A1 - Pectoral Girdle & Shoulder Flashcards
What 2 components does the bone framework for the shoulder consist of?
- pectoral girdle (clavicle and scapula) 2. proximal end of the humerus
What does the pectoral girdle consist of?
the clavicle and the scapula
What are the 2 superficial muscles of the shoulder?
trapezius and deltoid
What is significant about the acromedial (lateral) end of the clavicle? What feature is present there?
it is flat it has a small oval facet for articulation with the acromion of the scapula
What is the shape of the sternal (medial) end of the clavicle like? What feature is present there?
It is more robust and quadrangular in shape It has a large facet for articulation with the manubrium of the sternum and first costal cartilage
What is the distinct tuberosity on the inferior surface of the lateral third of the clavicle?
the conoid tubercle along with the trapezoid line, this forms the attachment for the coracoclavicular ligament
Label the clavicle
What are the 3 angles, 3 borders, 2 surfaces and 3 processes of the scapula?
Angles - lateral, superior, inferior
Borders - superior, lateral, medial
Surfaces - costal, posterior
Processes - acromion, spine, coracoid process
Label the borders and angles of the scapula
Label the features of the scapula
What is the lateral angle of the scapula marked by?
What does this feature articulate with?
it is marked by the glenoid cavity
this articulates with the head of the humerus to form the glenohumeral joint
What does the spine of the scapula subdivide the posterior surface of the scapula into?
a small superior supraspinous fodda
a larger inferior infraspinous fossa
What are the infraglenoid and supraglenoid tubercles attachment sites for?
the infraglenoid tubercle is an attachment site for triceps brachii
the supraglenoid tubercle is an attachment site for biceps brachii
What is the costal surface of the scapula characterised by?
a shallow concave subscapular fossa
How is the lateral border of the scapula different to the medial & superior borders?
Why?
it is strong and thick for muscle attachment
What is the superior border of the scapula marked on its lateral end by?
- coracoid process
- suprascapular notch (lies medial to the root of the coracoid process)
Label the muscles and features
What features of the scapula are palpable on a patient?
- spine and acromion
- tip of coracoid process
- inferior angle
- most of the medial border of the scapula
What features does the trapezius attach together?
it attaches the scapula and the clavicle to the trunk
What are the 2 main functions of the trapezius muscle?
- powerful elevation of the scapula
- rotation of the scapula during abduction of the humerus above horizontal
What are the functions of the middle and lower fibres of the scapula?
the middle fibres retract the scapula
the lower fibres depress the scapula
What is the trapezius muscle innervated by?
the motor spinal part of accessory nerve XI
What structures does the deltoid attach to which location?
the deltoid attaches the scapula and the clavicle to the trunk
What is the main function of the deltoid muscle?
abduction of the arm beyond the intial 15 degrees
What is the function of clavicular fibres and posterior fibres of the deltoid?
clavicular fibres assist in flexing the arm
posterior fibres assist in extending the arm
What nerve innervates deltoid?
axillary nerve
Label the 3 muscles
What are the 3 muscles contained within each anterior pectoral region?
- pectoralis major (largest and most superficial)
- pectoralis minor
- subclavius
What is the function of pectoralis major?
It adducts, flexes and medially rotates the arm
Where does the subclavius muscle originate and insert?
it passes laterally from the anterior and medial part of rib I to the inferior surface of the clavicle
Where does pectoralis minor originate and insert?
It passes from the anterior surfaces of ribs III to V to the coracoid process of the scapula
What is the function of both subclavius and pectoralis minor?
they pull the tip of the shoulder inferiorly
Label the extrinsic muscles of the back
What are the 5 muscles of the superficial group of back muscles?
- trapezius
- latissimus dorsi
- rhomboid major
- rhomboid minor
- levator scapulae
How can the trapezius muscle be identified?
it has inferior diagonal fibres and transverse middle fibres
Where do the superior fibres of the trapezius attach to?
What does contraction of the superior fibres acheive?
superior fibres attach to the lateral third of the clavicle and the acromion of the scapula
contraction elevates the scapula
What is the action of the superior and inferior fibres of the trapezius?
they work together to rotate the lateral aspect of the scapula upward when raising the upper limb above the head
Where does most innervation of the trapezius muscle come from?
the accessory nerve
What are the 3 blood supplies of the trapezius muscle?
