Humeroulnar joint
Encyclopedia
The humeroulnar joint, is part of the elbow-joint or the Olecron Joint, between the ulna
and humerus
bones is the simple hinge-joint, which allows for movements of flexion, extension and circumduction. The Humero-Ulnar Joint is the junction of trochlear notch of the ulna and the trochlea of the humerus.
Owing to the obliquity of the trochlea of the humerus, this movement does not take place in the antero-posterior plane of the body of the humerus.
When the forearm is extended and supinated, the axis of the arm and forearm are not in the same line; the arm forms an obtuse angle with the forearm (the carrying angle). During flexion, however, the forearm and the hand tend to approach the middle line of the body, and thus enable the hand to be easily carried to the face.
The accurate adaptation of the trochlea
of the humerus, with its prominences and depressions, to the semilunar notch
of the ulna, prevents any lateral movement.
Flexion is produced by the action of the Biceps brachii and Brachialis, assisted by the Brachioradialis
, with a tiny contribution from the muscles arising from the medial epicondyle of the humerus.
Extension is produced by the Triceps brachii and Anconæus, with a tiny contribution from the muscles arising from the lateral epicondyle of the humerus
, such as the Extensor digitorum communis.
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
and humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
bones is the simple hinge-joint, which allows for movements of flexion, extension and circumduction. The Humero-Ulnar Joint is the junction of trochlear notch of the ulna and the trochlea of the humerus.
Owing to the obliquity of the trochlea of the humerus, this movement does not take place in the antero-posterior plane of the body of the humerus.
When the forearm is extended and supinated, the axis of the arm and forearm are not in the same line; the arm forms an obtuse angle with the forearm (the carrying angle). During flexion, however, the forearm and the hand tend to approach the middle line of the body, and thus enable the hand to be easily carried to the face.
The accurate adaptation of the trochlea
Trochlea
Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
of the humerus, with its prominences and depressions, to the semilunar notch
Semilunar notch
The semilunar notch of the ulna is a large depression, formed by the olecranon and the coronoid process, and serving for articulation with the trochlea of the humerus....
of the ulna, prevents any lateral movement.
Flexion is produced by the action of the Biceps brachii and Brachialis, assisted by the Brachioradialis
Brachioradialis
Brachioradialis is a muscle of the forearm that acts to flex the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm...
, with a tiny contribution from the muscles arising from the medial epicondyle of the humerus.
Extension is produced by the Triceps brachii and Anconæus, with a tiny contribution from the muscles arising from the lateral epicondyle of the humerus
Lateral epicondyle of the humerus
The lateral epicondyle of the humerus is a small, tuberculated eminence, curved a little forward, and giving attachment to the radial collateral ligament of the elbow-joint, and to a tendon common to the origin of the Supinator and some of the Extensor muscles. In birds, where the arm is somewhat...
, such as the Extensor digitorum communis.