- unique to pancreas
What hormone stimulates the release of digestive enzymes by serous acinar cells?
CCK
What do ductal epithelial cells release?
bicarbonate-rich, alkaline fluid
Which hormone stimulates the release of bicarbonate-rich, alkaline fluid by ductal epithelial cells?
Secretin
Do acini of the pancreas have striated ducts or myoepithelial cells?
NO
What is the synthesis and secretion of digestive enzymes controlled by?
peptides secreted by duodenal enteroendocrine cells
Where are inactive proenzymes synthesized at in the pancreas?
Digestive enzymes are synthesized as inactive proenzymes on the RER of acinar cells.
Where are digestive enzymes stored at in the pancreas?
concentrated and stored in vesicles by Golgi
What hormone regulates the secretion of bicarbonate ions?
secretin
** secreted by duodenal enteroendocrine cells when stimulated by food entering the small intestine **
What is the synthesis of bicarbonate ion mechanism?
- carbon dioxide diffuses into intercalated ducts from blood
- carbon dioxide + water –> carbonic acid (requires carbonic anhydrase)
- carbonic acid dissociates into bicarbonate and H+
- bicarbonate ion is actively transported to lumen of intercalated duct
- sodium and hydrogen ions are exchanged with sodium flowing into duct lumen and hydrogen flowing into the blood
True or False:
The intercalated duct is a continuation into the connective tissue stroma ofthe centroacinar cells.
True
Which 3 cell types are found in the Islets of Langerhans in the pancreas?
- A-cells (alpha cells):
- have fine cytoplasmic granules and are presumed to form glucagon
- B-cells (beta cells):
- have coarse cytoplasmic granules; they are more numerous than alpha cells and produce insulin
- D-cells (delta cells):
- secrete somatostatin, which helps to control levels of insulin and glucagon
Which cell type of the Islets of Langerhans of the pancreas secretes somatostatin?
D-cells (delta cells)
What does somatostatin, released by delta cells in the pancreas, function to control?
helps to control levels of insulin and glucagon
What do beta cells of the pancreas secrete/produce?
insulin
Does alpha cells or beta cells have more numerous granules?
beta cells
What does alpha cells of the pancreas form/secrete?
glucagon
Which cell type found in the Islets of Langerhans in the pancres has fine cytoplasmci granules and which has coarse cytoplasmic granules?
- Fine Cytoplasmic Granules = alpha cells
- Coarse Cytoplasmic Granules = beta cells