- superficial branch of the transverse cervical artery
- acromial branch of the suprascapular artery
- dorsal branches of posterior intercostal arteries
What are the functions of latissimus dorsi?
- extension, adduction and medial rotation of the upper limb
- depression of the shoulder to prevent upward movement
What is the innervation of latissimus dorsi?
thoracodorsal nerve of the brachial plexus
What is the blood supply of latissimus dorsi?
- primary blood supply comes from thoracodorsal artery
- additional small arteries from dorsal branches of posterior intercostal and lumbar arteries
What is this muscle?
serratus anterior
Where does serratus anterior originate and insert onto?
it originates as a number of muscular slips from the lateral surfaces of ribs I to IX
it inserts onto the costal surfaces of the medial border of the scapula
What is the function of serratus anterior?
it pulls the scapula forward over the thoracic wall and faciliates scapular rotation
What is serratus anterior innervated by?
long thoracic nerve
What is the rotator cuff?
a group of muscles and tendons that surround the shoulder joint
Label the muscles of the rotator cuff
What is significant about the greater and lesser tubercles of the humerus?
they serve as attachment points for the 4 rotator cuff muscles of the glenohumeral joint
What are the 3 facets of the greater tubercle of the humerus?
Which muscles attach to them?
supraspinatus attaches to the superior facet
infraspinatus attaches to the middle facet
teres minor attaches to the inferior facet
What muscle attaches to the lesser tubercle of the humerus?
subscapularis
What are the 4 muscles of the rotator cuff?
- supraspinatus
- infraspinatus
- teres minor
- subscapularis
What structure separates the lesser and greater tubercles?
What tendon passes through this structure?
the bicipital groove (intertubular sulcus)
the tendon of the long head of the biceps brachii passes through this sulcus
Where does the subscapularis muscle originate from and insert onto?
It originates from (and fills) the subscapular fossa
It inserts on the lesser tubercle of the humerus
What is the function of the rotator cuff muscles?
they stabilise the glenohumeral joint
What is subscapularis innervated by?
superior and inferior subscapular nerves
Label the muscles and spaces on the diagram
Label the features of the scapula
Label the 2 features of the scapula/clavicle on the X-ray
What are the 2 “necks of the humerus”?
Which part articulates with the glenoid cavity?
the surgical and anatomical neck
the head of the humerus articulates with the glenoid cavity
Label the features of the humerus on the X-ray
What is the difference between abduction and adduction?
adduction is the movement of a limb towards the midline of the body
abduction is the movement of a limb away from the midline of the body
What are the following movements of the shoulder joints?
What is meant by flexion and extension?
flexion brings the bones that form a joint closer together so that the angle between the bones is decreased
extension is a movement that increases the angle between 2 body parts
What is circumduction?
a combination of flexion, extension, adduction and abduction, leading to the movement of a body region in a circular manner
What are the 2 main movements of the scapula?
the scapula slides on the ribs and can move backwards and forwards
it is involved in protraction and retraction
What is protraction?
the action of extending a part of the body
involves the scapula moving laterally and anteriorly along the chest wall
what is retraction?
the movement of a body part in the posterior direction
this involves pulling the scapulae towards each other and the spine
What are the 3 general muscle rules that apply to all muscles?
- when a muscle contracts, it becomes shorter
- when muscles run between 2 bony points, they will move the bony landmark that is most flexible when they contract
- a muscle cannot move a joint unless it crosses the joint
Where does levator scapulae attach to?
What action is it responsible for?
it attaches to the upper portion of the medial border of the scapula
it is responsible for scapular elevation
Where do the rhomboid muscles attach to?
What is their function?
they run from the thoracic vertebrae and attach onto the lower part of the medial border of the scapula
they are responsible for retraction of the scapula
Label the back muscles
Where does latissimus dorsi attach to?
What is its function?
originates from lower thoracic vertebrae and attaches to anterior aspect of humerus
it allows for adduction and medial rotation of the arm
Where does teres major originate and insert?
What is its function?
it originates at the inferior angle of the scapula
it inserts onto the anterior aspect of the humerus
it is involved in adduction and medial rotation of the arm
Where is infraspinatus found?
