Anatomy Flashcards
The liver is invested in peritoneum except for the
gallbladder fossa
porta hepatis
posterior aspect of the liver on either side of the IVC in two wedge-shaped areas.
bare area of the liver
This region of liver to the right of the IVC, which is devoid of peritoneal coverage
coronary ligaments , right and left triangular ligaments, falciform ligament
The diaphragmatic peritoneal duplications are referred to as the coronary ligaments
whose lateral margins on either side are the right and left triangular ligaments.
From the center of the coronary ligament emerges the falciform ligament, which extends anteriorly as a thin membrane connecting the liver surface to the diaphragm, abdominal wall, and umbilicus.
The ligamentum teres, umbilical fissure
The ligamentum teres (the obliterated umbilical vein) runs along the inferior edge of the falciform ligament from the umbilicus to the umbilical fissure
umbilical fissure is on the inferior surface of the left liver and contains the left portal pedicle.
ligamentum venosum
On the posterior surface of the left liver, running from the left portal vein in the porta hepatis toward the left hepatic vein and the IVC is the ligamentum venosum (obliterated sinus venosus) that also runs in a fissure
Venous drainage
Venous drainage is through the right, middle, and left hepatic veins that empty directly into the suprahepatic IVC
caudate lobe lies where
The lesser omentum terminates along the edge of the ligamentum venosum, and thus the caudate lobe lies within the lesser sac and the rest of the liver lies in the supracolic compartment
The right liver is divided into
The right liver is divided into
- anterior (segments V and VIII)
- posterior (segments VI and VII) sectors
by the right scissura, which contains the right hepatic vein.
The umbilical fissure contains what ?
The umbilical fissure is not a scissura and does not contain a hepatic vein;
it contains the left portal pedicle, which contains the left portal vein, hepatic artery, and bile duct.
left liver is split into
The left liver is split into
- anterior (segments III and IV)
- Posterior (segment II, the only sector composed of a single segment) sectors by the left scissura
The portal vein provides approximately ?? of the hepatic blood inflow
The portal vein provides approximately 75% of the hepatic blood inflow.
Despite being postcapillary and largely deoxygenated, its high flow rate provides 50% to 70% of the liver’s oxygen requirement.
The left branch of the portal vein
The left branch of the portal vein runs transversely along the base of segment IV and into the umbilical fissure, where it gives off branches to segments II and III and feedback branches to segment IV.
most significant portosystemic collateral locations
- the submucosal veins of the proximal stomach and distal esophagus receive portal flow from the short gastric veins and the left gastric vein and can result in varices
- the umbilical and abdominal wall veins recanalize from flow through the umbilical vein in the ligamentum teres, resulting in caput medusae
- the superior hemorrhoidal plexus receives portal flow from inferior mesenteric vein tributaries and can form large hemorrhoids
Liver CT 1
(A) At the level of the hepatic veins,
- the caudate lobe (segment 1) is seen posteriorly embracing the vena cava.
- Segment 2 is separated from segment 4A by the left hepatic vein.
- Segment 4A is separated from segment 8 by the middle hepatic vein
- segment 8 is separated from segment 7 by the right hepatic vein.
Liver CT 2
(B) At the level of the portal vein bifurcation
- segment 3 is visible as it hangs inferiorly in its anatomic position and is separated from segment 4B by the umbilical fissure.
- Note that segment 2 is not visible at this level.
- Terminal branches of the middle hepatic vein separate segment 4B from segment 5
- terminal branches of the right hepatic vein separate segment 5 from segment 6.
Liver CT 3
(C) Below the portal bifurcation, one can see the inferior tips of segments 3 and 4B.
- The terminal branches of the middle hepatic vein and the gallbladder mark the separation of segment 4B from segment 5.
- Segments 5 and 6 are separated by the distal branches of the right hepatic vein
Normal Variant of Main PV
The standard configuration, where main portal vein divides into the left and right branches and the right portal vein then divides into right anterior and right posterior portal vein, is found in up to 70% of individuals.
The most common variant from this configuration is the so-called “portal vein trifurcation,” where the main portal vein divides into three branches: the left portal vein, the right anterior portal vein, and the right posterior portal vein.
The second most common variant is the right posterior portal vein originating as the first branch of portal vein.
This can also be envisioned as the right anterior portal vein arising from the left portal vein.
left hepatic artery
The left hepatic artery heads vertically toward the umbilical fissure to supply segments II, III, and IV.
The left hepatic artery usually also gives off a middle hepatic artery branch that heads toward the right side of the umbilical fissure and supplies segment IV.
The right hepatic artery
The right hepatic artery usually runs posterior to the common hepatic bile duct and enters Calot triangle, bordered by the cystic duct, common hepatic duct, and liver edge, where it gives off the cystic artery to supply the gallbladder
accessory vessel Vs replaced vessel
- accessory vessel is described as an aberrant origin of a branch that is in addition to the normal branching pattern.
