Definition :

• The Brachial plexus is a group or network of nerves in the shoulder.
• Moreover the Brachial plexus carries movement and sensory signals from the spinal cord to the arms and hands.

Parts of Brachial plexus :

• Roots
• Trunks
• Divisions
• Cords and also
• Branches

Roots :

• The Brachial plexus constitutes the anterior primary rami of spinal nerves from C5 – C8 and T1.
• This may be occasionally contributed by anterior primary rami of C4 and T2.
• The origin of the plexus may either shift by one segment either upward or downward.
• And this results in a prefixed or postfixed plexus respectively.
• Most importantly in a prefixed plexus, the contribution by C4 plexus is maximum.
• Whereas C5 is present, T1 is small and moreover T2 often absent.
• In a postfixed plexus, the contribution by T1 is large and also T2 is always present.
• Whereas C4 is absent and C5 is often reduced or smaller in size.
• Finally the above mentioned roots join to form the Trunks.

Supraclavicular part of Brachial plexus – Roots and Trunks :

• The Roots of C5 and C6 join to form the Upper trunk.
• Root C7 forms the Middle trunk.
• Root C8 and T1 together form the Lower trunk.
• Moreover the supraclavicular part lie in the neck between the Scalenus anterior and Scalenus medius muscles.
• Further this supraclavicular part of the brachial plexus carries the axillary sheath from prevertebral fascia.

Retro clavicular part of Brachial plexus – Divisions of the trunks :

• All three trunks divides into ventral and dorsal divisions.
• Finally, they supply the anterior and posterior aspects of the limbs.
• Further these divisions join to form the cords.

Infraclavicular part of Brachial plexus – Cords and Branches :

• The union of Upper and the Middle trunks (two divisions) forms the Lateral cord.
• Whereas the medial cord is formed by the ventral division of the lower trunk (One division).
• The dorsal division of all three trunks forms the Posterior cord.
• Above all these are named according to the relation of cords to the second part of the axillary artery.

Branches :

Branches of the roots :

• Firstly, Nerve to Serratous anterior or Long thoracic nerve (C5-C7).
• It supplies the serratous anterior muscle.
• Moreover it is the key muscle for overhead abduction.
• Secondly, Nerve to Rhomboids or Dorsal scapular nerve (C5).
• This nerve supplies the rhomboid minor and the rhomboid major muscles.
• In addition these muscles are responsible for the retraction of the shoulder girdle.
• Further it gives a branch to Levator scapulae.
• Thirdly, Branches to the Longus colli and scaleni muscles (C5-C8).
• Finally, Branches to the phrenic nerve (C4).
• The roots of phrenic nerve is from both C4 and C5.
• Though the root from C5 is small whereas C4 is very large.
• This supplies the Thoracoabdominal diaphragm.
• In addition, it also carries the afferent fibres from mediastinal pleura, fibrous pericardium and also part of the Parietal peritoneum.

Branches of the Trunks :

• These branches arises only from the Upper trunk.
• One is the Suprascapular (C5, C6) which supplies the Supraspinatous and Infraspinatous muscles.
• The second is the nerve to Subclavius (C5, C6) which supplies the subclavius muscle.
• Moreover it may also give a root for phrenic nerve.

Branches of the cords :

Branches of the Lateral cord :

• Lateral pectoral nerve (C5-C6) supplies both the Pectoralis major and also minor muscles.
• Musculocutaneous nerve (C5-C7) nerve supplies the muscles of front of arm.
• That is it supplies Coracobrachialis, both the long and short head of biceps brachii and also the Brachialis muscle.
• Lateral root of Median nerve (C5-C7).
• The above root joins the medial root of median nerve.
• Moreover it is the chief nerve of muscles of front of forearm and also of the muscles of Thenar eminence.

Branches of the Medial cord :

• Medial pectoral (C8,T1) nerve also supplies both the Pectoralis major and also minor muscles.
• Medial cutaneous nerve of arm (C8 , T1) carries sensory impulses from a small area of the medial side of arm.
• And also the Medial cutaneous nerve of forearm (C8,T1) carries sensory impulses from large area of medial side of the forearm.
• Ulnar (C7,C8,T1) nerve supplies the one and half muscles of front of forearm and 15 intrinsic muscles of the palm.
• The Medial root of median nerve (C8, T1) joins the lateral root and also gets distributed with branches of median nerve.

Branches of Posterior cord :

• Upper subscapular nerve (C5,C6) supplies large multipennate subscapularis muscles.
• Nerve to Latissimus dorsi (C6 – C8) supplies the muscle of its name.
• Moreover it is also called Thoracodorsal nerve.
• Lower subscapular nerve (C5,C6) helps upper subscapular nerve in supplying the Subscapularis muscle.
• In addition, it also supplies the teres major muscle.
• Axillary (Circumflex) (C5,C6) supplies the deltoid muscle.
• And also it supplies the small portion of Teres minor muscle.
• Radial (C5-C8,T1) nerve is the thickest branch of the brachial plexus.
• It supplies all three heads of Triceps brachii muscle.
• And also it supplies 12 muscles on the back of the forearm.

Special features :

• The lateral cord, medial cord and their branches form the letter M with three corners extended.
• Moreover the lateral cord gives the musculocutaneous and also the lateral root of median nerve.

Blood supply of Brachial plexus :

• Firstly, Vertebral artery
• Secondly, Thyrocervical trunk
• Thirdly, Suprascapular arteries
• Finally, transverse cervical arteries

Clinical features of Brachial plexus :

• Erb’s paralysis
• Klumpkes’s paralysis
• And also Injury to the Nerve to Serratous anterior

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