Week 2.3 - Gastric Motility and Pancreatic Function

Question 1

What are peristaltic waves?

Answer 1

move food from body to antrum

Question 2

What produces peristaltic waves and how many?

Answer 2

peristaltic rhythm - 3 waves per minute. produces by pacemaker cells in longitudinal muscle layer

Question 3

stomach body muscle vs antrum muscle and how this effects mobility?

Answer 3

stomach body is thin so weak contractions.
antrum is thick with 3 layers - longitudinal muscle, circular muscle and oblique - powerful contractions

Question 4

Why is it important that the antrum has powerful contractions?

Answer 4

to contract the sphincter to allow food into the duodenum

Question 5

Why is contraction of the pyloric sphincter important?

Answer 5

• control acid into duodenum
• allows food to re-enter stomach for further mixing like cycles

Question 6

What does it mean that the slow wave depolarisation is sub-theshold?

Answer 6

alone doesn’t produce enough waves to produce AP to cause contraction. must be paired with hormone/chemicals like ACh or gastrin

Question 7

What determines if a contraction is strong or weak?

Answer 7

no. of action potentials - more=strong

Question 8

What forms of control cause a stronger or weaker contraction?

Answer 8

neural or hormonal.
- neural is vagal/local ENS distending stomach, causing release of ACh.
- hormonal is ACh or gastrin
- ….or fats/amino acids in duodenum inhibit motility by releasing GIP/CCK/secretin

Question 9

How is acid in the duodenum neutralised? 2 ways

Answer 9

• acid triggers vagal/ENS response, releasing bicarbonate from submucosal glands in duodenum.
• acid causes secretin release, increasing bicarbonate secretion.

Question 10

What is the name of the duodenal gland which secretes HCO3-?

Answer 10

brunners gland duct cell

Question 11

Where do the pancreas head and tail face?

Answer 11

head is in duodenum curvature. tail is towards the spleen

Question 12

What endocrine activity do we see in the pancreas?

Answer 12

has pancreatic islets which have alpha cells secreting glucagon and beta cells secreting insulin, controlling metabolism

Question 13

What exocrine activity do we see in the pancreas?

Answer 13

has acini cells which produce enzymes and hormones.

Question 14

What is the journey from acini to duodenum?

Answer 14

acini, intracalated ducts, intercalated ducts, main pancreatic duct, combines with common bile duct, sphincter of oddi and then major duodenal papilla

Question 15

What is the journey of pancreatic juice in the case of a defect in one of the pathways?

Answer 15

accessory pancreatic duct which takes pancreatic juice and bile into the lesser duodenal papilla

Question 16

Which type of epithelium are found in the exocrine cells and duct cells of the pancreas?

Answer 16

acini are columnar epithelium while duct cells are cuboidal. all simple.

Question 17

What do duct cells secrete?

Answer 17

HCO3- bicarbonate

Question 18

How are zymogens activated?

Answer 18

• acini cells secrete zymogens including trypsinogen.
• once reach duodenum, enterokinase enzyme on brush border converts trypsinogen to trypsin. this converts all other zymogens to active form.

Question 19

What are the 5 categories of pancreatic enzymes?

Answer 19

lipase
phospholipase
protease
elastase (collagen)
nuclease (nucleic acid)

Question 20

What are the 2 pancreatic functions we control?

Answer 20

control of zymogen release and bicarbonate secretion

Question 21

What controls bicarbonate release in the pancreas?

Answer 21

-release by duct cells
- acid in chyme in duodenum stimulates secretin release which stimulates bicarbonate secretion

Question 22

What controls zymogen release in the pancreas?

Answer 22

• fats/acid in duodenum cause CCK release, which controls release of all pancreatic enzymes
• neural control - local reflexes and vagal nerves release ACh into pancreas causing zymogen release