Digestion and Absorption Flashcards
What secretions does the small intestine receive?
bile, pancreatic juice, chyme
What receptors do all secretions of the small intestine act on?
G-protein coupled
Which control mechanisms enhance small intestine secretion?
distension, gastrin, CCK, secretin, parasympathetic nerve activity
Which control mechanism decreases small intestine secretion?
sympathetic nerve activity
Does small intestine secretion contain digestive enzymes?
No
What does excessive activity of small intestine secretion cause?
secretory diarrhoea
What is segmentation?
mixing
Which cells initiate mixing?
pacemaker cells, and in empty ileum, gastrin
Which has more mixing, the duodenum or ileum?
duodenum
What inhibits peristalsis in the small intestine?
feeding, vagal activity, gastrin, CCK
What triggers peristalsis in small intestine?
motilin, lack of feeding
Can pancreatic enzymes digest food in absence of all other enzymes?
Yes
Which cells secrete HC03 rich fluid into the duodenum?
duct cells
What happens to fluid secretion in patients with cystic fibrosis?
is reduced
Is bile produced continuously?
Yes
What digests carbohydrates in the small intestine?
pancreatic amylase and oligosaccarrides
Which glycosidic bonds does amylase break?
alpha 1-4, NOT alpha 1-6 or beta 1-4
What causes lactose intolerance?
lactase deficiency
What method are glucose and galactose absorbed by?
secondary active transport
What method is fructose absorbed by?
Facilitated diffusion
What in the stomach cleaves proteins into peptides?
pepsin
What type of enzymes are peptidases?
brush border enzymes
By what method are most amino acids absorbed?
active transport
What increase surface area for attack by pancreatic lipase bu block access of the enzyme to the lipid with the hydrophobic core of the small droplets? What solves this problem?
bile salts
solved by colipase
What is colipase?
an ampipathic polypeptide secreted with lipase
Where are the final products of lipid digestion stored?
mixed micelles
Where are long chain fatty acids and monoglycerides resynthesized to triglycerides?
endoplasmic reticulum
By what vein does chylomicron enter the systemic circulation?
subclavian
What does absorption of di and tripeptides occur via?
the H+ dependent mechanisms at brush border (co-transport_
What is the brush border?
Striated border, microvilli covered surface of epithelium
Where do sodium ion independent systems of facilitated transport occur?
basolateral membrane
In the stomach, why is lipid hydrolysis initially slow?
due to largely separate aqueous/liquid interface
As hydrolysis of fats proceeds, what happens to rate?
increases
Are bile salts amphipathic?
Yes
What do bile salts have increased surface area for?
action of lipase
What does failure to secrete bile salts result in?
Lipid malabsorption and steatorrhea
