2.3 Exocrine Pancreatic Function and Biochemical Digestion

Question 1

What do the gastric (oxyntic) glands secrete?

Answer 1

HCL, pepsinogen, IF and mucus

Question 2

What do the pyloric glands secrete?

Answer 2

mucus and gastrin

Question 3

What stimulates gastrin release?

Answer 3

stretching of the stomach

Question 4

What cell types are the gastric glands made of?

Answer 4

Mucous neck cells - secrete mucus
Peptic (chief cells) - secrete pepsinogen
Parietal cells - secrete HCl and IF

Question 5

What are the inhibitory factors of gastric emptying?

Answer 5

Duodenal distension 
Duodenal irritation 
Acidity of duodenal chyme 
Osmolality of the duodenal chyme 
Presence of certain substances such as protein degradation products

Question 6

What is the role of pepsinogen and how is it activated

Answer 6

when it comes in contact with HCl it is converted into pepsin - will degrade proteins into peptides

Question 7

What are the signals for release of pancreatic products?

Answer 7

• Secretin from duodenal and jejunal mucosa (secreted when acid enters duodenum)
• CCK from duodenal and jejunal mucosa (secreted when fat and AA enter the duodenum)

Question 8

What is the role of secretin?

Answer 8

produce bicarbonate and prevent further release of gastrin

Question 9

What is the role of bile salts?

Answer 9

Emulsify fat into small particles that can then be digested by lipase

Question 10

Where are carbohydrates digested?

Answer 10

Some in the stomach but mainly in the small intestine by amylase that is secreted from the pancreas
Disaccharides are digested by enzymes in the intestinal microvilli

Question 11

Where are Fats digested?

Answer 11

a small amount in the stomach by linguinal lipase but mainly in the small intestine

Question 12

Where are proteins digested?

Answer 12

Some in the stomach by pepsin but most in the duodenum from pancreatic proteases

Question 13

Where are lipids digested and how?

Answer 13

duodenum - required to be emulsified with bile salts and lectithin
Lipase will hydrolyse triglycerides to mono glycerides and FFAs
Requires co-lipase for activity which will bind to water-lipid interface and activate lipase

Question 14

Where are lipids absorbed and how?

Answer 14

In the jejunum - micelles deliver the lipid to the brush border where the FFA and MAGs will be taken up into enterocytes
Within the enterocyte the absorbed FFA will be converted into triglycerides which are released into the thoracic duct as chylomicrons

Question 15

How are proteins broken down?

Answer 15

1. Trypsin and chymotrypsin split proteins into smaller proteins
2. Carboxypeptidase cleaves protein into amino acids