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GI 1 > Phys 3 > Flashcards

Phys 3 Flashcards

1
Q

how much bile does the liver produce?

A

up to 1L per day

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2
Q

what is bile production stimulated by?

A
  • secretin

- enterohepatic bile salt return

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3
Q

what is the function of bile?

A
  • elimination of wastes

- emulsification of intestinal lipids

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4
Q

what stimulates the intestinal hormone secretin?

A

acidic chyme in the duodenum

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5
Q

What are the actions of secretin on the stomach?

A

decrease gastric secretion and motility

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6
Q

what is the action of secretion on the liver?

A

bile production

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7
Q

what is the composition of bile?

A
  • 97% water
  • bile salts
  • electrolytes
  • FA
  • cholesterol
  • phospholipids
  • bilirubin
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8
Q

what is bile salt?

A
  • conjugated bile acid in deprotonated form (cations)
  • it is not excreted but returned to the liver
  • contain bile acids
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9
Q

bile acids

A
  • produced by normal flora
  • produced by cytochrome p450 mediated oxidation of cholesterol
  • insoluble unless congugated
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10
Q

what must bile acids be conjugated with in order to be soluble?

A
  • taurine or

- glycine

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11
Q

bilirubin

A
  • breakdown product of heme
  • released from splenic macrophages
  • congugated in liver to glucuronid which is more water soluble
  • eliminated in feces
  • some returns to liver
  • can also be eliminated in urine
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12
Q

gall bladder

A
  • thin walled muscular sac that lays in the ventral surface of the liver
  • functions to store and concentrate bile (up to 10X)
  • capacity: 30-40 mL
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13
Q

describe the route of the biliary tree

A
  • left and right hepatic ducts merge to form common hepatic duct
  • common hepatic duct and cystic duct merge to form common bile duct
  • common bile duct and main pancreatic duct merge at hepatopancreatic ampulla in duodenum
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14
Q

what are the 2 sources of gall bladder contraction and therefore bile release?

A
  • vagal stimulation (weakly)

- CCK (mainly)

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15
Q

CCK actions

A
  • gall bladder contraction
  • sphincter of Oddi relaxation
  • pancreatic secretions
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16
Q

what stimulates the action of CCK?

A

fatty chyme in the duodendum

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17
Q

What happens after bile is released into the duodenum?

A
  • it mixes w/ chyme and intestinal juices
  • bile salts emulsify fats for absorption
  • remainder of bile is eliminated in feces
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18
Q

monomer

A
  • monoshaccharides

- glucose, fructose, galactose

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19
Q

polymers

A
  • disaccharides

- lactose, maltose, sucrose

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20
Q

starches

A
  • glucose polymers
  • amylopectin
  • salivary amylase
  • pancreatic amylase
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21
Q

What is the important take away for digestion/absorption of carbohydrates?

A

there is an enzyme for each specific thing

i. e:
- lactose enzyme = lactase (SI)
- maltose enzyme = maltase (SI)
- sucrose enzyme = sucrase (SI)

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22
Q

Where does carb absorption occur?

A

along the length of the SI

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23
Q

In terms of carb absorption, what happens at the apical surface of SI cells?

A

-Glucose, galactose and fructose all move in to the cell

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24
Q

How are glucose and galactose transported into the epithelial cells along the SI?

  • name of transporter
  • type of transport
A
  • by SGLT-1
  • Na is high in the lume, moves along concentration gradient into cell
  • secondary active transport
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25
Q

How is fructose moved into the SI cells?

  • name of transporter
  • type of transport
A
  • GLUT-5

- facilitated transport

26
Q

In terms of carb absorption, what happens at the basal surface of cells in SI?

A
  • contents are transported to the interstitium

- use GLUT-2 transporter

27
Q

Where does protein digestion begin?

A

stomach

28
Q

Describe the beginning of protein digesting in the stomach

A
  • chief cells produce pepsinogen (prohormone)

- low pH activates pepsinogen to pepsin which releases polypeptides

29
Q

What is the function of the polypeptides released by pepsin in protein absorption?

A
  • enteropeptidase activates trypsinogen to trypsin
  • trypsin activates pancreatic carboxypeptidases at SI brush border
  • trypsin activates chymotrypsinogen to chymotrypsin
30
Q

What are the structures when peptides are further broken down into “smaller chunks”

A

oligopeptides

31
Q

What works on the oligopeptides?

