Part 1. Blood supply to the upper limb Flashcards
The upper limb receives its blood from the
SUBCLAVIAN ARTERY (under the clavicle)
The subclavian artery comes directly from the arch of the aorta but the left one forms the brachiocephalic trunk first. the artery passes just over the first rib to go to the upper limb.
Subclavian artery is divided into three parts
The subclavian artery passes through a triangle called the scalene triangle
The scalene triangle is Divided into 3 parts by the scalenus anterior (Anterior scalene muscle):
1st - sits Medial to the muscle
2nd - sits directly Behind the muscle
3rd - sits Lateral to muscle
*The scalene triangle is formed by the first rib which is the floor and anterior and middle scalene muscle. scalene muscles come from the transverse cervical processes from the vertebra and inserts into the first rib. the scale muscles are accessory respiratory muscles and when you take a deep breath towards the end of inspiration, the scalene muscles contract and lift up the first rib to expand the thorax so you can get more air in.
Branches of the 1st, 2nd and 3rd branch of the subclavian artery
1ST BRANCH/Medial ;
has 3 branches.
a) vertebral artery heading up towards the head.
b) Thyrocervical trunk (to thyroid region, cervical region, scapular region). gives off the suprascapular artery which forms anastomosis around the scapula region of the shoulder.
2nd branch/behind ;
costocervical trunk (not relevant to 204)
3rd branch/lateral
usually comes off the third branch but sometimes it comes off the 2nd.
The Dorsal scapular artery (this also contributes to anastomosis around the scapula region along with the suprascapular artery from the thyrocervical trunk..
Axillary Artery
When the subclavian artery crosses the first rib, it changes its name to become the axillary artery. it has not entered the armpit region.
The 3 parts of the axillary artery
The axillary artery is divided into 3 parts by the PECTORALIS minor.
-pectoralis minor muscles comes from, rib 3, 4, and 5 and inserts into the coracoid process. it is a protractor of the shoulder region (moving forward)
1st part = Medial to the muscle
2nd part= Behind the muscle
3rd part= Lateral to the muscle
- First and second parts closely associated with the brachial plexus
- Once the axillary artery crosses the Teres Major muscle, it changes it name again and become the brachial artery that enters the arm,
- The TERES MAJOR muscle comes from the inferior angle of the scapula and inserts into the medial lip of the intertubercular sulcus of the bicipital grove
- The lateral lip is where pectoralis major inserts
Branches of the axillary artery
1st part- there is a branch given off to supply to the thorax
2nd part- there is a trunk given off which supplies lots of the structures of the scapula in the axillary region, you don’t need to know the name of these to be branches.
3rd part - the subscapular artery is given off which contributes to the anastomosis around the shoulder region with the dorsal scapula and the suprascapular arteries.
this 3rd part also gives off the anterior circumflex humeral and a posterior circumflex humeral. these arteries form a circle around our surgical neck of the humerus (shown in the dotted line).
-so if you were to fracture your humerus on the surgical neck, you risk damaging the anterior and posterior circumflex humeral arteries which can affect the blood supply to the region of the shoulder.
Brachial artery
The axillary artery crosses the Teres major muscle and becomes the BRACHIAL ARTERY.
- the brachial artery passes down the media side of the arm towards the anterior aspects of the elbow. its very superficial as it passes through the arm.
- it sits int the neurovascular bundle in the medial aspect of the arm.
- it’s giving off of little muscular branches to supply the flexor (anterior) muscles such as the Biceps Brachi, the coracobrachialis and the brachialis muscles in the anterior compartments.
- its also give off a large branch known as the - Profunda brachii artery. this artery passes posteriorly to the back fo the humerus in a grove called the spiral or the radial grove. this grove is formed by the borders of the origins of the lateral and medial heads of the triceps muscle.
- that profunda brachial artery supplies the extensor muscle so the triceps muscle . the brachial artery/profunda brachii gives off collateral branches that contribute to an anastomosis around the elbow.
