Upper Limb 2 Flashcards
what is a nerve plexus?
Formed when peripheral spinal nerve roots split + merge to produce a network of nerves from which new multisegmental peripheral nerves emerge
Plexus supplying upper limb?
Brachial plexus
Plexus supplying lower limbs?
Lumbo-sacral plexus
Describe organisation of brachial plexus from spine → divisions in upper limbs
- The roots enter the inferior neck from the spinal cord where the form trunks.
- Superior (enters from C5 and C6), middle (C7) and inferior trunk (C8 and T1)
- Trunks pass under clavicle to enter axillary region, where they form 6 divisions
- the trunks divide to each give anterior and posterior division (fibres of anterior division supply anterior structures -> posterior innervates posterior structures)
- anterior division from superior and middle trunk form the lateral cord
- single anterior division from inferior trunk forms medial cord
- all 3 posterior divisions merge to form posterior cord
- cords give off terminal branches which are the larger peripheral nerves of the upper limbs
Summarise brachial plexus organisation
Roots > trunks > divisions > cords >
How are the cords of the brachial plexus named?
Named according to relationship of axillary artery e.g. posterior cord = posterior to axillary artery
Also named with functional significance-> lateral cord innervates lateral structures, medial cord innervates medial structures +
Label this diagram
Where do spinal nerves leave the spinal cord?
Invertebral foramina of vertebral column
What are the three trunks that form the brachial plexus?
Superior
Middle
Inferior
Which 2 nerves arise from the superior trunk? (supraclavicular branches)
Suprascapular nerve and subclavian nerve
Which spinal nerves form the superior trunk?
Union of anterior rami of c5 & C6
Which root forms the middle trunk?
Directly from anterior rams of C7
Which roots form the inferior trunk?
Arises from anterior rami of C8 and T1
Which nerve is continuous with the lateral cord?
Musculocutaneous nerve
What are supraclavicular branches?
From the roots and the trunks (dorsal scapular nerve, long thoracic nerve)
What are infraclavicular branches?
side branches to pectoral girdle muscles and the main peripheral nerves. e.g. branches to some scapular muscles and the large terminal branches e.g. radial, ulnar and median.
What nerve is formed from the merger of the terminal parts of the lateral and medial cords (lateral and medial root)?
Median nerve
What nerve is the major terminal branch of the medial cord?
Ulnar nerve
Nerves formed from the lateral or parts of lateral cord?
Musculocutaneous and median nerve (lateral root merges with medial root)
What is the musculocutaneous nerve and what does it innervate?
Terminal branch of the lateral cord of the brachial plexus.
Muscular innervation to the anterior muscles of the arm.
Cutaneous innervation of the lateral forearm.
Does the musculocutaneous nerve innervate any muscles in the forearm or hand?
No
Outline pathway of musculocutaneous nerve
- Branches off from the lateral cord of the brachial plexus
- exits the axilla into the anterior arm piercing the coracobrachialis muscle
- It then gives off branches to the biceps and the brachialis muscle.
- Terminal branch of the nerve crosses the elbow
- supplies cutaneous innervation to the anterolateral surface of the forearm
- This branch is termed the lateral cutaneous nerve of the forearm.
Label this diagram
What is the ulnar nerve?
Terminal branch of medial cord of the brachial plexus
Where does the ulnar nerve pass?
Passes behind the medial epicondyle of the humerus
Where is the ulnar nerve easily damaged?
Medial epicondyle of the humerus
Outline pathway of ulnar nerve
- passes from axilla to medial aspect of arm
- crosses elbow by passing posteriorly to medial epicondyle of humerus
- after crossing elbow, ulnar nerve gives branches to 2 of the more medial of the anterior forearm muscles
- bulk of the nerve continues to pass distally, crossing wrist at anterolateral aspect
- enters hand to innervate many of intrinsic muscles + region of cutaneous innervation
Where is the ulnar nerve most palpable and what can this make it more susceptible to?
Medial epicondyle
More susceptible to injury
Does the ulnar nerve innervate the arm?
No innervation on the arm
Where does the ulnar nerve cross to enter the hand?
Crosses the wrist
Does the ulnar nerve innervate the forearm?
Limited innervation in forearm
Does the ulnar nerve innervate the hand?
Cutaneous innervation of the medial aspect of hand (middle half of ring finger and little finger)
What muscles does the ulnar nerve innervate?
Flexor carpi ulnaris muscle
Medial flexor digitorum profundus muscle
Branches to intrinsic hand muscles -> muscles of hypothenar eminence + 2 medial lumbricals (palmar interossei + dorsal interossei)
Cutaneous innervation to medial aspect of hand, including the little finger, and the medial half of the ring finger.
Label this diagram
How is the median nerve formed?
C6-T1
Branches of lateral cord + medial cord (cores of brachial plexus)
Does the median nerve innervate the arm?
No significant innervation in arm
What does the median nerve innervate?
Most of the anterior forearm muscles
Innervates some intrinsic hand muscles
Cutaneous innervation of lateral hand
Outline pathway of the median nerve
- Passes distally out of the axilla to run medially in arm (no significant branches in the arm)
- Crosses the elbow joint into the forearm where it supplies most of the anterior muscles.
- Passes under flexor digitorum (forms roof of carpal tunnel)
- crosses wrist and enters hand through carpal tunnel
- Supplies thenar eminence muscles + large part of skin of palm and digits
What muscles in the forearm does the median nerve not innervate + what nerve innervates it?
Doesn’t innervate the flexor carpi ulnaris and medial half of flexor digitorum profundus
innervated by ulnar nerve
Common sites of damage to median nerve?
Wrist + elbow
Which peripheral nerves emerge from the posterior cord of the brachial plexus?
