Directional terms and body planes

Do you sometimes feel like studying anatomy is almost like learning a foreign language? We all know that learning anatomy lingo is a must when studying the human body, but sometimes even just figuring out what direction we’re looking in can be a challenge. If you’re like me, spending time trying to figure out cranial from caudal and ventral from dorsal is a pretty dangerous game, because before you know it, you find yourself looking more like you’re trying to learn Macarena than trying to learn anatomy.

Yes, I know. Too much. But fear not, it’s not as bad as it might first seem. Yes, there’s a method to this directional madness, and if you stay with me for this tutorial, you’ll soon find out why, as we master the directional terms and body planes in human anatomy.

So, today’s tutorial is effectively Anatomy 101. Before you learn about a single muscle, artery, nerve, or vein in your anatomy class, you first need to learn about the directional terms and body planes we use to orientate ourselves in human anatomy. These terms act as a universally accepted language that enables precise communication between anatomists and health professionals. However, since my left is not always the same as your left and your anterior may be the opposite direction of my anterior, we need to all consider our bodies in the same common position with all our body parts pointing and facing in specific directions.

This is known as the anatomical position, and is used to describe body parts and positions of patients regardless if they’re lying down, on their side, or facing downwards. So, what exactly is it?

Well, in the anatomical position, we always consider the person as standing upright with arms to the side, palms facing forward, and thumbs pointing away from the body. The feet are slightly apart and parallel to each other with the toes pointing forward and the head facing forward and the eyes looking straight ahead.

So, let’s dive into the bone of this tutorial and talk about some general directional terms which help us to compare the location of one body part in relation to another.

So coming back to our lovely model here, the first directional term we’re going to be talking about is anterior. And as you can see in the illustration, anterior indicates that the structure or body part in question is in front of something else. For example, in this image, you can see that the toes are in front of the heel. Therefore, you could say, the toes are anterior to the heel. Of course, if we have a specific term for in front of, we must have another term which means the opposite, and that word is posterior, which indicates that a body part is behind something. Flipping the extreme which is used around, we can now say the heel is posterior to the toes.

Our next term is ventral, which denotes something towards the front of the body. It comes from the Latin word “venter”, which means stomach, so it laterally means towards the stomach, therefore, it’s often used interchangeably with anterior. For example, you can see in the right image the transversus abdominis muscle which is a muscle of the anterior surface of the trunk or ventral trunk.

Dorsal is the opposite of ventral which means that it must imply a direction towards the back of the body and is now sometimes used interchangeably with the term posterior. For example, in this image, the trapezius muscle is highlighted and this is a muscle of the posterior surface of the trunk or the dorsal trunk.

As I’m sure you already know, lots of structures in our body are what’s referred to as being bilateral – meaning, we have one of them on either side of the body. So, it naturally makes sense that we differentiate between the two sides and luckily for us, this one is very straightforward. It’s either right or left.

Of course, it goes without saying why it’s important for us to be able to make the distinction between right and left structures. For instance, a patient with a damaged right kidney would not do well at all if their left one was accidentally removed. One point to remember especially when working in clinical practice is that when standing at our patient’s feet, their right is on your left and their left is on your right. It’s the same when examining CT or MRI scans, so always be sure to keep that in mind when taking patient notes.

Moving on to our next directional term which is the word distal, and you’ll most often see this term used in the context of your upper and lower limbs. It indicates that a body part is away or farthest away from the trunk of the body or the point of origin of the body part. For example, the wrist joint is distal to the elbow joint. You’ll also see the term distal used in the context of the gastrointestinal tract where distal implies in the direction of the anus. How wonderful.

A related term to distal which you might have heard of before is terminal, which refers to a structure which would be considered most distal. For example, the terminal branches of the sciatic nerve are the tibial nerve and the common fibular nerve.

Proximal is the opposite of distal meaning that it refers to a structure or body part closer to the trunk of the body or point of origin, and just like distal, you’ll most often see this term used in the context of your upper and lower limbs. Using the example we used before, we can say that the elbow joint is proximal to the wrist joint.

Now, our next term is one that sometimes creates confusion, so be sure to take a special note of it. So median generally refers to what we call the midline, which is a term used to refer to an imaginary line down the middle of the body that splits the body into equal left and right parts. Median can also be translated as middle. For example, we have the median nerve in the upper limb which is located centrally between the ulna and radial nerves.

Medial is a term closely related to and often confused with median, and it’s used to refer to something located or pointing towards the median or the midline or when a body part is closer to the median than another. For example, your ring finger is medial to your middle finger.

The opposite of medial is lateral, and it’s a term used to describe when a body part is situated or points away from the midline and towards the side of the body. So using the example we used before, we can say that the middle finger is lateral to the ring finger.

Our next term, superior, is used to refer to upwards or towards the vertex or the top of the head. For example, we can say that the nose is superior to the mouth. You may often also see the term superior abbreviated to supra-. For example, the supraclavicular lymph nodes highlighted in green here which are located superior to the clavicle.

