Ulna

Definition

The ulna is one of the two long bones located in the forearm, positioned parallel to the radius. It plays a crucial role in the structure and function of the arm, articulating with both the humerus at the elbow and the radius at the wrist. Understanding the ulna is essential as it contributes to movements such as flexion and extension of the elbow, while also providing stability to the forearm.

5 Must Know Facts For Your Next Test

1. The ulna is typically longer than the radius and has a prominent projection called the olecranon, which forms the bony tip of the elbow.
2. The ulna has a distinctive U-shaped notch at its proximal end, known as the trochlear notch, which fits over the trochlea of the humerus during arm movement.
3. At its distal end, the ulna has a small projection called the styloid process, which can be felt on the wrist's medial side.
4. Fractures of the ulna are common in activities such as falling or sports injuries, often referred to as 'nightstick fractures.'
5. In terms of anatomy, the ulna serves as an attachment point for various muscles involved in wrist and finger movements.

Review Questions

• How does the structure of the ulna contribute to its function in arm movements?
  • The ulna's structure is specifically designed to facilitate arm movements by providing stability at the elbow joint and acting as a lever for muscle attachment. Its U-shaped trochlear notch allows it to fit securely over the humerus during flexion and extension, making it essential for these motions. Additionally, its length compared to the radius enables effective force transfer during activities such as lifting or throwing.
• Compare and contrast the roles of the ulna and radius in forearm mechanics.
  • While both bones are crucial for forearm mechanics, they serve different roles. The ulna primarily provides structural support and stability at the elbow, whereas the radius allows for rotation of the forearm and wrist movements due to its articulation with both the humerus and carpal bones. Together, they enable complex movements such as pronation and supination while maintaining overall strength in various arm functions.
• Evaluate how injuries to the ulna affect overall arm function and what implications this may have for rehabilitation.
  • Injuries to the ulna can significantly impair arm function by limiting both mobility and strength. A fracture can lead to decreased range of motion at the elbow and wrist, which complicates basic tasks like lifting or pushing. Rehabilitation must focus on restoring strength and flexibility while ensuring proper healing, often involving physical therapy exercises that target both the ulna and surrounding muscles to regain full function.

Related terms

radius: The radius is the other long bone in the forearm, located on the thumb side, which works in conjunction with the ulna to enable forearm movements.

humerus:

The humerus is the bone of the upper arm that connects with the ulna and radius at the elbow joint, forming part of the skeletal framework of the arm.

elbow joint: The elbow joint is a hinge joint formed by the articulation of the humerus, ulna, and radius, allowing for flexion and extension of the forearm.