GI4 & 6 Intstinal function &pancreas

Question 1

What is the effect of the following stimuli being detected in the chime that enters the small intestine on the stomach :

1) hyperosmotic solution
2) carbohydrares
3) Fats and proteins
4) Acid

Answer 1

1) endocrine cells reduces gastric motility
2) GIP is secreted which reduces acid secretion in stomach,
3) CCk secreted which inhibits acid secretion and reduces gastric motility
4) secretin secreted which inhibits acid secretion and reduces gastric motility

Question 2

What is the effect of the following stimuli being detected in the chime that enters the small intestine on the pancreas :

1) hyperosmotic solution
2) carbohydrares
3) Fats and proteins
4) Acid

Answer 2

1) n/a
2) GIP and GLP-1 is secreted which stimulates insulin secretion in pancreas
3) CCK stimulates pancreatic enzyme secretion
4) secretin secreted which stimulates pancreatic bicarbonate secretion

Question 3

What negative feedback loop occurs between the small intestine and pancreas

Answer 3

Acid detected= secretin secreted which stimulates pancreatic bicarbonate secretion
therefore less acid in stomach so less secretion of bicarb.

Question 4

What is the length of the following:

1) duodenum
2) jejunum
3) ileum

Answer 4

1) 4 cm
2) 2.5m
3) 3.5m

Question 5

What divides the ileum from the large intestine:

Answer 5

ileocecal valve

Question 6

Describe mechanical digestion of chime in the small intestine:

Answer 6

1) Weak peristalsis in comparison to the stomach
2) Chyme remains here for 3 to 5 hours
3) Segmentation means chime mixed local with intestinal juices and sloshed back and forth

Question 7

Chemical digestion of chime in the small intestine:

a) What is released from the pancreas that isn’t an enzyme+ function:?
1) Where do the enzymes come form in the pancreas?
2) Where does the bile come from?
3) What is the function of bile?
4) What do goblet cells secrete?
5) What stimulates goblet cells?

Answer 7

a) SODIUM BICARBONATE (alkali) to neutralize chyme
1) acinar cells of pancreas
2) made in liver, stored in gallbladder, flows to the duodenum by the bile duct.
3) emulsifier for fats.
4) secrete mucus for protection and lubrication
5) Hormone Vasoactive intestinal polypeptide (VIP)
cos goblet cells are the VIPs of the intestine cos they get to mix with the epithelium

Question 8

Chemical digestion of chime in the small intestine:

1) What enzymes are present from pancreatic juices?
2) What enzymes are in the apical membrane i.e. brush-border enzymes: + reaction

Answer 8

1) Pancreatic juice: PROTEASES, LIPASES, AMYLASE,
2) Sucrase-isomaltase:
a) Hydrolyses sucrose → glucose + fructose
Lactase:
b) Hydrolyses lactose → glucose + galactose
c)Enterokinase (enteropeptidase) partially hydrolyses pancreatic zymogen proteases to release the active enzyme
d) eptidases: ]
Act on mixture of small peptides (already broken down by pepsin and pancreatic proteases)
• Produces mixture of free amino acids and small peptides

Question 9

What enzyme is not present in non-Caucasians?

Answer 9

¯ Expression of lactase after weaning in most humans – Caucasians are an exception

Question 10

What can cause lactose intolerance?

Answer 10

Lactose intolerance can occur due to damage
to intestinal mucosa (age, drug treatment or
chemotherapy

Question 11

What do brush border enzymes not act on?

Answer 11

NO brush border hydrolases act on lipids or nucleic acids

Question 12

What cell type absorbs nutrients in small intestine?

2) describe the peptides it can absorb?

Answer 12

enterocytes

2) Both free amino acids and di- and tri-peptides can be transported across apical membrane of enterocyte

Question 13

What type og gland is the pancreas?

