Upper Limb Anatomy Flashcards
Describe the structure of a synovial joint
Articular cartilage
- Avascular
- Aneural
Fibrous capsule
- May be reinforced by stabiliser muscles
- Strengthened by intrinsic ligaments
Extrinsic ligaments may be primary stabilisers
- Ligaments have rich nerve supply but poor blood supply
- Injury will cause pain but will take long time to heal
Synovial membrane lines all non-articular surfaces
- Has nerve supply and highly vascularised
- Tearing > haemarthrosis
- Increased fluid from overproduction of synovial membrane may > effusion
What are the special joint structures?
Labrum = fibrocartilaginous rim/lip > deepens socket in ball and socket joints
- May provide site of attachment for muscle which originates inside joint
- Tendon has bony attachment and labral attachment
- Therefore avulsion of head of biceps may detach labrum
Fat pad = intra-capsular but extra-synovial
- Spread synovial fluid around when they move
Ligaments = thickenings of capsule (intrinsic)/some distance from capsule (extrinsic)
Discs - present in some joints
- Meniscus = half-moon shaped disc
Bursa = sac containing synovial fluid, located wherever potential for friction
- Communicate with joint cavity - potential for spread of infection
What are the characteristic of a stable joint?
Congruent and often deep articular surfaces
Tight capsule with strong ligaments
Limited range of movement
What are the characteristics of a mobile joint?
Greater range of movement
Stability dependent on external structures and less dependent on intrinsic articular structures
Associated with increased susceptibility to sublaxation/dislocation
What are the joints of the shoulder complex?
Sternoclavicular Acromioclavicular Glenohumeral Scapulo-thoracic = pseudo-joint between scapula and fat of chest wall - Facilitates clavicular movements
When do most long bones of the skeleton commence ossification?
Shaft ossification occurs in utero at 8 weeks
Epiphyses most likely to appear after birth, but some may appear before birth
What are the common fracture sites for the humerus?
Surgical neck - common in elderly - Endangers axillary nerve Mid-shaft - Endangers radial nerve Supracondylar - Endangers median nerve and brachial artery
What is the function of the anatomical neck of the humerus?
Attachment for capsule, except its medial aspect
Describe the curves of the clavicle
Convex medial 2/3 anterior curve
Concave lateral 1/3 curve
What are the key features of the sternoclavicular joint?
Synovial saddle joint Very stable Composed of 3 articulating surfaces - Proximal end of clavicle - Clavicular notch of manubrium - 1st costal cartilage Intra-articular disc and strong capsule - Containing rich blood supply and nerve supply - Increases complexity of movement - Costoclavicular ligament = main limitation to movement
What are the movements of the sternoclavicular joint?
Elevation and depression with rotation about longitudinal axis
What structures are endangered with sternoclavicular sublaxation?
Subclavian artery and vein
What are the key features of the acromioclavicular joint?
Plane synovial joint
Articular surfaces lie in sagittal plane
Weak capsule
- Acromioclavicular ligament not very strong
Antero-posterior force tends to cause sublaxation/dislocation
Main stabiliser some distance from joint = coracoclavicular ligament
-2 parts separated by bursa
- Both parts prevent upward rotation of clavicle at acromioclavicular joint
What are the grades of acromioclavicular sublaxation?
Grade 1 = acromioclavicular ligaments stretched but not torn
Grade 2 = acromioclavicular ligaments torn and disrupted
Grade 3 = acromioclavicular and coracoclavicular ligaments ruptured with wide separation of joint
What are the five layers of the shoulder joint, from in to out?
Bones
- Large head of humerus fits into relatively shallow glenoid fossa of scapula
Labrum
- Attempt to compensate for lack of glenohumeral joint stability by deepening socket
- Has attachments for long head of biceps and glenohumeral ligaments
Capsule, reinforced by intrinsic ligaments
- Loose capsule, unstable, but allows greater range of movement
- Attaches to anatomical neck and surgical neck, creating dependent fold > allows greater movement
- Opening in capsules for
- Subcapsular bursa
- Tendon for long head of biceps
- Capsule may tighten, causing adhesive capsulitis = frozen shoulder
- Limits range of movement
Tendons = rotator cuff
- Primary stabilisers
- Tendinous insertions of muscles that reinforce joint blend into capsule
- No rotator cuff below joint
Coraco-acromial ligament/arch and sub-acromial bursa
- Subacromial ligament between 2 non-mobile bones - acromion and coracoid
- Subacromial bursa under arch and doesn’t communicate with joint
- Subacromial bursa susceptible to irritation during shoulder abduction, especially if rotator ccuff weak > can cause bursitis
How are the rotator cuff muscles organised around the shoulder joint?
