Take a mid point on gall bladder, and inferior vena cava, and join these points, which will form a line known as CANTLIE’s LINE, given by American Classification. Actually this cantlie line is the surface marking for middle hepatic vein.
Take the cautry and start cutting the liver, till you reach middle hepatic vein, continue your cutting, this way you will divide the liver into 2 surgical halves called as right and left surgical halves which is same as physiological halves.
Anatomically liver is divided into two halves by FALCIPARUM ligament.
You can know liver segmental anatomy at radiologyassesstant.nl
Liver is divided into 3 parts by three veins right hepatic vein, middle hepatic vein and left hepatic vein.
Portal Vein divides the liver in upper and lower segments, 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.
How to count the liver segments this way dissected?
This classification is known as Couinaud classification.
Counting is always started from left liver and done in clock wise direction when seen from front. The segment which is comma shaped is known as Caudate lobe, this caudate lobe lies partly in both right and left surgical liver. Segment 4 is very large is hiding segment 1 from front. Segment 4 is divided into 2 parts 4a and 4b.
Between 1 and 2 lies the fissure called fissure of ligamentum venosum, and between 3 and 4 is umblical fissure for ligamentum teres. You can cut in these fissures and you can remove 1 and 3 bloodlessly.