Biceps brachii muscle

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For other uses, see biceps.

In human anatomy, the biceps brachii is a muscle located on the upper arm. The term biceps brachii is a Latin phrase meaning "two heads of the arm", in reference to the fact that the muscle consists of two bundles with a common insertion point near the elbow. The biceps has several functions, the most important simply being to flex the elbow and to rotate the forearm.

The biceps brachii is arguably the best known muscle, as it lies fairly superficially, and is often well-defined even in non-athletes. The muscle is popular amongst bodybuilders, and can grow quite large through weight training. The world record measurement for the upper arm stands at 30 inches, although this was the result of development in both the biceps and the triceps.

Note that the word biceps is both singular and plural: the form bicep, although common, is incorrect. (The Latin plural bicipites is considered pedantic and rarely used.)

Contents

1 Anatomy
2 Functions

2.1 Supination

3 References
4 External links

Anatomy

Proximally, the short head of the biceps attaches to the coracoid process of the scapula. The tendon of the long head passes into the joint capsule at the head of the humerus, and attaches on the scapula at the supraglenoid tubercle.

Distally, biceps attaches to the radial tuberosity, and because this bone can rotate, the biceps also supinates the forearm. The biceps also connects with the fascia of the medial side of the arm, at the bicipital aponeurosis.

Two additional muscles lie underneath the biceps brachii. These are the coracobrachialis muscle, which like the biceps attaches to the coracoid process of the scapula, and the brachialis muscle which connects to the ulna and the humerus.

Functions

The biceps is tri-articulate, meaning that it has three functions. Its most important functions are to flex the elbow and to supinate the forearm, but it also serves as a secondary muscle in shoulder movement to elevate the arm.

Supination

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An example of an arm flexed in the pronated position; with the biceps partially contracted.
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An example of an arm flexed in a supinated position with the biceps fully contracted.
One of the main functions of the biceps is to allow supination of the forearm, which refers to the allowing the forearm, and subsequently, the palm, to be rotated or moved, not dissimilar to the movement of the biceps curl. This has also been achieved through the use of functional electrical stimulation as a means of emulating electical impulses used within the synapses, and allow slight movement within those with paralysis. Naito A, Yajima M, Fukamachi H, Ushikoshi K, Handa Y, Hoshimiya N, Shimizu Y. (1994) Functional electrical stimulation (FES) to the biceps brachii for controlling forearm supination in the paralyzed upper extremity. Tohoku journal of experimental medicine


An example of an arm flexed in the pronated position; with the biceps partially contracted.

An example of an arm flexed in a supinated position with the biceps fully contracted.

It has also been proved through several tests into muscle group stimulation, that supination of the forearm with an isometric grip allows for close and normal-grip bench press exercises to have a much more profound effect on the biceps brachii and the clavicular portion of the pectorialis major. #redirect

Originally, supination of the forearm was attributed as a function of the brachioradialis muscle. However, the original idea of the biceps acting as a supinator was something hypothesised by Leonardo da Vinci, in a series of annotated drawings made between 1505 and 1510 (referred to as his Milanese period); in which the principle of the biceps as a supinator, as well as its role as a flexor to the elbow was devised. However, this function remained undiscovered by the medical community as Da Vinci was not regarded as a teacher of anatomy, nor were his results publicly released.

It was not until 1713, that this movement was re-discovered by William Cheselden, and subsequently recorded for the medical community, being rewritten several times by different authors wishing to present information to different audiences. Nevertheless, the most notable recent expansion upon Cheselden's recordings was achieved by Guillaume Duchenne in 1867 in a journal named Physiology of Motion, something which to this day is one of the major references on supination action of the biceps brachii.

References

External links

Muscles of the — — — — — LIST OF ALL MUSCLES

ANTERIOR AND LATERAL THORACIC WALLS: pectoralis major | pectoralis minor | subclavius | serratus anterior | (Gray's [s122])

SHOULDER: deltoid | rotator cuff (subscapularis, supraspinatus, infraspinatus, teres minor) | teres major | (Gray's [s123])

ARM: coracobrachialis | biceps brachii | brachialis | triceps brachii | (Gray's [s124])

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