medialinje

Medialinje is the anatomical term for the midline of a bilaterally symmetrical organism, most often used to describe the vertical line that runs along the center of the body, dividing left and right sides. It coincides with the sagittal midline of the body and with the linea alba in the anterior abdomen. The term derives from Latin medialis 'middle' and linea 'line'.

In human anatomy, the medialinje serves as a reference point in descriptions of location and orientation. Structures situated toward the medial side are described as being closer to the medialinje, while those toward the outer sides are lateral. The corresponding plane is the midsagittal (or median) plane, which passes longitudinally through the body along the medialinje.

Clinically, the medialinje is used to guide incisions and imaging. Median sternotomy and midline laparotomy exploit this line for access to thoracic and abdominal cavities. In radiology and neurology, the midline is used to assess alignment, such as midline shift in brain injury or the position of the ventricles relative to the skull.

Variations exist: the exact position can vary with posture, body habitus, and congenital anatomy. While the concept applies to many bilaterally symmetrical organisms, the precise landmarks may differ among species.