- Liver is the largest gland of body situated in right upper quadrant of abdominal cavity and occupies whole of the right hypochondrium, greater part of epigastrium with extension into left hypochondrium. It weighs about 1500-1600 gm in males and 1200-1300 gm in females.
- Liver has five surfaces: anterior, posterior, superior, inferior and right. It has only one prominent border, inferiorborder.
- Liver is covered by Glisson's capsule. Interior of liver is divided into hexagonal lobules. Lobule contains sinusoids which have fenestrated endothelium covering the subendothelial space of Disse. Two important cells in liver are hepatocytes (Parenchymal cells) and kupffer cells (monocytic-mocrophages).
Lobes of liver
The liver can be divided into right and left lobe anatomically and physiologically.
- Anatomical lobes
- Caudate lobe: - It is situated on posterior surface of right lobe. It is bounded on right by groove/or, on left by fissure for ligamentum venosum, and inferiorly by porta hepatis (containing hepatic artery, portal vein, hepatic duct bile duct, nerve plexus and 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 and is related to crura of diaphragm, right inferior phrenic artery and coeliac trunk.
- Quadrate lobe: - It is situated on the inferior surface and rectangular in shape. It is bounded anteriorly by inferior border of liver, posteriorly by porta hepatis, on right by fossa for gall bladder and on left by fissure for ligamentum teres.
- Physiological lobes
- Physiological right and 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 and left lobes have separate biliary drainage and vascular supply, i.e. they are supplied respectively by right and left branches of portal vein and hepatic artery and bile is conveyed by the corresponding hepatic ducts (bile ducts).
- Quadrate lobe (anatomical part of right lobe) belongs to physiological left lobe because it is supplied by a branch of left hepatic artery and left branch of portal vein and is drained into left hepatic duct.
- Caudate lobe (anatomical part of right lobe) belongs physiologically to both right and left lobes because it receives blood from right and left hepatic arteries; right and left branches of portal vein; and drains bile into both right and left hepatic duct.
Segmental anatomy of the liver
Based on the distribution of portal vein and hepatic vein, Couinaud divided each physiological (functional) lobe of liver into 4 segments each and hence liver is divided into 8 segments. The physiological left lobe is composed of 4 segments designated I to IV and is supplied by left branch of hepatic artery, left branch of portal vein and drained by left hepatic duct. The physiological right lobe consists of segment V, VI, VII and VIIIand is supplied by right hepatic artery, right branch of portal vein and drained by right hepatic duct. Segment I corresponds to caudate lobe and segment IV to quadrate lobe.
Right lobe is subdivided into anterior and posterior segment and left lobe into medial and lateral segments. Thus the segments of liver are:-
- Right anterior -V (inferior), VIII (superior)
- Right posterior -VI (inferior), VII (superior)
- Left medial -IV (quadrate lobe) :divided into IV a (superior) and IV b (inferior)
- Left lateral - II (superior), III (inferior)
- Caudate lobe (Segment I) is considered as posterior segment.
Note: - According to text books of anatomy, segment I (caudate lobe) is a part of left lobe (left medial), but according to textbooks of surgery it is a separate posterior lobe.
- Liver has dual blood supply and receives 20% of its blood supply through hepatic artery and 80% through portal vein.
- Venous drainage is through hepatic veins into IVC.