Shoulder Muscles


What are shoulder muscles?

The shoulder muscles are a set of complex muscles that act as a link between the torso and the head or neck. It includes a range of muscles such as the finer stabilizer, prime mover and fixator muscles. The muscles shield a ball and socket joint which is the most freely moveable joint in the body.

picture of shoulder muscles

Image Source: en.wikipedia.org

Following are the various parts that make up the shoulder muscles:

Front View of shoulder muscles

  • Deltoid (anterior head): Helps in internal rotation by allowing the individual to rotate the upper arm inwards and in flexing it forward
    picture of deltoid muscle

    Image Source: en.wikipedia.org

  • Pectoralis minor: Aids in drawing the shoulder blade upward and downward
    picture of pectoral muscles

    Image Source: en.wikipedia.org

  • Coracobrachialis: The muscle enables the upper arm to flex in the forward direction
    coracobrachialis muscle

    Image Source: en.wikipedia.org

  • Biceps brachii: It facilitates slight flexing of the upper arm in the shoulder while it also helps in flexing and supinating the forearm
    picture of biceps brachii

    Image Source: en.wikipedia.org

  • Subclavius: Provides depression in the lateral part of the clavicle
    Subclavius muscle

    Image Source: en.wikipedia.org

Back View of shoulder muscles

  • Trapezius: Brings the shoulder blades together by retraction and enables elevation and depression of the shoulder
    picture of trapezius muscle

    Image Source: en.wikipedia.org

  • Deltoid (posterior and middle head): Helps in the sideways movement of the upper arm known as abduction, bringing it closer to the body known as adduction and extending it backward for external rotation.
  • Latissimus dorsi: Allows extension and medial rotation of the arm
    picture of latissimus dorsi

    Image Source: en.wikipedia.org

  • Rotator cuff muscle Helps in movement of the upper arm in the shoulder joint and has the following parts:
    – Subscapularis: Internal rotation of the upper arm
    – Supraspinatus: Abduction or sideways movement of the upper arm
    – Infraspinatus: External rotation of the upper arm
    – Teres minor: Moves the upper arm towards the body through abduction

    rotator cuff pictures

    Image Source: en.wikipedia.org

  • Levator scapulae: Aids in elevation of the shoulder blade
    Levator scapulae muscle

    Image Source: en.wikipedia.org

  • Teres major: Helps in backward extension and internal rotation of the upper arm
    picture of teres major

    Image Source: en.wikipedia.org

  • Rhomboid major and minor: Retraction of the shoulder blades
    Rhomboid major muscle

    Rhomboid Major Muscle. Image Source: en.wikipedia.org

    Rhomboid minor muscle

    Rhomboid Minor Muscle. Image Source: en.wikipedia.org

     

  • Serratus anterior: Facilitates protraction or moving apart of the shoulder blades
    serratus anterior picture

    Image Source: en.wikipedia.org

  • Triceps branch: Adduction or backward extension of the upper arm, moving it towards the body
    triceps brachii

    Image Source: en.wikipedia.org

Functions of the shoulder muscles:

 

Muscles involved  Function 
Anterior deltoid, biceps brachii,
pectoralis major, coracobrachialis
Moving the arm forward
Triceps brachii, posterior deltoid,
teres major, latissimus dorsi
Moving an arm backward
Upper trapezius, serratus anterior,
posterior & middle deltoid, supraspinatus
Abduction or lifting the arm sideways
Teres major, pectoralis minor, pectoralis major,
latissimus dorsi, coracobrachialis
Adduction or moving the arm closer to the body
Anterior deltoid, pectoralis major Horizontal adduction or medial movement of the arm from a horizontal front position
Infraspinatus, posterior deltoid,
teres minor
External lateral rotation – arm flexes with the elbow toward the body
Subscapularis, teres major, anterior deltoid, latissimus dorsi, pectoralis major Internal medial rotation – arm flexes with the elbow moving away from the body
Lower trapezius, Pectoralis minor,
Latissimus dorsi, Subclavius
Depression of the shoulder or scapular depression
Pectoralis minor Scapular tilt – forward movement of the upper part of the scapula
Serratus anterior, trapezius Moving the lateral angle of the scapular upward or scapular upward rotation
Pectoralis major, Pectoralis minor,
Subclavius, Latissimus dorsi
Scapular downward rotation or moving the lateral angle of the scapula downward
Rhomboideus major and minor, Trapezius Scapular adduction or retraction – bringing the shoulder blades closer by moving the shoulders backward
Serratus anterior, Pectoralis major,
Pectoralis minor
Bringing the shoulders forward – scapular protraction or abduction

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