Supraspinatus on top
Infraspinatus and teres minor behind
Subscapularis in front
What is the action of supraspinatus?
Aids abduction
What is the primary abductor of the shoulder joint?
Deltoid
What is the action of infraspinatus and teres minor?
External rotation
What is the action of subscapularis?
Internal rotation
What are the types of shoulder dislocation?
Anterior
Posterior
What happens in an anterior dislocation of the shoulder?
Most common due to force applied to abducted and exterally rotated arm
Humerus initially moves anteriorly and then dislocated inferiorly
Common in sporting injuries
Axillary nerve endangered by inferior dislocation
- Sensory branches of axillary nerve supply skin over shoulder region (C5)
- Pin-prick test over military badge region to ascertain if there’s been nerve damage
What happens in a posterior dislocation of the shoulder?
Less common
May occur due to electric shock/epileptic fit
What are the two joints contained in the elbow complex?
Elbow joint between humerus and ulna
- Trochlea (medial condyle) of humerus articulate with coronoid process
- Capitulum (lateral condyle) of humerus articulates with radial head
Proximal radioulnar joint
Both joints share 1 synovial cavity
Describe the ligaments of the elbow joint complex
Medial collateral ligament
Lateral collateral ligament
Both resist abduction at elbow joint
Annular ligament encircles head of radius
Describe the medial collateral ligament
Originates from medial epicondyle and inserts onto ulna
Much stronger than lateral collateral ligament
Describe the lateral collateral ligament
Originates from lateral epicondyle of humerus and fuses with annular ligament distally
What muscles attach to the lateral epicondyle of the humerus?
Superficial extensor muscles of forearm
What does the annular ligament allow?
Pronation and supination
What is found inside the fossa of the elbow joint complex?
Intracapsular fat pads
Fill fossa when not occupied by bone
When is their maximal stability in the elbow joint?
Full extension
What is valgus angulation of the forearm and why may it be significant?
Forearm points laterally about 165 degrees when in full extension = cubitus valgus
May result in friction of ulnar nerve
What movements occur across the radioulnar joints?
Supination and pronation
Interosseus membrane = axis of rotation
What are the functions of the interosseus membrane?
Produce pronation and supination
Links 2 sets of radioulnar joints
Transmits forces from radius to ulna
Where are the articular surfaces of the distal radioulnar joint?
Head of ulna
Distal radius
What are the types of fractures and dislocations of the elbow?
Falling backwards with flexed elbow may cause fracture of coronoid process of ulna and posterior dislocation
Dislocation > stretch and spasm of brachial artery and its branches > Volkmann’s ischaemia of forearm musculature
If fracture of medial epicondyle > ulnar nerve susceptible to injury
What are the carpal bones from lateral to medial, proximal to distal?
Some = scaphoid Lovers = lunate Try = triquetral Positions = pisiform That = trapezium They = trapezoid Cannot = capitate Handle = hamate
Describe the scaphoid bone
Large articular surface (proximal)
Bulbous end (distal)
Narrow portion = waist, in between articular surface and bulbous end
- Has vascular foramina > contain blood vessels directed into bone by tendons/ligaments
- Vascular foramina never found on articular surfaces
Projection of scaphoid sitting up = tubercle
Floor of anatomical snuff box
Describe the lunate bone
Directly involved in movements at wrist joint
Describe the triquetral bone
Minimally involved in movement at wrist joint
- Only when in ulnar deviation
Describe the pisiform bone
Sesamoid bone
Found in insertion of tendon of flexor carpi ulnaris
Describe the trapezium bone
Has tubercle
Describe the capitate bone
Largest carpal bone
Describe the hamate bone
Contains hook
What is the flexor retinaculum?
Deep fascia seen when wrist flexed
Tendons of wrist pass into hand under flexor retinaculum
Describe the ossification of the carpal bones
Don’t start ossification until 2 years
Usually biggest bones start ossification 1st
From capitate, ossification happens in anti-clockwise direction
Ossification of pisiform last at 11/12 years
What are the joints of the wrist complex?
