Liver 

Introduction


The liver is the largest of the abdominal viscera, occupying a
substantial portion of the upper abdominal cavity.
  • It performs a wide range of metabolic activities necessary for homeostasis, nutrition and immune defence.
  • It is composed largely of epithelial cells (hepatocytes), which are bathed in blood derived from the hepatic portal veins and hepatic arteries.
  • Hepatocytes are also associated with an extensive system of minute canals, which form the biliary system into which products are secreted.
  • The liver lies in the upper right part of the abdominal cavity.
  • It occupies most of the right hypochondrium and epigastrium, frequently extends into the left hypochondrium as far as the left lateral line.
  • In adults the liver weighs 2% of body mass.
  • an overall wedge shape
The liver capsule plays an important part in maintaining the integrity of its shape.

Once the capsule is lacerated, the liver tissue is easily parted and provides only imited support for surgical sutures.

These features, in combination with its exceptional vascular supply, make the liver prone to potentially lethal
injuries if it is split open.

EXTERNAL FEATURES

The liver is attached to the anterior abdominal wall
diaphragm and other viscera by several ligaments, which
are formed from condensations of the peritoneum:
  • Falciform ligament
  • Coronary ligament
  • Triangular ligaments
  • Lesser omentum

Porta hepatis

The Porta hepatis is the area of the inferior surface through which all the neurovascular and biliary structures, except the hepatic veins, enter and leave the liver.
It is situated between the quadrate lobe in front and the audate process behind.
Right and left hepatic bile ducts emerge from it.
All these structures are enveloped in the perivascular fibrous capsule hepatobiliary capsule of Glisson - a sheath of loose connective tissue which surrounds the vessels

LOBATION AND SEGMENTATION

 The liver has four lobes or eight segments, depending on whether it is defined by its gross anatomical appearance or by its internal architecture. 
Gross anatomical lobes 
  • Right lobe. The right lobe is the largest in volume and contributes to all surfaces 
  • Quadrate lobe  The quadrate lobe is only visible from the inferior surface. it is functionally related to the left lobe.
  • Caudate lobe this lobe is said to arise from the right lobe, but it is functionally separate
  • Left lobe The left lobe is the smaller of the two 'main' lobes

VASCULAR SUPPLY

Two sources provide blood to the liver
  • Hepatic artery
Celiac trunk of aorta
  • Portal vein
  • Blood exits the liver via the central vein
  • 25% of cardiac output
  • Blood flow into the liver is controlled by number of factors
  • Muscular sphincters
  • Numbe of different stimuli, including the autonon
  • nervo
system, circulating hormones, bile salts, and metabolites


Portal vein
  • Portal vein is a valveless structure that is formed by the confluence of the superior mesenteric vein and the splenic vein.
  • 75% of the total liver
  • blood supply by volume
  • 2 PV in livèr
  • Pancreas
  • Left 2,3,4
  • Right 5,6,7,8

  • Portal vein is formed by the union of the superior mesenteric vein and thne splenic vein at the level of the second lumbar vertebra behind the head of pancreas
  • Portal vein is contained within the hilum of the liver