Histology of the Pancreas

Question 1

Wha does the dorsal pancreas form?

Answer 1

Part of the head, body, and tail of the pancreas

Question 2

What does the ventral pancreas form?

Answer 2

the head of the pancreas and associates with the common bile duct

Question 3

What happens by week 12 of the developing pancreas?

Answer 3

pancreatic acini develop from the ducts

Question 4

What does the exocrine pancreas consist of?

Answer 4

acini involved in the synthesis and secretion of digestive enzymes transported by a duct system

Question 5

What does the endocrine pancreas consist of?

Answer 5

Islets of Langerhans

Question 6

Each islet of Langerhans is supplied by afferent arterioles, forming a network of capillaries lined by fenestrated endothelial cells. What is the network called?

Answer 6

insuloacinar portal system

Question 7

What is the blood supply of the endocrine pancreas?

Answer 7

insuloacinar portal system

Question 8

What is the blood supply of the exocrine pancreas?

Answer 8

an independent arterial system - acinar vascular system

Question 9

What are the two components of the Islets of Langerhans?

Answer 9

Anastomosing cords of endocrine cells - A, B, D, and F cells - each secreting a single hormone

Vascular component - insuloacinar portal system

Question 10

Describe alpha cells found in the islets of langerhans and the functions of the primary hormones secreted

Answer 10

produce glucagon: released by exocytosis when there is a decrease in the plasma levels of glucose
Increases glucose blood levels by increasing hepatic glycogenolysis
Binds to its membrane bound receptor and makes cAMP

Preprogluccagon encoded by gene on chr 2

Can also be found in GI tract and brain

Question 11

Describe beta cells found in the islets of langerhans and the functions of the primary hormones secreted

Answer 11

Produce insulin: has an alpha and beta chain linked by disulfide bonds
preproinsulin->insulin
Increase of blood glucose stimulates release of insulin and C peptide
Stored insulin released in Ca-dependent manner

Question 12

Describe cells found in the islets of langerhans and the functions of the primary hormones secreted

Answer 12

Produce gastrin and somatostatin:
somatostatin inhibits release of insulin and glucagon, inhibits secretion of HCL by parietal cells, gastrin from enteroendocrine cells, secretion of bicarb and enzymes, and contraction of gallbladder

Question 13

What stimulates the release of glucagon

Answer 13

Fall in concentration of glucose in blood
increase of arginine and alanine in serum
stimulation of SNS

Question 14

Describe F cells found in the islets of langerhans and the functions of the primary hormones secreted

Answer 14

Produce pancreatic polypeptide

• inhibits the secretion of somatostatin
• inhibits secretion of pancreatic enzymes, secretion of bile by inhibiting contraction
• conserve digestive enzymes and bile between meals
• CCK stimulates its release

Question 15

Describe the synthesis of insulin by B cells

Answer 15

Preproinsulin: synthesized in RER and signal sequence removed to become..
Proinsulin: transferred to golgi and enclosed in secretory vesicle w specific protease. protease removes C peptide to make…
Mature insulin in the presence of Zn

Question 16

Describe the storage of insulin in B cells

Answer 16

once C peptide by specific proteases is removed, there is a separation of chains A and B, organization of a crystalline core consisting of hexamer and zinc atoms

C peptide surrounds the crystalline core

Question 17

Describe the secretion of insulin by B cells

Answer 17

Glucose is taken up by B cells by GLUT-2 (insulin-independent)
Increase of glucose->increase in ATP in cell
ATP-sensitive K channel closes
K accumulates in cell
Cell membrane depolarizes and Ca channels open
Influx of Ca triggers insulin exocytosis

Question 18

Describe insulin

Answer 18

Required to increase transport of glucose; primarily in hepatocytes, skeletal and cardiac m
Decreases blood glucose levels
Binds to alpha sub unit of its receptor; intracellular domain of beta subunit has tyrosine kinase activity and triggers intracellular responses - upregulates GLUT-4

Question 19

Describe glucagon

Answer 19

30-40% of glucagon in blood derives from pancreas
Liver is primary target
induces hyperglycemia by glycogenolytic activity in hepatocytes
No C peptide or Zn

Question 20

During the development of the pancreas, what happens by week 4?

Answer 20

two outpocketings from the endodermal lining of the duodenum develop as the ventral and dorsal pancreas, each with its own bile duct