Radiocarpal
Intercarpal/midcarpal
Describe the radiocarpal joint
Synovial ellipsoid joint
Involves
- Radius
- Scaphoid
- Lunate
Due to shape of joint, some movements blocked
Flexion greater than extension
- Because of bony blocks of joint
Ulnar deviation greater than radial deviation
- Radial styloid process limits radial deviation
Describe the intercarpal joints
Between proximal and distal carpal rows - excluding pisiform
Multiple articulatins
- Functional rather than anatomical joint
Movements generally opposite to wrist
- Extension more than flexion
- Radial deviation more than ulnar deviation
What is the role of the radiocarpal ligaments?
Resists tendency of carpal bones to slide into medial space between wrist and ulna
Palmar radiocarpal ligaments anchor carpal bones towards radius
Radio-scapho-lunate ligament passes over scaphoid and encircles lunate
- Provides archway across 2 proximal carpal bones, anchoring them
- Any damage to band > immobilisation of lunate bone
What is the most commonly sublaxed carpal bone?
Lunate, secondary to radio-scaphoid-lunate ligament injury
How do the flexor and extensor tendons of the forearm act to stabilise the wrist?
Tendons bypass wrist to attach to distal bones
Drag carpal bones closer to radius and ulna - act as stabilisers
Which of the carpal bones are most commonly fractured? What are the consequences of this?
Scaphoid, most commonly at waist
Significant due to blood supply from branches of radial artery through vascular foramina
If fracture not picked up/secured/stabilised, blood flow supplying distal pole becomes so disrupted that proximal pole undergoes avascular necrosis
What are the major joints of the hand?
Carpometacarpal
Metacarpophalangeal
Interphalangeal
Describe the carpometacarpal joints
All synovial joints
Joint of thumb = saddle allows opposition
Describe the metacarpophalangeal joints
Condyloid joints
Flexion/extension and abduction/adduction
Volar (palmar) and dorsal plates = fibrocartilaginous plates expanding surface area for articulation
Describe the interphalangeal joints
Flexion/extension only
Why is it easier to abduct and adduct the fingers in flexion?
Collateral ligaments taut in flexion
What are the types of interphalangeal injuries?
Palmar interphalangeal joint injury > swan neck deformity
- Volar plate may be damaged
Dorsal interphalangeal joint injury > boutonniere deformity
- Top of condyle may push through dorsal plate
Where does the pectoral girlde articulate with the axial skeleton?
Manubrioclavicular joint
Which muscles from the thoracic wall stabilise the pectoral girdle anterolaterally to the chest wall?
Pectoralis major
Pectoralis minor
Subclavius
Serratus anterior
Which muscles from the vertebral column stabilise the pectoral girdle posteriorly to the chest wall?
Trapezius Latissimus dorsi Levator scapulae Rhomboid minor Rhomboid major
What are the attachments of pectoralis major on the pectoral girlde?
Has clavicular and sternocostal head
- Attaches at clavicle
- Attaches to sternum and costal cartilages
Fibres converge >
Small insertion >
Clavicular fibres overlap sternocostal fibres >
Insert onto proximal humerus at lateral lip of intertubercular sulcus
What are the actions of pectoralis major at the shoulder joint?
Adductor Medial rotator Accessory muscle of inspiration - Fix humoral attachment - Pulls on ribs - Expands thoracic cage
Which muscles of the anterior chest wall that stabilise the pectoral girdle are underneath pectoralis major?
Subclavius
Pectoralis minor
Describe subclavius
Small
Fills space between clavicle and 1st rib
Passes laterally
What is the origin and insertion of subclavius?
Origin: anteromedial part of 1st rib
Insertion: undersurface of clavicle
What does subclavius do?
Stabilises clavicle
Describe pectoralis minor
Inferior to subclavius Origin: anterior surface of ribs 3-5 Fibres ascend and converge Insertion: coracoid process of scapula Stabilises scapula Depresses shoulder
Describe serratus anterior
Overlies lateral part of thorax Saw tooth attachment of anterolateral chest wall Origin: lateral surface of ribs 1-8 Heads posteriorly Underlaps scapula Insertion: medial border of scapula Protractor of scapula Holds scapula to chest wall
What is a winged scapula?
