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GI - Small Intestine Flashcards

1
Q

SI section length/time

A

2 - 4 hrs in total, 3/4 length GI

duodenum: 8 inches
jejunum: 8 ft
ileum: 12 ft

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2
Q

ways to increase SA in SI

A

circular folds (x3)
villi (x10)
microvilli (x20)
total = 250 sq m

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3
Q

crypts of lieberkuhn fxns

A

secrete water and electrolytes

nurseries - high mitotic activity makes cells that migrate up to replace old villi cells (100 million shed/min)

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4
Q

cells migrating from crypts to villi

A

[ ] of brush border enzymes goes up and absorptive capacity goes up as they get higher

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5
Q

segmentation description

A

circular contractions @ alternate sites

main mvmt in SI

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6
Q

segmental contraction rates by area

A

duodenum: 12/min
jejunum: 10 - 11/min
ileum: 8 - 9/min

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7
Q

peristalsis location

A

occur for only short length of intestine

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8
Q

types of SI motility

A

segmentation*
peristalsis
migrating motor complex

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9
Q

ileocecal juncture structure

A

valve-like folds of ileum protrude into cecum

SM of last few cm is thickened

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10
Q

ileocecal juncture regulation

A

neural and hormonal

ex: gastroileal reflex - gastrin stim extrinsic nerves relax sphincter

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11
Q

ileocecal juncture fxn

A

prevent contamination of SI by LI bacteria

makes for one way transit

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12
Q

places food can be digested

A

in GI secretions
on luminal surface of GI
inside epithelial cells

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13
Q

CHO digestion (main)

A

duodenum + jejunum

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14
Q

kinds of CHO we eat

A

amylopectin**
amylose*
cellulose
animal glycogen

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15
Q

amylopectin

A

plant starch
major source of CHO in most humans
glucose polymer
alpha-1,4 glycosidic bonds w. branch points at alpha-1,6

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16
Q

salivary amylase actions

A

catalyze the hydrolysis of internal alpha-1,4 bonds

not terminal alpha-1,4 or alpha-1,6

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17
Q

main products of starch digestion

A

maltose, maltotriose, branched oligosaccharides (alpha-dextrins?)

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18
Q

actions of maltase

A

cleaves terminal alpha-1,4 bonds

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19
Q

starch digestion

A

starch + salivary amylase –>
partially converted starch + pancreatic amylase –>
maltose, maltotriose, alpha-dextrins + maltase, maltase, isomaltase (brush border) –> GLUCOSE (in lumen)

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20
Q

how to absorb monosaccharides

A 
Into epi from lumen:
glucose: use SGLT1 w/ Na
galactose: use SGLT1 w/ Na
fructose: use GLUT5
out of epi into cap:
all use GLUT2
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21
Q

lactose intolerance

A

low levels of lactase
lactose isnt broken down
lactose is osmotically active
brings water into lumen –> diarrhea

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22
Q

protein digestion location

A

stomach

upper GI

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23
Q

is all CHO absorbed in SI?

A

5 - 15% CHO goes to colon

CHO metabolized by bacteria to make SCFA (important fuel for colon epi cells)

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24
Q

protein digestion in stomach

A

max 15% protein digested by pepsin in stomach

not totally necessary

25
intestinal protein digestion
proteins + pancreatic --> oligopeptides + brush border peptidases --> AAs, dipeptides, tripeptides
26
pancreatic enzymes that digest protein
trypsin chymotrypsin carboxypeptidase (A/B) elastase
27
brush border peptidases
amino-oligopeptidase amino peptidase dipeptidyl aminopeptidase
28
absorption of small peptides
single membrane transporter high affinity for di and tri peptides low affinity for larger peptides
29
absorption of AAs
7 diff AA transporters | some Na dependent, some independent
30
main locations of lipid digestion
duodenum | jejunum
31
digestion of fats
dietary fat + bile salts --> lipid emulsification + pancreatic lipase --> monoglyceride, FAs + bile salts --> micelles
32
where are bile salts reabsorbed
terminal ileum
33
absorption of fat
micelles absorbed passively
34
processing recycled bile salts
hepatocytes extract bile salts unconjugated bile salts reconjugated in hepatocytes secondary bile salts rehydroxylated
35
water in and out of GI system
GI absorb ~ 9 L /day 2 L water ingested 7 L GI secretions only 100 ml of water in feces
36
chyme tonicity
hypertonic in stomach | isotonic in duodenum
37
Na absorption
*cotransport w/ glucose and AAs (D/J) | cotransport w/ bile salts (I)
38
NaCl secreting cell actions
Cl into lumen via CFTR (when open) Na into lumen paracellularly need Na in lumen for Na-nutrient reabsorption (Na/K/Cl into cell from blood by cotransporter)
39
NaCl secreting cells and pathogens
cholera ups cAMP opens CFTR much Cl out much water follows
40
oral rehydration therapy
give glucose and Na actively pumped in together changes dire`ction of Na mvmt
41
cholera and CF
CF patients dont get diarrhea from cholera -- abnormal CFTR | carriers do -- sufficiently normal
42
Ca absorption locations
all portions of intestines | esp. duodenum and jejunum
43
things that make you Ca deficient
Ca deficient diet growth pregnancy lactation
44
Ca absorption based on Ca need
need for Ca up up synth of vit D precursor up Ca absorption
45
how vit D changes Ca absorption
1. rapid open Ca channels 2. increase calbindin synthesis (maintain Ca gradient so Ca can come in) 3. increase # of Ca ATPase (gradient)
46
excessive iron
toxic (mammals don't have excretion path)
47
iron absorption location (+cell)
proximal duodenum | enterocytes
48
iron adsorption and pH
need acidic environment | antacids/gastric acid secretion issues interfere w/ Fe absorption
49
iron absorption in enterocyte
leave enterocyte via ferroportin transporter | bind to ferritin and get sloughed off
50
how metals get into enterocytes
divalent metal transporter-1 (DMT-1) | zinc, lead, copper
51
iron absorption when iron stores full in liver
``` liver secretes hepcidin hepcidin binds to ferroportin ferroportin degraded all iron bind to ferritin instead limit iron intake ```
52
absorption in duodenum
CHO, PRT, FAT (high) Ca, Fe, folate (moderate) bile acids (very low)
53
absorption in jejnunum
CHO, PRT, FAT (moderate) | Ca, bile acids (low)
54
absorption in the ileum
CHO, PRT, FAT, Ca (low) cobalamin (B12) (moderate) bile acids (high)
55
results of intestinal inflammation
increase motility move too fast for proper absorption diarrhea, dehydration and pH imbalance
56
order of hormones during a meal
gastrin secretin/CCK motilin
57
colon fxns
absorption: Na, SCFAs, water secretion: K, mucus
58
colon motility
mix: haustrations - like segmentation but less frequent propulsion: mass mvmts - propel distances, gastrocolic reflex

Physiology (22 decks)

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