Proximal radioulnar articulation

The Proximal radioulnar joint ( " body lean ulnar- joint " ) is the pivotal connection between the forearm bones spoke ( radius) and Elle ( ulna ) and a partial joint of the elbow joint. Functionally, it is a pivot joint with one degree of freedom in which the spoke in a depression of the ulna rotates about the longitudinal axis and thus - allows Umwendebewegungen the hand ( pronation and supination ) - with involvement of the distal radioulnar joint.

Construction

The articular surface of the spoke is circumferentia articularis called radii. It is on the inside (medial ) is wider than at the outside ( lateral). The confiscation of the ulna is called the radial notch of the ulna and of the articular surface for the humerus ( trochlear notch ) by a narrow ridge separated. The joint is through the annular spoke tape ( annular ligament of the radius ) stabilized, which originates on both sides of the radial notch of the ulna, including the spoke head and pressed into the Ellenauschnitt. On the inside this band has a cartilage -like structure and serves as a joint surface.

Species differences

For many, mainly specialized in straight mammals, the motion in the radioulnar joint Proximal is severely limited. In ungulates, the joint is immobile. In pigs, the ulna and radius are fixed by tight ligaments. In ruminants and horses are Ellen and spoke head bone fused together, so that no ulnar- joint is designed.

In birds in the ulnar- joint meniscus ( meniscus radioulnaris ) is incorporated, its ventral margin is adherent to the joint capsule, while the thick dorsal edge remains free. The bond between the radius and ulna is called the transverse ligament radioulnar.