Brachial Plexus Shoulder Girdle Muscles.docx

Brachial Plexus Shoulder Girdle Muscles Brachial plexus Major nerve supplying upper limb begins in the neck + extends into axilla Formed via union of anterior rami of C5-C8 and T1 Roots of plexus pass through gap between anterior and middle scalene muscles In inferior part of neck, roots unite to f...

Brachial Plexus Shoulder Girdle Muscles Brachial plexus Major nerve supplying upper limb begins in the neck + extends into axilla Formed via union of anterior rami of C5-C8 and T1 Roots of plexus pass through gap between anterior and middle scalene muscles In inferior part of neck, roots unite to form 3 trunks: Superior trunk, from union of C5 and C6 roots Middle trunk, continuation of C7 root Inferior trunk, from union of C8 and T1 roots Each trunk of brachial plexus divides into anterior + posterior divisions as the plexus passes posterior to the clavicle Anterior divisions of trunk supply anterior (flexor) compartments of upper limb Posterior divisions of trunk supply posterior (extensor) compartments The divisions of the trunks form 3 cords of the brachial plexus: Anterior divisions of superior and middle trunks unite to form the lateral cord Anterior division of inferior trunk continues as medial cord Posterior divisions of all 3 trunks unite to form posterior cord Products of plexus formation are multi-segmental peripheral (named) nerves Brachial plexus is divided into: supraclavicular + infraclavicular parts by the clavicle 4 branches of supraclavicular part of plexus arise from the roots + trunks of brachial plexus: Dorsal scapular nerve (from C5 root) Long thoracic nerve (from C5, 6, 7) Nerve to subclavius (from superior trunk) Suprascapular nerve (from superior trunk) Branches of infraclavicular part of plexus arise from cords of brachial plexus + are approachable via axilla Branches of lateral cord: lateral pectoral nerve, musculocutaneous nerve Branches of medial cord: medial pectoral nerve, medial cutaneous nerve of arm, medial cutaneous nerve of forearm, ulnar nerve Branches of posterior cord: upper subscapular nerve, thoracodorsal nerve, lower subscapular nerve, axillary nerve, radial nerve The Brachial Plexus: 5 – 3 – 6 – 3 – 5 5 ROOTS 3 TRUNKS 6 DIVISIONS 3 CORDS 5 TERMINAL BRANCHES (PERIPHERAL NERVES) RED TEXANS DRINK COLD BEER Arrangement of Terminal Branches: ‘MARMU’ musculocutaneous – axillary – radial – median – ulnar ROOTS (5) Anterior branches of fully formed spinal nerves that have exited the intervertebral foramen and head laterally/inferiorly away from midline TRUNKS (3) Roots pass through scalene muscles on lateral aspect of neck + combine to form 3 trunks; superior, middle, inferior C5 + C6 = Superior Trunk C7 = Middle Trunk C8 + T1 = Inferior Trunk DIVISIONS (6) – each trunk gives off 2 branches (divisions) *Pass underneath clavicle as they head towards axilla* Superior Trunk ANTERIOR + POSTERIOR DIVISIONS Middle Trunk ANTERIOR + POSTERIOR DIVISIONS Inferior Trunk ANTERIOR + POSTERIOR DIVISIONS CORDS (3) – once anterior + posterior enter axilla, they combine together to form 3 cords, named by their positive relative to axillary artery Lateral cord: formed from anterior divisions of superior + middle trunk (lateral to artery) Posterior cord: formed from posterior divisions from all 3 trunks (posterior to artery) Medial cord: formed from anterior division of inferior trunk (medial to artery) TERMINAL BRANCHES (5) – 3 cords give rise to 5 branches *These nerves continue into upper limb to provide innervation to the muscles + skin present Lateral cord = MUSCULOCUTANEOUS NERVE (C5/C6/C7) Posterior cord = AXILLARY (C5/C6) + RADIAL NERVES (C5/C6/C7/C8/T1) Lateral and Medial cord = MEDIAN NERVE (C5/C6/C7/C8/T1) Medial cord = ULNAR NERVE (C8/T1) TRAPEZIUS ORIGIN INSERTION FUNCTION NERVE PICTURE Upper trap: external occipital protuberance and medial superior nuchal line of occipital bone, from ligamentum nuchae (SP of C7) Middle trap: SP of T1 – T5 Lower trap: SP of T6 – T12 All 3 parts together: lateral 1/3 of clavicle; acromion, spine of scapula Upper fibers: - Ext + lateral flex of head (mostly bilateral contraction) - Ext + lateral flex of neck - Contralateral rotation of head - Contralateral rotation of neck - Elevation of scapula - Upward rotation of scapula Middle fibers: - Retraction (adduction) of scapula (moving towards spine) Lower fibers (weakest): - Depression of scapula - Upward rotation of scapula Spinal accessory nerve (CN XI) RHOMBOIDS MINOR ORIGIN INSERTION FUNCTION NERVE PICTURE SPs of C7 and T1 Medial (vertebral) border of scapula at root of spine - Retraction (adduction) of spine - Elevation of scapula - Downward rotation of scapula Dorsal scapular nerve RHOMBOIDS MAJOR ORIGIN INSERTION FUNCTION NERVE PICTURE SPs of T2 – T5 Medial (vertebral) border of scapula inferior to spine - Retraction (adduction) of spine - Elevation