Gastric Motility and Pancreatic Function

Question 1

What is the direction of peristaltic waves?

Answer 1

Body -> antrum

Question 2

Is there mixing in the body of the stomach?

Answer 2

Thin muscle - weak contraction - no mixing

Question 3

Where is the powerful contraction in the stomach?

Answer 3

Antrum - thick muscle

Question 4

What is the result of closure of the pyloric sphincter?

Answer 4

Only a small quantity of gastric content (chyme) enters the duodenum

Antral contents are forced back towards the body which results in further mixing

Question 5

What generates the peristaltic rhythm?

Answer 5

Around 3 waves per min

•generated by pacemaker cells (in the longitudinal muscle layer)

Question 6

What produces the slow waves?

Answer 6

Spontaneous depolarisation/repolarisation

Question 7

What is the slow wave rhythm aslo known as?

Answer 7

Basic electrical rhythm

Question 8

How are slow waves conducted?

Answer 8

Through gap junctions along the longitudinal muscle layer

Question 9

How does the number of action potentials affect the strength of contraction?

Answer 9

More action potentials meakes a stronger contraction

Question 10

What is the effect of gastrin on contractility?

Answer 10

Gastrin increases contractility

Question 11

What is the effect of distension of the stomach on contractility?

Answer 11

Long/short reflexes - increased contractility

Question 12

What is the effect of Fat/acid/amino acid/hypertonicity in duodenum on motility?

Answer 12

Inhibition of motility

Question 13

What glands release bicarbonate in the duodenum?

Answer 13

Brunner’s glands (which are submucosal)

Question 14

How does acid in the duodenum result in HCO3 secretion?

Answer 14

Acid in duodenum triggers:
-Long and short reflexes -> HC03 secretion
-Release of secretin from S cells
Which leads to HC03 secretion in pancreas and liver

Question 15

What does acid neutralization fo

Answer 15

Inhibits secretin release

negative feedback control

Question 16

Where is the head of the pancreas located?

Answer 16

located within curvature of duodenum

Question 17

What are the three parts of the pancreas?

Answer 17

Head, body and tail

Question 18

What is the endocrine portion of the pancreas?

Answer 18

Pancreatic islets (islets of langerhans)

Islet cells produce insulin, glucagon and somatostatin (controls secretion of insulin and glucagon)

Question 19

What is the exocrine portion of the pancreas?

Answer 19

Acinar cells and lobules

Question 20

What changes occur from the lubules to the duodenum?

Answer 20

Connected by intercalated ducts - intralobular ducts - interlobular ducts - main pancreatic duct - common pancreatic duct - hepatopancreatic ampulla (sphincter of oddi) - duodenum

Question 21

What is the exocrine portion of the pancreas responsible for?

Answer 21

Digestive function of the pancreas

Question 22

What are the products of duct cells and acinar cells?

Answer 22

Duct cells - bicarbonate

Acinar cells - digestive enzymes

Question 23

What is the purpose of the bicarbonate produced by the pancreas?

Answer 23

Bicarbonate keeps the pH high so that the digestive enzymes stay at their optimum pH, they would become denatured in the acidic conditions

Question 24

What is a zymogen?

Answer 24

An inactive form of an enzyme, they are found in acinar cells and are stored as granules

They prevent autodigestion of the pancreas

Question 25

How does trypsinogen get converted into trypsin?

Answer 25

•Enterokinase (bound to brush border of duodenal enterocytes) converts trypsinogen to trypsin

Question 26

What is the effect of trypsin?

Answer 26

Converts all other zymogens to active forms, it is a proteolytic enzyme

Question 27

What are the categories of pancreatic enzymes?

Answer 27

Question 28

What stimulates bicarbonate production of the pancreas?

Answer 28

Secretin, which is released in response to acid in the duodenum

Question 29

What causes the release of zymogens?

Answer 29

Cholecystokinin

Question 30

When is CCK released?

Answer 30

• In response to fat/amino acids in duodenum
• Also under neural control (vagal/local reflexes) - triggered by arrival of organic nutrients in duodenum

Question 31

Summary of Secretin and CCK function

Answer 31