Scapula doesn’t glide along chest wall
Swings out like bird’s wing
Due to damage to nerve supply of serratus anterior
What is the clavipectoral fascia?
Fascia from clavicle Surrounds - Subclavius - Pectoralis minor Attaches to inferior fascia of axilla
Which muscles attach the humerus to the scapula?
Deltoid Subscapularis Supraspinatus Infraspinatus Teres minor Teres major
Which muscles make up the rotator cuff?
Subscapularis
Supraspinatus
Infraspinatus
Teres minor
From where does deltoid arise?
1 part from spine of scapula
1 part from aromion laterally
1 part from lateral third of clavicle anteriorly
What is the insertion of deltoid?
Fibres converge
Insert into deltoid tuberosity on humerus
What are the actions of deltoid?
Anterior fibres flex shoulder
Posterior fibres extend shoulder
As a whole, abducts arm
What does supraspinatus do?
Initiates abduction
Gets arm out of vertical
Deltoid fibres take over after that
Where is supraspinatus?
Above spine of scapula
Where is infraspinatus?
Below spine of scapula
Where is teres minor?
Edge to edge with infraspinatus
Arising from inferior angle of scapula
Where do supraspinatus, infraspinatus, and teres minor insert?
On greater tubercle of humerus, on 1 of 3 facets
- Superior = supraspinatus
- Middle = infraspinatus
- Inferior = teres minor
Where is subscapularis?
Deep to scapula, between it and chest wall
Origin: subscapular fossa
Insertion: lesser tubercle of humerus
What does subscapularis do?
Medially rotates shoulder
What do supraspinatus, infraspinatus, and teres minor do together?
Laterally rotate shoulder
Why is the most common dislocation of the shoulder inferiorly?
Supraspinatus reinforces joint from above
Infraspinatus and teres minor reinforce joint from side
Subscapularis reinforces joint anteriorly
No reinforcement inferiorly
Where is teres major?
Origin: inferior angle of scapula
Runs edge to edge with subscapularis
Heads forward to proximal humerus
What does teres major do?
Adducts and medially rotates shoulder
Which muscles are in the anterior compartment of the arm?
Coracobrachialis
Biceps
Brachialis
Which muscles are in the posterior compartment of the arm?
Triceps
Describe the shape of biceps
2 heads
1 belly
Tendon crosses elbow joint
What is the distal attachment of biceps?
Tuberosity on radius = radial/bicepetal tuberosity
What does biceps do?
Elbow extended: flexes elbow
Elbow flexed: supinates arm
What are the proximal attachments of biceps?
Short head of biceps: coracoid process
Long head of biceps: supraglenoid tubercle
Describe the long head of biceps
Intracapsular
Extrasynovial
Emerges through deficiency in capsule
Runs in intertubercular sulcus = bicepetal groove
Where is brachialis?
Deep to biceps
Arises from distal shaft of humerus and adjacent intermuscular septum
Crosses elbow joint
Inserts into coranoid process of ulna
What does brachialis do?
Flexes elbow in all positions
What is the origin and insertion of coracobrachialis?
Origin: coracoid process of scapula
Insertion: halfway down humerus
What does coracobrachialis do?
Organiser of neurovascular structures, especially brachial plexus
Not powerful alone
Assists flexion and adduction at shoulder
What are the three heads of triceps?
2 superficial
- Long: from infraglenoid tubercle
- Lateral: from proximal humerus
1 deep = medial
- From distal part of posterior aspect of shaft of humerus
All converge on common tendon of insertion: olecranon of ulna
What does triceps do?
Extend elbow
What are the muscles of the superficial layer of the anterior compartment of the forearm?
Pronator teres Flexor carpi radialis Palmaris longus Flexor digitorum superficialis Flexor carpi ulnaris
What is the common flexor origin of the anterior compartment of the forearm?
Medial epicondyle of humerus
Describe the course and insertion of pronator teres
Diagonal course across anterior aspect
Insertion: halfway down radius
Describe the course and insertion of flexor carpi radialis
Heads diagonally to radial side
Insertion: base of 2nd and 3rd metacarpals
Describe palmaris longus
Absent in 10% of people
Short slender body and long slender tendon
Superficial
Blends with aponeurosis of palm and flexor retinaculum
Describe flexor digitorum superficialis
Flexor of all 4 digits Beneath - Palmaris longus - Flexor carpi radialis - Pronator teres Common belly Splits into 4 tendons Inserts either side of base of middle phalanx
Describe flexor carpi ulnaris
Forms medial border of compartment Heads to medial side of wrist Goes to 5th metacarpal base Inserts into pisiform bone Ligaments to surrounding carpal bones and base of 5th metacarpal
Where does the second head of pronator teres come from?
