heptabilliray system Flashcards
how many lobes in kidney
2
how are they divided
left and right by the middle hepatic vein
inflow to liver
hepatic artery
portal vein
outflow
bile
hepatic veins x 3
how many segments to the. liver
8
how are they ordered
clockwise
what is the liver made up of
lobules which make up portal triads
Hepatic lobule is
Hexagonal structural unit of liver tissue
how is a portal triad made
Each corner consists of a portal triad
Links with 3x adjacent lobules
what is located in the centre of a lobule
central vein
what does the vien do
Collects blood from hepatic sinusoids → hepatic veins → systemic venous system
what does the hepatic artery bring
Brings O2-rich blood into liver to support hepatocytes ↑ more energy demands
Branch of portal vein
Mixed venous blood from GIT (nutrients, bacteria & toxins) and spleen (waste products)
Hepatocytes process nutrients, detoxify blood & excrete waste
bile duct and where does it go
Bile produced by hepatocytes drains into bile canaliculi
Coalesce with cholangiocyte-lined bile ducts around lobule perimeter
what is larger portal vien or hepatic artery
portal vein
how do sinusoid form
hepatic artery and portal vein
where does bile floe
in the opposite direction
what is the hepatic acinus
Functional unit of liver
diamond shape from a central vien to another central vein
how many zones in the acinus
3- zone 1 2 3
zone 1 in the centre of the 2 lobules
2 then 3
point a
Blood into hepatic acinus via point a (on the outside of a lobule)
point b
Blood drains out of hepatic acinus via (middle of a lobule)
what is the significance of zone 1
Hepatocytes near outer hepatic lobule(zone 1) receive early exposure to blood contents: Good components (O2) Bad components (toxins)
what is the o2 and toxin risk in z1
high
z2
middle
z3
low
strcuture of sinosodial endothelial cell
No basement membrane
Fenestrated (discontinuous endothelium
what does it allow
Allow lipids & large molecule movement to and from hepatocytes
what is a kuppler cell
Sinusoidal macrophage cells
where are they
Attached to endothelial cells
within sinosoid
function
Phagocystosis
Eliminate & detoxify substances arriving in liver from portal circulation
what does a hepatic stellate cell do/function/s
Store vit A in liver cytosolic droplets
Activated (fibroblasts) in response to liver damage
Proliferate, chemotactic & deposit collagen in ECM
how do they exist
in a dormant state
hepatocytes strcuture
cubical
function
albumin, clotting factors & bile salts
Drug metabolism
Receive nutrients & building blocks from sinusoids
Cholangiocyte location
sorrounds the bile duct
function
Secrete HCO3- & H2O into bile
3 main functions of hepatocsytes
Metabolic & catabolic functions:synthesis & utilization of carbohydrates, lipids and proteins.
Secretory& excretory functions:synthesis &secretion of proteins, bile and waste products.
Detoxification & immunological functions:breakdown of ingested pathogens & processing of drugs
what is the purpose of the cori cycle
glucose is metabolized to pyruvate and then to lactate in muscle, the lactate is released into the blood and carried to the liver, where it is reconverted to pyruvate and used for gluconeogenesis, and the resulting glucose is released and travels back to muscle.
non esential amino acid sythesis
by transaminiation
Different keto-acids can be converted into multiple amino acids depending on the transaminase enzyme (vital for production of non-essential amino acids)
what is the principle amino acid released from the body during starvation
alanine
Glucose-alanine cycle
involves muscle protein being degraded to provide more glucose to generate additional ATP for muscle contraction
alanine trasnported to liver
alanine is shuttled to the liver where the nitrogen enters the urea cycle and the pyruvate is used to make glucose.
