ulnar

Ulnar is an anatomical term relating to the ulna, one of the two long bones of the forearm. In humans the ulna runs on the medial side of the forearm (toward the little finger) in the standard anatomical position and pairs with the radius to form the forearm.

Anatomy and joints: The ulna’s proximal end features the olecranon and coronoid processes that form part of the elbow joint with the humerus, connected by the trochlear notch. The distal end includes the ulnar head and a styloid process. The interosseous membrane binds the ulna to the radius along most of their lengths. The ulna participates in the elbow joint and, via the distal radioulnar joint, helps stabilize forearm rotation. The ulna also serves as an origin or insertion point for many forearm and hand muscles.

Nerve and vessels: The term ulnar also appears in the ulnar nerve and ulnar artery. The ulnar nerve travels along the arm and crosses behind the medial epicondyle at the elbow, through the cubital tunnel, and into the hand, where it innervates several intrinsic hand muscles and provides sensation to the medial one and a half fingers. The ulnar artery courses the forearm with the nerve, contributing to the arterial supply of the medial forearm and hand.

Clinical relevance: The ulna is commonly involved in fractures, and the ulnar nerve is a frequent site of compression or injury, producing numbness or weakness in the hand (cubital tunnel syndrome). The elbow’s ulnar collateral ligament is a key stabilizer against valgus stress, especially in throwing sports, with injuries sometimes requiring reconstructive surgery.

Overall, ulnar denotes structures associated with the ulna, particularly the forearm bone, its nerve supply, and related ligaments and arteries.