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肝的分叶、分段

2014-08-21医学影像

单纯根据肝外形的沟裂,将肝分为左叶、右叶、尾状叶、方叶,此与肝内管道的分布并不完全符合。而根据腐蚀标本,依据肝内管道系统的分布并结合肝的外形可以看到叶与叶之间或段与段之间存在明显的裂隙。据此肝有三个叶间裂,三个段间裂。叶间裂包括肝中裂、左叶间裂、右叶间裂。段间裂有左外叶段间裂、右后叶段间裂和尾状叶段间裂。由这些裂将肝分为右半肝、左半肝,五个叶(右前叶、右后叶、左内叶、左外叶与尾状叶)、六个段(左外叶上、下段,右后叶上、下段,尾状叶左、右段)。现代肝脏外科即依据这些分叶及分段方式,施行半肝、肝叶或肝段切除术。

Couinaud根据肝内门静脉干和肝静脉的分布范围,将肝脏分为八段,门静脉分支分布于肝段内,而肝静脉位于肝段间。具体如下:以肝中静脉所在纵行平面将肝脏分为左右半肝,以肝左静脉为界将左半肝纵行分为左内与左外叶,而左外叶以门静脉左支为界水平分为上下两段,以肝右静脉纵向、门静脉右支横向将肝右叶分为上下前后四段,而肝尾叶为单独的一段,即S1为尾状叶,S2为左外叶上段,S3为左外叶下段,S4为左内叶,S5为右前叶下段,S6为右后叶下段,S7为右后叶上段,S8为右前叶上段 

五叶八段是根据门静脉和肝静脉在肝内的行程划分

Segmental anatomy

Segmental anatomy according to Couinaud.

Couinaud classification

The Couinaud classification of liver anatomy divides the liver into eight functionally indepedent segments. 
Each segment has its own vascular inflow, outflow and biliary drainage.
In the centre of each segment there is a branch of the portal vein, hepatic artery and bile duct.
In the periphery of each segment there is vascular outflow through the hepatic veins.

Right hepatic vein divides the right lobe into anterior and posterior segments.
Middle hepatic vein divides the liver into right and left lobes (or right and left hemiliver). This plane runs from the inferior vena cava to the gallbladder fossa.
Left hepatic vein divides the left lobe into a medial and lateral part.

Portal vein divides the liver into upper and lower segments.
The left and right portal veins branch superiorly and inferiorly to project into the center of each segment.

Because of this division into self-contained units, each segment can be resected without damaging those remaining. For the liver to remain viable, resections must proceed along the vessels that define the peripheries of these segments. This means, that resection-lines parallel the hepatic veins,
The centrally located portal veins, bile ducts, and hepatic arteries are preserved.

 

Clockwise numbering of the segments

Segments numbering

There are eight liver segments.
Segment 4 is sometimes divided into segment 4a and 4b according to Bismuth.
The numbering of the segments is in a clockwise manner (figure).
Segment 1 (caudate lobe) is located posteriorly. It is not visible on a frontal view.

On a frontal view of the liver the posteriorly located segments 6 and 7 are not visible.

 

The illustrations above are schematic presentations of the liversegments. 
In reality however the proportions are different.
On a normal frontal view the segments 6 and 7 are not visible because they are located more posteriorly. 
The right border of the liver is formed by segment 5 and 8.
Although segment 4 is part of the left hemiliver, it is situated more to the right.

Couinaud divided the liver into a functional left and right liver (in French 'gauche et droite foie') by a main portal scissurae containing the middle hepatic vein. This is known as Cantlie's line. 
Cantlie's line runs from the middle of the gallbladder fossa anteriorly to the inferior vena cava posteriorly.

On this illustration it looks as if the medial part of the left lobe is separated from the lateral part by the falciform ligament. However it actually is the left hepatic vein, that separates the medial part (segment 4) from the lateral part (segments 2 and 3).
The left hepatic vein is located slightly to the left of the falciform ligament.

 

Transverse anatomy

The far left figure is a transverse image through the superior liver segments, that are divided by the hepatic veins.

The right figure shows a transverse image at the level of the left portal vein.
At this level the left portal vein divides the left lobe of the liver into the superior segments (2 and 4A) and the inferior segments (3 and 4B).
The left portal vein is at a higher level than the right portal vein.

LEFT: above the level of the left portal vein.RIGHT: at the level of the left portal vein.

LEFT: at the level of the right portal vein.RIGHT: at the level of the splenic vein.

提供一个比较简便好记的方法: 第一肝门以上顺时针:7 8 4 2 第一肝门以下顺时针:6 5 4 3

 

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