Vessels and Nerves of the Upper Limb Flashcards
What is knowledge of the major arteries of the upper limb crucial for?
- Assessing perfusion of the upper limb - Assessing injuries - Managing bleeding - Avoiding puncturing arteries when trying to access veins - Obtaining an arterial blood sample for an ABG
What is knowledge of the major veins of the upper limb crucial for?
- Venepuncture and cannulation; - Assessing injuries - Managing bleeding
What is knowledge of the major nerves, dermatomes and myotomes is crucial for?
- Assessing patients for signs of nerve injury - Conducting a peripheral neuro examination
Where do the subclavian arteries arise?
From the brachiocephalic trunk on the right and from the arch of the aorta on the left
Where does the subclavian artery travel?
Under the clavicle
What does the subclavian artery continue as?
The axillary artery in the axilla
What does the axillary artery continue as?
The brachial artery in the arm
What does the brachial artery bifurcate into?
The radial and ulnar arteries - these supply the forearm and hand
There are anastomoses between the radial and ulnar arteries in the hand. What is the purpose of this?
Ensure perfusion of the hand is maintained in the event that one of these arteries is injured
Where do the circumflex humeral arteries arise?
From the axilla
- Anterior circumflex humeral
- Posterior circumflex humeral
Why are the anterior and posterior circumflex humeral arteries at risk of damage?
Form an anastomotic network around the surgical neck of the humerus and can be damaged in cases of fracture
What marks the boundary between the axillary artery becoming the brachial artery?
The lower border of teres major
Where does the brachial artery course?
Down the anterior aspect of the arm
What important branch does the brachial artery give rise to?
Profunda brachii (deep artery of the arm)
Describe the course of the profunda brachii i.e. what groove? what does it travel with?
Leaves brachial artery and travels behind the humerus and travels with the radial nerve in the radial groove of the humerus (posterior aspect)
What does the profunda brachii supply?
Supplies structures in the posterior aspect of the upper arm (e.g. triceps brachii).
Where does the brachial artery bifurcate?
In region of the cubital fossa
What is the anastomotic network surrounding the elbow joint?
Branches from radial and ulnar arteries form anastamoses with other branches of the brachial artery as well as terminal branches of the profunda brachii.
This forms collateral pathways
Purpose of collateral pathways in the arm?
The arm has relatively good anastomotic supply. This means that it is well protected from ischaemia in cases of temporary or partial occlusion of arteries.
What branch does the ulnar artery give rise to?
The common interosseous artery in the forearm
What does the common interosseous then divide into?
Anterior and posterior interosseous arteries, which supply deeper structures in the forearm.
What does the anterior interosseous arteries supply?
Supplies anterior compartment of forearm
What does the posterior interosseous artery?
Passes through the interosseous membrane to supply the posterior compartment of the forearm
What happens to the radial and ulnar arteries when they reach the hand?
They anastamose by forming 2 arches - the superficial palmar arch, and the deep palmar arch.
What route does the radial artery take to the hand?
Down the lateral part of the forearm (near thumb), through the anatomical snuffbox, through the muscle that sits in that region, and emerges into the palm of the hand
Where can the radial pulse be palpated?
The radial pulse can be palpated in the distal forearm, immediately lateral to the prominent tendon of the flexor carpi radialis muscle.
What are the superficial and deep palmar arteries formed by?
Anastamoses between the radial and ulnar arteries
Describe the blood supply of the hand
The hand has a rich arterial supply with many anastomoses between vessels. This allows the hand to be perfused even when under high resistance to flow (such as when grasping or applying pressure).
What branches do the superficial and deep palmar arteries give rise to?
Branches that supply the metacarpal region, the digits and the thumb
Describe arrangement of digital arteries
Digital artery sits either side of each digit
What vessels are at risk in serious fractures of the clavicle?
Subclavian / axillary artery
What vessels are at risk during fractures of the surgical neck of the humerus?
