بسم الله الرحمن الرحيم

BACK MUSCLES A- SUPERFICIAL LAYER 1- Trapezius 2- latissimus dorsi The superficial layer is formed of two muscles: 1- Trapezius 2- latissimus dorsi  

1- Trapezius muscle Insertion: 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 muscle Nerve 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 muscle Origin: 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 scapulae 2- Rhomboideus minor 3- Rhomboideus major muscles.

1- Levator scapulae muscle Origin: 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 muscle Origin: 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 muscle Origin: 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 muscle Origin: 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 muscle Origin: 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 muscle Origin: 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 and crest 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: Boundaries It is bounded by: Superiorly: Teres minor. Inferiorly: Teres major. Medially: the long head of the Triceps brachii. Laterally: the surgical neck of the humerus. Contents It 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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