Brachial plexus Flashcards
C5, C6, C7, C8, T1 Roots of the Brachial Plexus
Dorsal scapular
*coming off of C5 root, goes posterior and innervates the rhomboids and elvator scapuli
Long thoracic nerve
off of c5, c6, c7, goes along rib cage
a purely motor nerve
• runs posterior to the brachial plexus and inferiorly behind the clavicle
• supplies:
serratus anterior muscle segmentally:
- C5 supplies the upper two digitations (which pull on the upper angle of
the scapula)
- C6 the next two (vertebral border of scapula)
- C7 the lowest four (pull on the inferior angle of the scap
Nerve paralysis usually causes no deformity of the scapula when the arm is
at rest. If, however, the patient is asked to push the arm forward against resistance or
hold the arms up in front of the body, the scapula becomes winged (winged scapula),
especially in its lower two-thirds region.
Middle trunk of bracial plexus
C7 nerve root
Inferior trunk
C8 and T1
Subprascapular nerve
superior off of the superiror trunk
a purely motor nerve
• passes downward beneath the trapezius to the upper border of the scapula,
• Supplies:
the supraspinatus muscle
the infraspinatus muscle
Nerve lesion:
Supraspinatus paresis results in weakness of arm abduction, whereas
infraspinatus paresis results in impaired external rotations at the shoulder joint.
anterior division of inferior trunk
medial cord
medial brachial, m. antebracial, medial pectoral, ulnar nerve
anterior branch of middle trunk
lateral cord, musculocutaneous, lateral pectoral, median nerve.
what cords do the anterior divisions form?
medial and lateral
posterior cord
what are the terminal branches
posterior cord made from all three posterior divisions
makes radial and axillary nerves
lateral pectoral nerve coming off of the lateral cord c5, c6, c7
PIERCES PECTORALIS MUSCLE
purely motor nerve
• pierces the clavipectoral fascia, descends posteriorly to the clavicle
• supplies:
the clavicular and upper sternocostal portions of the
pectoralis major
NERVE LESIONS
• Isolated injury to the lateral pectoral nerve as the result of a seat-belt injury may
result in atrophy of the clavicular head of the pectoralis major.
MOTOR Signs:
- adduction and
- medial rotation of the upper arm are weak, and
- the patient notices difficulty in using the arm in climbing.
MEDIAL PECTORAL NERVE (C8,T1)
peirces through pecotralis major and minor muscles!
ANATOMY
• arises from the proximal section of the medial cord of the plexus
behind the axillary artery
• enters the deep surface of pectoralis minor, perforates the muscle
and enters the pectoralis major
• supplies
the lower sternocostal portion of pectoralis major and
the pectoralis minor muscle.
MEDIAL ANTEBRACHIAL (C8–T1)
• a large nerve SENSORY to forearm (ulnar side)
• divides above the elbow into anterior and posterior divisions that supply
the skin of the anteromedial and
124posteromedial forearms, respectively, down to the wrist.
NERVE LESIONS
• Injuries to the medial cutaneous nerve of the arm and forearm nerves may occur in the axilla, affecting the medial cord of the brachial plexus.
• The nerve may also be damaged as a complication of an ulnar nerve surgery at the elbow.
SENSORY signs.
A sensory loss occurs in the distribution of the individual nerve branches.
MUSCULOCUTANEOUS NERVE (C5–C7)
a mixed nerve
• arises from the lateral cord of the brachial plexus (C5, C6 and C7)
• proceeds obliquely downward between the axillary artery and the median
nerve
• the nerve supplies MOTOR:
coracobrachialis muscle
biceps
brachialis muscles
• then continues distally as the lateral cutaneous nerve of the forearm
(antebrachial) - SENSORY
MEDIAN NERVE (C6–T1)
from lateral and median nerves
Motor innervation is to most of the flexors muscles in the forearm and intrinsic muscles of the thumb (thenar muscles).
Sensory innervation is from the lateral ( radial) 3 & 1/2 digits ( the thumb and first 2 and 1/2 fingers)
ulnar nerve c8 t1
Ulnar nerve is derived from the medial cord
Motor innervation is mainly to intrinsic muscles of the hand
Sensory innervation is from the medial ( ulnar) 1 & 1/2 digits ( the 5th. and 1/2 of the 4th. digits).
Radial Nerve (C5,C6,C7,C8,T1)
Radial nerve is also derived from the posterior cord.
Called “Great Extensor Nerve” because it innervates the extensor muscles of the elbow, wrist and fingers.
Sensory innervation is from the skin on the dorsum of the hand on the radial side.
Axillary Nerve (C5,C6)
Axillary nerve is derived from the posterior cord.
Motor innervation is deltoid and teres minor muscles that act on the shoulder joint.
Sensory innervation is from the skin just below the point of the shoulder. (Figs. 2,3)
Middle Subscapular Nerve/Thoracodorsal Nerve (C6-C8)
*** penetrates the latismi dorsi muscle
purely motor nerve
branch of the posterior cord of the
brachial plexus and usually emerges from the plexus in a close association with
the upper and lower subscapular nerves
• runs along the posterior axillary wall to reach and pierce the latissimus
dorsi muscle
• supplies
latissimus dorsi muscle.
SUBSCAPULAR NERVES (C5,C6)
penetrates subscapularis and teres major musces
purely motor nerves
• arise from C5 and C6, as branches of posterior cord
• pierce the subscapularis muscle (the upper subscapular nerve travels
deeper than the lower subscapular nerve)
The upper subscapular nerve supplies:
the subscapularis muscle,
The lower subscapular nerve supplies:
the subscapularis (lower part of the muscle) &
the teres major muscles
SUBSCAPULAR NERVES (C5,C6)
(upper & lower)
ANATOMY
• purely motor nerves
• arise from C5 and C6, as branches of posterior cord
• pierce the subscapularis muscle (the upper subscapular nerve travels
deeper than the lower subscapular nerve)
The upper subscapular nerve supplies:
the subscapularis muscle,
what is 5?
Medial Root of the Median Nerve
- Serratus Anterior Muscle
is a muscle that originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula.
The thoracoacromial trunk
is one of two branches of the second part of the axillary artery. It travels laterally and splits into four smaller branches. The other branch of the second part of the axillary artery is the lateral thoracic artery, which can also be seen in this image traveling more medially towards the serratus anterior.
throacodorsal artery
branches off subscapular artery and immediately goes posterior like around scapula
Circumflex Scapular Artery
posterior humeral circumflex
The anterior humeral circumflex artery is considerably smaller than the posterior and arises nearly opposite it, from the lateral side of the axillary artery.
Anterior Humeral Circumflex Artery
oming off the axiliary artery
The anterior humeral circumflex artery is considerably smaller than the posterior and arises nearly opposite it, from the lateral side of the axillary artery.
biiceps brachii muscle long head
biiceps brachii muscle short head
Brachialis
brachial artery
Platysma Muscle
; innervated by CN VII (facial nerve); one of the muscles
of facial expression inferior border of the mandible
what is the red?
lateral cord
what is yellow?
musculocutaneous nerve
what is purple?
median nerve
has three small branches coming off of it
medial cord
goes to brachialis and biceps femoris
ulnar nerve
terminal branch from a fork
median nerve
lateral cord
medial cord
