Anatomical terminology relates, in some degree, to how we approach a body in the lab, or perhaps in a physical exam or during surgery. If the body is faceup, which in anatomy we call supine, the sternum is superficial, and the heart is deep to that. If the body is facedown, or prone, the ribs would be superficial and the kidneys would be deep to them.
Not Always Intuitive
Superficial is the only anatomical directional term that varies in terms of body position. In other words, you would never say that the sternum is superficial to the heart and heart is superficial to the spine, since the spine is so deep into the body, and is more associated with the dorsal aspect. You’d say the heart is anterior to the spine, meaning it’s in front of the spine. Some of this you just have to learn by convention; it’s not always intuitive.
Two other terms related to the sides of the body are ipsilateral, which means ‘on the same side of the body’, and contralateral, which means ‘on opposite sides of the body’. We occasionally use these terms when talking about body movements—like when a muscle on the right side of the body causes movement to the left.
The Usage of ‘Intermediate’
Lateral means ‘farther away from the midline of the body’, medial means ‘closer to the midline of the body’, and median means ‘right on the midline’. The term intermediate can be used to indicate something is between two structures.
An instance in which intermediate comes in handy is when talking about depths in the body. Superficial means ‘closer to the body’s surface’, deep means ‘farther from the body’s surface’, and intermediate could refer to a structure between those. If we compare the skin to the muscles, the skin is superficial and the muscles are deep, but if we compare the muscles to the bones, the muscles become superficial and the bones are deep.
If we compare all three of those, the skin is superficial, the muscles are intermediate, and the bones are deep. Now, superficial doesn’t necessarily mean ‘right on the body surface’; it just means ‘closer to the body surface when compared to something else’.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Everything Makes Sense When Used in Comparison
We have some particular directional terms that relate more so to the limbs. Those terms are: proximal and distal. Proximal means ‘closer to the origin of a structure’, like a limb, while distal means ‘farther away from the structure’s origin’. So, when comparing the shoulder to the elbow, the shoulder is proximal and the elbow is distal. But when comparing the elbow to the wrist, now the elbow becomes proximal, and the wrist is distal to it.
And, again, we only use these terms to compare two structures, so the statement, ‘the elbow is proximal’, doesn’t make any sense. Proximal to what? You could say that the shoulder is the most proximal part of the upper limb, but even then, the comparison is understood, it’s essentially being compared to the rest of the limb.
Occasionally, proximal and distal are used to refer to other structures. For instance, the proximal end of the small intestine is the region nearest the stomach because that’s where the small intestine originates, and the distal portion of the small intestine would be closer to the large intestine, which is where the small intestine terminates.
Body Planes and Surfaces
From the standard anatomical position, a vertical cut that divides the body into right and left halves creates what’s called a sagittal plane. If the cut is directly on the midline, it’s called a midsagittal plane, but if laterally, off the midline, it can be called a parasagittal plane. Individual organs or regions, such as the brain or the knee, can also have their own midsagittal plane.
A vertical cut that divides the body or a region into anterior and posterior portions is known as a coronal plane, sometimes called a frontal plane, which separates the front from the back.
Dividing the body or one of its structures into superior and inferior regions creates what is known as a horizontal plane, sometimes called a transverse plane or axial plane. An organ like the brain looks very different when it’s viewed in a sagittal plane, coronal plane, and a horizontal plane.
Common Questions about Anatomical Terminology
Not all of it is. Some parts of anatomical terminology are conventions that one learns gradually. For example, if a part of the body is deep in the body like the spine, one would talk about using the dorsal phrase instead of saying it’s deeper than the heart.
In anatomical terminology, intermediate is used to point to something that is between two structures. It can be used when one is talking about three structures and their relative depths. For example, one would be superficial, while another would be deep and the one in between would be intermediate relative to the other two.
After a vertical cut that divides the body into right and left parts, we have what in anatomical terminology is called a sagittal plane. If the cut is directly on the midline then we’ll call it a midsagittal plane. And if it’s not on the midline, it’ll be a parasagittal plane. The difference is where we make the cuts.