digestive system lecture 8 Flashcards

1
Q

What do you need in addition to pancreatic lipase to break down triglycerides into fatty acids?

A
  • you need colipase that is made from pro-colipase that is broken down by trypsin
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2
Q

What is the liver?
What are its 4 main functions?

A

Largest gland of the body
Functions: Storage, synthesis, detoxification, metabolism

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3
Q

where does the liver secrete bile from?
Where does bile travel in?
Where is bile released?

A

Secretes bile from hepatic ducts
-bile travels in the common bile duct
-bile is released into the SI at the same location as pancreatic juice

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4
Q

What is the liver bile volume per day?
What type of fluid is it?
What is its pH, what does it neutralize?

A

Volume: 0.5 –1.0 liters/day
ISOTONIC FLUID: Na+, K+, Cl-, HCO3-
-pH: 7.8 – 8.2, Helps neutralize acidic chyme

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5
Q

How much do solids compose in the liver bile?
What are the 4 components of bile?

A

SOLIDS ~3%but no digestive enzymes
-Bile Acids (Bile Salts)
Bile Pigments (hemoglobulin breakdown products, gives blood/feces its color)
Cholesterol
Phospholipids

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6
Q

What is bile secretion like in the liver vs the entrance into the duodenum?
How much does the liver release per day?
How much enters the SI?

A

Bile secretion by the liver is continuous.
The liver releases about 0.5 – 1.0 liter/day.
Entrance of bile into duodenum is intermittent and the volume of bile entering the small intestine is < 500-70

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7
Q

How much space does the gallbladder have?
What does the gallbladder do to get around its low storage space?

A

it has 50-100mL of space
Concentrates Solids :
-Hepatic Bile 3%
-Gall Bladder Bile 10 – 20% (gallbladder concentrates solids)
-Viscosity Increases

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8
Q

What is the pH of hepatic bile and the gallbladder bile?

A

Reduces pH
Hepatic Bile 7.8 – 8.2
Gall Bladder Bile 7.0 – 7.5

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9
Q

WHat is the role of the gallbladder?
What does CCK do?

A

Gall Bladder does NOT synthesize, Bile Salts – it stores and concentrates them
-CCK also causes gallbladder concentration, allowing more concentrated bile salts

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10
Q

What can block call bladder duct?
What can be done to fix it?

A

gallstones can block the duct
-cholecystectomy is gallbladder removal

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11
Q

What do bile salts do?
Where are they synthesized?
What do bile salts facilitate?

A

-they reduce surface tension of lipid droplets so they can be acted upon by lipase
-are synthesized in the liver from CHOLESTEROL
- facilitate digestion, transport, and absorption of FAT (including cholesterol) by forming water-soluble complexes with the fats

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12
Q

What do bile salts faciliate the transport and absorption of?
WHat do they reduce/stabilize?

A
  • facilitate transport and absorption of fat-soluble vitamins (A, D, E, K)
  • reduce surface tension and stabilize emulsions
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13
Q

What do bile salts form and which side is facing inwards/out?
What is charcteristics of bile salt?

A

an aggregation of bile salts forms a micelle which has non polar surface facing in, and outward surface is polar
-they are amphipaths

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14
Q

WHat is a mixed micelle?

A

when fats are incorportated in micelles

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15
Q

What happens with the more bile salts that you add?

A

-the more you add the smaller the lipid molecules you will have
-it allows easier breakdown

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16
Q

What is the bile salt pool in grams?
What is the dailt synthesis and daily release into intestine?

A

Bile Salt Pool: 3.5 g
Daily synthesis: 0.5 g
Daily release into intestine: 15 – 20 g

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17
Q

Where are most bile salts reabsorbed and returned?
Where is the entire bile pool recirculated?

A

Most Bile Salt is reabsorbed into the portal blood and returned to the liver via Enterohepatic Circulation (EHC)
-The entire Bile Salt pool is recirculated several times a day between the Liver → GIT → Liver

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18
Q

What is the hepatic circulation path?

