Session 1A - The Pectoral Girdle, Shoulder and Axilla Flashcards
What is the most commonly fractured bone?
Clavicle
What does the clavicle articulate with?
The manubrium of the sternum at its proximal (medial) end at the sternoclavicular joint.
And with the acromion of the scapula at its distal (lateral) end at the acromioclavicular joint.
What is the ridge on the posterior surface of the scapula?
The spine - lateral end extends to form the acromion
What does the acromion articulate with?
The clavicle at the acromioclavicular joint
- translates to highest point of shoulder
Where is the coracoid process?
Lies inferior too the acromion on the anterior surface of the scapula
- site of attachment for several muscles
- beak like appearance
Where is the glenoid fossa?
Shallow fossa on the Lateral aspect of the scapula
- articulates with prox. Humerus to form glenohumeral joint = shoulder joint
- poor fit
Why is the glenoid fossa a poor fit for the humerus?
increase range movement - not stability
What is inferior and superior to the glenoid fossa?
supraglenoid tubercle
infraglenoid tubercle
muscle att. Sites
What is the humerus?
Long bone of the arm
What is the proximal humerus made up of?
- head art. Glenoid fossa of scapula
- Distal to head - anatomical neck
- Lateral - greater tubercle
- Anterior/smaller - lesser tubercle
- tubercles are sites for muscle att.
What else is the prox. Humerus made up of that is distal to the tubercles?
Surgical neck
- when the bone narrows and becomes continuous with shaft
- upper Lateral aspect is the deltoid tuberosity
- site att. For deltoid muscle
Why is the surgical neck clinically important?
Commonly fractured - especially in elderly as a result of a fall
What runs close to the surgical neck of the prox. Humerus?
Axillary nerve - can be injured by fractures of surgical neck or dislocation of humeral head
What is another key landmark of the humerus?
Radial or spiral groove which marks the path of the radial nerve over posterior aspect of humeral shaft
Nerve Can be injured in midshaft humeral fractures
What are the movements of the pectoral girdle?
protraction - extends UL
retraction - squaring
elevation - shrug
depresion - lower
rotation - raise arm
What are muscles of the anterior pectoral girdle?
Anterior pectoral girdle muscles:
pectoralis major
pectoralis minor
serratus anterior (protracts scapula)
What are the posterior muscles of the pectoral girdle?
Large, flat, superior:
trapezius
latissimus dorsi
Three smaller, deeper muscles:
levator scapulae - elevates
rhomboid major - retracts
rhomboid minor - retracts
What are the large flat superior muscles of the posterior pectoral girdle like?
- Both attach to vertebral column
- trapezius also attaches to the skull too
- Lattisimus dorsi only attaches to the Anterior aspect of proximal humerus NOT the SCAPULA so it only moves the shoulder joint
Where do the smaller deeper muscles of the posterior pectoral girdle attach to?
attach to medial border of scapula and v.c.
Where do the smaller deeper muscles of the posterior pectoral girdle attach to?
attach to medial border of scapula and v.c.
What are the movements of the trapezius and the latissimus dorsi?
T- Rotation
L.D - extends, adducts and medially rotates the humerus
What is an origin and insertion point?
Origin - att. to fixed/stable bone
insertion - att. to bone that moves upon contraction
What is the origin for the muscles of the posterior pectoral girdle?
Trapezius - skull, cervical and thoracic vertebrae
Latissimus dorsi - lower thoracic vertebrae
Levator scapulae - upper cervical vertebrae
Rhomboid minor - C7 and T1 vertebrae
Rhomboid major - thoracic vertebrae
What is the insertion for the muscles of the posterior pectoral girdle?
T - clavicle and scapula (spine and acromion)
L.d - humerus - proximal and anterior
Levator scapulae - scapula medial border
Rhomboid minor - scapula medial border
Rhomboid major - scapula medial border
What are the muscles of the posterior pectoral girdle innervated by?
brachial plexus - UL
Trapezius - 11th CN - accesssory NOT BP
Latissimus dorsi - b. PL - thoracodorsal nerve
What are the movements of the glenohumeral joint?
Flex
ext
abd
add
internal (med) rotation
external (lat) rotation
circumduction
What type of joint is the shoulder joint?
Synovial ball and socket joint
Why is the shoulder joint commonly dislocated?
why? poor fit between glenoid fossa of scapula and head of humerus - allows extensive mobility - so less stable
Which muscles attach the scapula to the humerus?
- also move and stabilise shoulder joint
- except deltoid they all lie deep to the posterior pectoral girdle muscles
Deltoid
supraspinatus
infraspinatus
subscapularis
teres minor
teres major
Which muscles make up the rotator cuff?
supraspinatus
infraspinatus
subscapularis
teres minor
Which muscles make up the rotator cuff?
supraspinatus
infraspinatus
subscapularis
teres minor
Where does the deltoid lie?
