Anterior Thorax and Neck - LO 4

4. Define attachment sites for muscles? Differentiate between the terms: origin, insertion, & proximal/superior & distal/inferior attachments.

Bones may have numerous attachment sites (bone markings) that are attachment points for tendons (connecting muscle to bone), ligaments (connecting bone to bone), and fascia. The size and shape of attachments sites will change throughout life based on the activity (or lack thereof) at these points.

When describing the anatomy of a muscle, attachment points are commonly included. Knowing these attachment points gives the learner an understanding of what joint(s) the muscle crosses (and thus can directly affect) and a basic understanding of what types of actions can occur due to a muscle when concentrically contracting (muscle shortening).

Traditional terminology relating to muscle attachments

Origin

• Typically proximal or superior end of muscle

• Typically fixed (does not move during contraction)

Insertion

• Typically distal or inferior end of muscle

• Typically kinetic (will often move towards the origin of the muscle)

It is important to note that although the proximal or superior end of a muscle is typically fixed, this is not always the case. There has been a movement towards the usage of the more descriptive and accurate terms: proximal or superior attachments and distal or inferior attachments. You still may see the terms origin and insertion in other resources, but we will not use that terminology.