Anatomy of the liver Flashcards
What is the largest gland in the body?
Liver
What are the macroscopic features of the liver?
Wedge shaped reddish brown organ
Highly vascularised
Pliable to touch; easily lacerated
Where is the liver located?
- Below diaphragm
- Right of the stomach
- Above the colon
Overlies gallbladder
What are the main functions of the liver?
detoxification
protein synthesis
production of bile – aids lipid digestion
glycogen storage
Which quadrant (of 9) is the liver in?
Located below diaphragm: mostly the right hypochondrium & epigastrium, but extends into left hypochondrium
The liver is below the ribs
True or false?
False
The liver is covered by the ribs
Label the diagram
Label the anterior view of the liver
Label the posterior view of the liver
How does the diaphragm affect the gross anatomy of the liver?
Diaphagmatic upper surface blunt, dome shaped/ sharp inferior border
What are the lobes of the liver?
Ant. view – divided into two main lobes: left and right
• Post. view – two other lobes: quadrate and caudate
Which part of the liver is covered by peritoneum?
Surface covered by peritoneum except bare area, where it touches the diaphragm
What seperates the lobes?
Falciform (ant) and lesser omentum (post) ligaments separate right and left lobes
• Porta hepatis divides the quadrate and caudate lobes
What are the peritoneal folds?
•Falciform ligament
links anterior abdominal wall to liver
ligamentum teres (aka round ligament*) at lower end
- Coronary ligaments - links diaphragm to liver
- Lesser omentum - links liver to stomach
What is the round ligament?
Obliterated left umbilical vein
extends to umbilicus
Complete the diagram on periotoneal folds
Where is the lesser omentum?
•From the lesser curvature stomach to porta hepatis
Which omentum has a free edge?
Lesser omentum
What is the lesser omentum made of?
Ventral mesentry
What does the lesser omentum enclose?
hepatic artery
portal vein
bile duct
lymph vessels
• Close to the stomach it also encloses the gastric arteries and veins
Where does the blood supply to the gut originate from?
• All midline branches of the abdominal aorta
What is the blood supply to the gut?
Foregut – coeliac artery / trunk
Midgut – superior mesenteric artery
Hindgut – inferior mesenteric artery
Label the blood supply to the gut
What is the blood supply to the liver?
- Hepatic artery, a branch from the coeliac trunk brings oxygenated blood from the heart
- Portal vein, formed by the coming together of the sup mesenteric + splenic veins, brings deoxygenated blood from the gut, carrying nutrients, drugs, toxins etc
What are the 3 main branches of the coeliac artery/trunk/axis and what does it also supply?
left gastric (to stomach)
splenic (to spleen)
hepatic (to liver)
duodenum
pancreas
Where does the coeliac artery exit the aorta?
• Exits aorta at T12/L1 Level
Complete the diagram of arteries
Label the diagram on hepatic arteries
Hepatic artery variations are seen in _______% of people
40-45%
What are the common hepatic artery variations?
•Most common cases*:
right hepatic artery replaced to the SMA
left hepatic artery replaced to the left gastric artery
trifurcation of the common hepatic artery
- right hepatic artery
- left hepatic artery
- gastroduodenal artery (GDA)
When is a patient tested for hepatic artery variation?
• Critical test done prior to any surgery to the liver
Where is the porta hepatis?
At hilum of liver – visceral surface
What is the porta hepatis?
- Deep fissure – 5 cm
- Entry / exit point for
hepatic portal vein
hepatic artery proper
common hepatic duct
nerves and lymphatics
What happens to the porta hepatis once it enters the liver?
Why is the liver divided into lobes and segments?
- Metabolism – portal system
- Production and secretion of bile
and to perform these roles the liver is divided into lobes and segments
What are liver segements?
•Liver lobes are subdivided into segments (termed Couinaud) according to how the hepatic artery and portal vein subdivide
What does a liver segement contain?
- Branches of hepatic artery and portal vein carry blood into sinusoids
- Tributaries of the bile ducts accompany the two above, but carrying bile in the opposite direction. All three structures are called portal triad
Why is knowledge of liver segements important?
Knowledge as to how segments are vascularized is also crucial knowledge for liver transplants or surgery
What does a liver lobe contain?
- Each lobe of liver contains several lobules (functional units of the liver)
- Each hexagon (lobule) has a portal triad at each corner
What are lobules?
• Hexagon shaped and contain hepatocytes
(~60% of the liver cell population)
Complete the diagram of the lobule
Hepatocytes are responsible for what metabolic functions?
•Synthesis and release plasma proteins into blood, e.g.
albumin
clotting factors
- Deaminates amino acids, creating ammonia (this is then converted into urea in order to be safe)
- Converting bilirubin to bile pigment
- Production of bile salts, to emulsify fats
How does venous drainage of the liver work?
- The ‘mixed’ blood from the two sources (portal and hepatic) in the sinusoids passes through the hepatocytes and from there into the central vein
- Several central veins then drain into the interlobular (sublobular) vein
- Interlobular/sublobular veins then drain into hepatic veins
- Finally, hepatic veins drain into the inferior vena cava
Where is the central vein?
• The central vein is found at the center of a hepatic lobule
Complete the diagram of venous drainage of the lobule
Complete the diagram on venous drainage
What is the difference between the portal venous system and the systemic venous system?
- The portal venous system is described as blood draining the GI tract towards the liver
- This is distinct from the systemic venous system, which drains the rest of the body, E.g. muscles or skin, towards the heart
Where does portal vein blood come from?
What is the significance of portal circulation for drugs?
•Toxins, drugs etc. that are absorbed from the GI have to pass through the liver before reaching the heart
What is portocaval anastomosis?
- Communications between some branches of the portal and systemic systems is crucial for survival
- These are known as portocaval anastomosis
When is portocaval anasomosis important?
- This anastomosis is particularly important if the portal vein becomes blocked or passage via liver meets resistance – portal hypertension
- Blood is therefore allowing to travel collateral to the liver on its return to the heart, without which subject would die
Name 4 Examples of portal systemic anastomosis
What is portal hypertension?
- Is a fairly common clinical condition
- Any obstruction to the portal vein
What are common presentation signs of portal hypertension?
Varicoses
Caput medusa ; oesophageal varices
What is a Portacaval shunt?
- A shunt was traditionally employed to ameliorate hypertension
- It effectively diverted blood from portal vein to the IVC
What treatment replaced portacaval shunts?
• However this has largely been abandoned since the advent of TIPS (transjugular intrahepatic portosystemic shunting)
What is the livers role in bile production?
- Bile is secreted by hepatocytes into (bile) canaliculi, at a rate of around 40 ml/ hr
- Bile canaliculi join to form two main hepatic ducts – Left and Right – that drain the respective lobes
- Emerge from porta – unite to form common hepatic duct
How does bile enter the duodenum?
• Although bile flows continuously towards the duodenum it is prevented entry by a closed sphincter of Oddi, located at the end of the biliary tree
How is lymph drained from the liver?
- Liver produces vast amount of lymph, that drain into the coeliac nodes located in the vicinity of porta hepatis
- Coeliac nodes in turn drain to cisterna chyli
What does this ultrasound show?
Liver trauma
How does liver trauma occur?
- Closely related to lower ribs
- Fracture ribs / penetrating wounds
Why is liver trauma so dangerous?
• High vascularisation => severe haemorrhage
Why would a doctor remove portions of a liver?
• Remove portions due to segmental nature liver and vessels / ducts supplying it
liver biopsies
metastatic spread
cirrhosis
