Ulna

The ulna (plural: ulnae) is one of the two long bones of the forearm. It is located medially in the supinated anatomic position. It has a larger proximal end and tapers to a smaller distal end (opposite to the radius). 

Prominent features of the ulna include:

  • proximal: olecranon, trochlear notch, coronoid process, radial notch (lateral), sublime tubercle (medial)
  • shaft: ulnar tuberosity
  • distal: head, styloid process, groove for extensor carpi ulnaris
Articulations
Attachments
Musculotendinous

Anteriorly

  • proximal:
    • brachialis: ulnar tuberosity
    • pronator teres: ulnar head
    • flexor digitorum superficialis: ulnar head
  • shaft:
    • supinator
    • flexor digitorum profundus
    • pronator quadratus

Posteriorly

  • triceps, aconeus, supinator, flexor digitorum profundus, flexor carpi ulnaris (ulnar head), extensor carpi ulnaris (ulnar head), abductor pollicis longus, extensor pollicis longus, extensor indices
Ligamentous
  • proximal:
    • medial collateral ligaments of the elbow
      • anterior band: inferior medial epicondyle to the sublime tubercle
      • posterior band: medial epicondyle to medial olecranon
      • middle band (Transverse or Cooper's ligament): medial olecranon to medial coronoid process
    • anterior and posterior capsular ligaments of the elbow
  • medial:
    • anterior and posterior attachments of the annular ligament
    • quadrate ligament
    • oblique cord
    • interosseous membrane
  • distal:
    • triangular fibrocartilage
    • ulnar collateral ligament of the wrist
Relations and/or boundaries

The ulna and its attachments help to divide the forearm into anterior and posterior compartments. 

Its subcutaneous border lies posteromedially and the antebrachial fascia attaches on either end. 

Its interosseous border (anterolaterally) is attached to the interosseous membrane of the forearm.

Blood supply

The forearm (and ulna) is supplied by the ulnar artery and its continuation as the common interosseous artery with the anterior and posterior interosseous branches.

Nerve supply

Periosteum is supplied anteriorly by the anterior interosseous nerve (branch of median nerve).

Posteriorly, the periosteum is supplied by the posterior interosseous nerve (branch of radial nerve).

Lymphatic supply

Lymphatics of the hand and forearm drain either to the supratrochlear lymph node, or directly into the lateral group of axillary lymph nodes.

Carrying angle of the elbow of 15-20 degrees. Increased in females.

Intracartilaginous ossification begins in utero. Ossification centres include:

  • shaft/diaphysis (8 weeks gestation)
  • distal (5-7 years > 16-18 years)
  • proximal (8-10 years > 13-15 years)
Upper limb anatomy
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Article Information

rID: 34288
Section: Anatomy
Tag: anatomy
Synonyms or Alternate Spellings:
  • Elbow bone
  • Ulna bone

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