Ulna
Describe pronator quadratus
Deep muscle
Pronator
Rectangular
Clothes distal end of anterior aspect of shaft of radius and ulna
Where is the humeroulnar head of flexor digitorum superficialis from?
Common origin on humerus
Medial aspect of ulna
Origin from radius too
Forms fibrous arch between humeroulnar and radial heads
Describe flexor digitorum profundus
Flexor for all digits and wrists
- Only flexor of distal interphalangeal joint
Origin: anterior aspect of shaft of ulna and adjacent part of interosseus membrane
4 tendons for each finger
Comes through split in flexor digitorum superficialis at middle phalanx
Inserts at base of distal phalanx
Underlies flexor digitorum superficialis
Describe flexor pollicis longus
Flexor for thumb
Origin: shaft of radius and interosseus membrane
Runs on anterior aspect of thumb
Inserts at base of distal phalanx
Describe the flexor retinaculum at the wrist
Tendons go beneath
Attachments
- Scaphoid and trapezium laterally
- Hook of hamate and pisiform medially
What is the carpal tunnel?
Fibro-osseus tunnel
- Flexor retinaculum above
- Carpal bones below
What tendons goes through the carpal tunnel?
Flexor digitorum profundus tendons - Side by side Flexor digitorum superficialis tendons - 2 layers of 2 - 3 and 4 superficial - 2 and 5 deep Flexor pollicis longus tendon
Does flexor carpi ulnaris go through the carpal tunnel?
No
How does flexor carpi radialis cross the wrist?
Doesn’t really go through carpal tunnel
Goes through own tunnel as flexor retinaculum splits
What is the common extensor origin?
Lateral epicondyle of humerus
Which muscle arise from the common extensor origin?
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris
Describe brachioradialis
Arises from lateral supracondylar ridge of humerus
Forms radial border
Inserts into distal end of radius just above styloid process
Flexor of elbow
Describe extensor carpi radialis longus
Goes to base of 2nd metacarpal
Extend carpal joint
Describe extensor carpi radialis brevis
Goes to base of 3rd metacarpal
Extend carpal joint
What produces radial deviation?
- Flexor carpi radialis
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
All contract together
Describe extensor digiti minimi
Part of extensor digitorum
For 5th finger
Which muscles are located deep, extending between the radial and posterior group of muscles, and head to the thumb?
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
What is the course of extensor pollicis longus to the thumb?
Passes directly onto dorsal aspect of hand
Changes direction at radial tubercle
Heads to thumb
What forms the anatomical snuffbox?
Lateral: abductor pollicis longus and extensor pollicis brevis
Medial: extensor pollicis longus
Floor = scaphoid
Describe extensor digitorum
Onto dorsal aspect of hand Tendon fans out to form tendon hood/expansion Each tendon splits into 3 - Middle goes to base of middle phalanx - Laterals go to base of distal phalanx
Describe extensor carpi ulnaris
Forms medial border with flexor carpi ulnaris
Shared aponeurosis
Inserts into base of 5th metacarpal
What produces ulnar deviation?
Contract flexor carpi ulnaris and extensor carpi ulnaris together
Describe anconeus
Deep muscle of posterior forearm
Small
Triangular
Edge to edge with triceps
Describe supinator
Deep muscle of posterior forearm Covers proximal radius 2 heads - Deep - Superficial Nerve passes between heads
Describe extensor indicis
For index finger
Deep to extensor digitorum and extensor digiti minimi
Describe the extensor retinaculum of the wrist
On posterior aspect of wrist
Sends vertical septa creating compartments beneath
What are intertendinous connections?
Links between fingers
What are the layers of the palm, from superficial to deep?
Skin and palmaris brevis Palmar aponeurosis Thenar and hypothenar muscles Neurovascular plane Long flexor tendons and lumbricals Adductor pollicis and neurovascular plane Interossei and metacarpals
What is Dupuytren’s contracture?
