Figure 15­4
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The classic lobule in the liver is defined as a polyhedral structure centered at the central vein (or terminal hepatic
Holdings,
venule). The periphery of the lobule is bordered by connective tissue, in which are located the portal tracts consist-
ing of the hepatic artery, portal vein, bile duct, lymphatic vessel, and associated connective tissue. Radiating from
the central vein are plates of hepatocytes, on either side of which are sinusoidal capillaries. The lobule has been
LLC.
considered the classic structural and functional unit of the liver.
Not
to
In the image are portions of four hepatic lobules. The central vein is not visible in this specimen. A portal tract is
be
shown in the center of the field. The portal tract has a number of synonyms: portal triad and portal canal are two
redistributed
of the more frequently used terms. The portal triad consists of three structures: hepatic artery (A), portal vein (B),
and bile duct (C). A lymphatic vessel is also considered to be a component of the portal tract, but it is not always
present in the section. The portal canal refers to the space that contains the triad and surrounding connective tissue.
or
In our discussion, we will use the term portal tract for this region and its contents.
modified
It is important to remember that blood flows from the portal tract toward the central vein. In the sinusoids, which
are drained by the central vein, arterial blood from branches of the hepatic arteries mixes with venous blood from
in
any
the portal veins. Bile, which is produced by the hepatocytes, travels from the central area of the classic lobule to the
way
small bile ducts, which unite to form the hepatic ducts carrying the fluid to the gall bladder, where it is concentrated
and stored. Therefore, within the classic liver lobule, blood and bile move in opposite directions.
without
permission.
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