FRS 4. ANATOMY OF THE LIVER AND BILIARY SYSTEM Flashcards
What is the bare area of the liver?
section which is not covered by peritoneum
o Lies directly against the tissue of the diaphragm
o This region is bare because the connective tissue elements of the liver and diaphragm form from
a common sheet of tissue in the embryo the liver grows outward from this
Describe the venous drainage of the liver
The IVC lies in a groove on the back of the liver
Blood from the liver drains into 3 hepatic veins, which then open into the IVC
What is the Hepatoduodenal ligament?
the bile duct, hepatic portal vein and hepatic artery lie in the free edge of the lesser omentum
Portion of the lesser omentum extending
between the porta hepatis and the superior part
of the duodenum. Contains the portal triad
What is the pringle manoeuvre?
clamping of the hepatic pedicle
o Enables surgeons halt haemorrhage and find the source of bleeding by determining if it
originates from branches of the hepatic artery or the portal vein.
allows time for repair
o When a clamp is applied to the pedicle, haemorrhage ceases if it is from either of these sources.
o If haemorrhage continues, the other likely sources of bleeding include the retrohepatic vena cava
and hepatic veins
What are the four anatomical lobes of the liver?
o Left lobeand right lobes(that are separated along the attachment of thefalciform ligament
o Caudate and aquadrate lobes(which are part of the anatomical right lobe).
What are the functional lobes of the liver?
distribution of the portal blood supply and biliary drainage of the liver allows the organ to
be functionally divided into four sectors, which are subsequently divided to give a total of eight
segments.
o Drained and supplied by different blood vessels and can therefore undergo surgical resection
Where is the gallbladder located?
theright hypochondriac region
Lies in a fossa (groove) between the right and quadrate lobes on the inferior aspect of theliver
o Shares a minimal amount of connective tissue with the liver
What are the divisions of the gallbladder?
- fundus
- body
- neck
Describe the fundus of the gallbladder
rounded, end portion of the gallbladder; projects from the inferior border
of the liver.
o Fundus is located where the lateral rectus abdominis muscle reaches the
costal margin*
o The rectus abdominis muscle helps to flex the trunk (e.g. upon sitting up)
Describe the body of the gallbladder
largest part; Occasionally in contact with transverse colon and proximal duodenum.
Describe the neck of the gallbladder
gallbladder tapers to become continuous with the cystic duct, leading to the
biliary tree.
o Contains a mucosal fold calledHartmann’s Pouch.
o Thisis a common location for gallstones to become lodged, causing cholestasis.
What does tenderness of the right hypochondriac region indicate?
results from inflammation of the gallbladder, e.g. with gallstones or malignancy of the biliary tract.
Describe the lining of the gall bladder
o simple columnar epithelium - has an absorptive function (absorbs water to concentrate bile)
o some goblet cells
How does the gallbladder secrete bile into the GIT?
via a series of ducts, known as the biliary tree.
ducts extend from the liver, communicating with the gallbladder and pancreas, and end at an
opening into the duodenum.
Describe the biliary tree
Left + right hepatic ducts => common hepatic duct => common hepatic + cystic duct => common bile duct + pancreatic duct => hepatopancreatic ampulla of Vater
What is the arterial supply of the gallbladder?
Supplied by the cystic artery. o Derived from the hepatic artery proper, a branch of the common hepatic artery, which arises from the coeliac trunk.
What is the venous drainage of the gallbladder
Drained by the cystic vein
o Drains directly into the portal vein.
The gallbladder also communicates with the liver through several very small veins and arteries.
Lymph from the gallbladder drains into thecystic node, situated at the gallbladder neck.
What is the innervation of the gallbladder
The gallbladder receives parasympathetic, sympathetic and sensory innervation.
Sympathetic and sensory fibres: coeliac plexus
Parasympathetic innervation: vagus nerve
o Parasympathetic stimulation produces contraction of the gallbladder, and the secretion of bile
into the cystic duct.
