The Axilla and Brachial Plexus Flashcards
Define: axilla
pyramidal space inferior to the glenohumeral joint
passageway for neurovascular structures that supply the upper limb and anterior + posterior thorax
What forms the borders of the axilla
Anterior border
* pec minor
Posterior border
* subscapularis
base
* posterior axillary fold - latdorsi and teres major (primarily teres major
* anterior axillary fold - pec major
lateral wall
* intertubercular groove/sulcus
axillary artery
* travels where
* arises from where
* gives rise through?
* what are the 3 parts of the axillary artery
- through axilla
- arises from subclavian artery at the first rib
- gives rise to brachial artery at the inferior border of teres major
- 1st part: proximal to pec minor; 2nd part: deep to pec minor; 3rd part: distal to pec minor
- lateral border of rib 1 divides subclavian and axillary artery
What are the two main terminal branches of the brachial artery
radial and ulnar artery
How do we anatomically describe the axillary vein?
The axillary vein is anatomically described using the same borders as the axillary artery, but in reverse:
- The axillary vein arises from the** basilic vein** at the inferior border of teres major, and drains into (and continues as) the subclavian vein, at the first rib.
What drains into the axillary vein?
Cephalic lateral (superficial),
Brachial middle (deep)
Basilic medial (superficial)
Where can you find lymphatics in the upper limb
axilla has a dense collection of lymph nodes
The lymphatics of the upper limb travel closely with veins (“shadow” veins).
The plexes innervating the limbs arises from the _______ rami
anterior
dorsal vs ventral root
dorsal: sensory (posterior)
ventral: motor (anterior)
Are the dorsal and ventral ramus mixed?
Yes - they contain motor and sensory axons
not to be confused with dorsal and ventral ROOTS
Spinal nerve
Myotome
Dermatome
Spinal nerves arise from a segment of spinal cord.
Spinal nerves are mixed and innervate a distinct region of muscle and skin.
Myotome: unilateral portion of skeletal muscle innervated by a single spinal nerve.
Dermatome: unilateral portion of skin innervated by a single spinal nerve
Motor nerves arise from and sensory nerves project to the spinal nerves between ___ and ___
C5
T1
What are the 5 anatomical divisions of the brachial plexus
Real Teachers Drink Cold Beer
5 Roots (anterior rami)
3 Trunks
3 Divisions (3 anterior divisions and 3 posterior divisions)
3 Cords (lateral posterior, medial)
5 Branches
Brachial plexus
* emerges between
* deep to
* overlying
- the scalenes
- the clavicle and pectoralis minor
- subscapularis
What portions of the brachial plexus does the axilla contain?
cords and branches
What forms the M of the brachial plexus
- musculocutaneous nerve
- lateral and medial root that feeds into median nerve ( do not confuse with anterior rami roots. these link the lateral/medial cords to the median nerve)
- ulnar nerve
The axillary nerve arises from the ____ cord ____ (distally/proximally) in the plexus
- posterior
- proximally
What does the axillary nerve innervate?
deltoid and teres minor
The radial nerve arises from the ____ cord and travels ____
posterior
distally
What does the radial nerve innervate?
- posterior arm (all 3 heads of triceps)
- brachialis (often dually innervated)
- posterior forearm (extensors and supinators)
What is the wrist drop posture indicative of?
radial nerve injury
The musculocutaneous nerve arises from the ____ cord to innervate _____.
Sensory innervation is _____
lateral
arm flexors (coracobrachialis, biceps both heads, brachialis)
note that sensation innervation is distal to the innervation of the arm flexors (distal to elbow); and on the anterior surface of the arm
The median nerve arises from the ____ cords and travels ____. It innervates ____
lateral and medial
distally through the upper limb
anterior forearm (flexors and pronators) and thenar muscles
What are some signs of median nerve injury?
thenar atrophy
loss in sensation in first and second finger
**ape hand deformity: **Ape hand deformity is a condition in which the thumb is permanently rotated and adducted, resulting in a loss of its opposable function
The ulnar nerve arises from the ____ cords and travels ____. It innervates ____
medial
distally through the upper limb
medial flexors (flexor carpi ulnaris and medial half of flexor digitorum profundus), intrinsic hand muscles
What are some signs of ulnar nerve injury?
loss in sensation of pinky
claw hand deformity
interosseous atrophy
What are 2 main patterns of injury to the brachial plexus
superior (upper) plexus injury
* fall where head is forcefully pulled away from trunk; tractions upper portion of plexus
* vaginal injury can also cause brachial plexus injury; tugging on head during birth.
inferior (lower) plexus injury
* yanking the lower plexus away from the body; falling and catching self on tree
* tugging on the arm of a baby during birth. separating arm from body
What are the different mechanisms of injury to the brachial plexus
- avulsion (spinal cord)
- stretch
- rupture (more distal)
Describe Erb’s palsy
* how does it happen
* what does it preferentially affect
* what is the classic sign of it. why do you see this deformity
- damage to upper plexus (aka as upper trunk palsy)
- head is pulled away from shoulder during birth
- preferentially affects C5 and C6
- Waiter’s tip
- loss of innervation to the abductors, lateral rotators of the arm, forearm flexors, and wrist extensors
Describe Klumpke’s palsy
* what does it preferentially affect
* what is the classic sign of it. why do you see this deformity
- AKA lower trunk palsy
- C8 and T1
- claw hand
- loss of innervation to the pronators and intrinsic hand muscles (especially distal digit extenders)
What spinal cord roots are associated with: musculocutaneous nerve
C5, C6, C7
What spinal cord roots are associated with: axillary nerve
C5, C6
What spinal cord roots are associated with: median nerve
C6-T1
What spinal cord roots are associated with: radial nerve
C5-T1
What spinal cord roots are associated with: ulnar nerve
C8 and T1
Describe oxygenated blood flow through the arm
- Left subclavian artery (SCA) arises from aortic arch. Right SCA arises from brachiocephalic trunk
past rib 1, SCA continues as the axillary artery
past the lower border of the tendon of teres major, axillary artery continues as brachial artery
around the elbow, brachial artery divides into radial (lateral) and ulnar (medial) arteries
Describe deoxygenated blood flow through the arm
Divided into superficial and deep
Deep and superficial veins drain into the axillary veins which continue as left and right subclavian veins, then brachiocephalic veins, and into superior vena cava
