GI Deck 2 Flashcards

(40 cards)

1
Q

2 forms of primary regulation of colon

A
  • local reflexes- activated by bolus, secrete Cl & fluid

- long reflexes- gastrocolic & orthocolic

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2
Q

what do enteroendorine cells secrete? what is the nickname for this molecule? what does it respond to?

A

PYY; ileal break; fat in terminal ileum

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3
Q

what two structures provide colonic motility? what type of muscle are they and what is the duration of their contractions?

A

haustra- circular muscle- short

taeniae coli- 3 layers of longitudinal muscle- long

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4
Q

what kind of stimulation enhances motility?

A

parasympathetic

  • vagal in haustra, cecum, ascending & transverse colon
  • pelvic nerves is descending, sigmoid colon, rectum and anus
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5
Q

what is an important product of colonic bacteria? what is it cotransported with?

A

SCFAs (short chain fatty acids)

cotransported with sodium using SMCTs

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6
Q

how is sodium absorbed in the distal colon? what is this known to be?

A

using ENaCs (epithelial sodium channels); is final defense mechanism for the absorption of water

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7
Q

what kind of muscle is in the rectum?

A

only longitudinal for storage (no circular for motility)

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8
Q

what kind of muscle is present in the anus?

A

smooth and skeletal (VOLUNTARY!!) muscle

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9
Q

filling of the rectum _____ the internal anal sphincter

A

relaxes

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10
Q

where does the majority of blood to the liver come from?

A
  • 70-80% is venous from portal vein
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11
Q

what is the major cell type in the liver and what are some of it’s important functions?

A

hepatocytes- metabolize major nutrients, are the origin for the biliary system (make bile acid)

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12
Q

what are HsCs in the context of the liver?

A

hepatic stellate cells- normally inactivated, serve as a storage site for vitamins; over-activation causes them to produce collagen (BAD)

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13
Q

what are sinusoids?

A

low resistance liver capillaries which can be collapsed during fasting, and expanded with flow

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14
Q

what is the portal triad

A

portal vein, hepatic artery, bile duct

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15
Q

what are zone 1 hepatocytes?

A
  • periportal
  • closest to triad
  • receive max nutrients and O2
  • affected by ischemia last
  • see virus/toxins first
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16
Q

what are zone 3 hepatocytes?

A
  • pericentric
  • closest to central vein
  • die first with ischemia
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17
Q

what are the cells that line the bile duct and modify bile called

A

cholangiocytes

18
Q

what are canaliculi?

A

adjacent hepatocytes form canals for biles

19
Q

why is carbohydrate metabolism important in liver?

A
  • has role in gluconeogenesis (sugar-glucose)

- if backed up, can cause hyperglycemia (stores glucose it produces)

20
Q

4 important functions of protein metabolism in liver

A
  • non-essential AAs
  • plasma proteins (albumins & clotting)
  • ammonia- urea
  • maintains oncotic pressure with albumin
21
Q

what are kupffer cells?

A

macrophages in sinusoids

22
Q

bile is a byproduct of ________ metabolism; what are the two types of primary bile acids?

A

cholesterol

- cholic acid, chenodeoxycholic acid

23
Q

What are secondary bile acids?

A

primary bile acids enter colon and are dehydroxylated by colonic bacterial enzymes

24
Q

T/F Primary and secondary bile acids are conjugated, making them more water soluble

A

TRUE- known as bile salts when ionized due to high pH of intestine

25
what are primary and secondary bile acids conjugated with?
glycine or taurine
26
T/F Conjugated bile acids are reabsorbed passively in colonic epithleium
False- UNconjugated forms are reabsorbed
27
Is bile acidic?
no- alkaline, due to CFTR Cl- channels and HCO3- exchange
28
what is bile outflow blocked by in between meals?
sphincter of oddi
29
what is enterohepatic circulation?
the recycling of bile from intestine to liver using ASBTs
30
where does bilirubin come from? is it soluble?
breakdown of heme when unconjugated is very un-soluble binds to albumin for transport
31
where is bilirubin taken up and by what; is it unconjugated or conjugated
liver by OATP | is unconjugated
32
What is UGT?
- UPD glucuronyl transferase; enzyme that conjugates bilirubin; lacking in newborns
33
where does bilirubin go after the liver?
1) excreted in urine OR 2) added to bile, deconjugated and converted to urobilogen by bacteria - can be absorbed via enterohepatic circulation - excreted in feces
34
two causes of high unconjugated bilirubin in blood
1) oversupply of heme, eventually overwhelms liver | 2) problem with UGT
35
two causes of high conjugated bilirubin in urine
1) defect in the transporter that secretes conjugated bilirubin into the bile 2) blockage of bile flow
36
what is the major source of urea for the urea cycle?
colonic bacteria (also have protein catabolism)
37
where does the urea cycle take place?
hepatocyte
38
what is the major stimulus for bile secretion? what are the two actions it causes?
CCK | - contraction of gall bladder & relaxation of oddi
39
what are gallstones?
precipitated bile constituents- cholesterol & Ca2+ bilirubinate stones
40
what is the precipitation of cholesterol inhibited by in most adults? what is precipitation increased by?
anti-nucleating proteins | prolonged storage of bile