L4: Vessels and Nerves of the Upper Limb Flashcards
Describe arterial supply to the upper limb.
• The subclavian arteries arise from the brachiocephalic trunk on the right and the arch of the aorta on the left.
• The subclavian artery travels under the clavicle,
• It continues as the axillary artery in the axilla,
• The axillary artery continues as the brachial artery in the arm,
• The brachial artery bifurcates in the cubital fossa, into the radial and ulnar arteries.
• These supply the forearm and hand
Anastomoses between the radial and ulnar arteries in the hand ensure perfusion of the hand is maintained in the event that one of these arteries is injured
Describe the deep veins of the upper limb.
Deep veins follow arteries. The subclavian vein is a deep vein and runs alongside the SCA. There it turns into the axillary vein, also at risk to penetrating wounds. Important branches of the axillary vein is the posterior and anterior circumflex humeral veins. Important tributaries of the axillary vein is the basilic and cephalic vein. The brachial veins are deep veins that follow the brachial artery - these are often paired. Most of the veins that follow arteries are often paired. They drain into the axillary along with basilic vein.
Deep veins follow the arteries. The radial artery and ulna artery are followed by one or two deep veins. The interosseous arteries are also followed by veins. There is also deep palmar venous arch. There is deep veins in the fingers. We also have palmar and dorsal digital veins. These all ultimate go back towards the axillary vein.
The teres major is also the point where the axillary vein becomes the basilic vein i.e. the brachial vein joins with thebasilic veinto form the axillary vein at the distal border of theteres majormuscle.
Describe the superficial veins of the upper limb.
Superficial veins lie in the subcutaneous tissue and can often be seen and / or palpated under the skin. They are used for venipuncture and cannulation.
An important tributary to the axillary vein is the cephalic vein - this is a superficial vein. It has its origins in the anatomical snuff box, it runs on the lateral side on the arm to drain to the axilla (often targeted in venipuncture). The basilic vein is also an important tributary. It runs from the medial side of the hand and wrist and travels up the medial side of the arm and drains into the axillary veins. The basilic and cephalic vein in the cubital fossa typically have a communicating vein, this is the median cubital vein. It is an obliquely placed vein connecting the two veins. We do not often see it in the same way in different individuals.
The cephalic and basilic vein drain the dorsum of the hand. The dorsal venous network can be seen under the skin. There is also a superficial palmar venous arch. From the dorsum and the superficial venous arch drain up through the cephalic and basilic back up to the axillary veins.
Where are upper limb arteries vulnerable?
Fractures:
- Fractures of the clavicle can risk the axillary or the subclavian artery
- Fractures of the surgical neck of the humorous can risk the posterior and anterior circumflex arteries
- Fractures of the humeral shaft could injure the profunda brachii or the radial nerve
- Supracondylar fractures could injure the brachial artery - this means that there is a lack of blood supply to the forearm and could lead to ischaemia of the forearm muscles
- The axillary artery is vulnerable in the axilla in the case of penetrating wounds- the bleeding for this laceration would be life threatening
- Injuries to the anterior cubital fossa could risk the brachial artery
- Any risk to the forearm could risk the radial and ulna arteries
- At the wrist, the radial an ulnar arteries are quite superficial. They are vulnerable to injury. You can palpate the artery but gently pressing the radial artery onto the radius. It is harder to palpate the ulna as it is partly covered by the flexor carpii ulnaris tendon.
Any injuries deep enough in the palm could affect the superical and deep palmar arteries
Describe the path of the radial nerve.
How do we test for damage?
The posterior cord continues as the radial nerve. It innervates triceps. It sends off branches as it travels through the arm, into the posterior compartment in the radial (or spiral) groove of the humerous (with the profunda brachii). The radial nerve then continues to the forearm. It divides into a superficial branch (sensory branch to innervate the skin) and a deep branch (motor branch).
The deep branch innervates a couple of muscles in the posterior aspect of the arm. It continues as the posterior interosseous nerve. It travels deep in the posterior compartment of the forearm and supplies all the muscles of the posterior forearm. A couple are supplied by the deep branch.
The superficial branch runs down the lateral aspect of the posterior compartment and innervates some of the skin an some of the skin over the anatomical snuff box and skin over some of the hand near the thumb on the dorsum.
In radial nerve injury we test whether they can extend the elbow (triceps), can they extend the wrist and the fingers (posterior forearm muscles). Sensory component is test they can feel sensation over the anatomical snuff box and on the dorsum of the hand near the thumb.
Describe the path of the ulnar nerve.
- The ulnar nerve innervates almost all of the small muscles of the hand. It is very important. It is very important for precision, dexterity, grip etc.
