Brachial plexus Flashcards
the brachial plexus contains nerve roots from where
anterior (ventral) rami of C5-T1
axillary nerve is what roots
C5 C6
what would the implication of damaged C5 be in terms of the axillary nerve and deltoid
C6 fibres would still allow some innervation of deltoid - abduction of arm would be weaker but still possible
the brachial plexus is found where
in the axilla
the brachial plexus originates where
nerves originate from C5-T1 nerve roots in the neck and upper thorax (for T1)
where do the brachial plexus nerve roots lie
posterior triangle of neck
the brachial plexus nerve roots pass between what muscles
anterior and middle scalene
what innervation do the nerve roots of the brachial plexus receive
grey rami communicantes so carry post-ganglionic sympathetic fibres
what forms the superior trunk
C5 and C6
what forms the middle trunk
C7
what forms the inferior trunk
C8 and T1
the trunks of the brachial plexus pass where
over rib 1 and enter axilla
what makes up the phrenic nerve
C3 and C4 fibres from above the brachial plexus but also includes C5 fibres from C5 root
what other nerve gets its C5 component directly from this root
dorsal scapular nerve
what is the long thoracic nerve derived from
directly from C5 6 7 roots
what trunks give rise to nerves
middle and inferior do not, superior does
what nerves does the superior trunk form
suprascapular nerve
nerve to subclavius
the phrenic nerve innervates what
diaphragm
the dorsal scapular nerve innervates what
rhomboid major and minor
long thoracic nerve innervates what
serratus anterior
suprascapular nerve supplies
infraspinatus and supraspinatus
suprascapular nerve and nerve to subclavius roots
C5 6
nerve to subclavius innervates what
subclavius muscle
each trunk divides into an anterior and posterior ____ as they enter the axilla
division
all of the posterior divisions form the
posterior cord
the anterior division from the superior and middle trunks forms what
lateral cord
anterior division from inferior trunk forms
medial cord
what forms the posterior cord
all the posterior divisions of the trunks
what forms the lateral cord
anterior division of superior and middle trunk
what forms the medial cord
anterior division of inferior trunk
are there any peripheral nerves direct from the divisions
no
the 3 posterior divisions are the ultimate pathway for what
nerves assoc. with the posterior compartments of the arm and forearm
the 3 anterior divisions are the ultimate pathway for what
nerves assoc. with anterior compartments of the arm and forearm
what nerves will the anterior divisions form
musculocutaneous median and ulnar nerves
what nerves will the posterior divisions form
radial nerve and axillary nerve
what is the nerve of the posterior compartment of the arm and forearm
radial nerve
the cords are named dependent on what
relation to the axillary artery
which cord lies closer to the humerus
lateral cord
what cord lies closer to the body wall
medial cord
what cord lies behind the axillary artery
posterior cord
the lateral cord has what fibres
C5 - C7
the lateral cord originates from what
anterior divisions of the superior and middle trunks
lateral cord is origin of what nerve
lateral pectoral nerve
the posterior cord originates from what
posterior divisions from all trunks
the posterior cord has what fibres
C5-T1
the posterior cord is the origin of what nerves
subscapular and thoracodorsal
the medial cord is formed from what
continuation of anterior division of inferior trunk
medial cord has what fibres
C8 T1
how does the medial cord get C7 fibres
often communication with middle trunk or its divisions which allows some C7 fibres in its terminal branches - some texts will say ulnar nerve has (C7) C8 T1 fibres meaning minor contribution from C7 root
is it common to see non-standard patterns of the nerves of the brachial plexus
yes especially for lateral cord and median nerve
anterior compartments of arm and forearm supplied by what cords
medial and lateral cords
posterior compartments of arm and forearm supplied by what cords
posterior cord
the medial cord is the origin of what nerves
medial pectoral and cutaneous nerves
all of the cords of the brachial plexus form branches and terminal branches where
branches in the axilla and terminal branches as they exit the axilla
what does the lateral cord form
lateral pectoral nerve before it forms the musculocutaneous nerve and the lateral part of the median nerve
the lateral pectoral nerve supplies what
pec major
the musculocutaneous nerve supplies what
anterior compartment of arm
the median nerve supplies what
main nerve of anterior compartment of forearm
the posterior cord forms what
subscapular nerves and thoracodorsal nerve before forming terminal branches of axillary nerve and radial nerve
subscapular nerves supply what
subscapularis and teres major
thoracodorsal nerve supplies what
latissimus dorsi
axillary nerve supplies what
deltoid and teres minor
radial nerve supplies what
posterior compartment of arm and forearm
the medial cord forms what
medial pectoral nerve and 2 cutaneous nerves to the arm and forearm before ending in the ulnar nerve and medial root of the median nerve
the medial pectoral nerve supplies what
pec major and minor
ulnar nerve supplies what
anterior compartment of forearm and many intrinsic muscles of the hand
what nerve supplies anterior compartment of the arm
musculocutaneous nerve
what nerve supplies the posterior compartment of the arm
radial nerve
what nerve supplies the posterior compartment of the forearm
radial nerve
what nerve supplies the anterior compartment of the forearm
mainly median nerve but also ulnar nerve
each terminal branch also carries ____ fibres
sensory
the axillary nerve supplies motor and sensory to what
motor - deltoid and teres minor
sensory - skin of upper lateral arm (badge patch area)
what nerve goes from the lateral cord and disappears into the coracobrachialis
musculocutaneous nerve
how can you identify the median nerve
forms from the lateral and medial cords in the M shape
what is the course of the median nerve
descends the anterior compartment of the arm to pass through cubital fossa and later also carpal tunnel at the wrist to pass into the hand
the ulnar nerve lies _____ in arm
medially
describe the course of the ulnar nerve
lies medially in the arm before passing behind the medial epicondyle of the humerus to lie in medial side of forearm and then pass into hand
how can the posterior cord be identified
lies behind the axillary artery and forms terminal branches deep to the M shape
what nerve wraps around the neck of the humerus
axillary nerve
describe the course of the axillary nerve
wraps around neck of the humerus to pass through the quadrangular space to enter deltoid and teres minor
when might axillary nerve be damaged
antero-inferior dislocation of glenohumeral joint as it lies close to the joint
describe the course of the radial nerve
passes deep in the arm before leaving the anterior surface of the humerus and passing through the triangular hiatus to reach posterior compartment of arm. It then travels at the lateral side of the cubital fossa to reach the posterior compartment of forearm
what nerve passes through the quadrangular space
axillary nerve
what nerve passes through the triangular hiatus
radial nerve
anterior compartments of the arm and forearm are often called
flexor compartments
posterior compartments of the arm and forearm are often called
extensor compartments
how is the spiral groove created
radial nerve courses around the humerus in the arm creating the spiral groove
what attaches either side of the spiral groove
lateral and medial heads of the triceps brachii attach to humerus either side of spiral groove
how can radial nerve be damaged
mid-shaft fracture of humerus as it is close to the bone here
musculocutaneous nerve fibres
C5-7
axillary nerve fibres
C5 C6
radial nerve fibres
C5-T1
median nerve fibres
lateral root: C6,C7
medial root: C8,T1
ulnar nerve fibres
C8 T1 (often C7)
the lateral root of the median nerve is a terminal branch of what
lateral cord (C6 7)
the medial root of the median nerve is a terminal branch of what
medial cord (C8 T1)