Anatomy of the liver Flashcards
Where is the liver located?
Located below diaphragm: mostly the right hypochondrium & epigastrium, but extends into left hypochondrium
Below diaphragm
Right wrt stomach
Above the colon
Overlies gallbladder
Top part of liver in between the 4th and 5th rib on the right hand side. Liver has ribs covering it
State the main functions of the liver
detoxification
protein synthesis
production of bile – accessory GI organ
glycogen storage
Describe the intensity of the blood supply of the liver
Highly vascularised
Describe the shape and colour of the liver
Wedge shaped reddish/brown organ
Describe the structure of the liver
Diaphragmatic upper surface blunt, dome shaped/ sharp inferior border
Ant. view – divided into two main lobes: left and right
Post. view – two other lobes: quadrate and caudate
Surface covered by peritoneum except bare area, where it connects with diaphragm
Falciform (ant) and lesser omentum (post) ligaments separate right and left lobes
Porta hepatis divides the quadrate and caudate lobes
List the peritoneal folds
Falciform ligament
Round ligament
Coronary ligaments
Lesser omentum
Describe the falciform ligament
Links diaphragm to upper surface liver Ligamentum teres (aka round ligament) at lower end
Describe the round ligament
Obliterated left umbilical vein
Extends to umbilicus
Describe the coronary ligaments
Links diaphragm to liver
Describe the lesser omentum and its function
Links liver to the stomach - From lesser curvature stomach to porta hepatis Has a free margin (ventral mesentery) Encloses hepatic artery portal vein bile duct lymph vessels Close to the stomach it also encloses the gastric arteries and veins
What do all the blood supply to the gut have in common?
All from the midline at the abdominal aorta
Which artery is derived from the foregut?
Coeliac artery/trunk
Which artery is derived from the midgut?
Superior mesenteric
Which artery is derived from the hindgut?
Inferior mesenteric
Describe the blood supply to the liver
Coeliac artery (aka trunk or axis)
- Left gastric
- Splenic
- Hepatic
Which vertebral level does the coeliac artery divide?
T12/L1 Level
What other structures does the coeliac artery supply?
Duodenum
Pancreas
Describe the 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)
Describe the porta hepatis
At hilum of the liver- visceral surface Deep fissure Entry/exit point for - hepatic portal vein - hepatic artery proper - common hepatic duct - nerves and lymphatics
What reaches the liver through the hepatic artery?
Oxygenated blood
What reaches the liver through the portal vein?
Deoxygenated blood
Nutrients
Drugs
Toxins
What is the portal vein composed of?
sup mesenteric + splenic
What is a portal triad?
According to how the hepatic artery and portal vein subdivide, the liver anatomic lobes are subdivided into segments (Couinaud)
Branches of hepatic artery and portal vein carry blood into sinusoids
Branches of the bile duct accompany those of the hepatic artery and portal vein. All three structures are called portal triad and supply each segment
Why is knowledge of coinauds segments important?
Knowledge of vascular supply to segments is vital for liver transplants or surgery
Describe liver lobules
Each lobe of liver contains several lobules Functional units of the liver Hexagon shaped Contains hepatocytes (60% liver cells) Portal triads at corners
Describe the metabolic functions of hepatocytes
Synthesis and release
- plasma proteins into blood
- albumin
- clotting factors complement cascade components
- Deaminates amino acids – urea into blood
- Bilirubin to bile pigment
- Bile salts – emulsification of fats
Describe the venous drainage of the liver
The ‘mixed’ blood from the two sources (portal and hepatic) in the sinusoids passes through the hepatocytes and into the central vein
The central vein is found at the center of a hepatic lobule
Central veins then drain into the sublobular vein
Sublobular vein then drain into hepatic veins
Describe portal systemic anastomosis and why they are important
Communications between some branches of the portal and systemic systems
aka portocaval anastomosis
Very important if portal vein blocked or passage via liver meets resistance – portal hypertension
Allow collateral return of blood to heart without which subject would die
List some portal systemic anastomosis
Abdominal part of oesophagus – left gastric tributaries with oesophageal branches azygos
Anal canal – superior rectal anastomoses with middle and inferior rectal
Umbilicus – paraumbilical veins with epigastric veins
Veins of colon, duodenum, pancreas, liver with renal, lumbar and phrenic
What is portal hypertension?
Common clinical condition caused by obstruction of portal vein
Pressure rises – hypertension
Anastomoses between portal and systemic means backflow of blood to heart then lungs
Signs include: Varicoses, Caput medusa ; oesophageal varices
Describe a portacaval shunt
Procedure carried out in attempt of Reduction of hypertension
Divert blood from portal to systemic
Blood diverted from portal to IVC
Portal vein conveys 70% blood to liver
Largely been abandoned since the advent of TIPS (transjugular intrahepatic portosystemic shunting)
Describe the pathway and secretion of bile
Secreted by hepatocytes into bile canaliculi
Closed sphincter Oddi to duodenum => bile flows to gall bladder to be stored and concentrated
Right and left hepatic ducts – relevant lobes
Emerge from porta – unite to form common hepatic duct
How much bile is secreted in an hour?
40ml
Describe the lymphatic drainage of the liver
Liver produces vast amount of lymph
Lymph nodes in porta hepatis
Pass to coeliac nodes
Drain to cisterna chyli
Describe the risk of liver trauma
Closely related to lower ribs
Fracture ribs / penetrating wounds
High vascularisation => severe haemorrhage
Remove portions due to segmental nature liver and vessels / ducts supplying it
liver biopsies
metastatic spread
cirrhosis
