Origin: evagination of the wall of the foregut.
Location: upper right quadrant of the abdominal cavity.
- Protein synthesis and secretion (albumin, prothrombin, fibrinogen)
- Bile formation and secretion
- Metabolism of lipid-soluble drugs (including detoxification) and steroids (including
- Lipoprotein synthesis and secretion
- Carbohydrate metabolism
- Urea formation from ammonium ion (urea cycle).
- The largest mass of glandular tissue in the body and also the largest internal organ.
- About 75% of the blood supply it receives from hepatic portal vein, which carries venous
blood from the digestive tube, pancreas,
and spleen. Remaining 25% of the blood supply provides the
hepatic artery with oxygenated blood. Blood from the two sources is mixed as it perfuses
the hepatocytes of the liver parenchyma.
- The "classic" liver lobule is the sixsided polyhedral prism with portal
triads (hepatic artery, portal vein, and bile duct) at each of the
corners. The vessels of the portal triads send distributing branches along the sides of
the lobule, and these branches open into the sinusoids. The long axis
of the lobule is transversed by the central vein,
and this vessel receives blood from the sinusoids. Interconnecting sheets of hepatocytes are disposed in a radial pattern from the central vein to the
perimeter of the lobule.
- The portal lobule - its morphologic axis is the interlobular bile duct
of the portal triad of the "classic" lobule. Its outer
margins are imaginary lines drown between the three central veins that are closest to that
portal triad. The portal lobule emphasizes the exocrine function of the liver - bile secretion.
- The liver acinus is described as diamond or lozenge shaped. Its short axis
is defined by the terminal branches of the portal triad that lie along
the border between two "classic" lobules. The long axis is the line drown
between the two central veins closest to the short axis. It allows interpretation of
patterns of degeneration, regeneration and toxic effects in the liver parenchyma relative
to the degree of vascular perfusion of the hepatic cells.
Function: constitute about 80% of the cell population, large polygonal (20 - 30
mkm in diameter).
Composition and functions:
- Nucleus - in the adult liver are tetraploid, genetic information
- Rough endoplasmic reticulum and free ribosomes - protein synthesis and secretion
- Numerous mitochondria (as many as 800-1000 per cell) - energy generation, urea formation
from ammonium ion
- Large deposits of glycogen - energy and metabolic storage, carbohydrate metabolism
- Lipid droplets - energy and metabolic storage, lipoprotein synthesis and secretion
- Several Golgi complexes - protein and lipoprotein synthesis and secretion
- Peroxisomes - (as many as 200-300 per cell) - gluconeogenesis, metabolism of purins,
alcohol, and lipids
- Smooth endoplasmic reticulum - detoxification of drugs and conjugation of other noxious
- Lysosomes - storage site for iron
Location: at each of the corners of the "classic" lobule, in the
loose stromal connective tissue designated as portal
areas or portal canals. Between stroma and hepatocytes is a small space called space
of Mall - one of sites where lymph originates.
Composition: portal vein, hepatic artery - interlobular vessels, bile duct, lymphatic vessels.
Location: between the anastomosing plates of hepatic cells.
They receive mixed portal and arterial blood from the smallest portal triads
and lead to the venous network - central vein.
Function: provide for the exchange of substances between the blood and the
Composition: discontinuous capillaries
Function: final breakdown of damaged erythrocytes,
lipoprotein metabolism, immunological defense.
Location: between the basal surfaces of hepatocytes and
the basal surfaces of endothelial cells and Kupffer cells.
Composition: microvillous processes of hepatocytes, lipocytes (Ito cells), type Ø collagen (reticular) fibers.
Function: conduit the bile centrifugally from the hepatocytes
to the gallbladder as well as the intestine.
- Canaliculi are the small canals formed by grooves in neighboring hepatocytes.
- Canals of Hering - small ductules that constitute a network with cuboidal epithelium and basal lamina.
- Intralobular bile duct - a part of the portal triad, 15 - 40 mkm in
Composition: cuboidal or columnar epithelium, dense connective tissue with numerous elastic fibers.
- Right and left lobar ducts
Composition: columnar epithelium
with well-developed microvilli, dense connective
tissue with numerous elastic fibers and near
the hilum smooth muscle cells.