Final answer:
The main difference between extrinsic and intrinsic tendons is that extrinsic tendons originate in the forearm, aiding in gross motor functions, while intrinsic tendons originate and insert within the hand or foot, assisting in fine motor control and arch support.
Step-by-step explanation:
The difference between the contribution of extrinsic and intrinsic tendons to the extensor mechanism lies primarily in their location and function. Extrinsic muscles and their tendons originate in the forearm and extend into the hand, contributing to wrist movement and gross motor function. For instance, the extensor pollicis longus muscle extends the thumb and the extensor radialis longus muscle assists in extending and abducting the hand at the wrist. These extrinsic tendons are sheathed by the extensor retinaculum, a band of connective tissue over the dorsal surface of the hand.
On the other hand, the intrinsic muscles of the hand originate and insert within the hand itself. These muscles include the intrinsic muscles of the hand, which are responsible for fine motor control such as typing or writing. These muscles, like the extensor digitorum brevis in the foot, provide precise movements and contribute to the support of the arches of the foot.