muscles of shoulder

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MUSCLES OF THE SHOULDER REGION (THORACOAPPENDICULAR AND

SCAPULOHUMERAL REGION)

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• Muscles of the pectoral region are divided into anterior and posterior muscles.

• Four anterior thoracoappendicular (pectoral) muscles move the pectoral girdle:

Pectoralis major, pectoralis minor, subclavius, and serratus anterior.

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MUSCLE ORIGIN INSERTION INNERVATION ACTION

Pectoralis major

Clavicular head: anterior surface of medial half of clavicle .Sternocostal head: anterior surface of sternum, superior six costal cartilages, and aponeurosis of external oblique muscle

Lateral lip of intertubercular groove of humerus

Lateral and medial pectoral nerves; clavicular head (C5 and C6), sternocostal head (C7, C8, and T1)

Adducts and medially rotates humerus; draws scapula anteriorly and inferiorly Acting alone: clavicular head flexes humerus and stemocostal head extends it .

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Pectoralis major muscle

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Pectoralis minor

3rd to 5th ribs near their costal cartilages

Medial border and superior surface of coracoid process of scapula

Medial pectoral nerve (C8 and T1)

Stabilizes scapula by drawing it inferiorly and anteriorly against thoracic wall

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P. minor

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Subclavius

Junction of 1st rib and its costal cartilage

Inferior surface of middle third of clavicle

Nerve to subclavius (C5 and C6)

Anchors and depresses clavicle

Serratus anterior

External surfaces of lateral parts of 1st to 8th ribs

Anterior surface of medial border of scapula

Long thoracic nerve (C5, 66, and 07)

Protracts scapula and holds it against thoracic wall; rotates

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Serratus anterior and subclavius

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POSTERIOR THORACOAPPENDICULAR

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• The two most superficial muscles of the shoulder are the trapezius and deltoid muscles.

• Together, they provide the characteristic contour of the shoulder:

trapezius attaches the scapula and clavicle to the trunk;

deltoid attaches the scapula and clavicle to the humerus.

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• Both trapezius and deltoid are attached to opposing surfaces and margins of the spine of the scapula, acromion, and clavicle.

• The scapula, acromion, and clavicle can be palpated between the attachments of trapezius and deltoid.

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• Deep to trapezius the scapula is attached to the vertebral column by three muscles-levator scapulae, rhomboid minor and rhomboid major.

• These three muscles work with trapezius (and with muscles found anteriorly) to position the scapula on the trunk.

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Trapezius

1. Superior nuchal line, 2. external occipital protuberance, 3. medial margin of the ligamentum nuchae, 4. spinous processes of CVII to TXII and 5. the related supraspinous ligaments

1. Superior edge of the crest of the spine of the scapula, 2. acromion, 3. posterior border of lateral one-third of clavicle

Motor spinal part of accessory nerve (CN XI). Sensory (proprioception) anterior rami of C3 and C4

1. Powerful elevator of the scapula; 2. rotates the scapula during abduction of humerus above horizontal; 3. middle fibers retract scapula; 4. lower fibers depress scapula

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Deltoid1. Inferior edge of the crest of the spine of the scapula, 2. lateral margin of the acromion, 3. anterior border of lateral one-third of clavicle

Deltoid tuberosity of humerus

Axillary nerve [C5,C6]

Major abductor of arm (abducts arm beyond initial 15° done by supraspinatus); clavicular fibers assist in flexing the arm; posterior fibers assist in extending the arm

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Levator scapulae

Transverse processes of CI and CII vertebrae and posterior tubercles of transverse processes of CIII and CIV vertebrae

Posterior surface of medial border of scapula from superior angle to root of spine of the scapula

Branches directly from anterior rami of C3 and C4 spinal nerves and by branches [C5] from the dorsal scapular nerve

Elevates the scapula

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Rhomboid minor

Lower end of ligamentum nuchae and spinous processes of CVII and TI vertebrae

Posterior surface of medial border of scapula at the root of the spine of the scapula

Dorsal scapular nerve [C4,C5]

Elevates and retracts the scapula

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Rhomboid major

Spinous processes of TII-TV vertebrae and intervening supraspinous ligaments

Posterior surface of medial border of scapula from the root of the spine of the scapula to the inferior angle

Dorsal scapular nerve [C4,C5]

Elevates and retracts the scapula

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MUSCLES OF THE POSTERIOR SCAPULAR

REGION( SCAPULOHUMERAL REGION)

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• The posterior scapular region occupies the posterior aspect of the scapula and is located deep to the trapezius and deltoid muscle.

• It contains four muscles, which pass between the scapula and proximal end of the humerus:

• the supraspinatus, infraspinatus, teres minor, and teres major muscles.

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• The posterior scapular region also contains part of one additional muscle, the long head of the triceps brachii, which passes between the scapula and the proximal end of the forearm.

• This muscle, along with other muscles of the region and the humerus, participates in forming a number of spaces through which nerves and vessels enter and leave the region.

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• The supraspinatus, infraspinatus, and teres minor muscles are components of the rotator cuff, which stabilizes the glenohumeral joint.

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SupraspinatusMedial two-thirds of the supra-spinous fossa of the scapula and the deep fascia that covers the muscle

Most superior facet on the greater tubercle of the humerus

Suprascapular nerve [C5,C6]

Rotator cuff muscle; initiation of abduction of arm to 15° at gleno-humeral joint

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SUPRASPINATUS

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Infraspinatus

Medial two-thirds of the infra-spinous fossa of the scapula and the deep fascia that covers the muscle

Middle facet on posterior surface of the greater tubercle of the humerus

Suprascapular nerve [C5,C6]

Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint

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infraspinatus

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Teres minor

Upper two-thirds of a flattened strip of bone on the posterior surface of the scapula immediately adjacent to the lateral border of the scapula

Inferior facet on the posterior surface of the greater tubercle of the humerus

Axillary nerve [C5,6]

Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint

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Teres major

Elongate oval area on the posterior surface of the inferior angle of the scapula

Medial lip of the intertubercular sulcus on the anterior surface of the humerus

Inferior subscapular nerve [C5 to C7]

Medial rotation and extension of the arm at the glenohumeral joint

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Long head of triceps brachii

Infraglenoid tubercle on scapula

Common tendon of insertion with medial and lateral heads on the olecranon process of ulna

Radial nerve [C6,C7,C8]

Extension of the forearm at the elbow joint; accessory adductor and extensor of the arm at the glenohumeral joint

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muscles of shoulder

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