Ecay 5

Front 1

WHat bile does

Back 1

Bile is responsible for the principal digestive function of the liver. Bile is required for
the digestion and absorption of lipids. Bile emulsifies fats so that they can be digested by
lipases. Bile solubilizes fatty acids into micelles, which are essential for absorption. Also,
bile is a vehicle for the elimination of toxic substances and wastes from the body. These
include cholesterol and bile pigments, drugs and heavy metals.

Front 2

secretion of bile draws with it ions and water, and duct cells add more ions and water similar to pancreatic method

Back 2

yep

Front 3

bile secretion increaes hydrosatic pressure

Back 3

in the bile duct which causes the gall bladder to fill.

Front 4

bile in the gallbladder must be concentrated

Back 4

water and ions are reabsorbed by the interstitium

Front 5

release of bile is controlled

Back 5

by CCK and acetylcholine

Front 6

Most bile aids are reabsorbed by

Back 6

a secondary active process in the illeum

Front 7

bile acids are synthesized in the liver from

Back 7

cholesterol

Front 8

they have a side chain of 3-9 carbons

Back 8

ending in cooh groups, there are 4 main acids

Front 9

2 main bile acids

Back 9

cholic and chenodeoxycholic acid.

Front 10

in the gut bacteria dehydroxylate primary bile acids to

Back 10

in the lumen of the gut, bacteria dehydroxylate the primary bile
acids to deoxycholic and lithocholic acids.

Front 11

bile acids are returned to the liver through the portal system and are secreted

Back 11

back into bile

Front 12

Liver conjugates bile acids with glycine and taurine to lower their pKa
to about 3.7 and 1.5 respectively. WHY

Back 12

This increases bile acid solubility at the neutral pH of
the intestine.

Front 13

purpose of bile

Back 13

This increases the surface area of fatty acids and
facilitates digestion by lipases.

Front 14

Above a certain concentration, amphipaths form micelles
(40-70 A in diameter).

Back 14

This is known as the critical micellar concentration or CMC.

Front 15

Phospholipids - mainly lecithins.

Back 15

Account for 30-40% of organic composition of bile.
They become solubilized in micelles and facilitate bile acid formation of micelles

Front 16

Cholesterol - Bile is the primary excretory pathway for cholesterol (about 4% of bile
organics)...what if more cholesterol

Back 16

If there is more cholesterol than can be solubilized, the excess will form crystals,
which serve as nidus for gall stones.

Front 17

Bile Pigments - about 2% of organics. Bilirubin is a byproduct of hemoglobin
degradation.

Back 17

Bilirubin is insoluble so the liver conjugates it with glucuronic acid. Bilirubin is
secreted as the soluble salt, bilirubin glucuronide, which is not found in micelles

Front 18

Bile flows
toward the periphery of the organ, countercurrent to blood flow

Back 18

This minimizes the
concentration gradient between blood and bile, which increases the efficiency of bile
formation.

Front 19

bile canaliculi

Back 19

lie between adjacent hepatocytes

Front 20

while the illeum actively absorbs conjugted bile salts. the colon and jejunum

Back 20

passively absorb ionized unconjugated and conjugated bile salts

Front 21

Total bile acid pool in the body is about 2.5 g.

Back 21

about 15-30g day (recylced)

Front 22

The rate of BA synthesis is inversely proportional to the return of
BAs via the portal vein.

Back 22

Normally, 600 mg of BA are synthesized/day. Returning BAs are a
negative feedback on the rate limiting enzyme in BA synthesis from cholesterol. IMPORTANT

Front 23

bile active reabsorb is mediated through a

Back 23

Na+ gradient

Front 24

In the duodenum,
100% of BA are conjugated and fully dissociated. Therefore, they are charged and not
readily absorbed.

Back 24

SOLVED BY Intestinal bacteria deconjugate BA, increasing their lipid solubility 9
times. Bacteria also dehydroxylate BA increasing lipid solubility another 4 fold.

Front 25

The active reabsorption mechanism
positioned in the distal ileum insures that critical micelle concentration is maintained
throughout most of the intestine and that BA are not fully reabsorbed until all fatty acid
digestion products are absorbed.

Back 25

Almost all fatty acids are absorbed by the late jejunum.

Front 26

Some BA pass into the large intestine and are deconjugated/dehydroxylated by
bacteria.

Back 26

These may be passively reabsorbed or excreted in stool.

