anatomy of the liver Flashcards
where is the liver located
Largest gland in the body (exc skin) as is 1.4-6 kg in weight
Wedge shaped reddish brown organ
what is the liver’s main function
detoxification, protein synthesis, produce bile (aid lipid digestion), glycogen storage
Highly vascularised
Pliable to touch, easily lacerated
where is the liver in relation to other organs
Below diaphragm mostly in the right hypochondrium and epigastrium, but extends to left hypochondrium
to the right of stomach, above colon, overlies gallbladder
what is the shape of the liver
Diaphragmatic upper surface blunt, dome shaped/sharp inferior border
Surface covered by peritoneum except bare area, where it touches diaphragm
how is the liver viewed anteriorly
divided into two main lobes – L and R
Falciform (anterior) and lesser omentum (posterior) ligaments separate left and right lobes
how is the liver viewed posteriorly
two other lobes – quadrate and caudate
Porta hepatis divides the quadrate and caudate lobes
what are the peritoneal folds of the liver
Falciform ligament – links anterior abdominal wall to liver, ligamentum teres (aka round ligament, obliterated left umbilical vein extends to umbilicus) at lower end
Coronary ligaments – link diaphragm to liver
Lesser omentum – links liver to stomach
what is the lesser momentum
From lesser curvature stomach to porta hepatis
Has a free margin (ventral mesentery)
Encloses hepatic artery, portal vein, bile duct, lymph vessels
Close to stomach, also encloses gastric arteries and veins
how is blood supplied to the gut
Resort to embryological terms – foregut, midgut, hindgut
Each division with specific artery
All midline branches of abdominal aorta
what does the hepatic artery in the liver
branches from coeliac trunk brings oxygenated blood from the heart
what does the portal vein do in the liver
formed by coming together of superior mesenteric + splenic veins, brings deoxygenated blood from gut, carries nutrients, drugs, toxins etc
what does the coeliac artery do for the liver
Aka trunk or axis, has 3 main branches – left gastric (to stomach), splenic (to spleen), hepatic (to liver)
Exits aorta at T12/L1 level
Also supplies duodenum and pancreas
No coeliac vein
can the hepatic vein vary
40-45% people
Most common right hepatic artery replaced by SMA, left HA replaced by LGA, trifurcation of common hepatic artery into RHA, LHA, gastroduodenal (GDA)
Critical test prior to any liver surgery
what does the aorta hepatic do
At hilum of liver visceral surface
Deep fissure – 5cm
Entry/exit point for hepatic portal vein, hepatic artery proper, common hepatic duct, nerves and lymphatics
Once in – branching of vessels (and ducts) > division of liver into lobes and segments
what is the functional anatomy of the liver
Broad range of processes
Metabolism – portal system
production and secretion of bile
to perform these the liver is divided into lobes and segments
Each lobe of liver contains several lobules (FUs of liver)
Hexagon shaped and contain hepatocytes
Hepatocytes also secrete bile, each has a portal triad at each corner
what are the segments of the liver
lobes subdivided into segments (Coinaud’s segments) according to how HA and PV divide
branches of HA and PV carry blood into sinusoids
tributaries of bile ducts accompany two above, carrying bile in opposite direction, all three structures caused portal triad
Hepatocytes – metabolic function
Synthesis and release plasma proteins into blood eg albumin and clotting factors
Deaminates amino acids, creating ammonia (converted to urea)
Converting bilirubin to bile pigment
Produce bile salts to emulsify fats
Venous drainage of liver
The mixed blood from two sources (portal and hepatic) into the sinusoids passes through hepatocytes and from there central vein
Central vein found at centre of hepatic lobule
Several central veins drain into interlobular (sublobular) vein
Then drain to hepatic veins which drain into vena cava
Hepatic portal system
Portal venous system – blood drains the GI tract towards liver
Distinct from systemic venous system, drains rest of body towards heart
Toxins, drugs absorbed from GI have to pass liver before reaching heart
Portal system anastomosis
Communications between some branches of the portal and systemic systems are crucial for survival
Known as portocaval anastomosis
Particularly important if portal vein blocked/passage via liver meets resistance eg portal hypertension
Blood travels collateral to liver on its return to heart
examples of portal system 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
Portal hypertension
Fairly common clinical condition
Any obstruction of portal veins
Common presentation – varicoses and caput medusa (oesophageal varices)
Portacaval shunt
Traditionally used for hypertension, effectively diverts blood from portal vein to IVC
Largely abandoned since TIPS (transjugular intrahepatic portosystemic shunting)
Liver role in bile production
Bile secreted by hepatocytes into canaliculi at rate of 40ml/hr
Canaliculi join to form two main hepatic ducts – L and R – that drain into respective lobes
Emerge from porta – unite to form common hepatic duct
Bile flows continuously towards duodenum, it is prevented entry by closed sphincter of Oddi, located at end of biliary tree
Lymphatic drainage
Produces vast amount of lymph, drain into lymph nodes located in vicinity of porta hepatis
Nodes are coeliac – match artery – and drain into cisterna chyli
Liver trauma
Closely related to lower ribs so fractures can lead to penetrating wounds
High vascularisation – severe haemorrhage
Remove portions due to segmental nature liver and vessels/ducts supplying it
Liver biopsies, metastatic spread and cirrhosis
