Brachial muscle is the flexor of the upper arm, which starts from the gap between the medial and lateral muscles in the lower half of humerus and ends at the rough surface of ulna tuberosity, and has the functions of elbow flexion and supination. It has dual innervation of musculocutaneous nerve and radial nerve. The brachialis branch of radial nerve is a branch of radial nerve extending from elbow to ulnar side, which branches in the muscle space between brachialis and brachioradialis, and there is no blood vessel accompanying fibrous tissue.
Physiological position of triceps brachii
It is located under the skin behind the upper arm and has three heads. The long head starts from the subscapular tubercle, the lateral head starts from the outer upper part of the posterior radial nerve groove of humerus, and the medial head starts from the inner lower part of the posterior radial nerve groove of humerus. These three heads form a muscular abdomen, and its tendon stops at the olecranon of the ulna.
Its physiological cross section is 22.60 square centimeters. Near fixation, the forearm extends at the elbow joint, and the long head also extends the upper arm at the shoulder joint, which is the main muscle to straighten the elbow joint. When far fixed, keep the upper arm and forearm straight at the elbow joint (e.g. handstand push-ups).
Refer to the above contents: Baidu Encyclopedia-Biceps Brachialis, Baidu Encyclopedia-Brachial Muscle, Baidu Encyclopedia-Triceps Brachialis.