A

brush border enzymes (SI)

32
Q

brush border enzymes from the SI:

A
  • aminopeptidase
  • dipeptidase
  • tri and di monomers released
33
Q

Describe the physiology of trimer and monomer digestion/absorption

A

trimer:
-through PepT1 proton cotransporter
-cytosolic preteases release aa
monomer:
-aa-Na cotransporters
-duodenum and jejunum distribution

34
Q

How does infantile protein absorption occur?

A

by endocytosis d/t immaturity of intestinal mucosa

35
Q

How are nucleic acids digested down after ingesting them?

A
  • into pentose sugars
  • nitrogenous bases
  • phosphate ions
  • all done by nucleases
36
Q

What are the nucleases that digest nucleic acids?

A
  • pancreatic nucleases: RNA and DNA nucleotides

- intestinal mucosa nucleases

37
Q

what happens to the pentoses and bases during nucleic acid absorption

A
  • pentoses absorbed w/ other sugars

- bases absorbed by active transport

38
Q

Where does most lipid digestion occur?

A

duodenum

39
Q

lipid digestion by lipase

A
  • TG digested to 2 FFA + monoglyceride

- use lingual, gastric and pancreatic lipases

40
Q

What is the function of cholesterol esterase?

A

-hydrolyze cholesterol esters

41
Q

What does cholesterol esterification do to the cholesterol?

A

increases hydrophobicity

42
Q

Function of bile salts in terms of lipid digestion/absorption

A

to emulsify lipid droplets which organizes them into micelles

43
Q

What all lipids can diffuse across the brush border membrane? (4)

A
  • FFA
  • monoglycerides
  • cholesterol
  • fat-soluble vitamins
44
Q

chylomicron

A

-lipoprotein composed of TG, FFA, chol, and vitamins

45
Q

Where does chylomicron formation occur?

A

golgi

46
Q

Explain the path of the chylomicron

A
  • extruded from basal membrane
  • enters lacteal
  • travels vis lymph system to enter venous circulation at the thoracic duct
47
Q

What are the fat soluble vitamins?

A
  • AKED

- are absorbed w/ lipids

48
Q

Where are water soluble vitamins absorbed?

A

in the upper SI by diffusion

49
Q

absorption of vitamin B12

A

-binds to intrinsic factor
which is produced by gastric parietal cells
-absorbed in the ileum

50
Q

absorption of K and B vitamins

A
  • produced by normal flora

- absorbed in the colon

51
Q

What is the source of electrolytes?

A
  • foods

- GI secretion

52
Q

cation and anion digestion/absorption

A

cations:
- Na: cotransported w/ glc and aa
- K: dimple diffusion; absorbed in SI, secreted in LI
anions:
- Cl
- HCO3
- both follow electrochemical gradients

53
Q

What is the cofactor for Ca absoprtion

A

vitamin D

54
Q

What happens if there is a decrease in blood Ca?

A
  • parathyroid gland secrete parathyroid hormone
  • stimulates bone to release Ca
  • increases kidney reabsorption of Ca
  • increases renal activation of vit. D increasing intestinal absorption
55
Q

What are our sources of iron

A
  • heme iron from hgb and myoglobin (only 10-15% but higher bioavailability)
  • non heme iron from cereals, veggies, fruits etc
56
Q

how is iron absorbed?

A
  • ferric reductase enzyme on brush border reduced ferric to Fe2+
  • DMT1 transporter actively transports divalent metals into enterocyte
  • binds to ferritin = mucosal iron barrier
57
Q

What happens when Fe is needed?

A

it is absorbed and carried by transferrin

58
Q

What happens when Fe amount is adequate?

A

it is sloughed off and eliminated

59
Q

How much fluid enters the intestine daily? And what is the breakdown?

A

about 10 L

  • 8 L secreted
  • 1-1.5 as saliva
  • 2-3 by stomach
  • 1 as bile
  • 1 as pancreatic secretions
  • 2 secreted by SI
60
Q

How much fluid makes it to the colon?

A
  • about 1 L

- 90% is absorbed across the SI epithelium

61
Q

how much fluid is lost in feces daily?

A
  • about 150 mL

- the rest is absorbed by colon

62
Q

intestinal absorption of water

A
  • passive process

- requires movement of solutes

GI 1 (16 decks)

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