318
UNIT 3
Organ Systems
Liver
Portal
Portal
triad
triad
Portal
triad
Central
Central
vein
vein
Central
vein
Central
Central
vein
vein
Central
Central
vein
vein
Central
Central
vein
vein
Central
vein
Central
vein
Central
vein
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Portal triad
Zone 1
Zone 1
Zone 2
Zone 3
A
Figure 16-12A.
Liver acinus.
Silver stain,
3
89 (
left
); H&E,
3
42 (
right
)
Left:
An example of the architecture and general pattern of the
liver
is shown. The hepatocytes are supported by a network of reticular
F bers (
black
). The
red dotted line
indicates a portion of the classic lobule. The diamond-shaped
hepatic acinus
(
blue dotted line
) is located
between two central veins and two portal triads. The hepatic acinus has three zones.
Zone 1
is closer to the portal triads and receives the
most blood fl ow from the portal veins and hepatic arteries in the portal triads. Hepatocytes in this region are more likely to survive than
cells in zone 3 in case of insufF cient oxygen and nutrient supply in the liver, such as in heart failure. However, hepatocytes in zone 1 are
also exposed to blood-borne toxins F rst and are more likely to be damaged than the cells in zone 3.
Zone 3
is far from the portal triads
and close to the central veins; it has a poor oxygen and nutrient supply, but is also less exposed to blood-borne toxins. In case of heart
failure, hepatocytes in zone 3 lack oxygen and appear necrotic F rst.
Zone 2
has an intermediate response to oxygen and toxins.
Right:
This image shows the general pattern of organization of the liver at a lower magniF
cation. The classic lobule is indicated by
the
white dotted line
.
Lymphatic
Lymphatic
vessel
vessel
Lymphatic
vessel
Hepatic
artery
Hepatic artery
Hepatic
artery
Bile ductule
Bile ductule
Bile ductule
Portal
Portal
vein
vein
Portal
vein
B
Figure 16-12B.
Portal triad, liver.
H&E,
3
277
Six
portal triads
make up one hexagon-shaped, classic
lobule. Each portal triad is composed
of a
portal vein
, a
hepatic artery
, and a
bile ductule
. These structures are surrounded by
connective tissues, which usually contains a
lymphatic vessel
. (1) The
portal
vein
has a large
lumen and thin vessel wall. The branches (portal venules) of the portal vein feed the hepatic
sinusoids. (2) The
hepatic artery
has a small lumen and a wall of smooth muscle that is 2 to 3
cell layers thick. The hepatic artery also has branches (hepatic arterioles), which feed into the
hepatic sinusoids. The hepatic sinusoids, therefore, receive glucose-rich blood from the portal
vein and oxygen-rich blood from the hepatic artery (see ±ig. 16-11). (3) The
bile ductule
is
lined by cuboidal cells with dark, round nuclei. The bile ductule collects bile from the bile
canaliculi and drains it into the hepatic duct.
CLINICAL CORRELATION
Portal area
with
neutrophils
Steatosis
Mallory
body
C
Figure 16-12C.
Alcoholic Fatty Liver (Steatosis).
H&E,
3
186
Alcoholic fatty liver
, or
steatosis
, is usually an asymptomatic and
reversible liver
condition associated with mild to moderate alcohol use in which lipid accumulates
within hepatocytes. Severe steatosis may lead to
hepatomegaly
and mildly elevated
serum bilirubin and alkaline phosphatase levels. Grossly, a fatty liver appears yel-
low and greasy compared to the normal red-brown appearance of liver tissues.
Chronic alcohol abuse, particularly heavy binge drinking, may lead to
alcoholic
hepatitis
, an infl ammatory condition of the liver characterized by abdominal dis-
comfort, malaise, hepatomegaly, and abnormal liver tests. Severe cases may result
in fulminant hepatic failure. Histologic features of alcoholic hepatitis include a
neutrophilic in± ltrate
, hepatocyte
edema
and
necrosis
, and the presence of
Mallory
bodies
, which are cellular accumulations of cytokeratin intermediate F laments.
Some patients will progress to
alcoholic cirrhosis
characterized by regenerating
nodules of hepatocytes with intervening F brous septae. This image shows
portal
± brosis
, inF ltration by neutrophils, fatty change, and Mallory bodies.
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