By Elizabeth A. Murray, Mount St. Joseph University
Anatomical terminology cannot be understood in simple English terms and are specific in their meaning. For example, 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. Thus, superficial doesn’t necessarily mean ‘right on the body surface’. It just means ‘closer to the body surface when compared to something else’. What other unique terms are used to refer to anatomical positions? Read on to find out.
Talking about Body Movements and Depth
When it comes to understanding the sides of the body, the two terms related to it are: ipsilateral and contralateral. Ipsilateral means ‘on the same side of the body’, whereas contralateral 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. For example, one can see that under the skin, as the right sternocleidomastoid muscle contracts, it turns the face toward the left. Therefore, the sternocleidomastoid muscle is said to have contralateral action.
There’s another instance in which the term ‘intermediate’ comes in handy; that is, when talking about depths in the body. 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.
Terminology for Physical Exam or Surgery
These terms also relate, in some degree, to how we approach a body in the lab, or perhaps in a physical exam or during surgery. It’s as if the body has a cylindrical core down its middle. If the body is faceup, which in forensics and anatomy we call supine, the sternum is superficial, and the heart is deep to that. If the body is facedown, or prone as we say, the ribs would be superficial and the kidneys would be deep to them. That, however, is the only anatomical directional term that varies in terms of body position.
In other words, one would never say that the sternum is superficial to the heart and heart is superficial to the spine. This is because the spine is very deep into the body, and is more associated with the dorsal aspect. One would say that the heart is anterior to the spine, meaning it’s in front of the spine. Some of this is just learnt by convention; it’s not always intuitive.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Proximal and Distal: Comparing Two Structures
In anatomy 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’. Thus, when comparing the shoulder to the elbow, the shoulder is proximal and the elbow is distal. And yet, when comparing the elbow to the wrist, the elbow becomes proximal, and the wrist is distal to it.
We only use these terms to compare two structures, so the statement, ‘the elbow is proximal’, doesn’t make any sense. It has to be specified that it is proximal to what. Though one 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.
In addition, occasionally, proximal and distal are also used to refer to other structures. For instance, the proximal end of the small intestine is the region nearest to the stomach because that’s where the small intestine originates. Similarly, the distal portion of the small intestine would be closer to the large intestine, which is where the small intestine terminates.
Anatomical Positions: A Universal Standard Reference
When referencing a limb, the terms superior and inferior are not used. Instead we use proximal and distal. With that said, medial and lateral still apply. Therefore, if one is in the standard anatomical position, their thumb is lateral, which means farther from the midline, and their little finger is medial.
Now, what if one turns their hands so that the palm is facing backward—what’s the relationship of their thumb and their little finger now? Trick question alert! Remember that anatomical position fixes us in space. So, even with their palm facing backward, their thumb is still lateral and their little finger is still medial, because anatomical position provides a universal standard reference. It doesn’t matter what pose one strikes, medial and lateral don’t change. That’s the beauty of anatomical position!
Common Questions about Understanding Some Anatomical Positions
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.
One would never say that the sternum is superficial to the heart and heart is superficial to the spine. This is because the spine is very deep into the body, and is more associated with the dorsal aspect. One would say that the heart is anterior to the spine, meaning it’s in front of the spine.
When referencing a limb, the terms superior and inferior are not used. Instead we use proximal and distal.