What is the main stimulator of bile secretion?
cholecystokinin, which is secreted by the
duodenum
Food enters the duodenum, stimulating the release of CCK
CCK stimulates:
o Gall bladder contraction
o Relaxation of the sphincter of the hepatopancreatic ampulla
Describe a classical liver lobule
Prism with a central vein (drains into hepatic vein) Prisms may differ in size Corners of lobules have portal triads o Hepatic artery o Hepatic portal vein o Bile duct
Describe a liver acinus
Roughly ellipsoidal area of hepatocytes centred around a bile ductule This area drains into said ductule Zones 1-3 in liver acinus: Zone 1: periportal o Hepatocytes actively synthesise glycogen and plasma proteins o Oxygen concentration in sinusoidal blood is high Zone 2: intermediate Zone 3: perivenular (venous drainage) o Low oxygen concentration o Detoxification o Hepatocytes susceptible to hypoxia
What is glisson’s capsule?
thin layer of connective tissue that covers the liver
A healthy liver contains a minimal amount of fibrous tissue
Describe the histology of the bile ducts
o Lined by simple columnar epithelium, may be simple cuboidal in smaller ducts
o Very round nuclei
o Some smooth muscle and fibrous tissue in the wall
Describe the histology of the hepatic artery
o Elongated nuclei (smooth muscle)
o Elastic layer
o Thick smooth muscle layer
o Endothelium appears convoluted
Describe the histology of the hepatic portal vein
o Large, irregularly shaped lumen
o Not much smooth muscle in its wall
What are the three types of alcoholic liver disease?
1) Fatty liver (steatosis)
2) Alcoholic hepatitis +/– hepatic fibrosis
3) Cirrhosis
Describe hepatic liver metabolism
Two main metabolic pathways:
- Cytoplasmic alcohol dehydrogenase (ADH)
- Microsomal ethanol oxidising system (MEOS)
o Both oxidise alcohol to produce acetaldehyde
o Acetaldehyde is converted to acetate then acetyl-coA
o Acetyl-coA enters tricarboxylic acid cycle in mitochondrion, leading to fatty acid formation
What are raised GGT levels a sign of?
GGT is found in the SER of hepatocytes, the site of MEOS. Induction of MEOS therefore stimulates an increase in GGT, as reflected by liver function tests
What is MEOS?
MEOS = Microsomal ethanol oxidising system
uses cytochrome P450
enzyme induction by excess alcohol alters metabolic activity, and affects
metabolism of drugs e.g. paracetamol
o Affects drug dosage and toxin (metabolite) production
What is steatosis?
Fatty liver is the accumulation of triglycerides and other fats in the liver cells.
The amount of fatty acid in the liver depends on the balance between the processes of delivery and
removal
Early and reversible consequence of excessive alcohol consumption.
In some patients, fatty liver may be accompanied by hepatic inflammation and liver cell death
(steatohepatitis)
How does alcohol increase hepatic lipid?
Altered hepatocyte fat metabolism
Increased peripheral fat mobilisation
Reduced lipoprotein synthesis
How does alcohol alter hepatocyte fat metabolism
Lipid synthesis promoted and catabolism impaired with accumulation of cholesterol esters &
fatty acids
How does alcohol increase peripheral fat mobilisation?
o Fatty acid formation from excess alcohol disrupts systemic lipid metabolism, causing dyslipidaemia
o The body is confused into thinking that there is not enough fat and mobilises peripheral fat stores
Describe alcohol steatosis on microscopy
Lipid droplets in hepatocytes o Initially small: microvesicular o Then coalesce and are larger: macrovesicular o Seen after only 2 days alcohol excess o Rapid reversal on abstinence
NB: the lipid droplets are in HEPATOCYTES, not in adipocytes
o There is no change in cell type
Describe the microscopy of alcoholic hepatitis
Fatty liver
Hepatocyte abnormalities:
o Ballooning (sub-lethal cell injury)
>Injured cells are unable to control their cell membrane and osmotic potential within
the cell, leading to ballooning
o Mallory bodies in cytoplasm
> Cell’s cytoskeleton crumbles and clumps together
o Necrosis
o Neutrophil polymorph infiltration (inflammation) => many nuclei visible
Fibrosis
o Initially perivenular & pericellular
> Initially occurs in zone 3 because this is the site of alcohol metabolism
o Later fibrous septa & maybe cirrhosis
What are the complications of alcoholic cirrhosis?
o Portal hypertension Portal-systemic shunts and varices Ascites Splenomegaly o Liver failure o Hepatocellular carcinoma in 3-6%
