GI Deck 2

Question 1

2 forms of primary regulation of colon

Answer 1

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

- long reflexes- gastrocolic & orthocolic

Question 2

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

Answer 2

PYY; ileal break; fat in terminal ileum

Question 3

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

Answer 3

haustra- circular muscle- short

taeniae coli- 3 layers of longitudinal muscle- long

Question 4

what kind of stimulation enhances motility?

Answer 4

parasympathetic

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

Question 5

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

Answer 5

SCFAs (short chain fatty acids)

cotransported with sodium using SMCTs

Question 6

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

Answer 6

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

Question 7

what kind of muscle is in the rectum?

Answer 7

only longitudinal for storage (no circular for motility)

Question 8

what kind of muscle is present in the anus?

Answer 8

smooth and skeletal (VOLUNTARY!!) muscle

Question 9

filling of the rectum _____ the internal anal sphincter

Answer 9

relaxes

Question 10

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

Answer 10

• 70-80% is venous from portal vein

Question 11

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

Answer 11

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

Question 12

what are HsCs in the context of the liver?

Answer 12

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

Question 13

what are sinusoids?

Answer 13

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

Question 14

what is the portal triad

Answer 14

portal vein, hepatic artery, bile duct

Question 15

what are zone 1 hepatocytes?

Answer 15

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

Question 16

what are zone 3 hepatocytes?

Answer 16

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

Question 17

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

Answer 17

cholangiocytes

Question 18

what are canaliculi?

Answer 18

adjacent hepatocytes form canals for biles

Question 19

why is carbohydrate metabolism important in liver?

Answer 19

• has role in gluconeogenesis (sugar-glucose)

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

Question 20

4 important functions of protein metabolism in liver

Answer 20

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

Question 21

what are kupffer cells?

Answer 21

macrophages in sinusoids

Question 22

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

Answer 22

cholesterol

- cholic acid, chenodeoxycholic acid

Question 23

What are secondary bile acids?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

what are primary and secondary bile acids conjugated with?

Answer 25

glycine or taurine

Question 26

T/F Conjugated bile acids are reabsorbed passively in colonic epithleium

Answer 26

False- UNconjugated forms are reabsorbed

Question 27

Is bile acidic?

Answer 27

no- alkaline, due to CFTR Cl- channels and HCO3- exchange

Question 28

what is bile outflow blocked by in between meals?

Answer 28

sphincter of oddi

Question 29

what is enterohepatic circulation?

Answer 29

the recycling of bile from intestine to liver using ASBTs

Question 30

where does bilirubin come from? is it soluble?

Answer 30

breakdown of heme
when unconjugated is very un-soluble
binds to albumin for transport

Question 31

where is bilirubin taken up and by what; is it unconjugated or conjugated

Answer 31

liver by OATP

is unconjugated

Question 32

What is UGT?

Answer 32

• UPD glucuronyl transferase; enzyme that conjugates bilirubin; lacking in newborns

Question 33

where does bilirubin go after the liver?

Answer 33

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

Question 34

two causes of high unconjugated bilirubin in blood

Answer 34

1) oversupply of heme, eventually overwhelms liver

2) problem with UGT

Question 35

two causes of high conjugated bilirubin in urine

Answer 35

1) defect in the transporter that secretes conjugated bilirubin into the bile
2) blockage of bile flow

Question 36

what is the major source of urea for the urea cycle?

Answer 36

colonic bacteria (also have protein catabolism)

Question 37

where does the urea cycle take place?

Answer 37

hepatocyte

Question 38

what is the major stimulus for bile secretion? what are the two actions it causes?

Answer 38

CCK

- contraction of gall bladder & relaxation of oddi

Question 39

what are gallstones?

Answer 39

precipitated bile constituents- cholesterol & Ca2+ bilirubinate stones

Question 40

what is the precipitation of cholesterol inhibited by in most adults? what is precipitation increased by?

Answer 40

anti-nucleating proteins

prolonged storage of bile