How to easily remember description of direction in anatomy
Today human anatomy is regarded as being a complete science. The “what is where” of the human body is largely known. But, remember as you struggle to learn anatomical names that it took about 3600 years to make it a complete science.
Ancient anatomists had their problems too. They needed reference points upon which to base their description of “what is where”. A uniform description of three dimensional anatomic orientation was devised in early studies, and it was largely kept and expanded upon. It is easier to communicate when everyone uses the same words.
A first issue to arise in naming human parts was the number of positions that flexible human bodies can acquire. A single position was needed that could be used as a reference for describing where the pieces were relative to each other. That single position became known as the “anatomical position” and is displayed by this skeleton. No matter what position a cadaver assumed, all descriptions were extrapolated back to where the body part would be in the “anatomical position”.
It takes a bit of imagination and focus to transfer what you are looking at into the anatomical position of another person. That is a standing person, head and eyes facing forward, feet together, arms to side, palms of hands facing forward.
Problems arise if you do not remember that for a person you are facing right and left may be reversed. Only if each of you is facing the same direction are right and left the same.
To get answers correct on anatomy practical exams, it is identification of the right and left body part that is important. Some of us become confused with the issue of right and left, because we are so accustomed to mirror images of ourselves. It is easy to forget that our mirror image is the reverse of our real self. Some people are uncomfortable with pictures of themselves, because a picture is not their mirror image.
Humans are said to be bilaterally symmetrical. The directional term lateral is used as a modifier for both sides of the body, left lateral and right lateral. As opposed to lateral, the term median is used to define a point in the center of the organism. The term medial means toward the median plane of the person.
For descriptors to remain fixed in their meaning the anatomic position is critical. Imagine where the bones of the forearm, the radius and the ulna, would be if our skeleton had the palms of its hands facing backward rather than forward. In the anatomic position, palms forward, the radius bone lies lateral and the ulna bone is medial. With rotation of the forearm as the palms turn toward the back, the radius moves to a medial position and the ulna is then lateral.
Appendages, arms, legs, and pelvis often move independently of the torso of the body. So, separate directional terms are used to describe them. The term proximal describes where the appendage joins the torso of the body. The term distal is used for the point farthest from the point of attachment to the torso. Proximal and distal are often used as relative terms. For example, the elbow is proximal to the hand . . .the elbow is closer to where the arm attaches to the torso than the hand is, but the elbow is distal to the shoulder . . .the elbow is in a position further away from the torso than the shoulder joint.
In the scheme of human orientation descriptors anterior is toward the front while posterior is toward the back. Superior is toward the head. The opposite term, inferior, is a relative descriptor generally used to mean below some other body part. Internal body organs are described as superficial meaning near the body surface, or deep meaning internal and away from the surface.
In most anatomy courses these human body orientation descriptors are learned early in the instruction. They are learned in isolation. Because anatomy descriptors appear easy you may not want to focus much of your precious time studying them. It all seems so obvious that it is natural to think, “I know that”.
Orientation descriptors are not used a lot until your instructor hands out long lists of muscles, nerves, and blood vessels to be learned. By then your memory of orientation descriptors may be lost in the fog of too many facts accumulated since the descriptors were last thought about.
The trick is not to blow off these terms early in your study of anatomy. Make friends with them instead. Practice describing all body structures you learn with these descriptors. It may feel strange at first, but stick with it.
For example when learning bones, you can decide whether the human sternum (colored set of bones) is located anterior or posterior, inferior or superior to the pelvis, medial or right lateral or left lateral when the body is in the anatomic position. In doing this, you will remember why you do not use the terms proximal and distal to locate the sternum.
Do this, and when it comes time to learn names of muscles, nerves, blood vessels you will be way ahead of your classmates.
There is a box below where I hope you will tell me if knowing the logic behind anatomical descriptions of orientation helps you remember and use them properly. Also, I would like your help in choosing other topics for future articles. Please tell me what areas of anatomy you find the most frustrating.
You may also like to read about the patterns used in naming Human Body Muscles. If you are struggling with your anatomy lab exams check out five ways to make the best of them in the post Anatomy Lab Tests.
Do you have questions?
Please put your questions in the comment box or send them to me by email at DrReece@MedicalScienceNavigator.com. I read and reply to all comments and email.
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Margaret Thompson Reece PhD, physiologist, former Senior Scientist and Laboratory Director at academic medical centers in California, New York and Massachusetts and Chief Scientific Officer at Serometrix LLC is now CEO at Reece Biomedical Consulting LLC.
Dr. Reece is passionate about helping students, online and in person, pursue careers in life sciences. Her books “Physiology: Custom-Designed Chemistry” (2012), “Inside the Closed World of the Brain” (2015) and upcoming “Step-by-step Guide for Study of Physiology” (2016) are written for those new to life science.
Dr. Reece offers a free 30 minute “how-to-get-started” conference call for students struggling with human anatomy and physiology. Schedule an appointment by email at DrReece@MedicalScienceNavigator.com.