Gastric Motility and Pancreatic Function

Question 1

Where do peristaltic waves travel from and to?

Answer 1

From the body of the stomach to the antrum

Question 2

What sort of movement is in the body ?

Answer 2

Since the muscle is thin here - contractions are weak

No mixing occurs, movements just pass food along

Question 3

What kind of movement is there in the antrum?

Answer 3

Thick muscular walls = powerful contractions

Cause mixing

Question 4

What causes further mixing of the chyme?

Answer 4

Contraction of the pyloric sphincter - only lets a small amount into duodenum meaning rest is pushed back up and mixed further

Question 5

What is the peristaltic rhythm?

Answer 5

3 per min

Question 6

What generates these waves?

Answer 6

Pacemaker cells in the longitudinal muscle layer

Question 7

What is the slow wave rhythm called?

Answer 7

Basic electrical rhythm (bER) - caused by spontaneous depolarisation/repolarisation

Question 8

What determines the strength of contraction?

Answer 8

Number of APs per wave

Question 9

What hormone increases contractions?

Answer 9

Gastrin

Question 10

What reflexes increase contraction?

Answer 10

Distension of stomach wall = long/short reflexes

Question 11

What inhibits motility of stomach ?

Answer 11

Fat
Acid
Amino acids
Hypertonic solutions

These in the duodenum

Question 12

What neutralises acid in the duodenum?

Answer 12

Bicarbonate secretion from brunner’s gland duct cells

Question 13

Where are brunner’s gland duct cells?

Answer 13

In the submucosa

Question 14

Describe the neural control of duodenal bicarb secretion.

Answer 14

Acid in duodenum triggers a long reflex (vagal) and short reflex (enteric NS) leading to bicarbonate secretion

Question 15

Describe the endocrine control of bicarb secretion.

Answer 15

Release of secretin from S cells leads to bicarb secretion from pancreas and liver

When acid is neutralised this inhibits secretin release

Question 16

Describe the shape of the pancreas.

Answer 16

Head - sits in curve of duodenum
Neck
Body
Tail - extends to spleen

Question 17

What is the endocrine portion of the pancreas?

Answer 17

Contains the pancreatic islets cells/ islets of langerhans

These make several hormones such as insulin, glucagon and somatostatin

Question 18

What is the exocrine portion of the pancreas responsible for?

Answer 18

Secreting digestive enzymes - duct cells

Secreting bicarbonate - acinar cells

Question 19

What is the exocrine portion made up of? How do all these connect and feed back to the duodenum?

Answer 19

-Lobules feed into an intercalated duct

-Goes on to an intralobular then an interlobular duct
Interlobular feeds into the pancreatic duct

• Pancreatic duct feeds back towards the head where it anastomoses with the common bile duct
• Then heads towards the duodenum through the sphincter of oddi

Question 20

What is another duct that feeds directly into the duodenum not through the sphincter of oddi?

Answer 20

Accessory pancreatic duct

Question 21

Do acinar cells store digestive enzymes?

Answer 21

Yes but in an inactive zymogen form

Question 22

How are zymogens activated when they enter the duodenum?

Answer 22

Enterokinase is bound to the brush border of duodenal enterocytes

Enterokinase converts trypsinoigen to trypsin

Trypsin converts all other zymogens to active forms

Question 23

What do proteases do?

Answer 23

Cleave peptide bonds

Question 24

What do nucleases do?

Answer 24

Hydrolyse DNA

Question 25

What digests collagen?

Answer 25

Elastases

Question 26

What turns phospholipids to FFAs?

Answer 26

Phospholipases

Question 27

What do lipases do?

Answer 27

TAG to FFA + glycerol

Question 28

What does alpha amylase do?

Answer 28

Starch to maltose + glucose

Question 29

What stimulates zymogen secretion?

Answer 29

Cholecystokinin - CCK which is released in response to fat/amino acids in duodenum

CCK is also released va vagal/ENS reflexes which are also triggered by arrival of fat/amino acids