- the brachial artery passes anteriorly over the elbows into a triangular region called the cubital fossa. when we mention the word cubital, its about the elbow.
- when it gets into the cubital fossa, it divides into the radial artery that passes laterally down the forearm and then an ulna artery that passes medially down the forearm.
Profunda brachii artery
- we are looking at the posterior view of the arm. you can see the lateral head coming from the lateral aspects of the humerus.
- you can see the spiral/radial groove formed between the lateral and radial head of the triceps muscle
- sitting in that grove is the Profunda brachial artery with the radial nerve as it passes obliquely across the back of the humerus
- if there is a fracture at the shaft of the humerus , you might damage that profunda brachii artery which is a branch of the brachial artery from the anterior area. when you damage it, it will affect the blood supply to the triceps muscle.
- more proximally, we have our trees major muscle in a little space called the Quadrangular space.
- passing through that space, we can see the posterior circumflex humeral arteries passing through with the axillary artery.
Radial artery
- The radial artery runs down the lateral side of the forearm. sits hidden under a muscle called the brachioradialis muscle.
- the muscles comes from the lateral aspect fo the humerus and inserts into the styloid process of the radius. its a flexor of the forearm when you are half pronated. i.e when you are picking up a glass/mug to drink something
- the radial artery eventually reaches the hand where it forms the deep palmer arch. that’s relative to our long flexor tendons. it passes deep to through the long flexor tendons to eventually anastomose with the ulnar artery.
Radial artery in the hand
The radial artery passes down the hand through a space called the anatomical snuffbox on the lateral side of the hands.
- The radial artery goes towards the thumb and pierces between the muscle that sits between the first digit and index finger (2nd digit) , basically into the first dorsal interosseous muscle.
- that muscle allows you to abduct (spread) the index finger.
- not the radial artery has now found a route to enter the palms of the hands. when it gets here, below the long flexor tendons, it anastomose with the ulna artery.
Ulnar artery
- The ulna artery is running down the medial side of the forearm
- it sits under a muscle called flexor carpi ulnaris muscle
- the muscle flexes the arm
- shortly after the ulnar artery is being formed. it gives off a branch, the Common interosseous artery which then divides into an anterior and posterior interosseous artery.
- interosseous means between the bones
- the interosseous membrane is the membrane between the radius and the ulna
- the anterior and posterior interosseous arteries. sits on either sides of the interosseous membrane. they are supplying deep structures of the forearm.
- when the ulnar artery reaches the arm, it forms the superficial palmar arch .l
- that superficial palmar arch is sitting above the long flexor tendon of the hand
Ulnar artery in the hand
- The ulnar artery goes into the hands where it forms the superficial palmar arch, it then anastomoses via radial artery on the lateral side.
- There are some branches given off the superficial palmar arch which are the palmar digital arteries that supply blood to the digits.
- clinically, you may want to find your deep and superficial palmar arch. ask the patient to extend their thumb like a thumbs up. you draw a line across the hand along with the thumb. that is the approximate location of the deep palmar arch.
Venous return
- Veins are always very variable
- veins in the upper limb all drain into the axillary vein which then drains into the subclavian vein .
- the axillary vein sits beside the axillary artery
Veins can be divided into;
1. Deep veins
-Tend to follow the arteries
–In the upper limbs, they are Paired. they are very small . they sit on the backof the arteries.
–Venae comitantes
2. Superficial veins
there are 2 main superficial veins in the upper limbs;
a) Cephalic vein; runs up the lateral side of the forearm and the arm.
b) Basilic vein; run up the medial side of the forearm and the medial side of the arm
they both arise from the dorsal, the back aspect fo the hand , from the dorsal venous arch.
- THE MEDIAN CUBITAL VEIN forms a bridge between the basilic and cephalic vein. if you are gonna take blood, you will probably take it from here.
- The basilic vein pierces the fascia just under the armpit region and dive into the axial.
