الرحيم الرحمن الله بسم

BACK MUSCLES

A- SUPERFICIAL LAYERThe superficial layer is formed of two muscles:

1- Trapezius 2- latissimus dorsi 

1- Trapezius muscle Origin:External occipital protuberance, superior nuchal line of the occipital bone.From the ligamentum nuchae, the spinous process of the seventh cervical.The spinous processes of all the thoracic vertebrae.

 Insertion:Posterior border of the lateral third of the clavicle.The medial margin of the acromion.The superior lip of the posterior border of the spine of the scapula.

1- Trapezius muscleNerve supply:Spinal part of accessory nerve (CN XI). The ventral rami of the third (C3) and fourth (C4) cervical nerves carries proprioception sensation. Action:1-The upper fibres elevate the shoulder.2-The lower fibres depress the scapula.3-The middle fibres retract the scapula.

2- Latissimus dorsi muscleOrigin: spinous processes of T7-T12 supraspinous ligament. thoracolumbar fascia. outer lip of iliac crest . inferior 3 or 4 ribs. inferior angle of scapula Insertion:Floor of bicipital groove of the humerus.Nerve supply: Nerve to latissmus dorsi (C6,C7,C8).Action:Adducts, extends and medially rotates the arm.

B- DEEP LAYER

The deep layer is formed by : 1-levator scapulae2- Rhomboideus minor 3- Rhomboideus major muscles.

1- Levator scapulae muscleOrigin:Transverse processes of C1 - C4 vertebrae.Insertion:Medial border of dorsal surface of scapula from the superior angle to the spine.Nerve supply:Dorsal scapular nerve (C5).Action:Elevates scapula.

2- Rhomboidus minor muscleOrigin:Nuchal ligaments and spinous processes of C7 to T1 vertebrae.Insertion:Small area of medial border of dorsal surface of scapula at level of spine. Nerve supply:Dorsal scapular nerve (C5).Action:1-Retracts the scapula 2-Rotates the scapula so that the glenoid cavity faces downwards (depress the shoulder).

3- Rhomboideus major muscleOrigin:Spinous processes of the T2 to T5 vertebrae.Insertion:Medial border of the scapula, inferior to the insertion of rhomboideus minor muscle.Nerve supply:Dorsal scapular nerve (C5).Action:Retracts the scapula and rotates the scapula so that the glenoid cavity faces downwards.

SCAPULAR REGION

Supraspinatus muscleOrigin:Supraspinous fossa (medial2/3) of scapula.Insertion:Superior facet of greater tuberosity of humerus.Nerve supply:Suprascapular nerve(C5,C6).Action:Abduction of arm from 0˚-18˚.

Infraspinatus muscle Origin:Infraspinous fossa (medial2/3) of scapula.Insertion:Middle facet at the back of the greater tuberosity of the humerus.Nerve supply:Suprascapular nerve (C5,C6).Action:Lateral rotation of arm.

Teres minor muscleOrigin:Lateral border(upper 2/3) of the scapula.Insertion:Inferior facet at the back of the greater tuberosity of the humerus.Nerve supply:Axillary nerve (C5,C6).Action:Lateral rotation and adduction of arm.

Teres major muscle Origin:

Posterior aspect of the inferior angle of the scapula.Insertion:Medial lip of bicipital groove of the humerus.Nerve supply:Lower subscapular nerve (C5,C6).Action:Medial rotation,adduction and extension of the humerus.

Subscapularis muscleOrigin:Subscapular fossa (medial 2/3).Insertion:Lesser tuberosity of humerus.Nerve supply:Upper and lower subscapular nerves (C5, C6).Action:Rotates the humerus medially.

Deltoid muscle Origin:anterior border of lateral 1/3 of clavicle. ,lateral margin of the acromion andcrest of the spine of the scapula.Insertion:Into deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus.Nerve supply:Axillary nerve (C5, C6).Action: Anterior fibers: flexion and medial

rotation of humerus. Middle fibers: abduction from1 8˚-90˚. Posterior fibers: extension and

lateral rotation of humerus.

ROTATOR CUFF MUSCLES Rotator cuff

muscles surround the shoulder joint, they include:

Subscapularis.Supraspinatus.Infraspinatus.Teres minor.

INTERMUSCULAR SPACES 1- Quadrangular space:BoundariesIt is bounded by:Superiorly: Teres minor. Inferiorly: Teres major. Medially: the long head of the Triceps brachii. Laterally: the surgical neck of the humerus. ContentsIt transmits the axillary nerve and posterior circumflex humeral artery. 

2-Medial triangular space

Boundaries:Teres minor superiorly.Teres major inferiorly. Long head of the Triceps laterally.Contents:It contains the circumflex scapular vessels. 

3- Lateral triangular space

Boundaries:Teres major superiorly. Long head of the Triceps medially.Humerus laterally. Contents:The radial nerve and profunda brachii artery.

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