The Ulna Anatomy Quiz

The Ulna

• The ulna is one of two long forearm bones, forming the antebrachium, spanning from the elbow to the wrist on the medial side of the forearm in anatomical position.
• The ulna acts as a stabilizing bone, while the radius pivots to produce movement.
• The proximal end includes the olecranon process (tip), crucial for the triceps insertion, and the coronoid process. It also has a trochlear notch (semilunar notch) and a radial notch.

The Proximal Ulna

• The proximal end of the ulna articulates with the humerus' trochlea, sometimes called the head of the ulna.
• Key components include the olecranon, a bony projection that forms part of the trochlear notch.
• Also the coronoid process and the radial notch positioned on the lateral surface of the trochlear notch.

The Shaft and Distal Ulna

• The shaft is the long middle portion, attaching to the interosseous membrane, which connects the radius and ulna.
• The distal end forms a rounded head with a distal projection, the ulnar styloid process.
• The distal head articulates with the ulnar notch of the radius to create the distal radio-ulnar joint.

The Radius

• The radius is the other long bone of the forearm, positioned laterally beside the ulna.
• It pivots around the ulna for movement at the proximal and distal radio-ulnar joints.

The Proximal Radius

• The proximal end of the radius articulates at the elbow and proximal radioulnar joints.
• The head of the radius is a disc-shaped structure with a concave surface on top.
• The neck of the radius is just below the radial head, and the radial tuberosity is connected to the biceps brachii muscle.
• The shaft expands in diameter distally.

The Distal Radius

• The distal radial shaft forms a rectangular end.
• The styloid process extends distally on the lateral side, connecting with the ulnar notch.
• The distal radius connects with the scaphoid and lunate carpal bones, forming the wrist joint.

The Carpal Bones

• Eight carpal bones form two rows (proximal and distal).
• The scaphoid and lunate bones in the proximal row form the wrist joint.

The Metacarpal Bones

• Five bones form the middle section of the hand, corresponding to the fingers.
• Each metacarpal bone consists of a base, shaft, and head.
• They each connect to a corresponding finger with the medial and lateral sides of each metacarpal allowing muscle attachment.

The Phalanges

• These are the bones of the fingers.
• The thumb has a proximal and distal phalanx, while other fingers have proximal, middle, and distal phalanges.

Sesamoid Bones

• Small bones embedded within tendons near joints function as pulleys, reducing stress on the muscle or tendon.