- the cephalic vein carries on a bit further and its in a grove called the Deltopectoral groove. this grove is formed between the deltoid muscle and pectoralis major muscle but eventually dives down piercing the fascia passing into the axillary vein beside the axillary artery.
Lymphatic drainage
- All the lymph from the upper limbs drains into lymph nodes sitting within the axillar (axillary lymph nodes).
- those axillary lymph nodes sits around our axillary vein
- small cluster of lymph nodes that sits around the elbow beside the basilic vein and we call those CUBITAL LYMPH NODES.
-we have the Deltopectoral node which sits beside the cephalic vein in the deltopectoral groove.
-all the lymph pass through the axillary lymph nodes, heading towards the venous system.
Nerve supply to the upper limbs is by the
BRACHIAL PLEXUS.
The brachial plexus is formed from the 5th, 6th , 7th, 8th, and the 1st thoracic spinal nerves.
The brachial plexus conveys motors axons, sensory axons as well as autonomic sympathetic axons.
The reason we have a plexus Is to produce mixed nerve.
- These are nerves that contain axons from multiple spinal nerves. this is really important because the upper limb contains large muscle groups and those groups require innervation from more than 1 spinal nerve.
- in the picture, you can see the spinal nerves divided into roots which form trunks, the trunk divide to form division, divisions come together to form the cords and finally, those cord form terminal branches which contain axons from multiple spinal nerves 9they are the mixed nerves).
Roots of the brachial plexus
This is different from the dorsal and ventral roots that come together to for spinal nerves. they are different.
- coming off C5, you can see a nerve branch called (Dorsal scapular nerve) which supplies the rhomboid muscles (major and minor) as well as the levator scapulae muscle.
- we can also see the long thoracic nerve which is formed from C5, C6, C7 and this nerve innervates the serratus anterior.
Motor innervation
Motor axons within each root innervate a different functional group of muscles and this is your myotomes.
a myotome is a group muscle innervated by single spinal nerves.
- Motor axons from the 5th cervical root of the brachial plexus mainly innervate the shoulder muscles. the arm abductors mainly the deltoid muscle.
- the motor axon in the 6th cervical. root, mainly innervate the forearm flexors, mainly the biceps
- the ones from the 7th cervical, innervates the forearm extension triceps , they also have axons that innervate the wrist flexors hand extensors. these are muscles sitting in the antertioir and posterior forearm.
- the axons from C8 will innervate those muscles that flex and extends the digits
- the motor axons sitting in the first thoracic T1 innervate intrinsic muscles of the hand that enable you to abduct and adduct the fingers.
Trunks
The roots come together to form the trunk. you can see the roots passing through the scalene triangle formed by the anterior and middle scalene muscle with the floor formed by the first rib.
- The 5th and 6th root gives rise to the superior trunk
- the 7th roots forms the middle trunk
- c8 and t1 forms the inferior trunk
*you can see the Inferior trunk sitting just over the first rib as they pass through the scalene traingle
Divisions
Each trunk divides into anterior and posterior divisions
- The anterior division forms eventually the lateral and medial cord of the brachial plexus which will innervate most of the flexor muscles.
- The posterior division eventually come together to form the posterior cord. the motor axons from here are mostly gonna innervate the extensor muscles.
Cords of the brachial plexus
The cord sits under the pectoralis minor muscle. pectoralis minor comes from the 3, 4, 5 ribs and inserts into the coracoid process.
- we have lateral, medial and posterior cord.
- They are named in relation to their position to the axillary artery
- The lateral cord sits lateral to the axillary artery
- the medial cord sits medial to the axillary artery
- the posterior cord sits behind the artery
Cords of the brachial plexus
- The lateral cord has 1 branch coming off it and that 1 branch supplies our pectoralis muscles and its called the PECTORAL NERVE.
