T3: Musculoskeletal system - Upper limb

upper limb bones and joints - summary (4)

• Upper limb attaches to anterior aspect of axial skeleton

• Distinct pattern of 1 proximal arm and 2 distal forearm bones

• Pentadactyl hand

• Thumb is rotated 90° in relation to the hand

shoulder girdle - composition (2)

clavicle and scapula

clavicle - role

provides the only upper limb articulation between the appendicular and axial skeletons and protects underlying neurovascular

clavicle - key features (4)

long bone

sternal and acromial ends → more round end is acromial end

distinct S curvature

roughened inferior surface → attachment of ligaments that anchor clavicle

scapula - key features (5)

flat bone with significant muscle attachment

Spine of scapula

Processes -> acromion and coracoid

Fossae > for attachment

Glenoid fossa -> for humorous

sternoclavicular joint - type of joint

synovial saddle joint

only joint connecting upper limb to the axial skeleton

features of sternoclavicular joint (2)

Intra-articular disc -> improves congruency (how articulations join together) and promotes stability

costoclavicular ligament promotes strong capsule

acromioclavicular joint - joint type

synovial plane joint

acromioclaicular joint - features (2)

strong coracoclavicular ligament

weak capsule → allows more shoulder blade movement

clavicular joints - summary (3)

sternoclavicular joint

acromioclavicular joint

body prefers to fracture clavicle rather than dislocate clavicular joints

humerus - key features (6)

• Round and smooth head

• Anatomical and surgical neck

• Greater and lesser tubercles

• Bicipital/ intertubercular groove

• Lateral and medial epicondyles

• Capitulum and trochlea condyles

shoulder joint - joint type

glenohumeral joint

synovial ball and socket joint

shoulder joint - key features (3)

Large humeral head with shallow glenoid fossa -> relatively incongruent

Labrum deepens socket to improve congruency

Loose joint capsule -> allows large range of motion but unstable joint

shoulder joint - supportive features (3)

1. specialised fibrocartilage → glenoid labrum

2. musuclar → rotator cuff muscles and biceps brachii (long head) blend into capsule to provide extra support

3. ligamentous → glenohumeral and coracohumeral both blend into capsule

ulna and radius - relationship (4)

Ulna and radius = long bones connected via interosseous membrane

2 articulations with each other → distal and proximal

Both articulate with humerus

Radius articulates with carpal bones (wrist)

ulna - key features (6)

trochlear notch

olecranon process

radial notch

ulnar tuberosity

head

styloid process

radius - key features (4)

head

radial tuberosity

ulnar notch

styloid process

elbow joint - joint type

synovial hingge joint

elbow joint - features (3)

strong collateral ligament support

humero-ulnar = primary boney contact → radius contacts humerus when moving into flexion

shares synovial cavity with proximal radio-ulnar joint

proximal and distal radioulnar joints - features (4)

Pronation and supination occurs at proximal and distal radioulnar joints -> results in forearm bones crossing each other

both = synovial pivot joints

proximal: radial head pivots in radial notch on ulna and annular ligaments encircle head to support pivoting

distal: ulnar head pivots in ulnar notch on radius

bone groups of wrist and hand - key feature

sesamoid bones → floating bones within soft tissue

radiocarpal joint - joint type

synovial condyloid joint

radiocarpal joint - features (3)

Scaphoid and lunate articulate with radius

Articular disc between ulna and carpels

Ligamentous support is very complex

joints of hand - type of joints (3)

intercarpal = synovial plane joints

carpometacarpal = synovial saddle (first digit) and synovial plane (second-fifth digits)

first carpometacarpal joint = vital for unique functions of the thumb and most degenerative joint in body

joints of fingers - joint types

metacarpophalangeal joint = synovial condylar joint → allows large amounts of flexion and extension but less adduction and abduction

interphalangeal joint = synovial hinge joints → commonly subluxed or dislocated

axio-appendicular muscles - posterior list (5)

• Latissimus dorsi

• Trapezius

• Levator scapulae

• Rhomboid minor

• Rhomboid major

axio-appendicular muscles - anterolateral list (1)

Serratus anterior -> attaches deep along anterior aspect of medial border

axio-appendicular muscles - anterior list (2)

• Pectoralis major -> fans along clavicle and sternum and attaches to humerus

• Pectoralis minor -> does not attach to humerus but vertical and obliquid arrangement from ribs to coracoid process

role of pectoralis minor (2)

More involved in internal rotation

Helps tilt scapulae up and over thoracic cage

scapulohumeral muscles - rotator cuff (4)

• Supraspinatus -> superior to spine and scapula

• Infraspinatus

• Teres minor -> attaches more laterally than infraspinatus

• Subscapularis -> only one that is more anterior

rotator cuff muscles all blend with joint capsule → compress humeral head into glenoid fossa for improve stability

scapulohumeral muscles - major movements and muscles (3)