Thickening and scarring of palmar aponeurosis in epileptic, diabetic, alcoholic, and manual workers
Where is the thenar muscle?
On lateral side of hand, under thumb
Where is the hypothenar muscle?
On medial side of hand, under 5th finger
Where are the lumbricals?
Between metacarpals
On which aspect does the single stem artery run?
Flexor aspect
What is the single stem artery of the upper limb?
Subclavian artery
What does the subclavian artery become when it goes over the border of the first rib and enters the axillary?
Axillary artery
What does the axillary artery become when it crosses the lower border of teres major and enters the arm?
Brachial artery
Where does the brachial artery divide into its two terminal branches, and what are they?
Divides distal to elbow joint, roughly at neck of radius into
- Radial artery
- Ulnar artery
What do the radial and ulnar arteries form in the palm?
2 palmar arches
To which muscle does the axillary artery run deep, and how does this divide it?
Deep to pectoralis minor Divided into 3 parts - Before - Beneath - After
What does the axillary artery supply?
Walls of axilla
- Anterior and posterior chest wall
- Breast
What is the deep branch of the brachial artery?
Profunda brachial artery
What does the profunda brachial artery supply?
Posterior compartment of arm
What is the course and supply of the profunda brachial artery?
Spirals around back of humerus from medial to lateral into posterior compartment of arm
Supplies triceps
Runs with radial nerve in groove
Feeds in from above to anastomosis around elbow joint
What is the course of the radial artery?
Tucks under brachioradialis
Superficial branch of radial nerve on radial side
Winds onto dorsum of hand
Superficial branch goes through anatomical snuffbox over scaphoid bone
Pierces dorsum interosseus
Reaches palm of hand
In deeper neurovascular plane
What is the course of the ulnar artery?
Goes under flexor carpi ulnaris on medial side of forearm with ulnar nerve
Goes with ulnar nerve over top of flexor retinaculum
In superficial neurovascular plane in palm
What is the common interosseus artery a branch of?
Ulnar artery
What is the course of the common interosseus artery?
Heads down to top of interosseus membrane
Splits into anterior and posterior interosseus artery
With which nerve does the posterior interosseus artery run?
Posterior interosseus nerve
What forms the superficial palmar arch?
Ulnar artery
Superficial branch of radial artery
Where is the superficial palmar arch?
Over top of flexor retinaculum
What arteries does the superficial palmar arch give off?
Digital arteries
What do the digital arteries split into?
Proper digital arteries
What forms the deep palmar arch?
Radial artery
Deep palmar branch of ulnar artery
Which palmar arch is proximal, and which is distal?
Proximal: deep
Distal: superficial
What arteries does the deep palmar arch give off?
Metacarpal arteries
What are the deep veins of the arm, and what do they accompany?
Accompany arteries
Radial and ulnar vein > brachial vein > axillary vein > subclavian vein
What venous structures runs on either side of the radial and ulnar veins?
Vena comitantes
Where is the dorsal venous arch?
On dorsum of hand
What branches of the superficial venous system are given off by the dorsal venous arch?
Radial side: cephalic vein
Ulnar side: basilic vein
What is the course of the cephalic vein?
Ascends up radial side Winds around radial border of forearm up to cubital fossa Ascends up radial side of arm Lateral to bulge of biceps Enters deltopectoral groove Pierces clavipectoral fascia Joins axillary vein
What is the course of the basilic vein?
Winds around medial border of forearm Ascends up flexor aspect Gets halfway up arm Pierces deep fascia Joins brachial vein > axillary vein > cephalic vein
How do the cephalic and basilic veins communicate?
Via medial cubital vein
Where do the lymph nodes from the upper limb drain to?
Axillary lymph nodes
What do the deep lymphatics follow?
Arteries
What do the superficial lymphatics follow?
Veins
What is the nerve plexus of the upper limb?
Brachial plexus
Which vertebral segments contribute to the brachial plexus?
C5-T1
What three trunks do the nerve roots develop into?
C5-6 = superior trunk C7 = middle trunk C8-T1 = inferior trunk
What do the anterior divisions of the trunk supply?
Flexor compartment
What do the posterior divisions of the trunk supply?
Extensor compartment
What are the cords of the brachial plexus arranged around, and what are they called?
Arranged around axillary artery
Medial cord
Lateral cord
Posterior cord
What divisions make up each cord?
