The anatomical position is a frame of reference that is used when people describe anatomy and movement. Because organisms often change position and orientation, using a standardized position when describing their features is important, as it allows people to clearly understand the anatomical location of features of interest, the relationship between various anatomical features, and the overall structure of an organism.
In an example of why this is important, when a human is standing upright, the top of the skull is considered “up,” and the soles of the feet are “down.” When the same human lies on his or her back, however, suddenly the positions of “up” and “down” change, with the front of the body facing up, and the back of the body facing down. The situation becomes even more complicated with organisms like fish, making it very difficult to describe anatomy in absolutes; if, for example, a structure is said to be “at the top” of an organism, the location of that structure might be unclear because the “top” varies depending on position.
Creating an absolute anatomical position eliminates this confusion. In humans, this position is a standing human facing forward, with the feet together and the arms relaxed at the sides, with the palms out and the thumbs facing away from the body. Many people may have noticed that anatomical illustrations and guidebooks usually show the body in this position for convenience, and to get people familiar with thinking of it as a frame of reference when thinking about the human body.
Once the anatomical position is defined, people can start to create additional definitions that can be used in discussions of anatomy, such as anatomical planes, arbitrary divisions of the body at various cross sections. Additionally, people can develop anatomical terms of location to refer to specific areas of a body. Terms like “dorsal” and “ventral,” for example, can be used to describe to describe the back and belly of an organism, with no confusion about where the those sides are.
Anatomical position can be used in a variety of settings. In keys that help people identify organisms ranging from fish to mushrooms, for example, questions or prompts that involve anatomical features are usually framed with this position in mind. Health care practitioners and bodyworkers also usually use anatomical terms of location when they discuss their patients and take notes that they or other practitioners may need to reference.