Basic Reference Planes
Three basic reference planes are used in zoological anatomy: the sagittal plane, the coronal plane, and the transverse plane . A sagittal plane divides the body into sinister and dexter (left and right) portions. The midsagittal or median plane is in the midline and all other sagittal planes (also referred to as parasagittal planes) are parallel to it. A coronal plane or frontal plane divides the body into dorsal and ventral (back and front, or posterior and anterior) portions. A transverse plane, also known as an axial plane or cross-section, divides the body into cranial and caudal (head and tail) portions.
Sometimes the orientation of certain planes needs to be distinguished, as in the case of medical imaging techniques such as sonography, CT scans, MRI scans, or PET scans. 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.
For post-embryonic humans, a coronal plane is vertical and a transverse plane is horizontal. In contrast, for embryos and quadrupeds, a coronal plane is horizontal and a transverse plane is vertical. This is due to the bipedal structure of humans, while quadrupeds travel with their belly pointing downward.
A longitudinal plane is any plane perpendicular to the transverse plane. The coronal plane and the sagittal plane are examples of longitudinal planes.