Each sector can be subdivided into even smaller portions called segments. In total, the liver has eight segments:

The right posterior (lateral) sector contains segment 6 and segment 7.
The right anterior (medial) sector includes segment 5 and segment 8.
The left medial sector has segment 4 and segment 1. The upper part of segment 4 is usually referred to as segment 4a, while the lower portion is recognized as segment 4b. The caudate lobe corresponds to the segment 1.
The left lateral sector includes segment 2 and segment 3.

Initially, segments were numbered using Roman numerals I to VIII, but nowadays, the Arabic numerals 1 to 8 are being used instead of the Roman numerals.

Note: The numbering of the segments goes in the clockwise direction. It starts with the caudate lobe (segment 1) and continues from the left to the right side of the liver.

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Liver segments