Medical YouTube

Model presentation of muscles of head and neck

Learning the muscles of head and neck

Source: www.answers.com , www.wikipedia.com

Pronators of the forearm:

1. Pronator teres: It has two heads; humeral and ulnar. The humeral head, larger and more superficial, arises immediately above the medial epicondyle of the humerus and from the common flexor tendon. The ulnar head is a thin fasciculus, which arises from the medial side of the coronoid process of the ulna, and joins the prcending at an acute angle.
2. Pronator quadratus: It is a square shaped muscle on the distal of the forearm that acts to pronate the hand. Its fibers run perpendicular to the direction of the arm, running from the most distal quarter of the anterior ulna to the distal quarter of the anterior radius.

The supinators of the forearm:

1. Supinator: This is a broad muscle, curved around the upper third of the radius. Its origin is the lateral epicondyle of humerus, supinator crest of ulna, radial collateral ligament, annular ligament. The insertion is on lateral proximal radial shaft. Exactly opposes the pronator teres.
2. Biceps brachii: Althoug the main function is known as the flexion of the elbow, another function is the supinate the forearm, this can be easily understood if we locate the origin and insertion of this muscle. The origin is: short head from the coracoid process of scapula, long head from the supraglenoid tubercle and is inserted to the radial tuberosity.

The main elbow flexors are:

1. Biceps brachii: A muscle with two heads or points of origin.
2. Brachialis A strong muscle lying immediately below the biceps brachii in the upper arm. Its origin is on anterior lower half of humerus and it inserts onto the anterior coronoid process of the ulna. Its primary action is elbow flexion, especially when the forearm is midway between full flexion and full extension.
3. Brachioradialis: The muscle of the arm that flexes the elbow joint, origin is the lateral supracondylar ridge of the humerus, and insertion is the lower end of the radius.

The main extensor of elbow joint is:

1. Triceps brachii: A large fleshy muscle at the back of the arm. It is commonly reffered to as the triceps. It opposes the action of biceps by straightening the arm. This three headed muscle originates from the humerus and the shoulder blade. A single tendon inserts the three heads of the muscle onto the olecranon process, the prominent protection of the ulna in the elbow. This tendon is easily damaged by forceful throwing or when falling on the hand with a fully extended arm.
2. Aconeus: A very small muscle assists in extension of the elbow joint.