PARTS

lobes
right lobe
left lobe
caudate lobe
segments (1-8)

The right and left lobe are divided by the middle hepatic vein also called Canti’s line.

right lobe
anterior segment
posterior segment

left lobe
medial segment
lateral segment
subsegments

lobule
liver trabeculae
cells
connective tissue

Riedel’s lobe is a variant and is
a inferior extension of the
right lobe of the liver

It has been said by the wise that “life depends on the liver!” Think twice on this statement. As we previously mentioned, the Babylonian civilization of some 4500 years ago looked upon the liver as a god. In modern biology and medicine we see the liver as the largest gland in the body and being central to many metabolic functions. It is a solid organ divided into two lobes, with the right lobe being larger than the left lobe. 

Middle hepatic vein

The red arrow points to the middle hepatic vein which is one of the three main hepatic veins. To the right of the middle hepatic vein is the right lobe and to its left is the left lobe. By convention we are describing the right as seen in cross sectional imaging (i.e. right side of patient as we see it from below). (Image courtesy of Ashley Davidoff M.D.)

 

Middle hepatic vein

The middle hepatic vein divides the liver into two lobes – right and left lobes. The middle hepatic vein runs parallel and superior to the long axis of the gallbladder. 

Middle hepatic vein

The cross sectional image of the liver shows the middle hepatic vein which is highlighted in the following image. (Image courtesy of Ashley Davidoff M.D.)

Transverse of the Gallbladder Dividing Liver into Left and Right Lobes

71327s gallbladder liver left lobe right lobe position interlobar fissure middle hepatic vein normal anatomy USscan copyright 2008 Courtesy Ashley Davidoff MD

A good way of defining the left from the right lobes of the liver is to use the gallbladder as a line of demarcation. The gallbladder runs in the same axis as the middle hepatic vein and performs the same structural function in dividing the liver into right and left lobes.

The gallbladder and the middle hepatic vein

The pear shaped gallbladder can be identified as the low density structure running in the same axis as the middle hepatic vein and performing the same structural function in dividing the liver into right and left lobes. (Image courtesy of Ashley Davidoff M.D.)

The gallbladder and the middle hepatic vein

A line drawn through the long axis of the gallbladder divides the liver into its two lobes.  (Image courtesy of Ashley Davidoff M.D.)

There have been numerous methods of dividing and naming the parts of the liver. The earliest methods divided the liver into the left lobe, the quadrate lobe, the right lobe and the caudate lobe. Subsequently, the liver divisions were based on the venous anatomy. The right lobe was separated from the left by the middle hepatic vein. The falciform ligament divided the left lobe into the medial segment (closest to the middle hepatic vein) and the lateral segment. The right lobe was divided by the right hepatic vein into an anterior segment and a posterior segment. The next several diagrams outline the current segmental nomenclature which is still based on the distribution of the hepatic veins: Segment I = caudate lobe Segments II, III & IV = left lobe Segments V, VI, VII & VIII = right lobe

vein anteriorly. (Image courtesy of Ashley Davidoff M.D.)

At a slightly higher level, the caudate lobe curls around the IVC giving it a woodpecker appearance. (Image courtesy of Ashley Davidoff M.D.)

“woodpecker

This image of the superior aspect of the caudate outlines (in red) its “woodpecker” shape. The yellow lines indicate the position of the ligamentum venosum.

The basic functional unit of the liver is the liver lobule, which is approximately 1-2mm in diameter. The lobule consists of a central vein from which hepatic cells (hepatocytes), usually two cells thick, radiate like spokes of a wheel. Within the lobules lie extensions of the portal vein, bile ducts, hepatic artery, hepatic veins, lymphatics, and nerves.

Portal triads

What is Mickey doing in the bowels of the liver? You will have to read the next few pages to find out. This image shows the spokewheel pattern of the liver lobule with the central ve

There are thousands of lobules, each with a central vein and each delivering the “goods” to the venules. The venules collectively join to form the hepatic veins, and eventually, merge with the inferior vena cava (IVC). Destination? The heart, from where the metabolic products will be delivered to the rest of the body.   (Image courtesy of Ashley Davidoff M.D.)