- Arises form the medial cord
- The ulnar nerve hooks behind the medial epicondyle as it runs down the medial aspect of the arm. It is quite superficial. It causes a funny pain when we hit it.
- It continues down in the medial part of the anterior compartment. It innervates a couple of muscles in the anterior forearm - gives off a branch that innervates the flexor carpii ulnaris and the medial half of flexor digitorum produndas.
- The main nerve travels down and OVER the carpel tunnel and into the hand.
- It gives an important motor branch - the deep branch of the ulnar nerve. It innervates almost all the small muscles of the hand - hypothenar eminence (the raised bump proximal to the little finger), abductor pollicis, interossei and medial 2 lumbricals.
- The sensory branches supply the remaining part of the skin. On the medial aspect of the hand, on the palmar aspect and the dorsum.
- There are also digital branches.
Describe the path of the musculocutaneous nerve.
Arises form the lateral cord. The motor part innervates the anterior arm muscles. The sensory components continues and heads down towards the lateral head of the forearm and innervates a region of skin on the lateral forearm.
Describe the path of the axillary nerve.
How do we test for damage?
It arises form the posterior cord. The axillary nerve leaves high up in the axilla and winds around the back of the surgical neck of the humerus through the quadrilateral space and innervates deltoid and teres minor. It also innervates a patch of skin around the upper lateral arm (sensory innervation). This would be apart of an examination to test if there is nerve damage. Check if it is the same on both sides.
Describe the path of the median nerve.
- Formed by a contribution form the lateral cord and a division from the medial cord.
- The median nerve does not innervate anything in the anterior arm. It heads straight through without acting.
- It travels through the cubital fossa and into the forearm.
- In the forearm it innervates most of the anterior forearm muscles.
- It is quite a big nerve. As it travels through the anterior forearm it gives off small branches which innervate muscles of the anterior forearm. It then goes through the carpel tunnel into the hand.
- It gives off the anterior interosseous nerve. This runs with the anterior interosseous artery. This innervates the deep muscles of the anterior compartment - flexor digitorium profundas (only half - the radial side - index and middle finger), flexor pollicis longus and pronator quadratus.
- The median nerve continues in the middle part of the anterior forearm deep to the muscles and travels though carpel tunnel. Here it is prone to being compressed - median nerve entrapment (carpel tunnel syndrome). The median nerve travels under the roof of the carpel tunnel. In the hand it gives rise to the recurrent branch of the median nerve. Here it innervates the small muscles of the thumb. Hand on the thumb are called eminences. The eminences bulge as they hold small muscles. The recurrent branch of the median nerve supplies the bulge under the thumb - thenar eminence. The muscles here are small muscles of the thumb.
The sensory component of this nerve go onto to innervate the skin over the medial aspect of the palm and over the digits (lateral 3.5) - the lateral half of the 4th finger.
What vessels are found around the surgical neck of the humerus?
The axillary artery gives rise to the posterior and anterior circumflex artery which anastomose around the surgical neck of the humerus.
Describe the dermatomes of the upper limb.
Dermatome = The region of skin supplied by a single spinal nerve.
This is important for the peripheral neuro-examination - this gives us information about the individual spinal anterior and posterior.
Test using image
Describe the myotomes of the upper limb.
Myotome = the muscle mass innervated by a single spinal nerve/spinal cord segment.
Muscles are innervated by peripheral nerves which contain fibres from more than one spinal segment. When we test the strength of a muscle e.g. biceps we do this by testing motor function and so by flexing the elbow and against resistance. We test myotome to test individual functions of C5, C6 and C7. We test the movement most strongly associated with each spinal nerve.
C5 - Shoulder adbuction C6 - Elbow flexion C7 - Elbow extension C8 - Finger flexion, thumb extension T1 - Finger abduction and adduction
What does the Profunda brachii artery supply?
The posterior compartment of the upper arm.
At what point does the brachial artery bifurcate?
The brachial artery bifurcates into the radial and ulna arteries at the cubital fossa. The radial artery travels at the radial side (by the thumb). The ulna artery travels down the medial side. The ulna and radial artery give off small branches. These branches anastomose with vessels of the produnda brachii and branches of the brachial artery. These form collateral branches in a major blockage.
What is the path of the radial artery?
The radial and ulna artery continue down towards the hand and they anastomose with each other. The radial artery goes through the anatomical snuff box, through a muscle and emerges into the palm of the hand. The radial artery can be palpated on the distal radius. Once in the palm of the hand, it anastomoses with branches of the ulna arteries which also travels into the palm of the hand. The radial and ulna artery therefore form superficial and deep palmar arches. These arches give rise to the vessels that supply the metacarpal region, the digits and the thumb. There is a digital artery on each side of the finger.