Answer 13

trick, its mixed

Question 14

Endocrine gland vs exocrine gland:

Answer 14

• Endocrine glands: ductless glands, secretion is directly release into blood circulation
• Exocrine gland : open to outside medium through duct

Question 15

Describe development of acinar cells:

Answer 15

• Develop as evagination from the embryonic endoderm (epithelial cells which line foetal gut)

Question 16

1) Describe the structure of exocrine cells in pancreas:
2) what is the role of acinar cells
3) What is the role of Centro-acinar cells

Answer 16

1) Arranged around a central cavity (lumen). Lumen connects with others via intralobular duct to form ductules – eventually coalesce into main pancreatic duct
2) Produce many inactive enzyme precursors
2) Centro-acinar cells modify ionic composition of secretion

Question 17

1) What secretes Cholecystokinin (CCK)?
2) What is it?
3) What stimulates 1?
4) How does CCK reach acinar cells?
5) What does it do when it gets there?

Answer 17

1) duodenal enteroendocrine cells
2) mixture of peptide hormones ( octapeptide most active)
3) partially digested proteins and fats in gut lumen.
4) chyme enters duodenum, CCK is released into blood, circulates to basolateral membrane of acinar cells
5) binds to receptors on basolateral membrane of acinar cells

Question 18

Describe the strcutre of acinar cells:

Answer 18

Imagine Emperor Zurgs rocket with one eye.
The top of the rocket is the apical surface it contains enzymes stored in membrane lined secretory vesicles usually as zymogen (emperor Zurg)
The eye is the nucleus
the launchers as the receptors they are on the basolateral surface of the rocket. Nutrients enter through basolateral membrane as well and are used for digestive enzyme synthesis.

Question 19

What is secretin?

2) What secretes it?
3) what is the stimulus for secretion?
4) What does secretin do?
5) What is the receptor for secretin on the basolateral surface of acinar cells?

Answer 19

1) 27 amino acid peptide
2) enteroendocrine cells
3) acid in duodenum
4) cause secretion of bicarbonate from pancreas
5) 7 membrane spanning domains and characteristics of a typical G protein-coupled receptor

Question 20

How does protease actually appear in the duodenal lumen?

Answer 20

Synthesised and packaged into secretory vesicles as inactive proenzymes
Converted into active forms by partial hydrolysis by enteropeptidase in duodenal lumen

Question 21

How are all the inactive enzyems secreted by the pancreass activated?

Answer 21

1) trypsinogen is one of many inactive enzymes secreted
2) trypsinogen is activated by enteropeptidases into typsin
3) trypsin activates other proenzymes
e. g. chymotrypsinogen goes to chymotrypsin , procolipase goes to colipase

Question 22

What does pancreatic lipase produce?

2) What does phospholipase A2 to?
3) What does amylase do?

Answer 22

1) Hydrolyse triglycerides to yield 2 free fatty acids and 2-monoglyceride.
2) digest phospholipids
3) Hydrolyse starches to yield maltose, maltotriose and small branch-point fragments called limit dextrins

Question 23

What is used to treat obesity?

Answer 23

Orlistat (Xenecal) is a pancreatic lipase inhibitor

Question 24

ribonuclease, deoxyribonuclease, gelatinase and elastase

What are these?

Answer 24

hydrolases produced by pancreas

Question 25

What enzyme does bicarbonate secretion from pancreas depend on?
2) What cell type secretes water and bicarbonate in pancreas?

Answer 25

1) carbonic anhydrase

2) Epithelial cells in pancreatic ducts

Question 26

What is secretes in islets of langerhan pancreas and by what cell type?
2) exo or endocrine cell?

Answer 26

Islets secrete hormones
Alpha cells : glucagon 
Beta cells: insulin
D cells: somatostatin
2) endocrine cells , they are called islets of langerhan in pancreas and are embedded in exocrine tissue

Question 27

Where does vitamin K come from?

2) why is vitamin K important?
3) How is it absorbed?

Answer 27

bacteria in large intestine
2) blood clotting factor
and needed for proteins involved in bone formation
3)Absorbed in in chylomicrons formed by lipolysis of fats (lipases from pancraes do this

Question 28

What can cause pancreatic insufficiency?

2) What is pancreatic insufficiency?
3) Why is it risky to extract a tooth of someone with pancreatic insufficiency?

Answer 28

Alcohol, gall stones, viruses (e.g. HIV)

2) Endocrine and exocrine functions reduce
3) excessive bleeding as not enough lipases therefore vit K absoprtion goes down