Bones of the Forearm

Watch this AnatomyZone video by Dr. Peter de Souza on the radius and ulna.

The radius

This is a lateral bone of the forearm. It has a characteristic enlarged, disk-like head (a.k.a. radial head) that articulates with the capitulum of the humerus.  This disk-like nature of the head makes possible the rotary pronation-supination of the hand. 

Visit this AnatomyZone site to view the radius in 3D. Click the arrows in the info panel and move the bone around with your mouse. Using the thumb, as your landmark, make a note of whether the radius is medial or lateral.

Find the following characteristics on the radius:

1. radial tuberosity:  on the medial surface a few centimeters distal to the head; raised and rough surface that is the point of attachment of the biceps brachii muscle
2. styloid process:  enlarged distal process, articulates with the wrist. 

The ulna

The ulna is a medial bone of the forearm. The proximal end has an olecranon, which fits into the olecranon fossa of the humerus when the arm is extended.  Anterior to the olecranon is a rounded groove called the trochlear notch (not visible on Figure 3), into which the trochlea of the humerus articulates. The notch makes the distal end resemble an ice cream scoop.

·  styloid process:  at distal end the ulna, on the posteromedial surface; can easily be felt through the skin of the wrist.  Locate this process on your own wrist.

Visit this AnatomyZone site to view the ulna in 3D. Click the arrows in the info panel and move the bone around with your mouse. Using the thumb, as your landmark, make a note of why the ulna is considered medial or lateral.

Study Hint = Radius bone is on the same side as the thumb! Another fun hint = “Thumbs Up is Right!” = radius or hitching a ride with thumbs up.