of scapula - Downward rotation of scapula Dorsal scapular nerve LEVATOR SCAPULAE ORIGIN INSERTION FUNCTION NERVE PICTURE TPs of C1 – C4 Medial border of scapulae (above spine of scapula) **inserts above rhomboid insertion** - Extension of neck @ spinal joints - Lateral flexion of neck @ spinal joints - Ipsilateral rotation of neck @ spinal joints - Elevation of scapula @ scapulocostal joint - Downward rotation of scapula @ scapulocostal joint Dorsal scapular nerve PECTORALIS MINOR ORIGIN INSERTION FUNCTION NERVE PICTURE 3rd to 5th ribs **specifically used during forced inhalation** Coracoid Process - Protraction (abduction) of scapula - Downward rotation of scapula - Depression of scapula - Elevation of ribs 3 – 5 @ sternocostal & costospinal joints (during forced inhalation when scapula is fixed) Medial pectoral SUBCLAVIUS ORIGIN INSERTION FUNCTION NERVE PICTURE First rib Subclavian groove of clavicle - Depression of clavicle @ sternoclavicular and acromioclavicular joints **RELIEVES ANXIETY** Nerve to subclavius SERRATUS ANTERIOR ORIGIN INSERTION FUNCTION NERVE PICTURE Upper 9 ribs Anterior surface of vertebral (medial) border of scapula - Protraction (abduction) of scapula - Upward rotation of scapula Long thoracic nerve (C5, C6, C7) PECTORALIS MAJOR ORIGIN INSERTION FUNCTION NERVE PICTURE CLAVICULAR HEAD: medial half of clavicle STERNOCOSTAL HEAD: sternum + costal cartilages of 1st – 7th ribs Lateral lip of intertubercular (bicipital) groove of the humerus - Flexion of arm (clavicular head) - Adduction of arm - Medial rotation of arm - Horizontal adduction of the arm Medial + lateral pectoral LATISSIMUS DORSI ORIGIN INSERTION FUNCTION NERVE PICTURE SPs from T7 to L5 Crests of ilium + sacrum Lowest four ribs (via thoracolumbar fascia) Floor of the inter-tubercular groove of the humerus - Extension of arm - Adduction of arm - Medial rotation of arm - Anterior tilt of the pelvis Thoracodorsal nerve Winged Scapula Paralysis of serratus anterior = due to injury of long thoracic nerve = winged scapula Inferior angle of medial border of scapula = excessively prominent Unable to do pushing action, nor can he raise his arm above head because serratus anterior is unable to rotate glenoid cavity superiorly to allow complete abduction of arm Muscles of Rotator Cuff and Shoulder Joint DELTOID ORIGIN INSERTION FUNCTION NERVE PICTURE 1. Lateral clavicle (anterior fibers) 2. Acromion (lateral fibers) 3. Spine of scapula (posterior fibers) Deltoid tuberosity of humerus - Anterior fibers = flexion of shoulder joint - Posterior fibers = extension of shoulder joint - Posterior fibers = lateral rotation - Posterior fibers = extension of shoulder joint - Abduction of shoulder joint = ENTIRE MUSCLE **DOES ALL EXCEPT ADDUCTION** Axillary Nerve (C5, C6) SUBSCAPULARIS ORIGIN INSERTION FUNCTION NERVE PICTURE Subscapular fossa Lesser tubercle of humerus - Medial rotation of shoulder joint Upper and lower subscapularis (C5, C6) SUPRASPINATUS ORIGIN INSERTION FUNCTION NERVE PICTURE Supraspinous fossa Greater tubercle of humerus - Abduction of shoulder joint Suprascapular (C5, C6) INFRASPINATUS ORIGIN INSERTION FUNCTION NERVE PICTURE Infraspinous fossa Greater tubercle of humerus - Lateral rotation of shoulder joint - Horizontal abduction of shoulder joint **If the muscle is anterior to the axis, it is able to do medial rotation, if posterior to the axis, it is able to do lateral rotation** Suprascapular (C5, C6) TERES MINOR ORIGIN INSERTION FUNCTION NERVE PICTURE Superior lateral border of scapula Greater tubercle of humerus - Lateral rotation of shoulder joint Axillary (C5, C6) TERES MAJOR ORIGIN INSERTION FUNCTION NERVE PICTURE Inferior lateral border of scapula Medial lip of intertubercular (bicipital) sulcus (groove) of humerus - Medial rotation of shoulder joint - Extension of shoulder joint - Adduction of shoulder joint Upper & Lower Subscapular Rotator Cuff Muscles Includes 4 Muscles: SUPRASPINATUS + INFRASPINATUS + TERES MINOR + SUBSCAPULARIS Strengthen shoulder joint capsule all around except inferiorly = explains dislocations of the humerus occur most commonly in a downward direction Supraspinatus: Abduction = Deltoid: Abduction Infraspinatus: Lateral Rotation = Posterior Deltoid: Lateral Rotation Teres Minor: Lateral Rotation Subscapularis: Medial Rotation = Pectoralis Major: Medial Rotation INSERTION FUNCTION INNERVATION SUPRASPINATUS GREATER TUBERCLE ABDUCTION SUPRASCAPULAR INFRASPINATUS GREATER TUBERCLE LATERAL ROTATION SUPRASCAPULAR TERES MINOR GREATER TUBERCLE LATERAL ROTATION AXILLARY SUBSCAPULARIS GREATER TUBERCLE MEDIAL ROTATION LOWER + UPPER SUBSCAPULARIS Axillary Spaces: refers to 3 main spaces around scapular region created by muscles QUADRANGULAR SPACE: Axillary N, Posterior humeral circumflex artery TRIANGULAR INTERVAL: Radial N., Profunda brachii artery TRIANGULAR SPACE: Circumflex scapular artery