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The forearm contains two bones, the radius and the ulna.
Compare and contrast the radius and ulna
The radius and the ulna are long, slightly curved bones that lie parallel from the elbow, where they articulate with the humerus, to the wrist, where they articulate with the carpals.
The radius is located laterally, near the thumb, and the ulna medially, near the little finger. The radius and the ulna have a styloid process at the distal end; they are also attachment sites for many muscles.
The forearm contains two bones—the radius
and the ulna—that extend in parallel from the elbow, where they articulate with
the humerus to the wrist, where they articulate with the carpals. The space
between the two bones is spanned by the interosseous membrane.
Anatomically, the ulna is located medially to the radius, placing it near the little finger. The ulna is slightly larger than the
Proximally, there are five key regions of the ulna:
The olecranon is a
projection of bone that extends proximally from the ulna.
The triceps brachii
muscle attaches to the ulna superiorly.
The cornoid process, together with the olecranon, forms the trochlear notch where it articulates with
the trochlea of the humerus.
Laterally to the trochlear notch lies the radial
notch, which articulates with the head of the radius to form the proximal
Immediately distal to the coronoid process is the
tuberosity of ulna, to which the brachialis muscle attaches.
The shaft of the ulna is triangular and
numerus muscles involved in pronation and flexion of the forearm attach to its
Distally, the ulna is much smaller and
terminates with a rounded head that articulates with the ulnar notch of the
radius to form the distal radioulnar joint. The styloid process of the ulna
extends distally and is the site of attachment for ligaments found in the
Anatomically, the radius is located laterally to the ulna placing it near the thumb. The radius is slightly smaller than the
ulna and pivots around the ulna to produce movement at the proximal and distal
Proximally, the radius terminates with a disk-shaped head that articulates with the capitulum of the humerus and the radial notch of the
ulna. Immediately below the head lies the radial tuberosity to which the biceps
brachii attaches. As with the ulna, the shaft of the radius is triangular in
shape and numerous muscles, including the protonator teres, attach to it.
Distally the radius expands, medially the
ulnar notch articulates with the head of the ulnar. Immediately adjacent to the
ulnar notch, the radius articulates with the scaphoid and lunate carpal bones to form part of the wrist.