Muscle Function

Nothing can replace the hands-on experience of isolating muscles. By tracing them from their point of origin to their insertion a better understanding of their function can be gained. This brief tutorial is intended to reinforce what can more easily be learned working with an actual cat. Think of muscles in terms of antagonistic (opposite) actions. When one muscle of an antagonistic pair contracts its antagonist will relax. Also keep in mind that several muscles may have similar actions and that the exact movement of a bone will be the result of a coordinated effort involving many muscles. In these simplified diagrams, arrows indicate the direction in which the force is exerted. Follow the links provided under the different types of joints for illustrations of how the muscles interact with the skeletal elements.

Flex - a motion that decreases the angle between two bones. An example of a flexor is the biceps brachii.

Extend - a motion that increases the angle between two bones. An example of an extensor is the triceps brachii.

Hinge Joints



At the shoulder joint muscles that extend the forelimb move the limb anteriorly while at the hip joint muscles that extend the hindlimb move it posteriorly.

Flexion of the shoulder results in a movement of the limb posteriorly and flexion of the hip results in movement of the limb anteriorly.

Retract - a motion that moves a bone parallel to the longitudinal axis and in a posterior direction.

Ball & Socket Joints



Adduct -Moving a skeletal element toward the ventral midline.

Abduct - Moving a skeletal element away from the ventral midline.



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