The elbow and wrist are tied in via the wrist flexor and extensor muscles. These muscles cross the wrist and elbow joints from their attachment on the hand to their attachment on the humerus. Because of this the wrist muscles have a role at the elbow in addition to the wrist even though they are primarily wrist muscles. Their major action (function) is at the wrist.
At the elbow joint the wrist flexor muscles are relatively weak and their angle of pull is more into the joint rather than in helping to move the forearm. Thus their function is to act more as stabilizers when you execute elbow joint exercises. The forces created by the wrist extensors are also directed into the joint. Thus they act similar to the wrist flexors as stabilizers at the elbow.