Veterinary Gross Anatomy

ULNA
(Ox, Sheep and Goat, Horse, Pig, Dog, Rabbit, Fowl)

Ox

• It is a long bone and longer than the radius.
• It situated on the posterolateral aspect of the radius.
• It is fused with the radius in the adult, except at the two inter-osseous spaces above and below. View image...
• Shaft
• It is complete, three sided and strongly curved.
• Its proximal part contains the medullary cavity, which extends somewhat into the proximal end.
• The dorsal face is rough except at two places where it is smooth and is applied to the volar aspect of the radius.
• The medial face is wide.
• The lateral face presents the radio-ulnar groove between it and the radius.
• Proximal extremity
• It forms the major part of the bone and is made up of the semilunar notch and the olecranon process.
• The olacranon process is quadrilateral in shape directed upward and backward. The medial surface is concave and smooth while the lateral is convex and rough above. The anterior border bear on its middle a pointed projection the anconeus process that is for anconeus and during extreme extension of the elbow joint it passes into the olecranon fossa of the humerus. The posterior border is thick and concave. The summit of the olecranon process forms the point of the elbow and gives attachment to triceps.
• The semilunar notch is placed below the anconeus process and articulates with the posterior part of the medial division of the articular area of the humerus. Below the notch are two facets for articulation with the like facets on the posterior face of the proximal extremity of the radius.
• Distal extremity
• It is fused with the radius.
• It projects below the level of the radius forming the styloid process of ulna, which furnishes a part of the facet for the ulnar carpal.

TOP

Sheep and Goat

• Shaft of the ulna is more slender especially in the distal half.
• Fusion with the radius occurs in the later part of the life and the fusion is much less extensive than the ox.

TOP

Horse

• It is shorter, reaching only the distal third of the radius. It forms only the proximal radio-ulnar arch.
• There is no articulation with the ulnar carpal.

TOP

Pig

• The proximal extremity is large and the olecranon process is prominent.
• The distal extremity is small and tapers to a blunt point. View image...

TOP

Dog

• It is well developed and crosses the volar face of the radius medio-laterally closing a narrow interosseous space.
• The olecranon is grooved and shows three prominences of which the posterior one is large and rounded.
• Below the semilunar notch is concave surface for the radius.
• The styloid process articulates dorso-medially with radius and low with ulnar and the accessory carpals.

TOP

Rabbit

• Similar to that of dog.

TOP

Fowl

• It is larger and thicker than the radius.
• It is curved in its length.
• The proximal extremity has two concave articular areas.
• The olecranon process is short.
• The distal extremity is expanded and presents a trochlea and articulates with radial and ulnar carpal bones.

TOP