Axillary and radial nerves
What does the axillary nerve innervate?
Deltoid muscle and upper lateral aspect of arm
What does the radial nerve innervate?
Innervates all arm and forearm posterior muscles
Cutaneous branches in arm and forearm
Cutaneous innervation of lateral hand and 3.5 digits
Which nerve is larger: axillary or radial nerves?
Radial nerve larger by far
Outline pathway of axillary nerve
The axillary nerve passes laterally under the shoulder joint
meets the deep surface of the deltoid muscle which it innervates
Upper lateral cutaneous brance of nerve pierces the muscle to supply the skin + that region
Outline pathway of radial nerve
Exits the axillary region posteriorly
Enters the arm, radial nerve gives branches to triceps brachii muscle
Passes distally running in radial groove of shaft of humerus
As it approaches elbow, passes anteriorly to lateral epicondyle of humerus, where it divides to give superficial + deep branches
Superficial branch is sensory branch + supplies dorsum/ back of hand
Deep branch supplies motor innervation to posterior forearm muscles
What are the 2 branches of the radial nerve and what does each innervate?
Superficial branch - cutaneous to the dorsolateral/posterolateral region of the hand. (Runs laterally towards the hand
Deep branch - motor supply to the posterior muscles of the forearm. (Passes distally in the posterior proximal forearm)
Which digits do the ulnar and median nerves supply?
Ulnar nerve - medial 1 1/2 digits
Median nerve - lateral 3 1/2 digits
Label this diagram
Label this diagram
Which nerve innervates the teres minor?
Axillary nerve
Clinical importance of the arteries of the ipper limb (besides supplying blood to tissues)
- Assessing heart rates
- Blood pressure
- Accessing the heart for cardiac procedures like angiography and angioplasty
Where is the vast majority of blood supply to the upper limbs from?
Left and right subclavian arteries
What is the axilla?
Inferior space between the shoulder and the arm
Where do the subclavian arteries pass under?
Pass under the right or left clavicle to enter the axilla
What does the subclavian artery become after it has passed under the clavicle?
Axillary artery
How many divisions does the axillary artery have?
3
What arteries encircle the superior part of the shaft of the humerus?
Anterior and posterior circumflex branches of humeral arteries
What artery is the main supply to the arm?
Brachial artery is the main supply to the arm
What is the largest branch of the brachial artery?
Profunda brachii -> deep artery of the arm
What is the name of the region in which the brachial artery crosses the elbow joint?
Cubital fossa
What does the brachial artery divide into?
After crossing elbow joint at cubital fossa, divides to give:
- radial arteries
- ulnar arteries
Where does the radial artery run?
Radial side of forearm (lateral side)
Where does the ulnar artery run?
Ulnar side (medial side)
What does the ulnar artery give off a branch?
Interosseous artery -> branches into anterior and posterior interosseous arteries immediately
Where does the anterior interosseous artery run?
Distally on anterior surface of interosseous membrane (between shafts of radius and ulnar)
Where does the posterior interosseous artery run?
Pierces the superior region of interosseous membrane and passes distally on posterior surface
Label this diagram
On the posterior aspect of the wrist and hand, what arch does the posterior interosseous artery form?
Dorsal carpal arch (receives a contribution from the radial artery)
Where do all of the large arteries in the forearm pass in order to cross to enter the hand?
Pass the wrist
Where does the left subclavian artery arise from?
Directly from the arch of the aorta
Where does the right subclavian artery arise from?
From the brachiocephalic trunk
Which muscle does the axillary artery lie deep too?
Pectoralis minor
What encloses the axillary artery?
Axillary sheath
What is the axillary sheath?
Fibrous layer that crosses the artery and the three cords of the brachial plexus
What do forearm arteries form when they cross the wrist?
They form arterial arches
What arches do the ulnar artery contribute to?
- Superficial palmar arch
- contributes to deep palmar arch
What arches do the radial artery contribute to?
Enters thenar eminence and forms deep palmar arch
- contributes to superficial palmar arch
What arteries form the dorsal carpal arch?
Posterior interosseous artery crosses the wrist and forms dorsal carpal arch
Radial artery contributes to dorsal carpal arch
Label this diagram
What are the 2 groups of venous return in the upper limbs and what do they both work together to do?
Deep (accompanying the arteries)
Superficial (on the limb surface)
Work together toward drainage of limbs
Label this image of deep veins of the upper limb
Describe venous return and arterial flow in terms of distal and proximal
Venous return - distal to proximal
Arterial flow - proximal to distal
What are venae comitantes? Function?
Veins that accompany arteries as groups of smaller veins
Allow heat exchange
Arrangement of venae comitantes?
Usually in:
- pairs
- groups of 3
- groups of 4
What does pulsation of arteries do to veins/venae comitantes? What does this arrangement allow?
Arteries squeeze the veins -> helps increase their venous return
Allows blood that has been cooled by extremities to be warmed on its way back to the trunk
Label this diagram of the superficial veins
In the cubital fossa, which veins connect the cephalic and basilic veins?
Median cubital vein
What is the median cubital vein used for?
Routinely used for venepuncture to take blood
What is used for venepuncture if this vein is too narrow or not present?
Either cephalic or basilic veins
Outline pathway of basilic vein
Basilic vein pierces deep fascia to go deep to join venae comitantes of brachial veins to form larger basilic vein
Outline pathway of cephalic vein
What are deep veins?
Accompany arteries
Basilic vein pathway?
Cephalic vein pathway?
What are the 2 regions of the lymphatics of the upper limb and what do they drain?
Cubital nodes - distal limb (hand and forearm).
Axiolary nodes - most of the upper limb and breast
Label this diagram