Front 27

Following extraction from the portal blood, primary and secondary BA are
reconjugated and some are rehydroxylated.

Back 27

IMPORTANT
A loss of excess BA into the colon leads to diarrhea. Excess BA in the colon
inhibits reabsorption of sodium and water.

Front 28

Phospholipids and cholesterol

Back 28

their mechanism of secretion by hepatocytes is
unclear but the quantities secreted are directly related to the secretion of BA.

Front 29

making Bilirubin -

Back 29

Hemoglobin is degraded by reticuloendothelial cells where porphyrin is
converted to bilirubin.

Front 30

Insoluble bilirubin is carried through the blood by albumin.

Back 30

yep

Front 31

Hepatocytes extract bilirubin from the blood

Back 31

and conjugate it with glucuronic acid, which increases the soluability of the bilirubin

Front 32

uptake of bilirubin

Back 32

Uptake is mediated by an active anion transport
mechanism that is different from BA uptake mechanisms.

Front 33

Failure to extract bilirubin from blood leads to jaundice.

Back 33

Most bilirubin glucuronide is
excreted with the feces and is not reabsorbed in the intestine.

Front 34

Some is unconjugated and
reduced to urobilinogen in the distal SI and colon. Some of this is reabsorbed.

Back 34

The liver
can extract some urobilinogen from the portal circulation. This occurs by active transport.

Front 35

However, some urobilinogen enters the systemic circulation and is filtered and not
reabsorbed by the kidney.

Back 35

It is excreted in urine.

Front 36

Urobilinogen is colorless

Back 36

but it can be
oxidized to urobilin and stercobilin, which are yellow pigments.

Front 37

The higher the rate
of return of BA through portal circulation

Back 37

the faster they are secreted into bile, the more
water and electrolytes follow, and the larger the volume of bile. they= water and electrolytes

Front 38

Bile ducts contribute to bile as pancreatic ducts contribute to pancreatic juice.

Back 38

Secretin stimulates secretion of HCO3 and water by duct cells. HCO3 concentration in bile
duct fluid can be 2-3X plasma.

Front 39

During interdigestive periods
gallbladder (GB) is flaccid and sphincter of oddi is closed. Bile flows into the GB.

Back 39

GB
capacity ranges between 20-60 ml.

Front 40

The GB can concentrate bile by
active reabsorption of Na, Cl, HCO3.

Back 40

h20 flows down this gradient

Front 41

In humans, the GB lumen is -8 mV indicating

Back 41

Na+ must be reabsorbed

Front 42

Bile remains isotonic with plasma despite the increase in organic concentration. How

Back 42

Bile salts,
cholesterol, phospholipids are present in osmotically inactive micelles. Since bile acids
are anions many inorganic cations are also bound to micelles and osmotically inactive.

Front 43

The gallbladder contracts
rhythmically and expels bile within 30
min of a meal.

Back 43

cck is main stimulus.CCK contracts the smooth
muscle of the GB and relaxes the
sphincter of Oddi.

Front 44

Bile secretion is
affected by duodenal contractions.

Back 44

It
enters in spurts when duodenum
relaxes and not at all when duodenum
contracts.

Front 45

Gallstones form when the organic materials stored in the gallbladder precipitate out of
solution.

Back 45

80% are cholesterol

Front 46

pigment stones

Back 46

Pigment stones result
from precipitation of unconjugated bilirubin and calcium.

Front 47

Native Americans have a genetic predisposition to secrete high levels
of cholesterol in bile.

Back 47

They have the highest rate of gallstones in the U.S. Most Native
American men have gallstones by the age of 60.

Front 48

Cholesterol-lowering drugs -

Back 48

These drugs raise the cholesterol level in bile,
increasing the risk for stone formation.

Front 49

Rapid weight loss

Back 49

As the body metabolizes fat during rapid weight loss, it
causes the liver to secrete extra cholesterol into bile.

Front 50

Fasting

Back 50

Fasting decreases gallbladder movement, causing the bile to become
overconcentrated with cholesterol.

Front 51

lictholic acid is a secondary bile acid and

Back 51

Lithocholic acid is an extremely toxic chemical that causes DNA strand
breaks and mutations. VITamin D prevents

Front 52

There is little or no affect of neural stimulation on bile production. and

Back 52

CCK and gastrin have no affect on bile production.

Front 53

butt cck and neural vagal

Back 53

cause contraction of gb