Lateral = anterior divisions of upper and middle trunk Medial = anterior divisions of lower trunk Posterior = posterior divisions of all 3 trunks
Where are the roots and trunks of the brachial plexus?
Supraclavicular - in neck
Where are the divisions of the brachial plexus?
Behind clavicle
Where are the cords of the brachial plexus?
In upper limb, around axillary artery
What shape do the lateral and medial cords form?
M
Which limb of the M pierces coracobrachialis, and what is the peripheral nerve that it forms?
Lateral limb of M
Musculocutaneous nerve
Describe the musculocutaneous nerve
Branch of lateral cord Made of anterior divisions of C5-7 Nerve of anterior compartment of arm - Motor supply Pierces coracobrachialis Between biceps and brachialis Becomes cutaneous at elbow Changes name to lateral cutaneous nerve of forearm - Supplies skin down lateral side of forearm - In superficial fascia
Describe the course ulnar nerve
Branch of medial cord
Made of anterior division fibres of C8 and T1
Usually also has some C7 fibres at some levels
Heads down medial aspect of brachial artery
Behind medial epicondyle
1 of 2 nerves of flexor compartment of forearm and hand
Slips between 2 heads of flexor carpi ulnaris
Descends down medial side of forearm under flexor carpi ulnaris
Across flexor retinaculum next to pisiform
Into palm of hand
What does the ulnar nerve supply?
Flexor carpi ulnaris
Medial half of flexor digitorum profundus
Everything in hand except thenar eminents
Sensation to
- Medial 1.5 fingers on front and back
- Corresponding part of palm
Describe the course of the median nerve
Formed by 2 roots
- Medial root from medial cord
- Lateral root from lateral cord
From anterior division fibres of C5-T1
Shares anterior compartment of forearm and hand with ulnar nerve
Starts lateral to/on top of axillary artery
Crosses over and becomes medial to brachial artery when ulnar nerve leaves
Heads into anterior compartment of forearm
Goes beneath fibrous arch of flexor digitorum superficialis
Runs down middle of forearm between flexor digitorum superficialis and flexor digitorum profundus
Gives off palmar cutaneous branch
- Over flexor retinaculum
Goes through carpal tunnel
Comes into palm of hand past thenar muscles
What does the median nerve supply?
Everything in forearm except
- Flexor carpi ulnaris
- Medial half of flexor digitorum profundus
Thenar eminants via recurrent branch
Lateral 3.5 fingers on palmar aspet
Nail beds of lateral 3.5 fingers on dorsal aspect
What are the two terminal branches of the posterior cord?
Axillary nerve
Radial nerve
What is the course of the axillary and radial nerves?
Exit axilla through posterior wall
Emerge into extensor compartment of arm
Describe the axillary nerve
Only carries fibres from C5-6 Emerges above teres major Sinks into deltoid Divides into anterior and posterior branch supply deltoid Sends small branch to teres minor Passes beneath - Subscapularis - Shoulder joint - Teres minor
What nerve is damaged in an inferior dislocation of the shoulder joint?
Axillary nerve
What is the “regimental badge”?
Axillary nerve supplies skin over deltoid
Describe the radial nerve
Has posterior division fibres of C5-T1
Emerges below teres major
Spirals across posterior aspect of shaft of humerus, going medial to lateral
Gives branches to triceps during spiral
Pierces intermuscular septum
Tucks under brachioradialis
Superficial branch continues under brachioradialis down radial side of forearm
What nerve is damaged in a fracture of the shaft of the humerus?
Radial nerve
How does the radial nerve supply posterior sensation?
Posterior cutaneous nerve of arm
Posterior cutaneous nerve of forearm
What does the radial nerve supply on the dorsum of the hand?
Lateral 3.5 fingers - minus nail beds
Corresponding dorsal hand area
What nerve roots control shoulder abduction and flexion?
C5
What nerve roots control shoulder adduction?
C6
C7
(C8)
What nerve roots control elbow flexion?
C5
C6
What nerve roots control elbow extension?
C7
C8
What nerve roots control supination?
C6
What nerve roots control pronation?
C7
C8
What nerve roots control wrist flexion and extension?
C6
C7
What nerve roots control finger abduction and adduction?
T1
What nerve roots control finger flexion and extension?
C7
C8