Anterior/posterior circumflex humeral arteries
What vessels/nerves are at risk during fractures of the humeral shaft?
Profunda brachii artery, radial nerve (run alongside each other)
What vessels are at risk during supracondylar fractures (just above epicondyles of the humerus)?
Brachial artery
What can rupture of the brachial artery cause?
Ischaemia of the forearm muscles
What do injuries near the cubital fossa risk?
Damage to brachial artery
What do injuries to the forearm risk?
Damage to radial and ulnar arteries
What arteries are at risk during injury to the wrist? Why are these vessels more vulnerable here?
Radial and ulnar arteries - these are relatively superficial at the wrist so are more vulnerable
What are the 2 systems of veins in the upper limb?
Superficial and deep
What do the deep veins of the upper limb follow?
The arteries
Where do the superficial veins of the upper limb lie?
In the subcutaneous tissue - can often be seen and / or palpated under the skin
What veins are used for venepuncture and cannulation?
Superficial
Do superficial and deep veins communicate with each other?
Yes - superficial veins drain into deep veins
How are the deep veins of the upper limb named?
The deep veins share the name of the artery they accompany.
E.g. subclavian vein, axillary vein
What are the anterior and posterior circumflex humeral arteries paired with?
Paired with deep veins (same name), these eventually drain back into the axillary vein
Are the anterior and posterior circumflex humeral veins deep or superficial?
Deep
What are the 2 major superficial veins of the upper limb?
Cephalic and basilic veins
Where does the cephalic vein arise? What is its route? What does it drain into?
In the anatomical snuffbox (dorsal venous network of the hand), runs along the antero-lateral aspect of the upper limb, drains into the axillary vein
Origin of the basilic vein? What is its route? What does it drain into?
Originates from the dorsal venous network of the hand and ascends the medial aspect of the upper limb.
It combines with the brachial veins from the deep venous system to form the axillary vein.
How is the axillary vein formed?
From contribution from basilic vein
From contribution from deep veins of arm (brachial veins that follow the artery)
How do the deep veins that follow an artery tend to differ?
There tends to be 2 deep veins that follow 1 artery (i.e. paired brachial veins follow the brachial artery)
Where are the basilic and cephalic veins typically connected?
In the region of the cubital fossa - by the median cubital vein.
What forms the boundary between the brachial vein and axillary vein?
Teres major
What is the median cubital vein?
Communication between the basilic and cephalic vein in the region of the cubital fossa
What side of the forearm is the cephalic vein found?
On lateral side
What side of the forearm is the basilic vein found?
Medial side
What is the median antebrachial vein? What does it drain? Where does it drain into?
A superficial vein of the forearm that drains the palm and anterior forearm into the basilic vein or median cubital vein
What do the deep veins accompany?
Usually 2 (sometimes 1) deep veins accompany arteries
E.g. radial, ulnar and interosseous arteries
What deep venous network drains the hand?
- The deep palmar venous arch - a network of deeper veins in the palm
- This drains into the deeper veins of the forearm
- Deep veins of the fingers
- Palmar and dorsal digital veins
What superficial venous networks drain the hand?
Dorsal venous network and superficial palmar venous arch
Where do the deep palmar and dorsal digital veins drain?
Drain back towards the deep palmar venous arch and up through the forearm, ultimately back towards the axillary vein
Where does the brachial plexus arise from?
C5-T1
What are the 5 terminal nerves of the brachial plexus?
the musculocutaneous, axillary, radial, median and ulnar.
The nerves of the upper limb are somatic. What does this mean?
Responsible for voluntary movement
The nerves of the upper limb are contain both motor and sensory fibres. What does this mean?
Motor: innervate the muscles of the limbs
Sensory: carry sensory information back to the CNS from the skin, joints and muscles
What does the posterior cord of the brachial plexus give rise to?
The radial and axillary nerves
Where does the axillary nerve leave the posterior cord? Where does it travel? What does it innervate?
