The Forearm Bone: Ulna and Radius

The bone that helps us bend and straighten our arm is the forearm bone. The forearm is made up of two long bones called the ulna and radius. These bones run parallel to each other and are connected by a joint at the elbow.

The Ulna
- The ulna is the longer and larger of the two forearm bones. It is located on the inner side of the forearm, opposite to the thumb.
- The ulna helps in the movement of the arm by providing stability and support.
- It is responsible for the bending and straightening of the arm at the elbow joint.
- The ulna articulates with the humerus bone of the upper arm at the elbow joint, forming a hinge joint that allows flexion and extension of the arm.

The Radius
- The radius is the shorter and smaller of the two forearm bones. It is located on the outer side of the forearm, opposite to the ulna.
- The radius also plays a crucial role in the movement of the arm.
- It allows the forearm to rotate, enabling movements such as supination (turning the palm upward) and pronation (turning the palm downward).
- The radius articulates with the humerus bone at the elbow joint and with the carpal bones of the wrist joint.

Working Together
- The ulna and radius work together to provide a wide range of motion to the arm.
- When the arm is straightened, the ulna and radius are aligned parallel to each other.
- When the arm is bent, the ulna slides along the humerus bone, while the radius rotates around the ulna, allowing the hand and wrist to move.
- This coordinated movement of the ulna and radius enables us to perform various activities that involve bending and straightening the arm, such as reaching, lifting, and throwing.

Conclusion
In conclusion, the bone that helps us bend and straighten our arm is the forearm bone, which consists of the ulna and radius. These bones work together to provide stability, support, and a wide range of motion to the arm.