routes of glucose in liver
glucose -> glycerol
glucose -> pyruvate -> acteyl CoA -> fatty acid or cholesterol
what next routes
glycerol and fatty acid to triglycerides
lioprotiens and cholesterol to apoprotiens phospholipids
function of cholesterol
make hormones
mantain cell membrane
what are the fat soluble vitamins that are stores
a d e k
what else is stored
ferritin
what other vit is stored
k
what happens in detoxification
Phase 1 (modification)
– more hydrophilic
Phase 2 (conjugation)
– attach water soluble side chain
to make less reactive
main component of bile
water
function of bile
Cholesterol homeostasis
Absorption of lipids & lipid soluble vitamins (A, D, E, & K)
Excretion of: xenobiotics/drugs cholesterol metabolites adrenocortical & other steroid hormones Alkaline phosphatase
what colour is bile
yelloe
biliverdin
green
what is responsible for primary secretion of bile
hepatocystes
Bile secretions reflect serum concentrations
Secretion of bile salts (acids), lipids & organic ions
60%
what are Cholangiocytes responsible for
Secrete 40% of total bile
Secondary modification
what are secondary modifications
Alteration of pH (alkaline electrolyte solution)
H2O drawn into bile by osmosis via paracellular junctions
Luminal glucose & organic acids reabsorbed
HCO3- & Cl- actively secreted into bile by CFTR (Cystic Fibrosis Transmembrane Regulator)
IgA exocytosed
what do bile transporters do
Biliary excretion of bile salts & toxins performed by biliary transporters on apical surface & basolateral membranes of hepatocytes + cholangiocytes
what is bile sythesised from
cholesterol
what happens to 2 primary bile acids i
produced in the liver
converted to secondary bile acids by gut bacteria
bile salt function
Reduce surface tension of fats
Emulsify fat prior to its digestion & absorption
define amphipathic
2 faces
what are they
hydrophobic
hydrophilic
what causes bile storage and release
Between meals Sphincter of Oddi closed → bile diverted into gall bladder for storage
Eating → Sphincter of Oddi relaxes
Gastric contents (FFAs, AAs > CHOs) enter duodenum causing release of cholecystokinin (CCK)
CCK causes gall bladder to contract
what happens to the bile
95% bile salts reabsorbed from terminal ileum
By Na+/bile salt co-transport Na+-K+ ATPase system
what happens to the other 5 percent
5% converted to 2o bile acids in colon:
All Deoxycholic acid absorbed
99% Lithocolic acid excreted in stool
absorbed B.salts back to liver & re-excreted in bile
how does the gall bladder (GB) constrict
and what does Gb do to the bile
. Stores bile (50 mls)
- concentrates bile
- acidifies bile
. GB contraction triggered by CCK
- Binds to CCKA receptors & neuronal plexus of GB wall (innervated by preganglionic parasympathetic fibres of vagus nerve)what is free Bilirubin
BR (indirect/unconjugated)
= H2O-INSOLUBLE, yellow pigment
what is the source of free BR
75% BR from Hb (erythrocytes) breakdown
22% from catabolism of other haemoproteins
3% from ineffective BM erythropoiesis
how does free BR get conjugated
in the liver
how
Free BR bound to albumin in blood
Most dissociates in liver & enters hepatocytes
BR conjugated with 2x molecules of UDP-glucuronate → bilirubin diglucuronide (direct bilirubin)
Secreted ACROSS concentration gradient into biliary canaliculi → GIT
what is a useful test for liver function
free BR –> low
albumin –> high
what happens when BR gets to the gut
85% excreted in faeces
15% enters enterohepatic circulation
1% enters systemic circulation & excreted by kidneys
how is Br converted to rubbish
BR → urobilinogen → stercobilinogen→ stercobilin (brown compound)
what gives feaces its brown colour
stercobilin
what happens in obstructive jaundice
bilrubin cant enter into the gut
so no stercobilin
pale feaces
but dark urine as enters systemic circulation
causes of jaundice
pre hepatic -> hemoloysis
intrahepatic
post hepatic
Endoscopic Retrograde Cholangiopancreatography (ERCP)
is a procedure to diagnose and treat problems in the liver, gallbladder, bile ducts, and pancreas. It combines X-ray and the use of an endoscope
PTC
an x-ray procedure that involves the injection of a contrast material directly into the bile ducts inside the liver to produce pictures of the bile ducts. This procedure is usually performed by an interventional radiologist.
