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Physiology > 3.6 Gastrointestinal Physiology > Flashcards

3.6 Gastrointestinal Physiology Flashcards

1
Q

What are the products or RBC destruction?

A

hemoglobin

1) globin= metabolized
2) heme= bilirubin + iron

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2
Q

where does bilirubin come from?

A

normally the spleen or liver from RBC destruction

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3
Q

is bilirubin glucuronide or free bilirubin more water soluble?

A

bilirubin glucuronide is more H2O soluble

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4
Q

what makes bilirubin glucuronide?

A

bilirubin + glucuronic acid

**oxidized glucose!!!

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5
Q

what is jeundice?

A

high concentration of bilirubin (when oxidized) causing the skin and eyes to look yellow

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6
Q

1) what is normal plasma bilirubin?
2) abnormal?
3) If abnormal, causes?

A

1) 0.5mg/ml= almost entirely free/unconjugated
2) up to 40mg/day= much can become the conjugated type
3) skin usually appears jaundiced (yellow) around 1.5 mg/dl

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7
Q

what are the two primary types of jaundice in adults?

A

1) hemolytic jaundice

2) obstruction jaundice

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8
Q

describe hemolytic jaundice

A

caused by increae in RBC destruction

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9
Q

describe obstruction jaundice

A

caused by damaged liver cells or obstructed bile ducts

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10
Q

measurement of plasma bilirubin level provides info regarding cause of jaundice… meaning?

A
  • high levels of UNconjugated bilirubin= hemolytic jaundice

* high levels of CONjugated bilirubin= obstructive jaundice

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11
Q

1) colon main secretion?

2) ions secreted?

A

1) mucus
2) K+ secreted with absorption of Na+
HCO3- secreted with absorption of Cl-

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12
Q

what are the major dietary nutrients?

A

carbohydrates
fats
proteins

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13
Q

carbohydrate digestion?

A

1/2 daily calory intake

  • 2/3 starch
  • 1/3 sucrose and lactose
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14
Q

carb digestion begins? continues? ends?

A
  • begins in mouth with salivary amylase (ptyalin)
  • continues in stomach INSIDE bolus (ptyalin)
  • ends in SI with pancreatic amylase and brush border enzymes
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15
Q

most of carb breakdown happens?

A

with pancreatic amylase (70%)

–30% with salivary

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16
Q

fats dietary intake?

A

1/3 daily caloric intake

*mostly triglycerides

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17
Q

fat or carb store more calories?

A

fat

*you can store twice as many calories per gram of fat than any other type of nutrient

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18
Q

where is fat digestion?

A

*begins in SI with pancreatic lipase

=triglyceride + lipase = monoglyceride + 2 fatty acids

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19
Q

protein dietary intake?

A

1/6 of daily caloric intake

*numerous kinds ingested and some secreted into GI tract

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20
Q

protein digestion happens where? with what enzyme?

A

BEGINS IN STOMACH and ends in SI via pepsin

*none in mouth

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21
Q

what is the only enzyme that adequately digests collagen?

A

pepsin

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22
Q

what three enzymes break down proteins?

A

trypsin, chymotrypsin and polypeptidases break down small proteins and polypeptides

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23
Q

what protein performs the final breakdown to AA?

how many?

A

BRUSH BORDER aminopeptidases

*20 different types

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24
Q

where is the bulk of water absorption?

not much water absorption where?

A

8 1/2 in SI!

  • more proximal= more absorption (duodenum best)
  • not much happens in stomach
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25
Q

breakdown of water absorption and the location

A
  1. 4 SI
  2. 4 prox colon
  3. 2 = feces
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26
Q

how much surface area available to absorption? WHY so much?

A

250 meters squared

BECAUSE MICROVILLI has VILLI on it

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27
Q

monosaccharides absorbed where?

A

SI

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28
Q

fructose absorption through?

A

facilitated diffusion

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29
Q

glucose and galactose abortion through?

how do they LEAVE?

A

secondary active transport coupled to Na+ in first 20% of SI

  • 2 Na+ binding sites; 1 sugar binding site
  • glu and galac are COMPETING
  • LEAVE epithelial cells via facilitated diffusion transporters in basolateral membranes
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30
Q

fat absorption?

A

micelles deliver lipids to surfaces in SI and release them

*DO NOT need special transport bc lipids DIFFUSE freely into intesinal epithelium (fat dissolves fat)

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31
Q

after diffusion into epithelium, what happens to fatty acids and monosaccharides?

A

re-synthesized into triglycerides in ER to maintain diffusion gradient for FA and MG to enter cell

32
Q

What is unique about newly re-synthesized into triglycerides in ER?

A

they are given a lipoprotein coat and called CHYLOMICRON

33
Q

what is a chylomicron?

A

a newly re-synthesized triglycerides in the ER that was given a protein coat

34
Q

what happens to chylomicrons once made? what is there path to blood?

A

1) diffuse out of the epithelial cell into the interstitium
2) then into lymphatic lecteals
3) lymphatics capillaries in intestinal villi
4) eventually into thoracic duct
5) into blood

35
Q

some of the short chain fatty acids diffuse out of the epithelial cells and directly into?

A

portal blood (not into chylomicrons in ER)

36
Q

proteins are absorbed in what form? How?

what mechanisms?

A

absorbed as AA via secondary active transport coupled to Na+ (but there are some Na_ independent processes)
**separate mechanisms for diff types of AA such as neutral, basic, acidic, proline, OH-proline

37
Q

AA are transported OUT of intestinal epithelial cells and into the blood via?

