Anatomical planes

An anatomical plane is a hypothetical plane used to transect the human body, in order to describe the location of structures or the direction of movements. In human and animal anatomy, three principal planes are used:

There could be any number of sagittal planes; however, there is only one cardinal sagittal plane. The term cardinal refers to the one plane that divides the body into equal segments, with exactly one half of the body on either side of the cardinal plane. The term cardinal plane appears in some texts as the principle plane. The terms are interchangeable.

The following terms are defined in reference to the anatomical model being in the upright orientation (standing):

The axes and the sagittal plane are the same for bipeds and quadrupeds, but the orientation of the coronal and transverse planes switch. The axes on particular pieces of equipment may or may not correspond to axes of the body, especially since the body and the equipment may be in different relative orientations.

Brain viewed from below. This is an example of a transverse plane.

Brain cut in half through the midsection. This is an example of a sagittal plane.

When describing anatomical motion, these planes describe the axis along which an action is performed. So by moving through the transverse plane, movement travels from head to toe. For example, if a person jumped directly up and then down, their body would be moving through the transverse plane in the coronal and sagittal planes.

A longitudinal plane is any plane perpendicular to the transverse plane. The coronal plane and the sagittal plane are examples of longitudinal planes.

Sometimes the orientation of certain planes needs to be distinguished, for instance in medical imaging techniques such as sonography, CT scans, MRI scans, or PET scans. One imagines a human in the anatomical position, and an X-Y-Z coordinate system with the y-axis going from front to back, the x-axis going from left to right, and the z-axis going from up to down. The z-axis is usually up (Tait-Bryan angles) and the right-hand rule applies.

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