Anatomical planes are imaginary flat surfaces that anatomists use as a system of reference to describe the location of structures or the direction of movement within the human body. The frontal plane is one of the three primary reference planes that provide a foundational structure for understanding human anatomy and biomechanics.
Defining the Frontal Plane
The frontal plane is a vertical plane that divides the body into two sections: an anterior (front) section and a posterior (back) section. This plane is often called the coronal plane, a name derived from the Latin word for “crown” because it runs in the same direction as the coronal suture of the skull. Visualizing the frontal plane means imagining a sheet of glass passing through the body from side to side, perpendicular to the ground. Any number of frontal planes can be drawn parallel to each other, but they all maintain this fundamental division of front and back. A mid-coronal plane, for instance, would transect the standing body into equal front and back halves, cutting through both shoulders.
Placing the Frontal Plane within the Anatomical System
The frontal plane exists as part of a three-dimensional coordinate system, forming an orthogonal relationship with the other two primary anatomical planes. The three planes—frontal, sagittal, and transverse—are arranged so that each one is perpendicular, or at a right angle, to the other two. The sagittal plane, which divides the body into left and right sections, runs perpendicular to the frontal plane. The transverse plane, which divides the body into superior (upper) and inferior (lower) sections, is also perpendicular to the frontal plane. The frontal plane’s associated axis of rotation runs from front to back, allowing movement to occur around this line.
Movements Defined by the Frontal Plane
Movement that occurs in or parallel to the frontal plane is characterized as side-to-side motion. These movements take place around the anterior-to-posterior axis. The two most commonly recognized joint actions in this plane are abduction and adduction. Abduction is the movement of a limb or body part away from the midline, such as raising an arm or leg straight out to the side. Conversely, adduction involves moving a limb or body part back toward the midline.
For example, the motion of a jumping jack, where the limbs move outward and then inward, is a classic example of simultaneous abduction and adduction. Other specific movements that occur in the frontal plane include lateral flexion, which is the side bending of the torso or neck. The complex actions of the scapulae (shoulder blades) use this plane, including elevation (shrugging the shoulders upward) and depression (pulling them downward). The foot also uses the frontal plane for inversion and eversion, where the sole turns inward or outward, respectively.