A

facilitated diffusion carrier protein in the basolateral membrane

38
Q

are intact proteins commonly absorbed?

A
  • very few absorbed in adults across intestinal epithelium
  • INFANTS have a greater absorptive capacity for intact proteins for getting antibodies from moms milk via passive immunity
39
Q

what mechanisms does water use to get absorbed?

A

osmosis. .. 80-90% in SI

* 0.5 to 1 L passed on to LI

40
Q

Requires energy to get Na in or out of the cell?

A

OUT =active transport

41
Q

what is the most abundant solute in chyme?

A

Na+

42
Q

What is the mechanism of transport to get Na+ in and out of cell?

A

considered active transport

  • passive diffusion INto mucosal cell thru lumenal membrane
  • active transport OUT basolateral membrane via Na+/K+ ATPase pump
43
Q

How is chloride like a “little brother”?

A

Cl- and HCO3- follow Na+ around

44
Q

How does Cl- and HCO3- cross membranes?

A

they follow electrochemical gradient estalished by the pumping of cations (aka Na+)

45
Q

How do we absorb K+?

A

1) we wait for Na+ to enter (and thenCl- and CHO3-) which is then followed by H2O. water dilutes conc and makes it more favorable for K+ to enter
2) Na+/K+ ATPase pump

46
Q

What vitamins are NOT absorbed in upper SI?

A

B12 and some Vit K

47
Q

What are the fat soluble vitamins?

How are they absorbed?

A

A D E K

  • solubilized in micelles
  • absorbed via same pathway as fat
  • interference with fat absorption = decrease in fat soluble vitamin absortion (ex: decrease panc enzymes or bile action)
48
Q

what vitamins are important for blood clotting?

A

calcium and K

49
Q

what vitamin is important for calcium absorption?

A

D

50
Q

what are water soluble vitamins?

A

thiamin, riboflavin, niacin, pyridoxine, pantothenate, biotin, ascorbic acid, folate, and vitamin B12

51
Q

what water soluble vitamins are absorbed via Na+ dependent contransporters?

A

thiamin, riboflavin, niacin, pyridoxine, pantothenate, biotin, ascorbic acid

52
Q

what water soluble vitamins are absorbed via Na+ INdependent contransporters?

A

folate

53
Q

what water soluble vitamins are absorbed via intrinsic factor?

A

vitamin B12

54
Q

what is Vit B12?

A

a large and charged molecule that binds to intrinsic factor (secreted by parietal cells in gastric glands)

55
Q

B12 is required for?

A

RBC formation

56
Q

what happens if you are deficient in B12 or intrinsic factor?

A

PERNICIOUS ANEMIA

*if no intrinsic factor then you must have injections of B12

57
Q

what determiens Ca absorption?

A

1) 30-80% of ingested Ca is absorbed depending on deficieny (increase) or excess (decrease) Ca++ found in body
2) Calcium is dependent on Vit D which makes Ca binding proteins in mucosal cells
3) Calcium active transport via Vit D dependent Ca++H+ ATPase pump

58
Q

What is an inhibitor of Ca absorption?

A

phosphate and phytates which form insoluble Ca++ compounds

59
Q

What are promoters of Ca++ absorption?

A

slight acidity and Ca+ binding proteins

60
Q

Ca++ facilitated diffusion from lumen mostly requires?

A

carrier protein such as IMCal (intestinal membrane calcium binding protein)

61
Q

Ca++ active absorption through basolateral membrane via a?

A

vitamin D-dependent pump (Ca++ ATPase)

62
Q

Fe++ absorption utilizes what carrier protein?

A

DMT1

63
Q

how much of absorbed Fe++ goes into blood?

A

10%

64
Q

Fe++ facilitated diffusion into mucosal cells, where most of it binds to?

A

apoferritin protein

65
Q

apoferritin VS ferritin?

A
  • apoferritin= ONLY protein

* Ferritin= protein AND iron complex for STORAGE

66
Q

what does ferritin do?

A

intracellular iron storage complex

67
Q

where is most Fe++ stores?

A

liver and intestine

68
Q

what happens to the small amount of Fe++ that does not bind to apoferritin?

A

it is actively transported out of the mucosal cells and into the blood, where it binds to the carrier protein called apotransferin and becomes transferin

69
Q

apotransferin vs transferin

A
  • apotransferin = ONLY protein

* transferin= protein AND iron complex that TRAVELS in the blood

70
Q

where is apotransferin found in significant amounts?

A

hepatocytes, where Fe++ binds with it and is stored as the compound ferritin (like in the intestinal epithelial cells)

71
Q

Fe++ is largely DEpendent on the saturation of?

A

protein

*when storage proteins and tranport proteins are saturated, absorption stops

72
Q

What does Vit D do?

A

1) promoate making of binding proteins in mucosal cells

2) making and activity of pumps that pump Ca+ outside the membrane into blood

73
Q

what is PTH?

A

a parathyroid hormone which activates vit D in kidney when Ca is LOW in the blood
*VERY IMPORTANT FOR REGULATING Ca+

74
Q

colon has active absorption of?

A

Na+ and Cl-

  • more proximal = more absorption
  • requires ATP because against conc gradient
75
Q

colon has passive absorption of?

A

water via osmosis

  • Vit K produced by intestinal bacteria (passive diffusion)
  • vit B12 (endocytosis, facilitated by intrinsic factor)78

Physiology (42 decks)

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