Abduction -> supraspinatus

External rotation -> infraspinatus and teres minor

Internal rotation -> subscapularis

scapulohumeral muscles - deltoid and teres major roles

Deltoid = broad fan from humerus to scapula and clavicle -> produces shoulder flexion, extension and abduction

Teres major = larger than teres minor and attaches more anteriorly to the humerus -> internal rotation at shoulder

both attach more distally on humerus than rotator cuff muscles

compartments of muscles - general def

separation of muscles into compartments largely by intermuscular septa

specialisations of deep fascia (3)

Interosseous membrane -> has muscle attachments posteriorly and anteriorly

Retinacula -> traverses region where tendons present -> reduce bow stringing

Aponeurosis -> connective tissue for muscles to attach to

anterior arm compartments - summary

all muscles cross anterior aspect of at least one joint

produce flexion

anterior arm muscles - list (4)

Biceps brachii -> attaches to radial tuberosity

Coracobrachialis -> attaches to coracoid process

Brachialis -> attaches to ulnar tuberosity

Brachium/ brachii → elbow to shoulder region

anterior arm compartments - muscle involved in supination

biceps brachii

brachialis does not produce pronation as ulnar stays still

posterior arm compartments - summary

all aspects of triceps brachii cross over posterior aspect of at least one joint to attach to olecranon process

produce extension

posterior arm muscles - list (3)

triceps brachii (long head) → superficial

triceps brachii (lateral head) → deep

triceps brachii (medial head) → deep

foarm anterior compartments - list by attachment location (3)

Attaches to carpals/ metacarpals = wrist flexion

Attaches to digits = finger flexion

Distal attachment into radius = pronation

foarm posterior compartments - list by attachment location (3)

Attaches to carpals/ metacarpals = wrist extensor

Attaches to digits = finger extensor

Lateral epicondyle = bony landmark on humerus that provides attachment for multiple superficial muscles

forearm compartments - optimal digit flexion

contraction of wrist extensors in a slightly extended position allows for optimal length to flex digits (max strength)

hand muscles - list (3)

thenar → base of first digit

hypothenar → base of fifth digit

interosseous → space between metacarpal bones in middle of hand

brachial plexus - summary

complex intertwining and mixing of axons for motor and sensory supply to distinct regions of upper limb

brachial plexus - sections (5)

1. roots

2. trunks

3. divisions

4. cords → named in reference to their anatomic relationship with auxillary artery

5. terminal branches (5)

brachial plexus - terminal branches list

1. musculocutaneous

2. median

3. ulnar

4. auxillary

5. radial

terminal branch - musculocutaneous nerve (3)

supplies muscle and then skin from elbow onwards

continuation of lateral cord

pierces coracobrachialis to enter anterior compartment of arm

terminal branch - median nerve (4)

receives contributions from medial and lateral cords

no branching in arm

travels across midline of anterior elbow to enter forearm → major supply for anterior compartment of forearm

travels across midline of anterior wrist to enter hand → minor supply of hand musculature (largely thumb)

terminal branch - ulnar nerve (5)

Continuation of medial cord

No branching in the arm

Travels posterior to the medial epicondyle -> hitting funny bone = compression of ulnar nerve

Minor supply for anterior compartment of forearm

Major supply of hand musculature

terminal branch - auxillary nerve (4)

Smaller branch of posterior cord

Immediately exits out the axilla (armpit)

Wraps around humerus posterior to supply deltoid and teres minor

Shoulder dislocations pose significant risk to axillary nerve -> wraps around surgical neck so dislocation stretches nerve

terminal branch - radial nerve (3)

Largest branch of posterior cord

Long posterior journey -> passes anteriorly for a short distance in distal arm, over lateral epicondyle

Significant supply to posterior upper limb -> posterior compartments of arm and forearm

major upper limb arteries - summary (2)

Traverses over flexor side of joints -> elbow extension would restrict supply

Anastomoses at joints -> if compression occurs at heavily flexed position, supply moves down another path

major upper limb arteries - radial and ulnar artery

Ulnar artery is larger branch and principal supply for forearm and hand

Radial artery anastomoses with ulnar artery via palmer arches -> easily palpable at wrist

major upper limb arterial pathway - steps (5)

1. subclavian artery → under clavicle, ending at outer border of first rib

2. axillary artery → becomes axillary when it enters the armpit and terminates at border of teres major muscle

3. brachial artery → main supply for arm, branches at elbow

4. radial and ulnar arteries

5. palmer arches and digital arteries

superficial veins - summary

highly variable and commonly visible

begin on posterior hand as dorsal venous arch

easily accessible → used for IV and blood samples

superficial veins and lymphatic network

lymphatic vessels follow superficial veins → flow in axillary lymph nodes

deep veins - summary

accompany major arteries

commonly two present either side of respective artery

main nerve - deltoid and teres minor

axillary

main nerve - posterior and anterior compartment of arm

posterior - radial

anterior - musculocutaneous

main nerve - posterior compartment of forearm

radial

main nerve - anterior compartment of forearm (major and minor)

major - median

minor - ulnar

main nerve - hand (major and minor)

major - ulnar

minor - median