By Elizabeth A. Murray, Mount St. Joseph University
In anatomy, terms such as, superior, inferior, anterior, and posterior, all relate to the space around us in which we navigate. There also is an equivalent directional term that relates to parts of the body, such as, cranial or cephalic, meaning ‘the head end’, and caudal meaning ‘toward the tail end’. What other anatomical terminology is used to understand our body and what do they mean? Read on more to find out.
Terms of Directionality
From the standard position, anatomy uses specific terms to express body directionality. For example, superior means ‘up’, away from the pull of gravity, so in humans, that’s the head end. Inferior means ‘down’, towards the pull of gravity, or towards the ground. Anterior means ‘forward’, or in the direction that we move, while posterior means ‘backward’, or opposite the direction of our typical movement.
Hence, considering this, which of the four terms—superior, inferior, anterior, or posterior—is equivalent to cranial? It would be the superior. Which body term means the same thing as inferior? That will be the caudal. And while one might say, we don’t have a tail- we did, as an embryo. What’s more, cranial and caudal are usually used to refer to the head and trunk of the body.
There are other terms of directionality to use for the limbs. Hence, in humans, superior and cranial are interchangeable, and inferior and caudal mean the same thing.
When it comes to anterior and posterior, we also have terms that are equivalent to them—dorsal and ventral. The dorsal side is the spine side in animals with a backbone. Thus, with regard to anterior or posterior, the anatomical equivalent of dorsal is posterior. Since posterior means ‘opposite the direction of movement’, its body part equivalent is the dorsal side of the body. Anterior is the same as the ventral side of the human body—that’s in the direction we typically navigate.
Ventral Equals Anterior
Interestingly, the front of the body is not the stomach. The stomach is a food-holding digestive organ inside the body. The ventral side of the torso can also be called the belly side. Belly is a perfectly adequate anatomical term for the side of the body opposite the spine. Therefore, in humans, ventral equals anterior—but ventral relates to the body itself, while anterior means ‘in the direction an animal moves’.
So, as an aside, if anterior means that, does anterior also equal ventral in our dog or cat? Nope. Anterior equals cranial in a four-legged creature, since its head is the same direction in which it moves. Posterior, then, equals caudal—our dog or cat’s tail end.
Accordingly, what is the equivalent of ventral in a dog? If one said inferior, they’re right! Dorsal—as the spine side—would be superior in a four-legged animal. That helps to reinforce that superior, inferior, anterior, and posterior refer to the space around us, while cranial, caudal, dorsal, and ventral relate to parts of the body itself.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Changing Relationships between Structures
Other anatomical terms we need to understand is medial and lateral. Medial means ‘closer to the midline of the body’, and lateral means ‘toward the side of the body’. Thus, when comparing the clavicle to the shoulder, the shoulder is lateral. In that comparison, the clavicle is also said to be medial to the shoulder.
But what if we compare the clavicle to the sternum? Then the clavicle is lateral and the sternum is medial—the relationships change depending on which two structures are being compared. In fact, the sternum could be said to be median, which refers to being on the midline of the body.
But other than median structures, since there is only one midline, it’s all about comparison. One could never simply say, “The clavicle is medial”, because that would beg the question, medial to what? These directional anatomical terms are used to compare structures to each other, and the relationships change depending on what’s being compared.
Anatomical Terms Can Change
To clarify it further, let’s consider the example of three people of different heights: Mary is five feet tall, Sam is five-and-a-half feet tall, and Paul is six feet tall. When comparing Mary to Sam, Sam is taller; but when we compare Sam to Paul, now Sam is shorter, by comparison to Paul. So, just as Sam can be both taller and shorter depending on whom we’re comparing her to, anatomical terms can change for a given structure, depending on what other structure it’s being compared with.
Thus, to conclude, 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’. But wait, there’s more! The term intermediate can be used to indicate something is between two structures. Hence, going back to our example about the sternum, clavicle, and shoulder, one could say that the clavicle is intermediate when compared to the sternum and shoulder, just as Sam was intermediate in height.
Clearly, in the study of gross anatomy, knowing and using these anatomical directional terms provides a good foundation. They not only delineate but also help minutely, and extremely specifically, identify structures, body planes, directions and depths and are indispensable.
Common Questions about Anatomical Terminology
The term superior means ‘up’, away from the pull of gravity, so in humans, that’s the head end. Inferior means ‘down’, towards the pull of gravity, or towards the ground. Anterior means ‘forward’, or in the direction that we move, while posterior means ‘backward’, or opposite the direction of our typical movement.
One could never simply say, “The clavicle is medial”, because that would beg the question, medial to what? These directional anatomical terms are used to compare structures to each other, and the relationships change depending on what’s being compared.
The term intermediate can be used to indicate something is between two structures.
