GI Deck 2 Flashcards Preview

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Flashcards in GI Deck 2 Deck (40):
1

2 forms of primary regulation of colon

- local reflexes- activated by bolus, secrete Cl & fluid
- long reflexes- gastrocolic & orthocolic

2

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

PYY; ileal break; fat in terminal ileum

3

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

haustra- circular muscle- short
taeniae coli- 3 layers of longitudinal muscle- long

4

what kind of stimulation enhances motility?

parasympathetic
- vagal in haustra, cecum, ascending & transverse colon
- pelvic nerves is descending, sigmoid colon, rectum and anus

5

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

SCFAs (short chain fatty acids)
cotransported with sodium using SMCTs

6

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

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

7

what kind of muscle is in the rectum?

only longitudinal for storage (no circular for motility)

8

what kind of muscle is present in the anus?

smooth and skeletal (VOLUNTARY!!) muscle

9

filling of the rectum _____ the internal anal sphincter

relaxes

10

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

- 70-80% is venous from portal vein

11

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

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

12

what are HsCs in the context of the liver?

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

13

what are sinusoids?

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

14

what is the portal triad

portal vein, hepatic artery, bile duct

15

what are zone 1 hepatocytes?

- periportal
- closest to triad
- receive max nutrients and O2
- affected by ischemia last
- see virus/toxins first

16

what are zone 3 hepatocytes?

- pericentric
- closest to central vein
- die first with ischemia

17

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

cholangiocytes

18

what are canaliculi?

adjacent hepatocytes form canals for biles

19

why is carbohydrate metabolism important in liver?

- has role in gluconeogenesis (sugar-glucose)
- if backed up, can cause hyperglycemia (stores glucose it produces)

20

4 important functions of protein metabolism in liver

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

21

what are kupffer cells?

macrophages in sinusoids

22

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

cholesterol
- cholic acid, chenodeoxycholic acid

23

What are secondary bile acids?

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

24

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

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