GI4 & 6 Intstinal function &pancreas Flashcards
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
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
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
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
What negative feedback loop occurs between the small intestine and pancreas
Acid detected= secretin secreted which stimulates pancreatic bicarbonate secretion
therefore less acid in stomach so less secretion of bicarb.
What is the length of the following:
1) duodenum
2) jejunum
3) ileum
1) 4 cm
2) 2.5m
3) 3.5m
What divides the ileum from the large intestine:
ileocecal valve
Describe mechanical digestion of chime in the small intestine:
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
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?
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
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
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
What enzyme is not present in non-Caucasians?
¯ Expression of lactase after weaning in most humans – Caucasians are an exception
What can cause lactose intolerance?
Lactose intolerance can occur due to damage
to intestinal mucosa (age, drug treatment or
chemotherapy
What do brush border enzymes not act on?
NO brush border hydrolases act on lipids or nucleic acids
What cell type absorbs nutrients in small intestine?
2) describe the peptides it can absorb?
enterocytes
2) Both free amino acids and di- and tri-peptides can be transported across apical membrane of enterocyte
What type og gland is the pancreas?
trick, its mixed
Endocrine gland vs exocrine gland:
- Endocrine glands: ductless glands, secretion is directly release into blood circulation
- Exocrine gland : open to outside medium through duct
Describe development of acinar cells:
• Develop as evagination from the embryonic endoderm (epithelial cells which line foetal gut)
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
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
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?
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
Describe the strcutre of acinar cells:
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.
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?
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
How does protease actually appear in the duodenal lumen?
Synthesised and packaged into secretory vesicles as inactive proenzymes
Converted into active forms by partial hydrolysis by enteropeptidase in duodenal lumen
How are all the inactive enzyems secreted by the pancreass activated?
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
What does pancreatic lipase produce?
2) What does phospholipase A2 to?
3) What does amylase do?
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
What is used to treat obesity?
Orlistat (Xenecal) is a pancreatic lipase inhibitor
ribonuclease, deoxyribonuclease, gelatinase and elastase
What are these?
hydrolases produced by pancreas
