Final answer:
Extension of the interphalangeal (IP) joints is the straightening of the fingers, while flexion is the bending of the fingers. Hyperextension and hyperflexion refer to excessive straightening or bending of the joint, respectively, which may lead to injury.
Step-by-step explanation:
Flexion and Extension of the IP Joint
The terms extension and flexion refer to movements that increase and decrease the angle between two body parts, respectively. In the context of the interphalangeal (IP) joints, which are the joints within the fingers and thumb, extension is the movement that increases the angle between the phalanges and straightens the joint, while flexion is the movement that decreases the angle and bends the joint. Hyperextension is the excessive extension of a joint beyond its normal range of motion, potentially causing injury. Hyperflexion is the excessive bending of a joint beyond its normal range, which can also result in injury.
In the fingers, extension of the IP joint straightens the fingers and increases the angle between the bones of the finger. Flexion, on the other hand, is the action of bending the fingers, thereby decreasing the angle between the bones of the finger. It is these movements that allow us to grasp objects or make a fist.