What is its function?
it fills the infraspinous fossa of the scapula
it inserts onto the posterior aspect of the humerus
it is involved in lateral rotation of the arm
Where is supraspinatus found?
What is its function?
it fills the supraspinous fossa of the scapula
it runs underneath the acromion to insert at the top of the humerus
it allows for the initial 20 degrees of abduction of the arm
Where does teres minor insert?
What is its function?
it insers on the posterior aspect of the humerus
it allows for lateral rotation of the arm
Which muscle is often affected in fracture of the surgical neck of the humerus and why?
injury at the surgical neck can injure the axillary nerve
this then impairs the function of deltoid
Where is subscapularis found?
What is its function?
it fills the subscapular fossa of the scapula and inserts onto the anterior aspect of the humerus
it is involved in adduction and medial rotation of the arm
What is the stability of the shoulder joint compromised by?
- incongruent joint surfaces
- thin and lax joint capsule
The joint is weakest inferiorly
What 4 methods help to improve the stability of the shoulder joint?
- glenoid labrum (lip of cartilage)
- ligaments
- biceps tendon
- rotator cuff muscles
Label the components of the shoulder joint
What 3 components make up the coraco-acromial arch?
What is its function?
- acromion
- coracoid process
- coracoacromial ligament
It is important in preventing superior displacement of the humerus
What injury is this?
Is it acute or chronic and how does it usually occur?
clavicular fracture (acute)
when someone falls, they put out their hand to protect their face
the force of the fall is transmitted up to the arm and to the clavicle
What is the difference between a ligament and a tendon?
a ligament connects a bone to another bone
a tendon connects a muscle to a bone
What is impingement?
a muscle or tendon is squeezed by the structures surrounding it
What may happen if a clavicular fracture is displaced or in lots of pieces?
a displaced fracture can stretch the skin
a fracture in lots of pieces can present a risk to the subclavian vessels
What injury is shown in the X-ray?
What causes this?
AC (acromioclavicular) joint disrupture
the AC joint springs open when the ligaments holding the acromion to the clavicle become torn or ruptured
How can AC joint disrupture affect the skin?
the skin may be stretched, which can lead to skin necrosis
What injury is shown in the picture?
What causes this?
Winging of the scapula
it is caused by injury to the long thoracic nerve, which innervates serratus anterior
serratus anterior becomes paralysed
How does serratus anterior control the position of the scapula?
How is this disrupted in winging of the scapula?
it keeps the scapula flat against the chest wall as it inserts on the ribs and the medial border of the scapula
the medial border of the scapula pulls away from the posterior thoracic wall
What are the 3 main categories that can cause winging of the scapula?
- penetrating injuries of the chest and axilla
- iatrogenic e.g. during chest drain or breast surgery
- neuritis
What injury is shown?
What significant feature can be identified when looking at the patient and why?
anterior dislocation
the acromion is prominent on the dislocated side
the humeral head comes to lie more underneath the coracoid process and is no longer in contact with the glenoid cavity
What nerve is vulnerable to damage in an anterior dislocation?
the axillary nerve
it runs close to the surgical neck of the humerus
damage to the axillary nerve leads to an impaired function of deltoid
What type of dislocation is this?
anterior dislocation
What sign should be looked for when trying to identify a posterior dislocation?
“lightbulb sign”
the asymmetry of the humeral head is lost and it looks more rounded and symmetrical
What type of dislocation is shown?
posterior dislocation
this is very rare and easily missed
What injury is shown here?
who is most at risk?
Surgical neck fracture
the elderly are most at risk
What is meant by the axillary nerve being a mixed nerve?
it contains sensory and motor fibres
the motor fibres innervate deltoid and teres minor
the sensory fibres innervate the skin in the C5 dermatome
How can axillary nerve injury be assessed?
the skin in the C5 dermatome region (upper arm) is touched on BOTH sides
The patient is asked if they can feel the touch, and whether the injured side feels different
How is the deltoid muscle affected in axillary nerve injury?
wasting/shrinking of the deltoid muscle occurs - deltoid atrophy
this occurs as the deltoid can no longer be used when the axillary nerve is injured
What tendon is most commonly injured in a rotator cuff injury?
What does injury to the rotator cuff tendons lead to?
the supraspinatous tendon
injury leads to pain, instability and weakness