And, of course, if there’s an up, we must also have a down. And the term that we’re looking for in this case is inferior, and it refers to a structure which is below, under something, or pointing towards the feet. So, using the previous example, we can say that the mouth is inferior to the nose. And just like superior, the term inferior can be abbreviated by a number of prefixes such as infra-, hypo-, or sub-. For example, the infraorbital artery is located inferior to the orbit. The hypoglossal nerve is inferior to or under the tongue and the submandibular lymph nodes are located between the mandible.

So, now that we’ve learned about some of the major directional terms, there’s something important I want to take note of before we continue on. So when we examine the position of one structure to another using one directional term is often not enough to describe the location of whatever we’re looking at. For instance, if we look at an anterior view of the face and wanted to describe the position of the ear relative to the mouth, how would we do that? So, we can see that the ear is above or superior to the mouth, however, we could also say that the ear is lateral to the mouth, right?

Fortunately, we can combine many of the directional terms we’ve just learned to give a more accurate directional term for examples just like these. For example, if the ear is both superior and lateral to the mouth, we can describe that as superolateral. To combine directional terms, we usually abbreviate the first term and add it to the second, like the list below.

The next term I want to discuss with you is superficial, which refers to a structure located close to or in the direction of the outer surface of the body. For example, when examining the thoracic cavity, we describe the ribcage as being superficial to the organs of the thorax. The opposite of this, of course, is deep, which basically means that it’s located under one or more overlying structures. In keeping with our example of the thorax, we could say that the great vessels are deep structures of the thorax.

The term external can have a number of meanings or interpretations and most obvious perhaps is that it means that the structure is open to the external environment. And as you can see in the left image, we’re showing the outer ear, the highlighted areas can be referred to as external as the structures are open to the outside environment.

In the right image, we can see this view giving you a visual representation of what external means so moving towards the exterior. External can also be used with reference to a structure which is considered more superficial than another – for example, the external intercostal muscles – or they can have a similar meaning to lateral – for example, external rotation.

One last point on external is that it is commonly abbreviated as the prefix ‘extra-’. For example, muscles which lie outside of the eyeball or oculus are known as the extraocular muscles.

Internal as the name suggests denotes a body part is away from the body surface or not open to the external environment. So, for example, the highlighted areas in the left image can be referred to as internal as they are not open to the outside environment. And if you remember, the highlighted areas in this image are the middle and inner ears.

In the right image, you can see this sphere giving you a visual representation of what internal means, and note that the arrows are moving towards the interior. With this in mind, we can see why internal can also have a similar meaning as the term deep, such as the internal abdominal oblique muscle which lies deep to the more superficial external abdominal oblique muscle. And similar to what we just saw with the term external, internal can also sometimes mean medial – for example, internal rotation.

So, we’ve spoken a lot about general directional terms relevant to all parts of the body, but before we move on speaking about the anatomical planes of the body, I just want to take a few moments to share with you about some regional directional terms which are specific to certain parts of the body. And the first area I want to look at are the hands.

If you can remember back to the beginning of our tutorial, we said that in the anatomical position, the palms of the hands face forwards with the thumbs facing outwards, and to describe that using the directional terms that we’ve learned today, we can now describe the palms of the hands as facing anteriorly with the thumbs facing laterally. But, of course, sometimes anatomists like to complicate the situation, so there’s some additional terminology for us to learn here.

So, in addition to calling the palm of the hands the anterior aspect, we can also call it the palmar aspect of the hand, which is pretty easy to remember. And in addition to palmar, you may also hear it referred to as volar, which is less common but good to know all the same.

The back of the hand, as in the opposite side to the palm, is unsurprisingly referred to as the posterior or the dorsal aspect of the hand or sometimes simply as dorsum.

We mentioned above that in the anatomical position, the thumb is pointing laterally which implies that this side of the hand is the lateral side of the hand. And as you would expect by now, we have another term for lateral when it comes to the hand and the forearm, and that word is radial. And as you might have guessed, radial refers to the radius bone of the forearm which is located along the lateral aspect of the forearm.

Similarly, the little finger of the hand is described as being situated along the medial aspect of the hand which you’ll commonly hear being referred to as the ulnar aspect of the hand.

So, we’re going to move inferiorly now towards the feet where we will also find some fairly specific regional terminology. So the aspects and directions related to the foot can often cause a little confusion amongst students, so it’s definitely worth taking note here.

So, since your feet are flat on the grand in the anatomical position, we refer to the toes as being located at the anterior of the foot with the heel sitting posteriorly as you would imagine, and the bottom or the sole of your foot has a specific name and is known as the plantar aspect of the foot. To help remember these terms, think of your feet as being firmly planted on the ground which will hopefully draw your memory to think of plantar.

Okay, so we’re now moving on to our final set of regional specific terminology which concerns the cerebrum and the brainstem, and this is another one of these tricky areas for students to remember. But, don’t worry, in just a few minutes, like the meaning of life, you’ll have it all figured out.

If you’re using the terms anterior and posterior or superior and inferior, this is very easy and straightforward. So, everything is exactly where you would expect to find it regardless of whether we’re looking at the cerebrum or the brainstem. Unfortunately, the brain is not always described using these terms and it has its own set of terminology which can make things just a little bit more complicated. So, if you watch closely, I’ll explain.

