Shoulder Muscles Anatomy

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Published: April 22, 2016
Last reviewed: August 21, 2017


Shoulder muscles move the shoulder blades and upper arm bones.

The main shoulder muscles are trapezius, deltoid, pectoralis major and 4 rotator cuff muscles: subscapularis, supraspinatus, infraspinatus and teres minor. The list of muscles and their functions are presented below. Muscle attachments (origins, insertions) are described in the video at the bottom of this article and in the articles about the shoulder girdle and shoulder blade.

Chart 1. Shoulder Muscles — FRONT View

Muscle

Main Function

Deltoid (anterior head) Flexes the upper arm forwards and rotates it inwards (internal rotation).
Pectoralis minor Draws the shoulder blade forwards and downward.
Coracobrachialis Flexes the upper arm forwards.
Biceps brachii Flexes and supinates the forearm and slightly flexes the upper arm in the shoulder.
Subclavius Depresses the lateral part of the clavicle.

 

Chart 2. Shoulder Muscles — BACK View

Muscle

Main Function

Trapezius Elevates and depresses the shoulder and brings together (retracts) the shoulder blades.
Deltoid (posterior and middle head) Moves the upper arm sideways (abduction), brings it to the body (adduction), extends it backward and rotates it outwards (external rotation).
Latissimus dorsi Adducts, medially rotates and extends the arm.
Rotator cuff muscles: Move the upper arm in the shoulder joint.
Rotates the upper arm inwards (internal rotation).
Moves the upper arm sideways (abduction).
Rotates the upper arm outwards (external rotation).
Rotates the upper arm outwards and brings it to the body (abduction).
Levator scapulae Elevates the shoulder blade.
Teres major Extends the upper arm backward and rotates it inwards (internal rotation).
Rhomboid major and minor Bring together (retract) the shoulder blades.
Serratus anterior Moves the shoulder blades apart (protraction).
Triceps brachii Extends the upper arm backward and moves it toward the body (adduction).

Shoulder muscles

Picture 1. Muscles at the back of the shoulder

Chart 3. Shoulder Muscles Functions

Function

Muscle

Flexion of an arm

(Forward movement of an arm)

  • Anterior deltoid
  • Coracobrachialis
  • Biceps brachii (both heads)
  • Pectoralis major (clavicular head)

Extension of an arm

(Backward movement of an arm)

  • Posterior deltoid
  • Triceps brachii (long head)
  • Latissimus dorsi
  • Teres major

Abduction of an arm

(Lifting an arm sideways)

  • Posterior and middle deltoid
  • Supraspinatus
  • Upper trapezius
  • Serratus anterior

Adduction of an arm

(Bringing an arm toward the body)

  • Pectoralis major
  • Pectoralis minor
  • Latissimus dorsi
  • Teres major
  • Coracobrachialis

Horizontal abduction of an arm

(Movement of an arm from a horizontal front position laterally)

  • Posterior deltoid

Horizontal adduction of an arm

(Movement of an arm from a horizontal front position medially)

  • Pectoralis major
  • Anterior deltoid

Internal (medial) rotation of an arm

(Rotation of an arm that is flexed in the elbow toward the body)

  • Anterior deltoid
  • Pectoralis major
  • Subscapularis
  • Teres major
  • Latissimus dorsi

External (lateral) rotation of an arm

(Rotation of an arm that is flexed in the elbow away from the body)

  • Posterior deltoid
  • Infraspinatus
  • Teres minor

Scapular elevation

(Elevation of a shoulder)

  • Upper trapezius
  • Levator scapulae
  • Rhomboid major and minor

Scapular depression

(Depression of a shoulder)

  • Lower trapezius
  • Pectoralis minor
  • Latissimus dorsi
  • Subclavius

Scapular tilt

(Bringing the upper part of scapula forwards)

  • Pectoralis minor

Scapular upward rotation

(Bringing the lateral scapular angle upwards)

  • Trapezius
  • Serratus anterior

Scapular downward rotation

(Bringing the lateral scapular angle downwards)

  • Pectoralis major
  • Pectoralis minor
  • Subclavius
  • Latissimus dorsi

Scapular protraction (abduction)

(Bringing shoulders forward)

  • Serratus anterior
  • Pectoralis major
  • Pectoralis minor

Scapular retraction (adduction)

(Bringing shoulders backward, that is shoulder blades closer)

  • Rhomboideus major and minor
  • Trapezius

Chart 3 references: 1,2,3


Video 1. 3D presentation of the shoulder muscles
with their attachments and functions

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