The study of human anatomy requires a precise and universal language to describe the location of body structures and the direction of movement. Anatomists use a standardized reference point called the Anatomical Position, defined as a person standing erect, with feet slightly apart, eyes directed forward, and arms hanging at the sides with palms facing forward. All descriptions of location and orientation are made as if the body is in this specific posture, ensuring clarity across all medical and scientific fields.
To refine this descriptive language, imaginary flat surfaces, known as body planes, are used to visualize “slices” or sections through the body or an organ. These planes provide a consistent way to describe internal organization and spatial relationships.
The Sagittal Plane
The sagittal plane is a vertical division that runs from front to back, separating the body or an organ into left and right portions. This plane describes movements involving forward and backward motion, such as walking or flexing and extending a joint. The directional terms medial and lateral describe positions relative to the body’s midline.
A structure is medial if it is closer to the center line, while it is lateral if it is farther away. For instance, the heart is medial to the lungs, and the shoulder is lateral to the neck. Sagittal planes include two specific types.
The Midsagittal Plane, also called the median plane, is the single, central vertical line that divides the body into two perfectly equal left and right halves. This plane passes precisely through midline structures, such as the navel and the spine. Any other sagittal plane parallel to the midsagittal plane is called a Parasagittal Plane. Parasagittal planes result in unequal left and right sections, allowing for precise reference points away from the center.
The Coronal Plane
The coronal plane, also referred to as the frontal plane, is a vertical division that runs perpendicular to the sagittal plane. This plane divides the body or an organ into anterior (front) and posterior (back) sections.
The terms anterior and posterior are the primary directional descriptors associated with this plane. Anterior describes structures toward the front, while posterior describes structures toward the back. The synonymous terms ventral (front/belly side) and dorsal (back side) are also commonly used.
Viewing the body in a coronal section provides a perspective for observing the relationship between front and back body cavities and organs. For example, a coronal view separates structures of the thoracic cavity, such as the lungs and heart, from the posterior muscles and vertebrae. Movements that occur within this plane are side-to-side actions, like moving a limb away from the midline (abduction) or toward it (adduction).
The Transverse Plane
The transverse plane, known alternately as the horizontal or axial plane, is the third main plane of reference. This plane runs horizontally, perpendicular to both the sagittal and coronal planes. It divides the body or an organ into superior (top) and inferior (bottom) portions.
The terms superior and inferior describe relative positions along the long axis of the body. Superior, or cranial, refers to a position closer to the head, while inferior, or caudal, refers to a position closer to the feet. For instance, the stomach is superior to the large intestine, and the knees are inferior to the hips.
The transverse plane holds clinical importance because it is the plane most often used in modern medical imaging. Techniques such as Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI) frequently produce “cross-sectional” or axial images. These axial views display internal structures as though the body has been sliced horizontally, which is valuable for detecting tumors, assessing organ damage, and examining the spine and brain.