- Classification
- Short muscle function
- Long muscle function
- Description of the muscles of the upper limb
- Muscles of the shoulder girdle
- Pectoral minor
- Subclavian
- Pectoralis major
- Serratus major
- Subscapularis muscle
- Teres major muscle
- Teres minor muscle
- Infraspinatus muscle
- Supraspinatus muscle
- Deltoid muscle
- Latissimus dorsi
- Arm muscles
- Anterior muscles
- Posterior muscles
- Forearm muscles
- Previous compartment
- Rear compartment
- Side compartment
- Intrinsic muscles of the hand
- References
The muscles of the arm or muscles of the upper limb, are all those that are inserted into the bones of the upper extremities in order to give them mobility. The upper limb of the human being is the part of the body with the widest range of movements.
This characteristic allows the human being to make movements simultaneously in three dimensions, hence a large number of muscles are needed acting synergistically to achieve such a range of movements, all of them extremely precise.
Image source:
In general all the muscles of the arm are long. Those that are closest to the shoulder are the thickest and strongest, since they must keep the upper limb attached to the body and support the loads that it may carry.
As they are closer to the hand, the muscles tend to be less thick and voluminous, they generate less power but have extremely long tendons that allow precision and accuracy in movements. This precision has not been reproduced by any machine so far.
Classification
The muscles of the upper limb can be divided according to their morphological characteristics into two large groups: the short muscles (usually flat) and the long muscles (thicker).
On the other hand, according to their anatomical position with respect to the bones, they are divided into muscles of the posterior compartment (oriented towards the back of the hand) and the anterior compartment (towards the palm of the hand).
Short muscle function
These muscles are the ones that go from the scapula and the anterior aspect of the thorax to the first bone of the upper limb, known as the humerus.
Its main function is to keep the arm attached to the shoulder girdle, in addition to producing certain very specific movements of the shoulder joint.
Long muscle function
The long muscles are responsible for most of the movements of the arm, forearm and hand.
Depending on whether they work agonically or antagonistically, they achieve flexion, internal rotation, external rotation, extension, and circumduction of the arm.
They are the muscles that are trained the most in the gym, since they are prone to acquire a lot of volume and generate a lot of force, something very desirable among people who want to show off an athletic and healthy figure.
Description of the muscles of the upper limb
The biomechanics of the human upper limb is so complex that volumes have been written in relation to the subject; understanding them requires a thorough understanding of not only function, but also bone structure and neurovascular elements, something that is beyond the scope of this publication.
In this sense, the main muscle groups will be mentioned considering their main function, so that it is easy to get a clear idea of which muscles are working to achieve each movement.
In order to facilitate understanding, the description will be divided according to anatomical regions: scapula-shoulder complex (shoulder girdle), arm, forearm and hand.
Muscles of the shoulder girdle
It includes all the muscles that go from the scapula, in the posterior region of the thorax, towards the humerus, as well as those that are located in the anterior aspect of the thorax, inserted in the clavicle and ribs on one side and in the medial aspect of the humerus on the other.
The muscles of the shoulder girdle are divided into anterior and posterior. The above include:
Pectoral minor
A small, short muscle that helps lower the shoulder.
Subclavian
Attach the underside of the clavicle to the ribs. In conjunction with the pectoralis minor, they contribute to shoulder stability
Pectoralis major
It is the largest of all the muscles of the shoulder girdle; Its function is as adductor (brings the arm closer to the thorax) and the internal rotator of the arm.
Serratus major
It runs from the spinal edge of the scapula to the ribs. They are very strong muscles that keep the scapula attached to the back wall of the thorax.
On the other hand, the posterior muscles of the shoulder girdle group:
Subscapularis muscle
It is located between the scapula and the ribs, and functions as the internal rotator of the shoulder (it is the deepest muscle of the rotator cuff).
Teres major muscle
It runs between the outer edge of the scapula and the medial aspect of the humerus. It functions as an adductor and internal rotator of the shoulder.
Teres minor muscle
Closely related to the previous one, this muscle is part of the rotator cuff. Its function is external rotation and transverse abduction (separation) of the arm.
Infraspinatus muscle
It is another of the rotator cuff muscles and acts synergistically with the teres minor, to the point that they are sometimes fused.
