What are the criteria for determining the origin and end of muscle anatomically? For example the pectoralis muscle starts from sternum region and ends on the acromion or coracoid process. Why you can't say that it starts acromion process and ends on the sternum?

This is more of a convention.

The start point or **origin** is considered to be:

* bone which is proximal
* bone with higher mass
* bone with higher stability during muscle contraction



The end point or **insertion** is:

* the structure that tends to be moved by contraction
* tendon
* distal end of a bone



Reference: Wikipedia - _Anatomical terms of muscle_