Part Of: [Neuroanatomy] sequence

Sagittal, Transverse, and Frontal

An efficient way to navigate three-dimensional spaces is to use three orthogonal axes.

• Pilots use roll, pitch, and yaw.
• Geometricians use x, y, z.
• Anatomists use sagittal, transverse, and frontal.

We also need a language to navigate anatomical space.

• Lateral/Medial means side/center (adjusting X, moving the sagittal plate left & right)
• Superior/Inferior means top/bottom (adjusting Y, moving the transverse plate up & down)
• Anterior/Posterior means belly/back (adjusting Z, moving the frontal plate forwards & backwards)

Notice how directions along the X axis (first bullet) are of a different style than other axes. While the other directions gesture at an infinite scale (-∞, +∞), the first gestures at [0, +∞).

This simplification is only possible because of symmetry: nearly all vertebrates exhibit bilateral symmetry along the sagittal axis.

Neuraxis Distortions

Anatomy maintains a lot of duplicate names (synonyms). Anatomy coordinate systems are no exception:

• Ventral/Dorsal is synonymous with front/back (Anterior/Posterior)
• Rostral/Caudal is synonymous with top/bottom (Superior/Inferior)

To be perfectly frank, anatomy naming conventions seem inefficient to me. I wonder if too much has been sacrified in pursuit of historical contiguity. But sometimes, “redundant” synonyms come in handy. Consider the following example:

Humans are bipedal. It turns out that this evolutionary innovation deforms the neuraxis.

 

Because of the bend in the human neuraxis, “front & back” is in danger of being confused with “top & bottom”.

Fortunately, we can use the above synonyms to disambiguate direction in the brain.

• In the brain alone, Ventral/Dorsal becomes synonymous with bottom/top (Inferior/Superior)
• In the brain alone, Rostral/Caudal becomes synonymous with front/back (Anterior/Posterior)

 

Perhaps humans should just give up this walking upright business altogether. It would make anatomy much easier!