Supraspinatus muscle
It is the last of the rotator cuff members, it works as an abductor of the arm.
Deltoid muscle
It is the most visible and voluminous muscle in the arm. Its three fascicles cover the shoulder above, front and back; Its function is as an abductor and rotator of the shoulder.
Latissimus dorsi
It is a muscle in the posterior region of the thorax that also takes insertion in the arm. When its fixed point is the thorax, its function is to move the arm back. If the shoulder is in the abduction position (the arm raised, separated from the thorax), this muscle contributes to adduction by working synergistically with the teres major.
Arm muscles
The muscles of the arm can be divided into two large groups: the muscles of the anterior compartment, whose main function is the flexion of the elbow; and the posterior compartment muscles, which do exactly the opposite, extend the elbow.
Anterior muscles
- Pronator teres muscle.
- Pronator square muscle.
- Flexor carpi radialis muscle.
- Long palmar muscle.
- Flexor carpi ulnar muscle.
- Superficial flexor muscle of the fingers.
- Deep flexor muscle of the fingers.
- Long flexor muscle of the thumb.
Posterior muscles
- Triceps brachii muscle.
- Anconeus muscle.
- Triceps brachii muscle.
- Anconeus muscle.
- Triceps brachii muscle.
- Anconeus muscle.
Forearm muscles
The muscles of the forearm can be divided into three large groups: the flexors of the fingers (located on the anterior face), the extensors of the fingers (located on the back) and the supinators or external rotators of the forearm (located on the edge radial (towards the thumb) of the arm.
The case of pronators (internal rotators) is very special, since they are located very deep in the forearm, practically on the interosseous membrane, and although they are part of the muscles of the anterior compartment, their attachments go from the ulna (ulna) to the radio.
This implies that they can rotate the forearm but are not involved in the movements of the fingers like the rest of the muscles of the anterior compartment.
The muscles of the forearm are:
Previous compartment
- Biceps brachii muscle.
- Coracobrachialis muscle.
- Brachialis muscle.
- Coracobrachialis muscle.
- Brachialis muscle.
- Coracobrachialis muscle.
- Brachialis muscle.
Rear compartment
- Extensor finger muscle.
- Extensor carpi ulnaris muscle or posterior ulnar muscle.
- Abductor pollicis longus muscle.
- Extensor pollicis brevis muscle.
- Extensor pollicis longus muscle.
- Extensor muscle of the index.
- Short palmar muscle or cutaneous palmar muscle.
Side compartment
- Short supinator muscle.
- First radial or long radial.
- Second radial or short radial.
- Long supinator muscle.
Intrinsic muscles of the hand
It includes the lumbrical and interossei, as well as the thenar and hypothenar eminences muscles. The detailed description of these muscles deserves a separate chapter given the complexity of their biomechanics.
References
- Holzbaur, KR, Murray, WM, Gold, GE, & Delp, SL (2007). Upper limb muscle volumes in adult subjects. Journal of biomechanics, 40 (4), 742-749.
- Lieber, RL, Jacobson, MD, Fazeli, BM, Abrams, RA, & Botte, MJ (1992). Architecture of selected muscles of the arm and forearm: anatomy and implications for tendon transfer. Journal of Hand Surgery, 17 (5), 787-798.
- Gielen, CCAM, & Van Zuylen, EJ (1986). Coordination of arm muscles during flexion and supination: Application of the tensor analysis approach. Neuroscience, 17 (3), 527-539.
- McDonagh, MJN, White, MJ, & Davies, CTM (1984). Different effects of aging on the mechanical properties of human arm and leg muscles. Gerontology, 30 (1), 49-54.
- An, KN, Hui, FC, Morrey, BF, Linscheid, RL, & Chao, EY (1981). Muscles across the elbow joint: a biomechanical analysis. Journal of biomechanics, 14 (10), 663-669.
- Nakatani, T., Tanaka, S., & Mizukami, S. (1998). Bilateral four-headed biceps brachii muscles: The median nerve and brachial artery passing through a tunnel formed by a muscle slip from the accessory head. Clinical Anatomy, 11 (3), 209-212.
- Wadsworth, DJS, & Bullock-Saxton, JE (1997). Recruitment patterns of the scapular rotator muscles in freestyle swimmers with subacromial impingement. International journal of sports medicine, 18 (08), 618-624.