brachial plexus Flashcards
what is the brachial plexus?
a network of nerve fibres which supply the skin and musculature of the upper limb
where is the brachial plexus found?
it begins at the root of the neck, passes through the axilla and runs through the entire upper extremity
what forms the brachial plexus?
-anterior rami (divisions) of the cervical spine nerves C5, C6, C7 and C8 and the first thoracic nerve T1
what are the 5 divisions that the brachial plexus can be split into?
Read That Damn Cadaver Book
Roots, Trunks, Divisions, Cords and Branches
what are the ‘roots’ in the brachial plexus?
-when talking about the ‘roots’ we are referring to the anterior rami of C5, C6, C7, C8 and T1
where do paired spinal nerves arise?
-at each vertebral level
where do paired spinal nerves leave the spinal cord?
-via the intervertebral foramina
what role do the anterior and posterior rami of C5-T1 have?
anterior rami- make up brachial plexus which is responsible for supplying the skin and musculature of the upper limb
posterior rami- supply the skin and musculature of the intrinsic back muscles
what do C5-T1 have to pass through to enter the base of the neck?
anterior and medical scalene muscles
what are the trunks formed by the brachial plexus?
- superior trunk
- middle trunk
- inferior trunk
what makes up the superior trunk of brachial plexus?
-combination of C5 and C6
what makes up the middle trunk of the brachial plexus?
C7
what makes up the inferior trunk of the brachial plexus?
-combination of C8 and T1
where are the trunks of the brachial plexus found?
-they run laterally, crossing the posterior triangle of the neck
what doe each trunk divid into?
- 2 divisions
- anterior division which travels towards the body
- posterior division which travels to the back of the body
(as there are 3 trunks there are then 3 anterior and 3 posterior divisions)
where are the anterior and posterior divisions of the brachial plexus found?
-they leave the posterior triangle of the neck and pass into the axilla before they recombine into the cords of the brachial plexus
where do the anterior and posterior divisions recombine to form 3 cords?
in the axilla
what are the 3 cords named after?
-theyre named by they’re position relative to the axillary artery
what is the lateral cord formed by?
- the anterior division of the superior trunk (C5, C6)
- the anterior division of the middle trunk (C7)
what is the posterior cord formed by?
- the posterior division of the superior trunk (C5, C6)
- the posterior division of the medial trunk (C7)
- the posterior division of the inferior trunk (C8, T1)
the is the medial cord formed by?
-the anterior division of the inferior trunk (C8, T1)
what do the cords give rise to?
-the major branches of the brachial plexus
what branches come from the lateral cord?
- muscocutaenous
- median
what branches come from the posterior cord ?
- axillary
- radial
what branches come from the medial cord?
- median
- ulnar
what are the roots of the muscocutaenous nerve?
-C5, C6, C7
what are the motor functions of the musculocutaneous nerve?
-innervates the brachial, biceps brachia and corabrachialis muscles
what is the sensory function of the muscocultaneous nerve?
-gives off the lateral cutaneous branch of the forearm, which innervates the lateral half of the anterior forearm and a small portion of the posterior forearm
what is the arterial supply to the anterior compartment of teh upper arm?
brachial artery
what is the function of the biceps brachii?
- supination of the forearm
- it also flexes the arm at the elbow and at the shoulder
what are the roots of the axillary nerve?
C5 and C6
what is the motor function of the axillary nerve?
-innervates teres minor and deltoid
what is the sensory function of the axillary nerve?
-gives off the superior lateral cutaneous nerve of the arm, which innervates the inferior region of the deltoid (‘regimental badge area’)
what are the roots of the median nerve?
C6-T1
some people however have strands of C5 as well
what is the motor function of the median nerve?
supplies LOAF:
- lateral two lumbrical (associated with index and middle fingers)
- opponens pollicis brevis
- abductor pollicis brevis
- flexor pollicis brevis
Most of the flexor muscles in the forearm:
- palmaris longus
- flexor carpi radialis
- pronator teres
- flexor digitorum superficialis
- flexor pollicis longus
- lateral half of flexor digitorum profundus
- pronator Quadratus
what is the sensory function of the median nerve?
- it gives off the palmar cutaneous branch which innervates the lateral part of the palm
- it also gives off the digital cutaneous branch which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand
what are the roots of the radial nerve?
C5 to T1
what is the motor function of teh radial nerve?
- innervates the triceps brachii
- innervates the muscles of the posterior compartment of the arm
what is the sensory function of teh radial nerve?
- innervates the posterior aspect of arm and forearm
- innervates the posterolateral aspect of the hand
what are the roots of the ulnar nerve?
-C8 and T1
what is the motor function of the ulnar nerve?
innervates:
- all the muscles of the hand apart from LOAF (lateral two lumbricals, opponens pollicis brevis, abductor pollicis brevis and flexor pollicis brevis)
- flexor carpi ulnas
- medial half of flexor digitorum profundus
what is the sensory function of the ulnar nerve?
-innervates the anterior and posterior surfaces of the medial one and a half fingers and associated palm area
