Gastric motility and pancreatic function

Question 1

How is foodstuff moved in the stomach?

Answer 1

Using peristaltic waves

Question 2

What are the differences between the muscle contractions in different parts of the stomach?

How is this relevant to mixing?

Answer 2

In the body, the muscle is thinner and contractions are weaker. Peristalsis moves stuff towards the antrum.

In the antrum; muscle is thicker and contractions are stronger. This allows mixing to take place.

Question 3

What does the pyloric sphincter do?

Answer 3

Controls exit from the stomach. Only small amounts of Chyme (stomach contents) make it into the duodenum before it closes again.

It also forces chyme back into the antrum which means more mixing takes place.

Question 4

How frequent is peristaltic rhythm in the stomach?

Answer 4

3 /min

(roughly)

Question 5

What controls the rate of peristaltic contractions?

Answer 5

Pacemaker cells in the longitudinal muscle layer

Question 6

Where is the peristaltic contraction conducted to?

Answer 6

Depolarisation carried from the stomach through the intestines through gap juntions in the longitudinal muscle layer

Question 7

What is the name given to the basic electrical rhythm (BER) that is in the stomach?

Answer 7

Slow wave rhythm

Question 8

What determines the strength of peristaltic contraction?

Answer 8

The number of Action potentials per wave

Question 9

What causes increased motility in the stomach?

Answer 9

Gastrin

Distension of stomach wall

^basically just parasympathetic stim

Question 10

What inhibits/reduces stomach motility?

Answer 10

Fat/acid/amino acid/hypertonicity in duodenum

(sphincter stays shut)

Question 11

How is acid in the duodenum neutralised?

Answer 11

Bicarbonate (HCO₃^-) secretion from Brunner’s Gland duct cells (submucosal glands)

Produces H₂O and CO₂

Question 12

How is bicarbonate secretion stimulated when there is acid in the duodenum?

Answer 12

Vagal (long) and Enteric (short) reflexes trigger HCO3- release from Brunner’s glands

Secretin release:

Acid causes S cells to release Secretin. This stimulates HCO3- secretion from the pancreas and liver. As acid is neutralised, secretion decreases accordingly (negative feedback)

Question 13

The pancreas has an endocrine function and an exocrine function

What does the endocrine portion do?

Answer 13

Insulin

Glucagon

Somatostatin

(secretes this into blood)

Question 14

What does the exocrine portion of the pancreas do?

Answer 14

Produces/secretes:

Bicarbonate (HCO3-)

DIgestive enzymes (amylase etc)

(into duodenum via ducts)

Question 15

What anatomical part of the pancreas carries out the endocrine function?

Answer 15

Insulin, glucagon, somatostatin produced by specific cells in Islets of Langerhans

Glucagon - produced by Alpha cells

Insulin - “ Beta cells

Somatostatin - “ delta cells

Question 16

What is the anatomical structure of the exocrine part of the pancreas?

Answer 16

Made of ‘lobules’ connected by intercalated ducts

In each lobule:

• Acinar cells produce Digestive enzymes
• Duct cells produce Bicarbonate

Question 17

What is the fate of intercalated ducts in the pancreas?

Answer 17

• Lobule
• Intercalated duct
• Intralobular duct
• Interlobular duct
• Pancreatic duct
• Common bile duct
• Hepatopancreatic ampulla (Sphincter of Oddi)
• Duodenum

Question 18

You want a photo of the pancreas histology?

Answer 18

Here you go

Question 19

How are digestive enzymes stored in the pancreas?

Answer 19

Stored and secreted as Zymogens (inactive precursors) in Acinar cells

Question 20

How are inactive pancreatic enzymes activated?

Answer 20

Enterokinase (bound to duodenal enterocytes) converts trypsinogen to trypsin

Trypsin converts the zymogens to their active form

Question 21

What are the classes of pancreatic enzymes?

Answer 21

• Proteases
• Nucleases - hydrolyse DNA/RNA
• Elastases - Collagen digestion
• Phospholipases - Phospholipids to fatty acids
• Lipases - Triglycerides to fatty acids+ glycerol
• α-Amylase - Starch to glucose and maltose

Question 22

What stimulates zymogen secretion (enzyme) by the pancreas?

Answer 22

CCK - cholecystokinin

which is released in response to fat/amino acids in the duodenum

and

Neural control (Vagal/local reflexes) which is triggered by arrival of organic nutrients in the duodenum

Question 23

Answer 23

xx