Brachial Plexus

<Upper Limb>   <Anatomy>

<Index>

 

 

Definition

-  Plexus of nerves supplying the upper limb

 

Features

-  Formed from ventral rami (C5, C6, C7, C8, T1)

-  Which form trunks (Superior, Middle, Inferior)

-   Which forms divisions (Superior Anterior, Superior Posterior, Middle Anterior, Middle Posterior, Inferior Anterior, Inferior Posterior)

-   Which form cords (Lateral, Posterior, Medial)

-  Which give rise to peripheral nerves

-  Nerves branch from brachial plexus along its course

-  Supraclavicular portion (rami and trunks) lie in the posterior triangle of the neck

-  Infraclavicular portion (divisions and cords) lie in the axilla.

-  Brachial plexus passes between anterior scalene muscle and the middle scalene muscle alongside subclavian artery

 

Branches

-  Median nerve

-  Radial nerve

-  Ulnar nerve

-  Musculocutaneous nerve

-  Axillary nerve

 

Pathway

-  Form 3 trunks at the neck of 1st rib which run over superior surface of rib posterior to subclavian artery

o     Superior Trunk

      Union of C5 ventral rami and C6 ventral rami

      Suprascapular Nerve (C4 - C6)

     Arises from posterior aspect of superior trunk of brachial plexus

     Passes laterally across posterior triangle of neck superior to brachial plexus

     Passes through the suprascapular notch of the scapula inferior to the transverse scapula ligament

     Passes lateral to the base of the acromium process of the scapula as it continues inferiorly

     Supplies:

o     Supraspinatus muscle

o     Infraspinatus muscle

o     Shoulder joint

      Nerve to Subclavius (??)

     Arises from ???

     Supplies

o     Subclavius muscle

o     Miiddle Trunk

      Is the continuation of C7 ventral rami

o     Inferior Trunk

      Union of C8 ventral rami and T1 ventral rami

-      Anatomical Variations

o                                    Prefixed Brachial Plexus

      Includes C4 ventral rami

o                                    Postfixed Brachial Plexus

      Includes T2 ventral rami

      More prone to compression on 1st rib

-      Each trunk branches into an anterior division and posterior division

o     Anterior divisions supply the anterior (flexor) components of the upper limb

o     Posterior divisions supply the posterior (extensor) components of the upper limb

o     The divisions then unite with other divisions to form cords

      Cords are named according to their position in relation to the axillary artery

      Each cord divideds into two terminal peripheral nerves

      Lateral Cord

     Union of the superior anterior division and middle anterior division

     Lies lateral to axillary artery

     Continues inferiorly as the musculocutaneous nerve

     Lateral Pectoral Nerve

o     Supplies pectoralis major muscle

     Lateral root of the median nerve

o     Passes medially to join the medial root of the median nerve from the medial cord and together form the median nerve

      Medial Cord

     Continuation of the inferior anterior division

     Lies medial to axillary artery

     Continues inferiorly as the ulnar nerve

     Medial Pectoral Nerve

o     Supplies:

     Pectoralis major muscle

     Pectoralis minor muscle

     Medial Cutaneous Nerve of the Arm

o      

     Medial Cutaneous Nerve of the Forearm

o      

     Medial root of the median nerve

o     Passes laterally to join the lateral root of the median nerve from the lateral cord and together form the median nerve

      Capital M formed from the junction of the lateral and medial cords:

     Musculocutaneous nerve forms lateral portion of M

     Median nerve forms the middle portion of M

     Ulnar nerve forms the medial portion of M

      Posterior Cord

     Union of the three posterior divisions (superior posterior division, middle posterior division and inferior posterior division)

     Lies posterior (deep) to axillary artery

     Continues inferiorly as the radial nerve

     Axillary nerve branches laterally

     Thoracodorsal Nerve

     Upper Subscapular Nerve

     Lower Subscapular Nerve

 

 

 

 

References

 

Moores Clinically Oriented Anatomy