ulna

(noun)

One of two forearm bones, it is located medially to the radius.

Related Terms

Examples of ulna in the following topics:

  • Ulna and Radius (The Forearm)

    • Anatomically, the ulna is located medially to the radius, placing it near the little finger.
    • The ulna is slightly larger than the radius.
    • The olecranon is a projection of bone that extends proximally from the ulna.
    • 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 radioulnar joints.

  • Muscles of the Humerus that Act on the Forearm

    • Attachments - Originates from the humerus and attaches to the ulna.
    • All three converge into one tendon which attaches to the ulna.
    • Attachments - Originates from the ulna and attaches to the radius.
    • Attachments - Originates from the humerus and attaches to the ulna.
    • Action - Moves the ulna during pronation and extends the forearm at the elbow.

  • Humerus (The Upper Arm)

    • Distally, the humerus articulates with the radius and ulna to form the elbow joint.
    • Distally, the humerus flattens to articulate with the ulna and radius at the elbow joint.
    • The medially located trochlea articulates with the ulna.
    • The humerus attaches proximally to the scapula (shoulderblade) at the humeral head and distally with the radius and ulna (lower-arm bones) at the trochlea and capitulum, respectively.

  • Muscles of the Wrist and Hand

    • Attachments - Originates from the ulna and attaches to the radius.
    • Attachments - Originates from the humerus and attaches to the ulna.
    • Actions - Moves the ulna during pronation and extends the forearm at the elbow.
    • Attachments - Originates from the radius and ulna attaching to the base of the thumb.
    • Attachments - Originates from the ulna and attaches to the index finger.

  • Overview of the Appendicular Skeleton

    • This consists of the left and right Humerus (two bones in the upper arm), the ulna (two bones), and the radius (two bones).
    • Both the ulna and the radius are in the forearm.

  • Interosseous Membranes

    • The interosseous membrane in the arm extends between the radius and the ulna in the lower arm .
    • This image shows the interosseous membrane connecting the radius and the ulna.

  • Syndesmoses

    • The interosseous membrane in the lower arm extends between the radius and the ulna.
    • Joints of this kind are found at several points in the human body, including the intermediate radioulnar joint, where the radius and ulna meet above the wrist, in the spine between the spinous processes of various adjacent vertebra, and above the ankle joint where the tibia and fibula converge.

  • The Appendicular Skeleton

    • Upper arms and forearms (6 bones) - Left and right humerus (upper arm, 2), ulna (2) and radius (2) (forearm)
    • The three regions of the upper limb arm (humerus), forearm (ulna medially and radius laterally), and the hand.

  • Functional Classification of Joints

    • Nonaxial (gliding) – An example are those found between the proximal ends of the ulna and radius.

  • Types of Synovial Joints

    • A hinge joint (ginglymus) is formed when the cylindrical end of a bone fits into a trough-shaped surface of another bone, like that of an elbow joint (between the humerus and the ulna).