High up in the axilla
Travels around back of surgical neck of humerus (vulnerable), through the quadrilateral space
Motor fibres: Innervates deltoid, teres minor
Sensory fibres innervate skin of upper lateral arm
How can axillary nerve be tested if thought to be an injury?
- Motor: test function of deltoid and teres minor
- Sensory: test skin over upper lateral arm, does it feel same as other side?
What does the posterior cord continue as?
The radial nerve
Route of radial nerve in the proximal arm? What does the radial nerve innervate here?
- Goes into posterior compartment, travelling in radial groove (acompanying profunda brachii artery) -
- Gives off branches that innervates triceps
Where does the radial nerve go after the proximal arm? How does the radial nerve terminate?
Passes through the cubital fossa and enters the forearm
Here it divides into a superficial and a deep branch
What does the deep branch of the radial nerve innervate?
Motor - innervates the muscles in the posterior compartment of the forearm.
What does the deep branch of the radial nerve then continue as?
Continues as the posterior interosseous nerve
What does the posterior interosseous nerve innervate?
Travels deep in the posterior compartment of forearm, innervating all the posterior forearm muscles.
What does the superficial branch of the radial nerve innervate?
Sensory - contributes to the cutaneous (skin) innervation of the posterior forearm, skin over region of ASB, skin of the dorsal hand and fingers.
How do you test for radial nerve injury?
Motor function:
- Can they extend elbow (i.e. is triceps working)?
- Can they extend wrist and fingers? (radial nerve is nerve of posterior forearm –> posterior forearm muscles allow for wrist and finger extension)
Sensory function:
- Asking patient if they can feel sensation over ASB and dorsum of hand
What cord of the brachial plexus does the musculocutaneous nerve come from?
Lateral cord
What does the musculocutaneous nerve innervate?
Motor: muscles in the anterior compartment of the arm (coracobrachialis, biceps and the brachialis) i.e. flexors of the elbow
Sensory: continues down to forearm - innervates skin on lateral aspect of forearm
How is the median nerve formed?
One branch of the lateral cord and one branch of the medial cord
Route of the median nerve?
Continues through proximal arm without innervating anything
Enters the anterior compartment of the forearm via the cubital fossa
What does the rest of the medial cord continue as?
The ulnar nerve
When the median nerve enters the forearm, what does it innervate?
- Gives off small branches that innervate the flexor and pronator muscles in the anterior compartment of the forearm (i.e. almost all of the anterior forearm muscles)
- Then passes through the carpal tunnel into the hand to supply some structures here
What are the 2 major branches that the median nerve gives off in the forearm?
- Anterior interosseous nerve
- Palmar cutaneous nerve
What does the anterior interosseous branch of the median nerve innervate?
Supplies the deep muscles in the anterior forearm:
- Pronator quadratus (PQ)
- Flexor pollicis longus (FPL)
- 1/2 of flexor digitorum profundus (FDP)
- Innervates the lateral 1/2 (nearest thumb)
What innervates the other 1/2 of the FDP?
Ulnar nerve
The median nerve passes through the carpal tunnel into the hand. How does it terminate?
Divides into 2 branches:
- Recurrent branch
- Palmar digital branch
What does the recurrent branch of the median nerve innervate?
Motor: The small muscles of the thumb (thenar eminence)
What is the thenar eminence?
Rounded fleshy part of the hand at the base of the thumb
What does the palmar digital branch of the median nerve innervate?
Sensory: innervates the palmar surface and fingertips of the lateral three and half digits (digital branches)
Motor function of the ulnar nerve?
Innervates the intrinsic muscles of the hand (apart from the thenar muscles and two lateral lumbricals), and two muscles in the forearm; flexor carpi ulnaris and medial half of flexor digitorum profundus.
Sensory function of the ulnar nerve?
Innervates the anterior and posterior surfaces of the medial one and half fingers, and the associated palm area.