- A replaced vessel is described as an aberrant origin of a branch that substitutes for the lack of the normal branch
Replaced Rt or Accessory
- Replaced or accessory right hepatic arteries come off the superior mesenteric artery and are present approximately 11% to 21% of the time
-Hepatic vessels replaced to the superior mesenteric artery run behind the head of the pancreas, posterior to the portal vein in the portacaval space. This is evident on cross-sectional imaging as well as during operative exploration by feeling hepatic artery pulsation in the lateral border of the hepatoduodenal ligament behind the portal vein and bile duct
Left Replaced or Accessory
. A replaced or accessory left hepatic artery is present approximately 3.8% to 10% of the time, originates from the left gastric artery, and courses within the lesser omentum, heading toward the umbilical fissure.
Other important variations include the origin of the gastroduodenal artery
which has been found to originate from the right hepatic artery and is occasionally duplicated
An accessory cystic artery
can originate from the proper hepatic artery or gastroduodenal artery, where it runs anterior to the bile duct.
A single cystic artery can originate anywhere off the proper hepatic artery or gastroduodenal artery or directly from the celiac axis
Hepatic Veins and Drianage
-The left and middle hepatic veins usually join intrahepatically and enter the left side of the IVC as a single vessel, although they may drain separately.
- The left hepatic vein runs in the left scissura between segments II and III and drains segments II and III
- the middle hepatic vein runs in the portal scissura between segment IV and the anterior sector of the right liver, composed of segments V and VIII, and drains segment IV and some of the anterior sector of the right liver.
- The umbilical vein is an additional vein that runs under the falciform ligament, between the left and middle veins, and usually empties into the left hepatic vein.
A number of small posterior venous branches from the right posterior sector and caudate lobe drain directly into the IVC
CBD
- The common bile duct usually measures 10 to 15 cm in length and is typically 6 mm in diameter.
- The common hepatic (bile) duct runs along the right side of the hepatoduodenal ligament (free edge of the lesser omentum) to the right of the hepatic artery and anterior to the portal vein.
- The intrapancreatic distal common bile duct then joins with the main pancreatic duct (of Wirsung), with or without a common channel, and enters the second portion of the duodenum through the major papilla of Vater.
CBD 2
- At the choledochoduodenal junction, a complex muscular complex known as the sphincter of Oddi regulates bile flow and prevents reflux of duodenal contents into the biliary tree.
Major Parts of the Sphincter
three major parts to this sphincter:
(1) the sphincter choledochus, which is a circular muscle that regulates bile flow and the filling of the gallbladder;
(2) the pancreatic sphincter, present to variable degrees, which surrounds the intraduodenal pancreatic duct; and
(3) the sphincter ampullae, made up of longitudinal muscle, which prevents duodenal reflux
what is the folds of Heister
The first portion of the cystic duct is usually tortuous and contains mucosal duplications referred to as the folds of Heister
CBD Supply
The supraduodenal and infrahilar bile ducts are predominantly supplied by two axial vessels that run at 3- and 9-o’clock positions.
These vessels are derived from the
1- superior pancreaticoduodenal
2- right hepatic
3- cystic
4- gastroduodenal
5- retroduodenal arteries
Nerves
- The innervation of the liver and biliary tract is through sympathetic fibers originating from T7 through T10 as well as parasympathetic fibers from both vagal nerves.
- The hepatic arteries are supplied by sympathetic fibers, whereas the gallbladder and extrahepatic bile ducts receive innervation from sympathetic and parasympathetic fibers
Lymphatics
Most lymph node drainage from the liver is to the hepatoduodenal ligament
Primary and Secondary Bile
- The primary bile salts cholic acid and chenodeoxycholic acid are produced in the liver from cholesterol and subsequently conjugated with glycine or taurine in the hepatocyte.
- Once secreted in the gut, the primary bile acids are modified by intestinal bacteria to form the secondary bile acids deoxycholic acid and lithocholic acid.
- Bile acids are reabsorbed passively into the jejunum and actively into the ileum.
The major organic solutes in bile
bile acids, bile pigments, cholesterol, and phospholipids.
Bile salts and absorption
-Bile salts also play a critical role in the absorption of dietary fats, fat-soluble vitamins (i.e., vitamins A, D, E, and K), and lipophilic drugs
-eliminating excess cholesterol
- Water movement from hepatocytes into bile and water absorption through the small bowel
Toxicity of free Bilirubin ( not Bound with Albumin )
Free bilirubin can
- uncouple oxidative phosphorylation
- inhibit ATPases
- decrease glucose metabolism
- inhibit a broad spectrum of protein kinase activities.
How to asses Hepatic Function
PT-INR
Albumin
factors V and VII, has been used to evaluate hepatic function in the transplantation population.
ALT Or ASt
ALT is liver specific.
portal hypertension
Portal hypertension in cirrhotic patients is usually manifested as
- thrombocytopenia
- splenomegaly
- presence of intraabdominal varices on imaging or at endoscopy.
The best evidence for portal hypertension is a hepatic vein wedge pressure higher than 10 mm Hg,
Child-Pugh classification.
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