What does it mean for muscles origins and insertions to be the other way around in the right than left limb?

Question

Herbert Srebnik writes in Concepts in Anatomy: > In the right limb, the muscle's origin is proximal to the joint and > the insertion is distal to it. In the left limb, the muscle's origin > is distal to the joint and the insertion is proximal to it. > (The text appears next to an image of the biceps brachii) What does that mean? What does it tell this paragraph tell me as someone new to human anatomy?

Answer 1

Hi Jane,

In all my anatomy courses I have never seen a book that flipped the origins and insertions of a muscle from left to right side of the body (other than that it may be in the opposite direction (left vs right) when we look at where the landmarks are because lateral on the right is to the right while lateral on the left is to the left.

With the biceps brachii the origin has always been taught to me as being proximal (on the supraglenoid tubercle and coracoid process of the scapula) and the insertion distal (on the radial tuberosity of the radius). However, it was also taught that insertion and origin are flipped when we look at what joint is moving. So, if in the picture, the biceps is flexing the elbow or supinating the forearm, the insertion would be on the radius and the origin on the scapula. While when it is assisting with shoulder motion (flexion or abduction) the origin would be distal (on the radius) and the insertion would be proximal at the coracoid or supraglenoid tubercle on the scapula.