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Physiology Renal ABS 2018 > Digestion and Absorption > Flashcards

Digestion and Absorption Flashcards

1
Q

Where does the final digestion of proteins and carbs take place?

A

Brush border of villus of small intestine via brush border enzymes
-you can not use carbs or proteins without this final digestion

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2
Q

What are the cells of the small intestine?

A

small intestine is 1-cell thick , enterocyte

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3
Q

What is the importance of the villous lining the small intestine?

A
  1. Major absorption

2. Buffer secretions

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4
Q

What part of the villous lining is associated with the glycocalyx?

A

brush border

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5
Q

What part of the villous lining is responsible for the secretion of buffers?

A

crypts of lierberkun

via CTFR, chloride channel, secretes mucous & Cl-; (Na+&H20 follow) into lumen to buffer acidic chyme

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6
Q

What form are majority of carbs ingested in?

A
  1. Starch

2. Dissacharides (2)

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7
Q

What are the 2 main types of dissacharides ingested?

A
  1. sucrose-(glc&fru)
    - table sugar
  2. lactose-(glc&gal)
    - milk sugar
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8
Q

What are the 4 brush border enzymes? and there resultant monosaccharides?

A 
1. Isomaltase- 
(2 glc)
2. Sucrase-
(glc + fru)
3. Maltase
(2 glc)
4. Lactase
(glc + gal)
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9
Q

What is the major difference in simple sugars and starch digestion?

A

when digestion takes place
simple sugars are already in dissacharide form, so they go straight to BB enzymes of villous

Starch digestion begins in the mouth
via salivary amlylase—-broken down to Maltose&isomaltose —further broken down in duodenum by pancreatic alpha amylase—same form—jejunum

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10
Q

What are the 3 monosaccharides that can be absorbed by blood?

A
  1. Glc
  2. Gla
  3. Fru
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11
Q

How much of starch is broken down by pancreatic alpha amylase?

A

70%

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12
Q

What are the complications undigested glucose can cause in digestive tract?

A

Glucose is an osmotic agent,

  1. It will pull water down the digestive tract, can cause diarrhea
  2. Bacteria within the tract feed on the undigested sugars and makes gases, fatty acids causing cramps and
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13
Q

A patient presents with lactose intolerance? What are her symptoms and her pathophysiology?

A

-Not enough lactase, lactose only partially broken down, undigested lactose moves down the tract pulling water–diarrhea—gas and cramping

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14
Q

What 2 mechanism do monosaccharides employ for movement into lumen?

A
  1. Sglt-1 glc/gal: Na+/glc or gal secondary active transport

2. Glut-5-fruc carrier

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15
Q

What is special feature of the glucose transporters in the intestinal tract regrading insulin?

A

Insulin-independent

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16
Q

What happens when glucose gets to liver?

A
  • Moves into the blood
  • Storage as glycogen
  • glucose metabolism
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17
Q

If we need more glucose how will the liver compensate ?

A
  1. Glucogenesis

2. Glycogenolysis

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18
Q

Where do protein digestion begin?

A

stomach

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19
Q

What enzyme digest protein in stomach? What % are digested pre-duodenally?

A

Pespin
*it secreted as pespinogen and cleaved to active form by HCl in stomach
25%

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20
Q

What enzyme continues protein digestion in the duodenum? What % occurs post-duodenally?

A

Pancreatic proteases

  • cleavage to active form by trypsin
  • 70%
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21
Q

What mechanism of protein digestion?

A

Break down first 25-30% of protein-oligo-peptides in the intestinal lumen—pancreatic enzymes break down the rest of protein into oligopeptides— brush border enzymes terminally digest oligopeptides to —-di+tripeptides (these must be further broken down via cytoplasmic peptidase) & amino acids(most)—only amino acid move out of cell into liver

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22
Q

What stimulates pancreatic enzymes?

A

CCK

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23
Q

What stimulates pancreatic and intestinal buffers ?

A

Secretin

24
Q

What activates trypsinogen to trypsin?

A

enterokinase

25
Q

What are the 4 pancreatic proteases?

A
  1. Trypsinogen
  2. Chymotrypsinogen
  3. Pro-Elastase
  4. Co-lipase
26
Q

Where is pepsin secreted?

A

Chief cells

27
Q

Where is gastrin secreted ?

A
  1. antrum of stomach

2. duodenum

28
Q

What mechanism compensates for extra protein digestion?

A

break amino acid into ammonium ions that make form urea and is excreted by kidneys

29
Q

What are the 2 fates of amino acids once transported liver?

A
  1. Synthesis of 90% plasma proteins

2. Urea

30
Q

Where does lipid digestion begin?

A

mouth-lingual lipase

31
Q

What is the pathway for lipid digestion?