- The lateral nerve gives rise or terminate as the MUSCULOCUTANEOUS NERVE
- Also terminates as the lateral part of the MEDIAN NERVE
Musculocutaneous nerve
- the Musculocutaneous nerve pierces right through our coracobrachialis muscle which is the muscle that comes from the coracoid and inserts into the shaft of the humerus. its our flexor of the arm just like the biceps.
- further down, the Musculocutaneous nerve then sits in between our brachialis and biceps muscle. its supplying the anterior compartment of the arm.
- its supplying the coracobrachialis, biceps brachii, and the brachialis muscle.
- the nerve then pops out on the lateral side of the elbow just under the biceps muscle and it changes its name to the LATERAL CUTANEOUS NERVE to the forearm. it has now become the cutaneous nerve.
- it carries on down the lateral side of the forearm to innervate the skin on the lateral side
- so the Musculocutaneous nerve innervates the anterior part of the arm and the lateral side of the forearm when it will become a cutaneous nerve.
Medial cord
There are 3 branches given off from the cord.
- The medial pectoral nerve supplies the pectoral muscles
- there are 2 cutaneous nerves. they supply the skin on the medial side of the arm as well as the medial side of the forearm.
- our medial cord terminates as the ulnar nerve and it also terminates as the medial part of the median nerve
- you can see how the lateral and medial cord come together to form the median nerve
Median nerve
runs down the medial part of the arm, the brachial.
- it does not innervate anything in the arm. it passes down the forearm within the cubital fossa, its sitting anterior as it enters the forearm through the cubital fossa
- it then dives down to sits sandwich in the anterior flexor compartment between the flexor muscles.
- it is innervating all of our flexor muscles in the anterior forearm except 2 of them.
- the 2 muscles it does not innervate are ;flexor carpi ulnaris and the median 2 bellies of flexor digitorum profundun.
- the median nerve then passes through the carpal tunnel
- when the median nerve enters the hand, it then supplies the intrinsic muscles on the lateral side other arm which are mainly associated with the the thumb
- its also supplies the skin on the lateral palm of the hand and the skin of the digit 1,2 3, and half of digit 4.
Ulnar nerve
The ulna nerve also passes down the medial side if the arm just behind the brachial artery and median nerve. it then passes the back of the elbow joint where it passes through a tunnel known as the cubital tunnel which is formed between the middle epicondyle and the olecranon of the ulna.
the ulnar nerve enters the forearm in the medial side from after passing through the cubital tunnel . it then sits sandwiched under flexor carpi ulnaris muscle with the ulna artery
-in the forearm, that nerve innervates flexor carpi ulnaris and it innervates the medial two bellies of flexor digitorum profundus.
Posterior cord
This will be sitting directly behind the axillary artery
-it has 3 little branches given directly from and this innervates muscles int he posterior axilla but it terminates as the radial nerve and the axillary nerve.
Radial nerve
- it passes posteriorly in the arm.
- it enters the extensor compartment and it passes through the spiral/radial grove.
- it’s innervating the extensor compartments of the muscles of the arm (triceps) remember triceps have 3 heads, hence the name.
- it enters the forearm from just under the brachioradialis muscle
- it then divides into 2 branches,
- A deep branch that enters the posterior compartment of the forearm and it innervates all of our extensor muscles in the forearm.
- it also gives off a superficial branch and then runs under the brachia radialis muscle all the way down towards the hand
Axillary nerve
Goes through the Quadrangular space which is bordered by teres minor, teres major, the long head of triceps and the shaft of the humerus.
Alos passing through that space with the axillary nerve is the posterior circumflex humeral artery .
-the axillary artery supplies the deltoid muscle . abductor of the arm
Terminal branches
dermatomes
A Dermatome is “An individual area of skin innervated by a single spinal nerve” and this was established during development of the somites.
-Lots of overlap/variation
Clinical: Altered sensation in the region of a dermatome indicates damage to specific spinal nerve of spinal cord segment (i.e. proximal nerve injury)
Cutaneous innervation by terminal branches
This is different from the dermatomes maps because it reflects mixed nerves. so innervated by more than 1 spinal nerve.
