Brachial Plexus Anatomy

• The upper limb enables precise movements needed for daily activities like eating, writing, buttoning clothes and using tools
• It also provides sensory perception for safe tactile interactions.
• The shoulder joint and associated muscles facilitate a wide range of motion, allowing you to reach, lift, and move objects.
• Elbow joint and muscles enable the shortening (flexion) or elongation (extension) and fine motor control.
• Precise hand and finger movements are possible with upper limb functionality
• Upper limbs aid in maintaining balance and stability, particularly during weight-bearing and stabilization tasks.

Brachial Plexus Anatomy

• The ventral root of the brachial plexus is responsible for motor function.
• The dorsal root of the brachial plexus is responsible for sensory function.
• The brachial plexus passes through the intervertebral foramina
• It is located between the anterior and middle scalene muscles

Brachial Plexus Roots

• C5: Roots may be dorsal scapula root level
• C8/T1 Roots (Lower Trunk) passes over the first rib behind subclavian vessels.
• C8/T1 can be affected in thoracic inlet pathologies e.g. cervical rib

Brachial Plexus Clinical Conditions

• Proximal trunks travel through intervertebral foramina.
• Compressed foraminal stenosis is caused by Osteophytes in Cx spondylosis and IV disc prolapse
• Scalene muscle hypertrophy compresses and narrows the intervertebral foramen
• Divisions of the brachial plexus are affected by clavicle fractures

Motor Innervation of the Upper Limb

• Anterior compartment muscles of the are flexors with Musculocutaneous nerve
• Flexors of the wrist are enabled by the Median Nerve
• Posterior compartment muscles are extensors with Radial N.
• Ulnar Nerve enables hand

Myotomes

• C5 enables shoulder abduction
• C5/6 enables elbow flexion and wrist extension
• C7/8 enables elbow extension and wrist flexion
• T1 enables finger adduction/abduction

Dermatomes

• C5 provides sensory input to the Lateral arm
• C6 provides sensory input to the Lateral forearm
• C7 provides sensory input to the index finger
• C8 provides sensory input to the middle finger
• T1 provides sensory input to the axilla

Injury effects

• A lesion above the pons leads to contralateral hemisensory loss in the face, trunk, and limbs
• Dissociated sensory deficits indicate spinal cord lesion (SC)
• Damage to a single spinal root/dorsal horn impacts its dermatome.

Scapulo-Thoracic Muscles

• Muscles attach the scapula to the axial skeleton.

Trapezius

• The trapezius is located at the most superficial muscle
• The trapezius attaches at the Superior nuchal line, Supraspinous ligaments the spine and acromion of scapula, and the Lateral part of the clavicle
• The trapezius elevates the scapula
• The trapezius enables Upward rotation of the glenoid
• The trapezius retracts the shoulder
• It is innervated by the Spinal accessory nerve

Rhomboids

• The rhomboids are located under the trapezius
• The rhomboids attach at the R. Major at the Upper medial border of the scapula and R. Minor at the Lower medial border of scapula
• The rhomboids enables Retraction of the scapula
• It enables Downward rotation of the glenoid
• Its innervation is by the Dorsal scapular N

Serratus Anterior

• The Serratus Anterior is located under the trapezius
• The serratus anterior attaches at the Lateral aspect of the first 9 ribs along the medial border of the scapula
• The serratus anterior hols the scapula against the rib cage
• The serratus anterior enables protraction of the shoulder girdle
• This muslce enables Upward rotation of the glenoid
• It is innervated by the Long thoracic nerve

Scapular Winging

• Paralysis of serratus anterior causes inability to hold scapula against thoracic wall
• Which leads to backward displacement and a prominence when pushing forwards on a wall.
• The commonest cause is Long thoracic nerve compression

SHOULDER ASSOCIATED MUSCLES

Scapulo-Humeral Muscles

• Attaches to the shoulder girdle.
• Its Powerful movers abduct and flex, stabilize with short movements

Latissimus Dorsi

• Its a superficial muscle.
• The latissimus dorsi attaches at the Thoracolumbar fascia, Iliac crest, Inferior angle of scapula, bicipital groove on the proximal humeral shaft
• The latissimus dorsi enables extension at GH joint.
• Its also aids with Internal rotation at GH.
• This muscle is good for adduction at GH joint.
• This innervation is by the Thoracodorsal nerve

Teres Major

• under lat dorsi
• Lateral border of scapula and medial lip in interior
• It aids with Internal rotation at GH joint
• This helps at adduction for GH joint
• This innervation is by the Lower subscapular N

Pectoralis major

• Its located at anterior chest
• It attaches at the Clavicle, Manubrium+Sternum costal cartilages, and Anterior, lateral lip.
• This aids with clavicular:Flexion at GH joint.
• It also aids at sternocostal:Adduction at GH joint
• Sternocostal: Internal rotation at GH joint
• Medial and Lateral pectoral nerves: innervation

Deltoid

• Clavicle Deltoid tuberosity on humerus: anterior
• posterior & lateral -Spine of scapula deltoid tuberosity on humerus: posterior
• flexion: anterior
• abduction: lateral
• abduction: posterior
• axiallary nerve: innervation

Axillary Nerve

• Comes from posterior cord
• It goes through quadrangular space.
• Motor: Deltoid, Teres minor, lateral and scapul
• Sensory skin: skin over deltoid

Rotator Cuff Muscles

• Supraspinatus: supraspinous fossa greater (superior)
• Infraspinatus: infraspinous fossa greater (mid)
• Teres minor: lateral great (inferior)
• Subscapularis: subscapulars: Lesser

Key info for muscles of the ARM

• There are proximal glenoid
• Anterior: musculocutaneous
• Posterior: radial

Triceps Brachii

• Posterior side of the arm.
• Its attached to the glenode
• Extension on both shoulder and elbow.

Radial nerve

• Posterior cord.
• Go to arm: radial
• Has to go to forearm.
• Posterior arm and dorsolateral hand.

Biceps Brachii

• Most anterior part of the arm; Crosses Glenohumeral.
• Short Head (Coracoid), and Long Head (Supaglenoid)
• It has 2 Joints attachment.

Coraco-Brachialis

• Deep inside, runs in brachial.
• Coracoid: short & medial.
• Flex: short and medial access to top of the arm.

Brachialis

• runs from posterior to inner
• Ulna: tendon too.