A

spincte of oddi to liver
then heart sends blood to the liver for nutrients (via the aorta)
-then heart sends blood via the aorta to the intestinal tract (SI)

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19
Q

What is the path of venous retunr in hepatic circulation?

A

-liver via the hepatic vein to inferior vena cava to heart
-then Hepatic portal vein from
intestinal tract to liver

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20
Q

What pathway is bile reabsorbed through?

A

enterohepatic circulation (EHC)

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21
Q

What are the intraportal functions of bile salts?
What type of feedback?

A

Regulate hepatic bile flow - the more Bile Salt returned via portal blood, the larger the volume of bile secreted
-positive feedback

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22
Q

What are the intrapotal functions of bile salts when new bile salts are synthesized?
What type of feedback?
What happens to bile salt synthesis if we remove the ileum?

A

Regulate the synthesis of NEW Bile Salts
- the more Bile Salt returned in Portal Blood, the smaller the amount of NEW Bile Salt being synthesized
-negative feedback
-bile salt synthesis increases

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23
Q

What is the intrahepatic function of bile salts?
What happens if cholesterol precipitates?

A

Keep cholesterol in solution ;Cholesterol is insoluble in water
-In bile, solubility of cholesterol is increased by 2 x 10^6
-it may give rise to GALLSTONES

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24
Q

What are the Intraintestinal Functions of Bile Salts, what does the lumen contain?

A

-Intestinal lumen contains a watery medium
-need fat to be in mixed micelle so they can be brokem up

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25
Q

What are the 2 intraintestinal functions of bile salts?
What would happen if we did not have bile salts?

A

1.Act as detergents and help form stable emulsions
2. Assist in the transport of fat and fat-soluble vitamins A,D,E,K from SI lumen into intestinal cell
-without bile salts fat would be secreted in feces

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26
Q

What are the 2 intracolonic functions of bile salts?
What happens when we have too much bile salt vs too little?
What does colon absorb?

A

Inhibit Na+ transport and H2O absorption
Excess Bile Salt in colon —>Diarrhea, too little can cause constipaiton
-colon absorbed water+ions but not nutrients

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27
Q

What are the intraportal and intrahepatic functions of bile salts?
What do they regulate/keep?

A

Intraportal – regulate volume of bile secreted by liver
– regulate synthesis of new bile salts
Intrahepatic – keep cholesterol in solution

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28
Q

What are the intraintestinal and intracolonic functions of bile salts?

A

Intraintestinal (SI) – emulsify & transport fats
Intracolonic – prevent too much water absorption

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29
Q

How are secertions regulated in the small intestine and liver?
What are the 3 phases of secretion?

A

-they are regulated by neuronal and hormonal inputs
-cephalic:pyschic and gustatory
-gastric
-intestinal

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30
Q

What does the pancrease contain cells that release what?

A

A large volume of juice rich in HCO3-
* A small volume of juice rich in enzymes (for protein/fat rich meal)

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31
Q

What are choleretics and cholagogues?
WHat is law of reciprocal activity?

A

CHOLERETICS – agents which cause the liver to secrete a larger volume of bile
CHOLAGOGUES – agents which cause an increase Gall Bladder emptying
-If the Gall Bladder is contracted the Sphincter of Oddi will be relaxed and vice versa

32
Q

What happens to the liver, GB, and pancreas when there is vagus (cephalic) input)

A

liver as minimal secretion
-GB highly contracts and spincter relaxes
-pancrease secretes low volume/high enzyme/low pH fluid

33
Q

What happens to the liver, GB, and pancreas when there is gastrin released?

A

it does not affect much in terms of secretion levels, everything secretes/is active slightly

34
Q

What happens to the liver, GB, and pancreas when there is CCK secretion?
When is it released?

A

liver secretion is inhibted
-high contraction of GB
-has high enzymatic secretion but inhibts the high pH secretion
-released when we have a protein/fat rich meal

35
Q

What happens to the liver, GB, and pancreas when there is secretin released/?
When is it usaully reelased?

