Liver

LIVER  

• Largest gland of the body.
• Situated: In right upper border quadrant of abdominal cavity.
• Occupies whole of the right hypochondrium, greater part of epigastrium with extension into left hypochondrium.
• Weight: 1500-1600 gm in males & 1200-1300 gm in females.
• Liver is covered by Glisson’s capsule.
• Interior of liver is divided into hexagonal lobules.
• Lobule contains sinusoids which have fenesterated endothelium covering the subendothelial space of Disse.
• Important cells in liver: Hepatocytes (Parenchymal cells) and Kupffer cells (monocytic-macrophages).

LOBES OF LIVER

• Liver can be divided into right & left lobe anatomically & physiologically.

ANATOMICAL LOBES:

• Anatomically liver is divided into a large right lobe & a small left lobe.

Right lobe:

1. Larger & forms five sixth of liver.
2. Caudate lobe & quadrate lobe are parts of anatomical right lobe.

• Left lobe– forms only one sixth of liver.

1. CAUDATE LOBE:

• Situated on posterior surface of right lobe.

Bounded:

1.  on right by groove for IVC,
2. on left by fissure for ligamentum venosum
3. inferiorly by porta hepatis (containing hepatic artery, portal vein, hepatic duct, bile duct, nerve plexus & lymphatics).

• Just behind the porta hepatis caudate lobe is connected to rest of right lobe by caudate process.
• There is a small rounded elevation to the left, called papillary process.
• Caudate lobe lies in superior recess of lesser sac & is related to crura of diaphragm, right inferior phrenic artery & coelic artery.

2. QUADRATE LOBE:

• Situated on the inferior surface & rectangular in shape.

Bounded:

1.  anteriorly by inferior border of liver
2. posteriorly by porta hepatis
3. on right side by fossa for gall bladder
4. on left side by fissure for ligamentum teres.

 PHYSIOLOGICAL LOBES:

• Physiological right & left lobes are equally divided by an imaginary line (cholecysto-vena caval line) running from fossa for gall bladder to the groove for IVC.
• The physiological right & left lobes have separate biliary drainage & vascular supply, i.e. they are supplied respectively by right & left branches of portal vein & hepatic artery & bile is conveyed by the corresponding hepatic ducts (bile ducts).

1. QUADRATE LOBE: (Anatomical part of right lobe) belongs to physiological left lobe because it is supplied by a branch of left hepatic artery & left branch of portal vein  & is drained into left hepatic duct.
2. CAUDATE LOBE: (Anatomical part of right lobe) belongs physiologically to both right & left lobes because it receives blood from right & left hepatic arteries: right & left phrenic vein; & drains bile into both right & left hepatic duct. Thus it is considered as physiological independent lobe. 

SEGMENTAL ANATOMY OF THE LIVER

• Based on the distribution of portal vein & hepatic vein, Couinaud divided each physiological (functional) lobe of liver into 4 segments each & hence liver is divided into 8 segments.
• The physiological left lobe is composed of 4 segments designated I to IV & is supplied by left branch of hepatic artery, left branch of portal vein & drained by left hepatic duct.
• The physiological right lobe consists of segment V, VI, VII & VIII & is supplied by right hepatic artery, right branch of portal vein & drained by right hepatic duct.

        Exam Question

• The physiological right & left lobes have separate biliary drainage & vascular supply, i.e. they are supplied respectively by right & left branches of portal vein & hepatic artery & bile is conveyed by the corresponding hepatic ducts (bile ducts).