Gastric Motility and Pancreatic Function

Question 1

How is the body of the stomach involved in peristalsis?

Answer 1

Contains thin muscle which produces weak contraction and therefore is not responsible for mixing

Question 2

How is the antrum of the stomach involved in peristalsis?

Answer 2

Contains thick muscle, as the oblique layer is more prominent, this produces a powerful contraction for mixing and contraction of the pyloric sphincter

Question 3

What is the benefit of contraction of the pyloric sphincter during digestion?

Answer 3

Only small volume of chyme allowed into duodenum (prevents dumping syndrome)

Further mixing as antral contents are forced back towards the body of the stomach

Question 4

What is the basic principle of gastric peristaltic waves?

Answer 4

Stomach muscle contractions a syncytium, with the pacemaker located in the top of the stomach located at the top in the longitudinal layer

Electrical depolarisations are transmitted through cells via gap junctions

Question 5

What produces gastric peristaltic waves?

Answer 5

Slow wave pattern sets the basic electrical rhythm - it is subthreshold and requires further depolarisation to induce the action potential (to allow contraction to occur)

Question 6

How does the myenteric plexus effect gastric peristaltic waves?

Answer 6

Has afferent nerves which deliver information from chemical and stretch receptors to the plexus

Stimulation causes plexus interneurones to send information via efferent nerves to smooth muscle cells, stimulating the to fire an action potential –> contraction

Question 7

What neural and hormonal input can influence gastric motility?

Answer 7

Gastrin
Stomach distension
Fat/acid/amino acid/hypertonicity in duodenum (inhibition of motility)

Question 8

How does gastrin affect gastric motility?

Answer 8

Increases contraction for mixing of the food

Question 9

How does distention of the stomach wall affect gastric motility?

Answer 9

Long (to CNS) and short (only in stomach wall) reflexes –> increased contraction

Increased distention = increased contraction

Question 10

How does fat/amino acid/hypertonicity in the duodenum affect gastric motility?

Answer 10

Inhibits motility

Increased tonicity inhibits motility as it indicates an increase in contents in the duodenum, meaning the stomach is empty and less need for motility

Question 11

Why does gastric acid need to be neutralised in the duodenum?

Answer 11

If gastric acid enters the duodenum, the epithelium will be burned causing chemical erosion which could form an ulcer that could penetrate the mucosa and submucosa

Question 12

What is used to neutralise gastric acid?

Answer 12

Bicarbonate (HCO3) from Brunner’s Gland duct cells in the submucosa

Question 13

What triggers the release of bicarbonate?

Answer 13

Long (vagal) and short (enteric NS) reflexes

Secretin

Question 14

How does secretin trigger he release of bicarbonate?

Answer 14

Released on S cells and acts on pancreatic and liver cells

Acid neutralisation inhibits secretin release (negative feedback control)

Question 15

What is the endocrine function of the pancreas?

Answer 15

Release of hormones insulin and glucagon into the bloodstream by diffusion, and therefore is surrounded by lots of vasculature

Question 16

What is the exocrine function of the pancreas?

Answer 16

Please of digestive enzyme and sodium bicarbonate into the gut lumen for digestion and neutralisation

Question 17

Where is the head of the pancreas located to with relation to the duodenum?

Answer 17

Within the curvature of the duodenum

Question 18

What part of the pancreas is responsible for the endocrine function?

Answer 18

Islet of Langerhans: produce cells, glucagon and somatostatin

Question 19

What part of the pancreas is responsible for the exocrine function?

Answer 19

Acinar cells in the lobules

Question 20

What is the organisation of ducts in the pancreas from lobules to the duodenum?

Answer 20

Intercalated duct (connects lobules)

• > intralobular duct
• > interlobular duct
• > Main pancreatic duct
• > Ampulla of vater
• > Duodenum

Question 21

What is the function of the accessory pancreatic duct?

Answer 21

Normally closed, but is there is a block in the common bile duct or after into the duodenum, the accessory duct is used to release pancreatic enzymes into the duodenum (only pancreas)

Question 22

How are zymogens converted into active enzymes?

Answer 22

The zymogen and trypsinogen are released from the pancreases

Enterokinase (bound to brush border of duodenal enterocytes) converts trysinogen -> trypsin

Trypsin converts all other zymogens to active proteolytic enzymes

Question 23

What are 6 different categories of pancreatic enzymes?

Answer 23

Preoteases
Nucleases
Elastases 
Phospholipases
Lipases 
A-amylase

Question 24

What is the role of proteases?

Answer 24

Cleave peptide bonds

Question 25

What is the role of nucleases?

Answer 25

Hydrolyse DNA/RNA

Question 26

What is the role of elastase?

Answer 26

Collagen digestion (connective tissue)

Question 27

What is the role of phospholipase?

Answer 27

Phospholipids to fatty acids

Question 28

What is the role of lipase?

Answer 28

Triglycerides to fatty acids and glycerol

Question 29

What is the role of A-amylase?

Answer 29

Starch to maltose + glucose

Question 30

What triggers the release of zymogens from the pancreas?

Answer 30

Cholecystokinin (CCK) -In response to fat/amino acids in the duodenum

Neural control - triggered by nutrients in the duodenum