rest of GI

Question 1

what are the three types of hepatocyte surface and describe them?

Answer 1

sinusoidal, intercellular and canalicular. sinusoid lacks a BM and has fenestrated membrane.

Question 2

describe other cells found in the liver

Answer 2

Kuppfer Cells- macrophages
Perisinusoidal- fat-storing
Lymphocytes

Question 3

What does bile contain?

Answer 3

bicarbonates, cholesterol, phospholipids, bile pigments and bile salts

Question 4

how is bile made?

Answer 4

bilirubin is the main pigment in bile which is made from the breakdown of haem.
this is done by macrophages e.g. Kupffer cells.
haem is broken by haem oxygenase to form biliverdin, then by biliverdin reductase to form bilirubin.
it is currently insoluble so it is bound to albumin and transported to the liver.

Question 5

what is bile used for?

Answer 5

they act as emulsifiers, promoting micelle formation great for digestion and absorption of lipids and certain vitamins e.g. A, D, E, K

Question 6

how is bile secretion regulated?

Answer 6

when fats and proteins enter the duodenum, cholecystokinin (CCK) is secreted which stimulates the gallbladder smooth muscle to contract and relax the sphincter of Oddi. this releases bile into the duodenum.

acidic chyme (food plus acid) leads to secretin release, further releasing bile and bicarbonates from the pancreas

Question 7

describe bile recycling

Answer 7

bile is absorbed in the ileum. from there it is taken to the liver by the hepatic portal vein. hepatocytes process the blood returning and secrete the bile back into the canaliculi

Question 8

`What causes jaundice?

Answer 8

jaundice is defined by higher levels of bilirubin (hyperbilirubinaemia)

normal ranges are <21micromol

generally it will be above 50 once visible

Question 9

what are the three classifications of jaundice?

Answer 9

pre-hepatic- elevated haemolysis

hepatic- damage to liver

post-hepatic- problems with bile transported into small intestine.

Question 10

what are the serum levels that indicate jaundice?

Answer 10

plasma serum levels looking for unconjugated bilirubin will show high levels pre-hepatic. for conjugated it will show high levels post-hepatic.

in urine, bilirubin will be absent pre, and high post. and for unconjugated (urobilinogen) it will be high pre and low post.

Question 11

what are some metabolic functions of the liver?

Answer 11

carb metabolism- storage (glycogen) and release (glycogenolysis).

gluconeogenesis- new synthesis of glucose from lactates etc

lipid metabolism- synthesis of fatty acids, triglycerides etc and beta oxidation of fatty acids

protein metabolism

production of 3 litres of bile a day, 1 litre excreted a day.