The human body can be divided using imaginary lines and planes to help understand its internal organization. When the body is upright, a straight line called the vertical axis is used as a clear and consistent reference to orient the location of body parts and the direction of movement. Additionally, planes section the body using imaginary flat surfaces. The three cardinal body planes are frontal, sagittal, and transverse. The frontal or coronal plane divides the body into the anterior and posterior portions. The sagittal plane divides the body vertically into right and left sides. Equal division of the body through the midline results in midsagittal sections. In contrast, sectioning through the parasagittal plane results in unequal sides. The transverse plane, perpendicular to frontal and sagittal planes, divides the body horizontally into upper and lower regions.