Axial vs. Appendicular

In order to have a good understanding of anatomical directional and positional terms, it is first helpful to know the difference between the axial skeleton and the appendicular skeleton. I’m thinking in particular of the terms proximal and distal, I’ll explain those more in a moment.


The axial skeleton includes the skull and all the cranial bones, the spine, the ribs and the hyoid bone. The hyoid bone is just inferior to the mandible (jaw bone) and it sits anterior to (in front of) the third cervical vertebrae. A little side note- the hyoid is the only bone in the body that doesn’t articulate with another bone. It serves as an attachment site for the suprahyoid and infrahyoid muscles. The small but strong suprahyoids elevate the tongue and open the mouth while the thin and more dainty infrahyoids act as an antagonist (do the opposite). 

The appendicular skeleton is everything else. It’s everything that attaches on to the axial skeleton. Think “appendages”. The pelvis, femur, fibula, tibia and all of the foot bones as well as the scapula, clavicle, humerus, radius, ulna and all of the hand bones are classified as appendicular.  All of those bones are essentially stuck on to the axial skeleton, which is the centermost part of your skeletonWe use the terms proximal and distal to describe the position of one thing to another in relation to the appendicular skeleton. If it’s closer to the appendicular skeleton it’s called proximal. Proximity means “close to” or nearness so you can remember it that way. Distal means distant or away from, so it’s farther away from the appendicular skeleton. 

Here are some examples:
The calcaneus is distal to the patella. The patella is proximal to the calcaneus.
The wrist is distal to the elbow. The elbow is proximal to the wrist.
The phalanges are distal to the metacarpals. The metacarpals are proximal to the phalanges.
The distal end of the femur articulates with the proximal end of the tibia. 

When we lengthen the spine, we are creating axial extension- creating more space between each of the vertebrae in the vertebral column. From either a seated or standing position, imagine your feet or your pelvis getting heavier on the floor while you actively reach the crown of the head toward the ceiling, like you’re balancing a heavy book. You should feel your spine grow a little longer- this is axial extension.