Pancreas Flashcards
The development of the pancreas
- The dorsal and ventral buds arise from the foregut-midgut junction with the ventral bud being part of the hepatobiliary bud (or gall bladder bud)
- The duodenum rotates into a c-shape and the ventral bud swings round adjacent to the dorsal bud and buds fuse
- The ventral bud duct then becomes the main pancreatic duct
What is the structure of the pancreas?
- The pancreas is split into: uncinate, head, neck, body, tail
- The order from the tail is T, B, N, H, Un
- Tail then extends to hilum of spleen
Where is the islet tissue most abundant?
In the tail
What is endocrine and give examples?
- Secretion into blood stream, distant effect
- Insulin, glucagon, somatostatin
- 2%
What is exocrine and give examples?
- Secretion into a duct, local effect
- pancreatic juices for digestion
Can pancreatic diseases affect both endocrine and exocrine functions?
Yes
How do pancreatic juices reach the duodenum?
Pancreatic juices reach the duodenum via the main and accessory pancreatic ducts
Which arteries supply the pancreas?
The coeliac and superior mesenteric arteries
Exocrine cells
- Arranged in ducts
- Acini are grape-like clusters of secretory units.
- Acinar cells secrete pro-enzymes into the ducts
Endocrine cells
- Derived from the duct system
- The braches then become islets
- Differentiate into alpha, beta and delta cells
- More prevalent at the tail-end
Pancreatic juices - 2 main components
- low volume, viscous, enzyme rich (from acinar cells)
- high volume, watery and bicarbonate rich (ducts and centroacinar cells)c
What is the composition of the islets?
Alpha = glucagon, (15-20%) Beta = insulin, (60-70%) Delta = somatostatin, (5-10%)
What is the location of the pancreas?
Lies mainly on posterior abdominal wall extending from C-shaped duodenum to hilum of spleen
What are centroacinar cells?
They are an extension of the intercalated duct cells into the pancreatic acinus
The pancreatic juice functions and pH
- Secretions rich in bicarbonate (pH ~ 7.5-8.0)
Functions to:
- Neutralise acidic chyme from stomach
- Prevent damage to duodenal mucosa
- Raise pH so pancreatic enzymes can function
- Wash low volume enzyme secretion out of pancreas
Effect of duodeunal pH on bicarbonate secretion rate
Duodenal pH <3 = not much more increase in bicarbonate secretion
Duodenal pH < 5 = significant linear increase in pancreatic bicarbonate secretion
Why does bicarbonate production stop when pH is still acidic?
- Bile contains bicarbonate and helps neutralise the acid chyme
- Brunnerโs glands secrete alkaline fluid
Mechanism of bicarbonate secretion
- Catalysed by carbonic anhydrase which produces HCO3- and H+. Sodium moves down gradient via paracellular tight junctions and H20 follows
- Cl/HCO3- exchanged at the lumen (antiporter) and Na/H+ exchanged (antiporter) at basolateral membrane into blood
High Na+ in blood compared to inside duct cell and high Cl- in lumen compared to in duct cell - Sodium gradient into cells from blood maintained by the Na+/K+ pump using ATP
- K+ returns to blood via K+ channel and Cl- returns to lumen via Cl- channel
This enables bicarbonate pumping to continue
SAME REACTION TO SECRETE HCL BY PARIETAL CELLS BUT REVERSED
What is the chloride ion also known as?
CFTR channel
What is different between gastric venous blood and pancreatic venous blood and why/
In the stomach, H+ goes into the gastric juice, HCO3- into the blood. Gastric venous blood is alkaline
In the pancreas, HCO3- secreted into the juice and H+ into the blood. Pancreatic venous blood is acidic
What are structures are near the posterior of the pancreas?
IVC
Abdominal aorta
Left kidney
What does stomatostatin do?
Suppress glucagon and insulin release
What type of epithelium lines the pancreatic ducts?
Columnar epithelium lines the pancreatic ducts
Acinar cells - features
They are large with apical secretion granules