A

-liver is is active and more bicarb rich
-inhibition of GB contraction and low pH secretion
-high amount of alkaline secretion
-released when we have acidic contents in SI

36
Q

What happens to the liver, GB, and pancreas when there is bile salt secretion?

A

there is increase liver secretion and everything else is inhibited/no secreting

37
Q

What is the final result of polysaccharides break down?

A

-Polysaccharides—> (broken down by Salivary and pancreatic amylase) Disaccharides—->Monosaccharide

38
Q

What is final result of protein breakdown?

A

Proteins—> (broken down by pepsin, trypsin, chymotrypsin) Small Peptides—>Amino acids, Di, tripeptides

39
Q

What is final result of fat breakdown?

A

-Fats —> (broken down by lipase, colipase, bile salts)–>Mono, Diglycerides, FAs

40
Q

What are final steps in digestion mediated by, what do they produce?

A

Final steps in digestion mediated by intestinal enzymes produced by mucosa at the site where absorption will take place

41
Q

What are the 3 main activities of GIT function?

A
42
Q

What does the small intestine secrete?
What does it receive?
What does it contain, what are these attached to?

A

Secretes intestinal juice
* Water
* Mucus
* Ions
-Receives pancreatic juice enzymes to aid digestion
-Contains brush border enzymes: Attached to the microvilli of SI epithelial cells

43
Q

What type of digestion does the SI help with?
What does it absorb?

A

-Mechanical digestion
Involves segmentation
-Chemical digestion
Occurs as chyme mixes with pancreatic juice, intestinal juice and bile
-Absorption of digested nutrients

44
Q

What do the tubular glands increase in the stomach?

A

increase SA for stomach secretion

45
Q

What are the absorptive cells in the SI?

A

villi and enterocytees are the absorptive cells of the SI

46
Q

What do crypt cells lack and secrete?

A

-Crypt Cells lack digestive enzymes but secrete a large volume (3 liters/day) of alkaline fluid known as Succus Entericus

47
Q

What are the secretions in the SI?
the amount?
What type of fluid is it and the pH?
What do villi not secrete?

A

crypts—>succus entericus
Volume: ~ 3 liters/day
ISOTONIC: Na+, K+, Cl-, HCO3-
-pH: ~7.5 - 9
-fluid

48
Q

What do the villi cells do?
What do enterocytes in villi do?

A

do NOT secrete fluid, but complete digestion and absorb nutrients and fluids
-they Synthesize Digestive Enzymes which remain in the brush border

49
Q

What are the SI enzymes?

A

-Enterokinase (lumen)
-Amylase
-Lipase
-Aminopeptidases
-Dipeptidases

50
Q

What are the 4 SI dissarcharides?

A

-Sucrase
-Maltase
-Isomaltase
-Lactase

51
Q

where do new cells migrate in the SI?
WHere do the old cells go?

A

-new cells migrate up into microvilli
-old cells slough off and get recycled into lumen

52
Q

What is the villi cells turnover time?
What happens in the crypt region vs the villus region?

A

-turnover=3-5 days
-crypt region=cells mature as they migrate up to the villus regions
-villus region-cells tip apoptose and slough off into lumen

53
Q

lumen of the small intestine anatomy

A
54
Q

What are fats absorbed via?
Where are carbs and sugars absorbed?
What will flow of bloodblow be after a meal?
Where are fats from chylomicron absorbed?

A

Fats absorbed via the lacteals
-via the capillary
-very rapid flow after ingesting a meal
-at level of lacteal

55
Q

What is the volume of colonic secretion?
-What are the secretions?
What is mucin important for?

A

Small Volume
- Alkaline [HCO3] = 100-150 mEq/L
[K+] = 100-150 mEq/L
- Mucin (Lots!!!) (imp for lubricating colon)

56
Q

What does the colon not have/do?
What is there lots of in the colon?
What helps keep it in the colon

A

NO Digestive Enzymes
NO Absorption of Nutrients
-bacterial activity, MMC (migrating motor complex) helps keep bacteria in the colon

57
Q

What are the 3 reflexes that regulate intestinal secretions?

