Brachial PlexusBrachial Plexus

There are 31 pairs of spinal nerves.

These are segmental in distribution and emerge from the vertebral canalfrom the vertebral canal between the pedicles of adjacent vertebrae.

There are 8 pairs of cervical, 12 thoracic, 5 lumbar, 5 sacral and one coccygeal.

After exiting the vertebral canal, each spinal nerve branches into:

A posterior ramus, collectively the small posterior rami innervates the back.

An anterior ramus, the much larger anterior rami innervate most regions of the body except the head, which is innervated by cranial nervesinnervated by cranial nerves.

The Brachial PlexusFormation:Formation:Anterior rami of C5, C6, C7, C8 and T1.

Course:Course:It originates in the neck, passes over the first rib then entersthe axillathe axilla.

Parts:From medial to lateral are:1. Roots2. Trunks3. Divisions 4 C d4. Cords

Roots

Enter the posterior triangle of the neck bytriangle of the neck by passing between the anterior scalene and

iddl lmiddle scalene muscles.

Lie superior and posterior to the Subclavian artery.y

TrunksThe three trunks (superior, middle and inferior) originate from the roots.

They pass laterally over the first rib.

The superior trunk is formed by the union of C5 and C6 rootsThe superior trunk is formed by the union of C5 and C6 roots.

The middle trunk is a continuation of C7 roots.

The inferior trunk is formed by the union of the C8 and T1 roots.

The inferior trunk lies on rib 1 posterior to the subclavian artery.

The middle and superior trunks are more posterior in position.

Divisions

Each of the trunks of the brachial plexus divides into an anterior and posterior

The three anterior divisions form parts of the brachial plexus that give rise to peripheral nerves associated with the anterior

t t f th d fcompartment of the arm and forearm.

The three posterior divisions combine to form parts of the brachial plexus that give rise to nerves associated with the posterior compartments.

No peripheral nerves emerge directly from the divisions.

CordsThe three cords of the brachial plexus originate from the divisions and are related to the second part of axillary

tartery.

The lateral cord results from the union of the anterior divisions of the upper and middle trunks and thereforedivisions of the upper and middle trunks and therefore has contribution from C5 to C7. It is positioned lateral to the second part of the axillary artery.

The medial cord is medial to the second part of the axillary artery and is the continuation of the anterioraxillary artery and is the continuation of the anterior division of the inferior trunk. It contains contribution from C8 and T1.

The posterior cord occurs posterior to the second part of the axillary artery and originates from the union ofof the axillary artery and originates from the union of all three posterior divisions. It contain contributions from all the roots of the brachial plexus.

Most of the major nerves of the upper limb originates from the cords.The nerves associated with the anterior compartments of theupper limb arise from the medial and lateral cords.

The nerves associated with the posterior compartments originate from the posterior cord.

Branches of the roots (2)Branches

( )The roots of the brachial plexus give rise to the dorsal scapular and long thoracic nerves.

Branches of the roots (2)Branches

( )The roots of the brachial plexus give rise to the dorsal scapular and long thoracic nerves.

Branches of the trunksThe only branches from the trunks are two nerves that yoriginate from the superior trunk (upper trunk), these are:

The suprascapular nerve

The nerve to subclavius muscle.

Roots (ventral rami):

Dorsal scapularC4

Upper

Nerve tosubclaviusSuprascapular

Dorsal scapular

Posterior

C5

C6C7

Middle Trunks

Lower

L th i

divisionsLateral

PosteriorCords

C7

C8

T1

Upper subscapular

Long thoracicMedial pectoralLateral pectoral

Medial

Axillary Uppe subscapu aLower subscapularThoracodorsalMedial cutaneous

f th

Musculo-cutaneousRadialMedian

nerves of the armand forearmUlnar

(a) Roots (rami C5 T1), trunks, divisions, and cords

Figure 13.9 (a)

Anteriordivisions

Posteriordivisions

Trunks Roots

Branches of the lateral cord

Branches of the cordsBranches of the lateral cordThree nerves originate from the lateral cord:

The lateral pectoral nerve The lateral pectoral nerve The musculocutaneous nerve The lateral root of the median nerveThe lateral root of the median nerve

Branches of the medial cordThe medial cord has five branches:The medial cord has five branches:

The medial pectoral nerve The medial cutaneous nerve of the arm The medial cutaneous nerve of the arm The medial cutaneous nerve of the forearm The medial root of median nerve The ulnar nerve.

Branches of the posterior cordpFive nerves originate from the posterior cord of the brachial plexus:

1. The superior scapular nerve2. The thoracodorsal nerve3. The inferior scapular nerve4. The axillary nerve5. The radial nerve

All these nerves except the radial innervates musclesAll these nerves except the radial innervates muscles associated with the axilla: the radial nerve passes into the arm and forearm.

Injuries to the brachial plexus

Spinal cord injuries in the cervical region and direct pulling injuries tend to affect the roots of the brachial plexus. Severe trauma to the first rib usually affects the trunks.

The divisions and cords can be injured by dislocation of theThe divisions and cords can be injured by dislocation of the shoulder joint.

Brachial plexus injuries are usually the result of blunt traumaBrachial plexus injuries are usually the result of blunt trauma producing nerve avulsions and disruption.

These injuries are usually devastating for the function of theThese injuries are usually devastating for the function of the upper limb and require many months of dedicated rehabilitation for even small amount of function to return.