The Shoulder Muscles - Deltoid, Supraspinatus, Infraspinatus, Teres Major and Minor

Posted on 27 Oct 2015 19:17



The shoulder muscle videos and information in this article provide information about muscles of the "shoulder girdle" and of the shoulder joint.

This distinction is frequently misunderstood.

For more information of this subject see The Shoulder Complex: Demystifying the Shoulder with Eric Beard.

Also see more information about particular muscles presented on this page.

Deltoid Muscle and Its Trigger Points
Teres Major and Its Trigger Points
Infraspinatus Muscle and Its Trigger Points

What follows are two videos giving a presentation of each muscle using an anatomical model, and then written information about the origin, insertions, and actions of each muscle discussed.


Shoulder Muscles Video 1: Deltoid, Supraspinatus, Infraspinatus, Teres Major and Minor

Deltoid Muscle

For indepth information on the deltoid muscle, including its origins, insertions, and actions, see link, as above.

Supraspinatus Muscle

Origin: medial two-thirds of suprispinatus fossa
of scapula

Insertion: greater tubercle of humerus

Action: weak abduction of arm (initiates abduction) and stabilization of humeral head in glenoid fossa

Infraspinatus Muscle

Origin: medial two-thirds of infraspinatus fossa just below spine of scapula

Insertion: posterior aspect of greater tubercle of humerus

Action: external rotation, horizontal abduction, extension of the glenohumeral joint and stabilization of humeral head in glenoid fossa

Teres Minor Muscle

Origin: upper and middle posterior aspect of lateral border of scapula

Insertion: posterior aspect of greater tubercle of humerus

Action: external rotation, horizontal abduction and extension of glenohumeral joint, stabilization of humeral head in glenoid fossa

Teres Major Muscle

Origin: posterior inferior aspect of lateral border of scapula just superior to inferior angle

Insertion: medial lip of intertubercular groove of humerus

Action: extension*, internal rotation and adduction** of glenohumeral joint.

Before we move on to the second group of muscles, here is a diagram of the scapula, to help you with anatomical landmarks.

Labeled Diagram of Scapula

labeled diagram showing anatomy of scapula


Shoulder Muscles Video Part 2: Pectoralis Major and Subscapularis

Pectoralis Major Muscle

Origin:

  • Upper Fibers (clavicular head): medial half of anterior surface of clavicle.
  • Lower fibers (sternal head): anterior surfaces of costal cartilage of first six ribs and the adjacent portion of sternum. Abdominal head (pars abdominal): external oblique aponeurosis.

**Insertion: Both heads: outer lip of the intertubercular groove of humerus. Flat wide tendon, 2 to 3 inches wide.

Action:

  • Upper Fibers (clavicular head): internal rotation, horizontal adduction, flexion, abduction and adduction of glenohumeral joint.
  • Lower fibers (sternal head): internal rotation, horizontal adduction, flexion, abduction and adduction of the glenohumeral (shoulder) joint.

Subscapularis Muscle

Orgin: anterior surface of subscapular fossa.

Insertion: lesser tubercle of humerus

Action: internal rotation, adduction and extension of shoulder (glenohumeral) joint and stabilization of humeral head in glenoid fossa.

View drbobrd's youtube channel.

This page created 27 Oct 2015 19:17
Last updated 19 Nov 2016 21:08

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