A

Local enteric reflexes
- Vago-vagal reflexes
- Hormonal factors

58
Q

What is the composition of the solids excreted daily, and the amount?

A

solids 50g, h2O 100mL
-30% bacteria
30% undigested fiber
10-20% lipids
10-20% inorganic matter

59
Q

How many liters of fluids are secreted, and how many are reabsorbed?

A

-2 liters ingested +fluids entering GIT=7 liter secreted
-9 liters must be reabsorbed in the lume of GIT

60
Q

What is daily secretion of salivary gland.
stomach, bile, pancrease, and intestine

A

-salivary gland=1500mL
-stomach=2500
-bile=500
pancreas=1500mL
intestine=1000mL

61
Q

What is also reabsorbed from lument of GIT?
What is the composition of protein released into GIT?
What is processed by intestine?

A

water and Very large quantities of ions
-50g as enzymes+30g as cells=80g protein
-lots of amino acids

62
Q

What are the sites of exchange characterized by?

A
  1. Very large surface area of Small Intestine
  2. Intimate contact with blood vessels
63
Q

How much do the circular folds, volli and microvilli increase SA of SI by?
What is the only organ essential to life
What can hypertophy lead to?

A

ciccular folds=3x
villi=30x
microvilli=600x
-Only SI organ essential to life (colon cant take over)
-hypertrophy of SI can increase SA

64
Q

What is the postparandial flow to intestine?
What does each villus have for efficient absorption
What is the lymph flow?
What does each enterocyte have?

A

-1-2 liters/minute
Each villus has a capillary loop and lacteal
Large surface area close to blood and lymph flow
-Lymph Flow 1-2 ml/minut
-each enterocyte has capillary network

65
Q

What are the major areas of absorption, what absorbs iron/Ca2+, CHo, protein/lipids and vitmin b12 and bile acids

A

duodenum has high level of absorpiton effciency for iron/ca2+, CHO, protein, lipids and na+, h2O
-ileum absorbs mainly vitamin b12 and bile acids

66
Q

What are the 5 main methods of diffusion/transport in which absorption takes place?

A

Simple Diffusion
Facilitated Diffusion
Active Transport
Pinocytosis
Osmosis – water always follows the osmotic gradient generated by the movement of ions and nutrients

67
Q

What are the 4 requirments for absorption?
What do we need adequeate amounts of

A

Adequate Digestion – Enzymes (activated), optimal pH and ionic composition
Adequate Sites for Absorption
Adequate Transit Time for Absorption
Adequate Co-factors, Transporters

68
Q

What amount is absorbed in SI and colon?

A

7 liter in SI and 2 liters in colon

69
Q

What is the maximum capacity for water absopriton per say in SI and colon

A

SI: Maximum capacity 15 liters/day
colon: Maximum capacity 4-5 liters/day

70
Q

What percent of carbs are digested/absorbed/

A

6% lactose
60% starch
30% sucrose

71
Q

What is the protein digestion and absorption per day?

A

35-200 grams per day

72
Q

What is the amount of carbs, fat and protein absorbed in GIT in percent
WHy is there a high efficiency?

A

CARBOHYDRATE 99%
FAT 95%
PROTEIN 92%
High efficiency due to effectivev coordination of activities
- neural, hormonal, motor, secretory, enzymatic -within an organ and between organs

73
Q

What is the fat digestion and absorption photo

A
74
Q

What happens to the waves in response to a meal?
What is closed in absence of meal?

A

-A wave of secretory activity, preceding, accompanying, and trailing behind meal
-A wave of motor activity which receives, accommodates, and conveys meal
-spincter is closed in meal absence

75
Q

What are the different transit times in the mouth, throat, stomach, large intesttin, colon?

A
76
Q

What are the first 3 protective mechanisms in GIT?

A

Mucin
* Inactive Proteases, Trypsin Inhibitor
* Gastric Mucosal Barrier

77
Q

What are the last 4 protective GIT mechanims?

A

Sphincters prevent reflux
* Negative Feedback Inhibition of Gastrin
* Neutralization of duodenal contents
* Myogenic Motor Complex = “HOUSEKEEPiING