anatomy of the liver Flashcards
where is the liver located?
below diaphragm: mostly right hypochondriac and epigastrum, but extends into left hypochondrium
what are the main functions of the liver?
- detoxification
- protein synthesis
- production of bile: aids lipid digestion
- glycogen storage
what are a few key characteristics of the liver?
- largest gland in the body (excluding skin)
- highly vascularised
- pliable to touch; easily lacerated
what is the gross anatomy of the liver?
- diaphragmatic upper surface blunt, dome shaped/sharp inferior border
- anterior view: divided into 2 main lobes (left and right)
- posterior view: 2 other lobes (quadrate and caudate)
- surface covered by peritoneum except bare area, where it touches the diaphragm
- falciform and lesser omentum ligaments separate right and left lobes
- porta hepatis divides the quadrate and caudate lobes
what does the falciform ligament link together?
- links anterior abdominal wall to liver
- ligamentum teres at lower end
what does the coronary ligament link together?
links diaphragm to liver
what does the lesser omentum link together?
links liver to stomach
what are the key characteristics of the lesser omentum?
- from the 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 is the general blood supply to the gut like?
- resort to embryological terms (foregut, midgut, hindgut)
- each division with specific artery
- all midline branches of the abdominal aorta
how does the liver work with metabolism?
- hepatic artery, a branch of the coeliac trunk brings oxygenated blood from the heart
- portal vein, formed by the coming together of the superior mesenteric and splenic veins, brings deoxygenated blood from gut, carrying nutrients, drugs, toxins, etc…
what are the 3 main branches of the coeliac artery?
- left gastric (to stomach)
- splenic (to spleen)
- hepatic (to liver)
where does the coeliac exit the aorta?
T12/L1 level
what does the coeliac artery also supply?
duodenum and pancreas
what are the key characteristics of the porta hepatis?
- at the hilum of the liver: is visceral surface
- deep tissue: 5cm
- entry/exit point for: hepatic portal vein, hepatic artery proper, common hepatic duct, nerves and lymphatics
- once in: branching of the vessels (and ducts) leads to division of liver into lobes and segments
what is the functional anatomy of the liver?
- metabolism: portal system
- production and secretion of bile
what are the characteristics of the liver segments?
- liver lobules are subdivided into segments according to how the hepatic artery and portal vein subdivide
- branches of hepatic artery and portal vein carry blood into sinusoids
- tributaries of the bile ducts accompany the 2 above, but carrying bile in the opposite direction
- all 3 structures are called the portal triad
what is the function microscopic anatomy of the liver?
- each lobe of the liver contains several lobules
- hexagon shaped and contains hepatocytes
- hepatocytes also secrete bile
- each lobule has a portal triad at each corner
what is the metabolic function of the hepatocytes?
- synthesis and release plasma proteins into the blood
- dominates amino acids, creating ammonia
- converting bilirubin to bile pigment
- production of bile salts, to emulsify fats
what is the venous drainage of liver?
- the mixed blood from the 2 sources in the sinusoids passes through the hepatocytes and from there into the central vein
- the central vein is found at the centre of a hepatic lobule
- several central veins then drain into the interlobular vein
- interlobular/sublobular veins then drain into hepatic veins
- hepatic veins drain into inferior vena cava
what is the hepatic portal 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
what are the key characteristics of portal systemic anastomoses?
- communications between some branches of the portal and systemic systems is crucial for survival
- these are called portocaval anastomoses
- this anastomoses is particularly important if the portal vein becomes blocked 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
what are some examples of portal systemic anastomoses?
- 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?
- fairly common clinical condition
- any obstruction to the portal vein
- common presentation signs include: varicoses, caput medusa
what is a portacaval shunt?
- a shunt was traditionally employed to ameliorate hypertension
- in effectively diverted blood from portal vein to the IVC
- 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 canaliculi at a rate of around 40ml/hr
- bile canacliculi join to form 2 main hepatic ducts - left and right - that drain the respective lobes
- emerge from porta: unite to form common hepatic duct
- although bile flows continuously towards the duodenum it is prevented entity by a closed sphincter of Oddi, located at the end of the biliary tree
what are the key characteristics of lymphatic drainage in the liver?
- liver produces vast amount of lymph that drain into lymph nodes located in the vicinity of porta hepatis
- these nodes are termed coeliac to match the coeliac artery
- coeliac nodes in turn drain into cisternal chyli