A

Mouth (lipid lipase -hydrolysis lipid)–stomach (gastric lipase-hydrolyisis lipid)—lipid is further digested in small intestine —in duodenum mixed with bile and emulsified—in jejunum the micelle is formed–transport lipids through unstirred water layer–Lipids diffuse through the enterocyte membrane, —-enter the SER, and are re-esterified with FFAs into TGs, PLs, and cholesterol—-these fat forms combine to form chylomicron(too big)—exocytosis lacteals—thoracic duct —subclavian vein–systemic circulation(heart, aorta, celiac trunk, common hepatic, hepatic artery) —lipid metabolism–formation of lipoprotein (vl,hd&ld), steroid hormones and shuttle them to there respective locations

32
Q

What are chylomicron?

A

combination of digested fats ready for lipid metabolism

33
Q

What is the main function of lipoproteins?

A

serve as shuttle for proteins and lipids through the blood to there functional location

34
Q

How does terminal illeum recycle bile?What is terminal illleum?

A

terminal illeum recycling recycles 90% of primary bile back to liver and it needs transporters to do so! (10% bile(containing cholesterol, bilirubin) secreted into feces)
Na+ via secondary active transport
–Na+/conjugated bile acid& unconjugated—portal blood —liver

35
Q

What 2 dissacharides yield the most glucose?

A
  1. Maltose

2. Isomaltose

36
Q

Where in the small intestine does the emulsification fats happen?

A

duodenum

37
Q

Where does micelle formation and fat absorption occur?

A

jejunum

38
Q

If a patient has been advised to fast for testing? What immediate indication can you use to make sure patient has been compliant?

A

Draw blood
Spin it down
*if you see large amounts of yellowish globs floating on top, these are chylomicrons—he has eaten within past several hours

39
Q

What 3 things happens when chyme leaves the duodenum?

A
  1. Decrease in CCK
  2. Decrease in Vagus stimulation
  3. Closure of sphincter of oddi
40
Q

What mechanism is employed to absorp water back into ECF?

A
  1. Primarily in jejunum and illeum
    Na+/H+&HCO3+/Cl and brings Cl & Na into cell and secretes H+ & HCO3 into lumen —-HCO3 +H—H2CO3— CO2 +H20—diffuses across into the ECF
  2. Colon
41
Q

What 2 factors affect the amount of the water in your feces?

A
  1. Bile

2. Fiber

42
Q

What is the importance of fiber in the colon?

A

Fiber helps promote efficient/increased motility of feces through the colon

43
Q

What factor can cause constipation?

A

feces sitting in colon for long amounts of time
*the longer the feces sit in colon, the more water is being absorbed causing constipation–which can lead to hemmorhoids and polyp formation(i.e colon cancer)

44
Q

How is iron transporter through body?

A

iron is always bound absorbed

There is no free iron in the body, it has to be bound

45
Q

What is the mechansims of B12 absorption?

A

In the mouth, transcobalamin-1 bind B-12 protecting it from digestive enzymes—parietal cells of the stomach secrete intrinsic factor to protect B12 from pancreatic protease —B12/IF bind form dimer

B12/IF dimer binds receptors on cells at the terminal ileum, —-internalized, and then the B12 exits into the blood and is bound to transcobalamin II, for transport to the liver or bone marrow.

46
Q

What is transferrin ?

A

blood bound iron

*there is no free iron

47
Q

How is iron lost daily?

A

loss of iron containing ferritin storages when epithelial cells slough off every 5 days, but this is balanced by iron intake.

48
Q

What are the two fates of iron bound to trasferrin n the blood?

A
  1. liver-storage

2. bone marrow for rbc production

49
Q

How is calcium absorped in small intestine?

A

Vitamin D 3 will increase amount of calbindin in cell—-increase Ca move from lumen into cell—Ca moves out into blood via Ca ATPase and Na/Ca anti-porters

50
Q

What is the importance of calbindin ?

A

Calmodulin binds Ca in cell to prevent secondary messenger cascades

51
Q

What two secretions come from stomach parietal cells?

A
  1. HCl

2. Intrinsic Factor

52
Q

What are the 2 fates of B12?

A
  1. Liver for storage

2. Bone marrow

53
Q

How is chyme dehydrated to feces?

A

Electrolytes and water absorbed as chyme moves through colon
Poor motility, cause more water and electrolytes to
be resorped from feces, constipation
High motility-diarrhea

54
Q

What secretes secretin? Function?

A

crypts of lieberkuhn via the CTFR protein
Secretes Cl- into the lumen which causes Na & Cl and water to move into lumen

Stimulates HCO3 secretion from exocrine of pancreas

together make buffer for incoming chyme

55
Q

What are the 3 possible causes of diarrhea?

A
  1. Bacterial Infection
  2. Irritation
  3. Osmotic agents

Physiology Renal ABS 2018 (5 decks)

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