Lecture 5: pancreatic secretions and the spleen

Question 1

What are the functions of the pancreas?

Answer 1

• it has 2 distinct functions in the body
• acts as an** endocrine gland** - secretes hormones insulin & glucagon into the bloodstream
• also has exocrine functions, it acts as an accessory digestive organ that secretes enzyme rich fluid into the duodenum through a series of ducts

Question 2

Describe the** structure of ducts in the pancreas

Answer 2

• the pancreas is made up of lobules consisting of acinar cells that secrete enzymes and fluid into a system of microscopic ducts
• these ducts then drain their enzymes into the interlobular ducts which in turn are emptied into the main pancreatic ducts

Question 3

What is another name for the main duct in the pancreas?

Answer 3

Duct of Wirsung

Question 4

What is the accessory pancreatic duct called? what is it’s function?

Answer 4

• duct of santorini
• this duct drains directly into the duodenum

Question 5

What cells are involved in the **endocrine function **if the pancreas?

Answer 5

• islet of langerhans
• they secrete insulin and glucagon

Question 6

What type of cells are involved in the exocrine function of the pancreas?

Answer 6

acinar cells and ductal cells
* acinar cells produce enzymes
* ductal cells produce the aqueous component

Question 7

what are the 2 components in pancreatic juice?

Answer 7

1. aqueous (watery) component
2. enzymatic component

Question 8

What is the exocrine pancreas stimulated and inhibited by?

Answer 8

• stimulated by the vagus nerve
• inhibited by the sympathetic system

Question 9

What is the aqueous component of pancreatic juice composed of?

Answer 9

• produced by centroacinar ductal cells
• fluid is slightly hypertonic, rich in bicarbonate ions (Na+ and K+ ions conc similar to plasma lvl)

Question 10

What is the function of the bicarbonate in the aqueous component of pancreatic juice?

Answer 10

• to neutralise the gastric acid that flows into the duodenum

Question 11

what hormone stimulates the secretion of bicarbonate from duct cells?

Answer 11

the hormone secretin

Question 12

How is the aqueous component produced by ductal cells?

Answer 12

1. Bicarbonate is** formed in the cell by the enzyme carbonic anhydrase - needs co2 and w**ater
2. bicarbonate also comes from the basolateral HCO3/Na+ symporter
3. bicarbonate is secreted into the pancreatic duct in exchange for chloride in the apical membrane (2 diff channels)

Question 13

What are the** 2 types of chloride channels** located on the apical membrane of the duct cell?

Answer 13

• CFTR Cl- channel which is regulated by cAMP NB this one is important for normal HCO3- secretion
• calcium dependent chloride channel

Question 14

What is the ionic composition of the bicarbonate dependent on?

Answer 14

it is dependent on the flow rate of the pancreatic juice
* ie if the flow rate is low, the bicarbonate concentration of secretion is low

Question 15

how is the pancreatic secretion of the aqueous component controlled?

Answer 15

- TO DO WITH LVL OF ACID IN SI
* if there is an increase in acid in the stomach, the S cells in the SI will release more secretin
* an increase in [secretin] in the plasma will cause an increase in bicarbonate secretion from the pancreas into the SI
* this will then neutralise the acid in the SI

Question 16

Give a summary of the key points involving the aqueous component of pancreatic juice

Answer 16

Question 17

What is the enzymatic component of pancreatic juice produced by? what is the component composed of?

Answer 17

produced by : acinar cells
* digestive enzymes
* including - amylase, DNAase, RNAase, 3 lipases and 3 proteolytic enzymes

Question 18

what hormone stimulates the secretion of enzymes by the acinar cells?

Answer 18

CCK released from the I cells of the duodenum and jejenum

Question 19

What are the 3 lipases in the enzymatic component?

Answer 19

1. triaglycerol hydrolase
2. cholesterol ester hydrolase
3. phospholipase

Question 20

What are proteolytic enzymes? What are examples of them in the enzymatic component?

Answer 20

• enzymes that play an important role in protein digestion
• examples : trypsinogen which is activated by enterokinase on the duodenum brush border to trypsin

Question 21

What 2 proteolytic enzymes does trypsin activate?

Answer 21

1. chymotrypsinogen
2. procarboxypeptidase

Question 22

How is the pancreas’ enzymatic secretion controlled?

Answer 22

by the level of intestinal fatty acids and amino acids
* if there is an increase of ^^, then the small intestine will increase CCK secretion
* CCK acts on the acinar cells and increases the enzymatic secretion and therefore increases the flow of enzymes into the pancreas

Question 23

What is pancreatitis?

Answer 23

• a disease characterised by the inflammation of the pancreas

Question 24

what is pancreatitis caused by?

Answer 24

• gall stones (stone in gallbladder made of precipitate of bile components - ie solids leave solution)
• excessive alcohol
• infection

Question 25

what is a good method used to diagnose pancreatitis?

Answer 25

• measurement of the serum lipases

Question 26

What is the spleen?

Answer 26

an organ of the lymphatic system

Question 27

what is the function of the spleen?

Answer 27

• it’s main function is to filter blood - ie can remove old rbc’s
• contains red pulp which functions to remove red blood cells and recycle iron
• contains white pulp which contains lymphocytes that produce antibodies