So, when we’re talking about the cerebrum specifically, the anterior aspect is referred to as the rostral aspect of the brain. And the word rostrum comes from the Latin word for ‘nose or beak’, so you can think of this term as pointing towards the nose. A similar term which can also be used here is frontal which means in the direction of the frontal bone which is the bone highlighted here.

Posterior aspect of the cerebrum is referred to as its caudal aspect. And yes, I know we mentioned earlier that caudal usually means inferior or towards the tail, but that’s not the case here. And the reason for this has to do with directional terminology used in both embryology and zoology which I won’t go into the detail of, but all you need to do is to make note of this exception and you’ll be a hundred percent fine.

I want to also quickly mention another term related to the posterior cranium and this word is occipital and this means towards the occipital bone.

Now when considering the underside or the inferior aspect of the cerebrum, we refer to this as the ventral aspect, and to remember earlier, we learned the opposite of ventral is dorsal. So that means that the superior aspect of the cerebrum must be referred to as the dorsal aspect of the brain. And of course, dorsal usually means posterior, but this is again one of those cases we need to remember things are a little bit different.

Alright, so moving on to the brainstem and below, things are fortunately a little bit more straightforward. So let’s first label the anterior, the posterior, the superior, and inferior directions to orientate ourselves. And as with the rest of the body, the anterior and posterior aspects of the brainstem, they also be referred to as the ventral and dorsal aspects respectively, while the superior and inferior aspects can also be called the cranial and caudal regions.

So, just a note, neuroanatomy is a pretty tricky subject for all of us, so if you were able to make a note of the specific terminology here, they’ll definitely help you get off onto the right foot when studying this region.

And now to our final part of our tutorial today, it’s time to talk about the body planes.

So what exactly is a body plane, I hear you asking. Is it an anatomical theory for a man in flight? Eh, not quite.

So, body planes are imaginary planes or flat surfaces that slice or section the body in its anatomical position. And there are three main body planes used in anatomy, and these are referred to as coronal, sagittal, and transverse. And knowing these body planes is very, very useful when looking at MRI or CT scans of the brain and other parts of the body as you often view these images in the differing planes.

The coronal plane which is also referred to as the frontal plane is a vertical plane that sections the body along the anteroposterior axis – meaning it divides the body into anterior or front and posterior or back part as you can see in this image. The sagittal plane is also a vertical plane which is perpendicular to the coronal plane meaning that it splits the body into left and right parts. The sagittal plane that runs directly through the midline is also called the mid-sagittal plane or the median plane.

The transverse plane is our last plane and it’s a horizontal plane and this is also referred to as the axial plane. It divides the body into superior or upper and inferior or lower portions. And in gross anatomy studies, transverse sections are also referred to as a cross-section.

And that concludes our tutorial on directional terms and body planes, but before we wrap up this video, let’s quickly recap over everything that we learned today.

So beginning with some general directional terminology, we first considered the body in the context of two main directions which were anterior meaning forward or in front of and posterior meaning backwards or behind. And these directions can be referred to as ventral and dorsal respectively.

When looking at the front of the body, we can divide the body right down the center at the midline or the median and structures which are relatively closer to or in the direction of the midline are referred to as being medial. All those away from the midline are said to be lateral.

We also mentioned the term superior which means above or upwards and inferior which of course is the opposite and means downwards or below. And when looking at the body in cross-section, we also used the terms superficial which means close to or in the direction of the surface of the body and deep which refers to something away from the surface of the body. Similarly, we looked at the terms external and internal which can have similar meaning to superficial and deep.

After that, we had a quick look at some regional directional terminology first focusing on the hand, and we remember that in the anatomical position, the palm of the hand faces forward and the back of the hand faces posteriorly, and this allowed us to refer to the palm of the hand as the anterior, palmar or volar aspect of the hand, and similarly, we were able to define the back of the hand as the posterior or dorsal aspect of the hand.

Moving onto the feet, we learned that the underside or the sole of the foot is known as the plantar aspect of the foot, while the back or the top of the foot is known as its dorsum, or its dorsal aspect.

And finally, we looked at the brain and learned about some interesting directional differences which are observed here. We first looked at the cerebrum and discovered that the anterior aspect could also be referred to as the rostral aspect and the posterior as the caudal, and the superior aspect of the brain can alternatively be called the dorsal aspect while the inferior aspect can be referred to as the ventral aspect.

Moving inferiorly to the brainstem, we learned that the directions varied somewhat compared to the cerebrum with the ventral aspect’s now facing anteriorly and the dorsal aspect facing posteriorly. And finally, in the case of the brainstem, we can refer to the superior side as being cranial and the inferior aspect as being caudal.

We then finished up our tutorial by discussing the three primary body planes that we used in anatomy and these were the coronal plane which moves along the anteroposterior axis of the body, the sagittal plane which divides the body into left and right, and finally, the transverse or axial plane which runs along the superoinferior axis of the body.

And that’s it, we’re done! I hope that the days of being confused and perplexed about anatomical directions are far behind you.

If you enjoyed this video, please be sure to check the hundreds of other video tutorials available on kenhub.com, and until next time, happy studying!