Anatomical lines, or "reference lines," are theoretical lines drawn through anatomical structures and are used to describe anatomical location. The following reference lines are identified in Terminologia Anatomica:Anterior median line Lateral sternal line: A vertical line corresponding to the lateral margin of the sternum. Parasternal line: A vertical line equidistant from the sternal and mid-clavicular lines. Mid-clavicular line: A vertical line passing through the midpoint of the clavicle. Mammillary line Anterior axillary line: A vertical line on the anterior torso marked by the anterior axillary fold. Midaxillary line: A vertical line passing through the apex of the axilla. Posterior axillary line: A vertical line passing through the posterior axillary fold. Scapular line: A vertical line passing through the inferior angle of the scapula. Paravertebral line: A vertical line corresponding to the tips of the transverse processes of the vertebrae. Posterior median line