Course of the ulnar nerve to elbow?
Passes down medial aspect of upper arm. At elbow it passes posterior to the medial epicondyle of the humerus –> here it is palpable and vulnerable to injury –> ‘funny bone’
Course of ulnar nerve after elbow?
Continues down medial aspect of anterior compartment of forearm towards the hand
What does the ulnar nerve innervate in the forearm?
Gives off a couple of muscular branches that inneravte the flexor carpi ulnaris and the medial half of flexor digitorum profundus
How does the ulnar nerve enter the hand?
NOT through the carpal tunnel but instead via the ulnar canal (Guyon’s canal
What does the ulnar nerve divide into when it reaches the hand?
Deep branch and superficial branch
Function of the deep branch of the ulnar nerve in the hand?
Motor: innervates almost all of the small muscles in the hand
- Hypothenar muscles (a group of muscles associated with the little finger)
- Medial two lumbricals
- Adductor pollicis
- Palmar and dorsal interossei of the hand
- Palmaris brevis
What is the hypothenar eminence?
Muscular bulge near the little finger
Function of the superficial branch of the ulnar nerve in the hand?
Sensory: innervates the palmar surface of the medial one and a half fingers.
Describe sensory innervation of the ulnar nerve
- 2 branches arise in forearm and travel into hand
- These innervate: the medial half of the palm, the dorsal surface of the medial one and a half fingers, and the associated dorsal hand area.
- 1 branch arises in the hand: the superficial branch
- This innervates the palmar surface of the medial one and a half fingers
Skin innervation: peripheral nerves
Regions of skin supplied by the major peripheral nerves
Skin innervation: dermatomes
The region of skin supplied by a single spinal nerve
Pretty much the same anterior and posterior
What is the importance of dermatomes?
Important for the peripheral neuro examination – tells you about the function of individual spinal nerves and perhaps the associated segment of spinal cord
Radial sensory innervation of the hand?
- Over the ASB
- Dorsum of the lateral hand and lateral 3 digits as far as the DIPJs of the 2nd and 3rd digits and the IPJ of the thumb
Median nerve sensory innervation of the hand?
- Over the middle and lateral palm
- Palmar surface of the lateral 3 ½ digits
- Dorsum of the lateral 3 ½ digits distal to DIPJ of the fingers and IPJ of the thumb
Ulnar nerve sensory innervation of the hand?
- Medial palm and dorsum of the hand
- Palmar surface medial 1 ½ digits
- Dorsum medial 2 digits excluding lateral ½ of tip of the 4th digit, distal to DIPJ
What are myotomes? How do they differ from dermatomes?
Myotomes: a group of muscles innervated by a single spinal nerve / cord segment
Dermatomes: a portion of the skin that is supplied by an individual spinal nerve
What is biceps inneravted by? Fibres from what spinal nerves are contained in this?
Innervated by C5, 6 and 7 via the musculocutaneous n.
Muscles are innervated by peripheral nerves (ulnar, radial, musculo etc) that contain fibres from more than one spinal nerve.
How can we infer the function of individual spinal nerves?
E.g. biceps
When we test myotomes / spinal nerves in the peripheral neuro exam we test the movements that are most strongly associated with each spinal nerve
What is the movement with the greatest association with C5?
Shoulder abduction
What is the movement with the greatest association with C6?
Elbow flexion
What is the movement with the greatest association with C7?
Elbow extension
What is the movement with the greatest association with C8?
Finger flexion, thumb extension
What is the movement with the greatest association with T1?
Finger abduction
Explain how shoulder abduction is the movement with the greatest assocation with C5?
- C5 contributes to the axillary nerve (innervates deltoid > shoulder abduction)
- C5 is also involved with elbow flexion: it contributes to the musculocutaneous n. (C5,6,7) which innervates biceps
- BUT –> shoulder abduction is the movement with the greatest association with C5
