The importance of cross-sectional anatomy

Your brain wants 3D

The human brain and mind thrives on complexity, colours and images to name a few. In other words, it loves anything that is coloured and in three dimensions. Similarly, it receives a constant stream of stimulations from a similarly elaborate 3D world. Humans automatically perceive things surrounding them in three axes: length, width/height and depth/thickness. You never stop to think if an everyday item is in 3D, but rather, you just know. In addition, if you think of an object, for example a chair, you do not think about five letters linked together appearing inside your mind. Quite the contrary, a real image of a chair appears in your mind having a length, width and depth. This is completely intuitive and natural. It is what the brain likes and is accustomed to. It is what it craves.

Therefore, it would be only wise to learn anatomy in a similar fashion. Anatomical cross-sections involve cutting a structure at right angles to its main axis and viewing the newly formed cut face in two dimensions. This view provides the essential view of “depth” often misused in medical education, which together with the usual length-width representation would result in a whole.

They are both 2D images but from totally different perspectives. In other words, it is a building “seen by morning light, at noon and by moonlight”. It is the same structure but in a different light. Your brain intuitively creates and stores 3D views and structures. In fact, it prefers them and has done so since the dawn of mankind. Imagine trying to eat a bowl of soup with a fork. It would eventually be possible after you get frustrated, put the fork away and drink the soup, but normally you would use a spoon. The brain is the same in that, it can handle simplicity but it gets frustrated. Instead, give it refinement and it will thank you for it.

Gives a different perspective

While drawings and paintings using perspective might appear sharp and clearly defined, anatomy is usually quite the opposite. The challenge lies in the fact that the human body is such an intricate machine that anatomical structures, more often than not, are not clearly delimited. For instance, think about the peritoneum and its folding pattern within the abdominal cavity. There are so many twists and turns that seeing it only in a frontal and sagittal section would give you an incomplete picture.

While this perspective is essential in helping you do well on your next anatomy exam, studying cross sections will make you a more competent and safer physician. A surgeon can read that intercostal vessels are embedded and follow the course of the intercostal muscles in the wall of the thorax. Similarly, it can take frontal and sagittal sections to aid his understanding. However, only a cross section would clearly illustrate the course of the vessels, between which muscular layers they are present, their relations to nerves and their depth within the thoracic wall. Each section type has its own purpose and they should be used together.

Makes learning easier

Without cross-sections, it is difficult to paint a complete picture. One might argue in favour of 3D models in replacing cross-sections or even being superior to them. While such interactive learning methods are definitely beneficial, they are not the be all and end all, just as this Kenhub article discusses. You can think of such a model as the “jack of all trades, master of none”. It can offer you a glimpse or a view from any direction, but it does not illustrate one point of view in an excellent way. Similarly, cross-sections are not the best ways of teaching but they are superior in one aspect - the resulting knowledge is personalised. This is similar to building a house. You can appreciate a nice house that you purchased but if you build it yourself, you can really make it your own in an unique way. While every brain thinks and experiences in 3D, building those images is slightly different from person to person. After all, we are humans and nuances are present between us. Completing an anatomical structure as a puzzle, piece by piece, allows you to recall it more easily in the future because you fitted all the pieces together. It is certainly more difficult and time consuming than looking at a three dimensional model but a wise man once said “the struggle you’re in today is developing the strength you need for tomorrow.”

Science also supports this aspect. If given the opportunity to examine cross-sections and use them side-by-side with frontal and/or sagittal sections obtained with a MRI scanner, medical students preferred to have the cross-section at hand. According to the future doctors, this view “made it easier to compare and contrast”, it “allows you to further differentiate structures”, “it is a form of repetition and a beneficial study tool”. More importantly, the cross sections were “easier to read” and they “better define the outlines and limits to better understand the MRI”. Stated more succinctly, cross-sections are essential.

So far, it appears that cross-sections tick the boxes of preference and understanding. However, it seems they tick the box of efficiency as well. Specifically, by correlating cadaver dissections with radiologic cross-sections of the same structures, medical students could be taught the equivalent of 2 hours and 40 minutes worth of information in just 20 minutes. The suggested explanation was the potential of more focused teaching by the instructors. Would you not like to learn faster so you have more time to study, enjoy life and experience it more? Of course you would!

Are cross sections the be all and end all?

This article might have given you the impression that transverse cuts are some magical solution providing all the clarifications. Incorporating them into medical education is a double edged sword. While they provide all the advantages discussed so far, they come at the price of potential confusion and information overload. Anatomy is complicated already and essentially a visual subject, already providing a challenge for non-visual learners. You would think that clarifying the outlines and the exact structural relations would facilitate understanding every single time. However, the living body contains so many overlapping pieces and edges that adding another dimension may just drown your mind. Although these disadvantages might be present, seeing all the sides of the story is required to be a competent physician. Rather than resisting the waves, you need to go with the flow because it is almost impossible to resist it.

Therefore, you need clear and strong waves to guide you, meaning that you need properly created cross sections. An excellent starting point is Kenhub’s cross-sectional atlas. With its crisp sections and labelled structures, you can build a mental 3D image in record time. Interested in seeing the pectoralis minor muscle? Just go here and start learning. The cross sectional images are even associated with surface and/or frontal views of the same structures in order to facilitate visualisation, understanding and to form complete mental connections inside your brain. Quizzes are also available to test your knowledge in cross-sections and help you learn and remember the material so you can use it further down the line in your daily practice.

As you can see, cross sections are very important in anatomy. Often underused both in teaching and in atlases, they are the key to dispelling the clouds, and bring clarity in your anatomy knowledge. More of an ingredient rather than a complete recipe, these sections are used simultaneously with other sources and views to turn you into the best physician that you can potentially be.