Function of SI Flashcards
How does the SI mechanically digest food?
Peristalsis
What does chemical digestion in the SI NOT target? (more than 1)
a) protein
b) fat
c) carbohydrates
d) Neutralisation of gastric acid
e) hormones
f) nucleic acid
e and f
What type of cells line the intestine?
Enterocytes
The peristalsis in the SI is stronger than in the stomach?
True or false?
False
It is weaker
How long does chyme remain in the SI for?
3-5 hours
Enteric reflexes respond to the presence of chyme by…?
Increasing intestinal motility
What is distension?
Enlargement
Distension of the SI causes
a) more vigorous peristalsis
b) weaker peristalsis
c) no change to peristalsis
a
How do sympathetic impulses effect intestinal motility?
Decrease
Where is pancreatic juice produced?
Acinar cells of pancreas
How do pancreatic juices enter the duodenum?
Through the pancreatic duct
What does pancreatic juice contain?
Protease, lipases, amylase and sodium bicarbonate
What is the function of sodium bicarbonate in the pancreatic juice?
Neutralise chyme
What 2 hormones regulate pancreatic juice production?
Hormone cholecystokinin (CCK) and secretin
What is the effect of CCK on stomach emptying?
Decreases
What is the effect of CCK on bile?
Causing contraction which moves bile into the duodenum
What hormone stimulates goblet cells?
VIP
What 2 enzymes are found on the apical membrane of enterocytes that digest carbohydrates?
a) peptidases
b) lactase
c) enterokinase
d) sucrose-isomaltase
b and d
What is the function of sucrose-isomaltase?
Hydrolyse sucrose
sucrose –> glucose + fructose
What is the function of lactase?
Lactose –> glucose + galactose
What 2 enzymes are found on the apical membrane of enterocytes that digest proteins?
a) peptidases
b) lactase
c) enterokinase
d) sucrose-isomaltase
a and c
What enzyme hydrolyses food proteins in the stomach?
Pepsin
What enzyme hydrolyses food protein in the duodenum onwards?
Pancreatic proteases
What do peptidases act on?
Mix of small peptides from the hydrolysis of food proteins
What do peptidases form?
AA and small peptides
Why are the products of peptidases important?
They are small enough to be transported across the apical membrane of the enterocytes
What is the function of enterkinase?
Partially hydrolyse pancreatic zymogen proteases to release active enzymes
Are there any brush border enzymes that act on lipids or nucleic acids?
No
What is the effect of tight junctions around enterocytes on the ECF?
ECF surrounding apical and basolateral membrane are seperated
What is the effect of tight junctions around enterocytes on diffusion of proteins?
Prevents
What are the consequences fo tight junctions between enterocytes? (3))
Prevent passage of molecules and ions between cells.
To pass through epithelium, materials must enter by diffusion or active transport, this allows regulation and protection