Location - lateral aspect of shoulder
inserts on humerus at deltoid tuberosity
att. Humerus to lat. clavicle and spine of scapula
What does the deltoid move?
abductor of shoulder joint
cannot innate abd - another muscle initiates first 15.
flex and ext shoulder by anterior + posterior fibres
What is the innervation of the deltoid muscle?
innervation - brachial pl - Axillary nerve
CR - injury to Axillary nerve - atrophy, weakness of deltoid
Where is the location of the teres major?
- arises from posterior aspect of scapula
- tendon slots under humerus, inserts onto anterior aspect of humerus
- influences action of internal rotator and adductor of shoulder joint
What do rotator cuff muscles all share?
Short muscles attach the scapula to tubercles of the humerus
Where do the rotator cuff muscles originate?
Supraspinatus, infraspinatus and teres minor - posterior surface of scapula
- insert onto greater tubercle
- Tendons fuse with fibrous capsule that surrounds the shoulder joint.
What is the clinical relevance of the Supraspinatus muscle?
- travels from Supraspinous fossa to greater tubercle under the acromion
- tendon can become inflamed and pinched between acromion and humerus - when shoulder moves
= impingement - common cause of shoulder pain
What is the quadrilateral space?
- square shape bounded by teres minor above, teres major below, long head of triceps medially and surgical neck of humerus laterally
- Axillary nerve travels through here to enter posterior scapula region and Innervstes deltoid and teres minor
Where does the subscapularis originate?
Anterior surface of scapula and inserts onto lesser tubercle of humerus
What is stability like at the shoulder joint?
Poor fit of surfaces - extensive range of movement - less stability
Rotator cuff muscles - provide stability
What facilitates extensive range of movement at shoulder joint?
Loose joint capsule
How do the four rotator cuff muscles provide vital stability?
Contraction of them holds head of humerus in the glenoid fossa
- tendons fuse with the capsule of the shoulder joint
What happens when rotator cuff muscles and tendons are injured?
Inflamed or degenerate
- pain, impaired movement, compromised stability
What other structures contribute to the stability of the shoulder?
- rim of fibre cartilage around margin of the glenoid fossa - glenoid labrum - deepens shallow fossa - aids stability
- capsule reinforced by ligaments
- tendon of biceps brachii - in the anterior arm - also reinforces joint
What is the axilla?
Term for armpit
What are the six boundaries around the axilla?
- anterior wall - pectoralis major and minor
- p wall - subscapularis, teres major and Latissimus d
- L wall - proximal humerus
- Medial wall - serratus anterior and thoracic wall
- apex - first rib, clavicle and scapula - passage between neck and axilla
- Base - Skin and fascia between thoracic wall and arm (skin of armpit)
What does the axilla contain?
Fat and:
- lymph nodes - drain upper limb, thorax, breast and abdominal wall - up to umbilicus
- Axillary artery - major artery of UL
- Axillary vein - major vein draining UL
- brachial plexus - plexus of nerves that innervate the UL
What are the five groups of lymph nodes in the axilla?
- in apex - apical nodes - receive lymph from all other lymph nodes in axilla
Where is the Axillary artery from?
- continuation for subclavian artery (lateral)
- from 1st rib, under clavicle to axilla
- Becomes Axillary artery after it passes over lateral border of first rib
What does the Axillary artery give rise to?
continues to the arm as the brachial artery - as it crosses inferior border of teres major
Where is the Axillary vein from?
- Continuous with Subclavian vein
- formed by unison of brachial veins with basilic vein
- Lateral border of first rib the Axillary vein becomes the subclavian vein
What course does the Axillary vein take?
travels alongside Axillary artery
cephalic veins also joins Axillary vein in axilla
What occurs when the shoulder dislocates?
the humeral head moves out of the glenoid fossa. Anterior dislocation, where the humeral head ends up resting anterior to the glenoid fossa, is much more common.
What is dislocation of the shoulder caused by? What confirms dislocation of the shoulder?
- often caused by blunt force trauma, such as a fall.
- X-ray imaging confirms the direction of displacement of the humeral head and whether there is an associated fracture
What nerve can be injured when the shoulder is dislocated?
Dislocation can injure the axillary nerve.
What can cause the rotator cuff to be injured?
The rotator cuff can be injured by acute trauma or by repetitive use. The tendons can also degenerate with age.
Is a rotator cuff injury painful?
Tears of the rotator cuff are usually painful at rest and on movement, and cause weakness. If the supraspinatus tendon becomes injured and inflamed it may become impinged between the acromion and the humeral head, as the space here is small.
What part of abduction is painful in a rotator cuff injury?
The first part of abduction is not painful, but between 60˚– 120˚ of abduction, the inflamed tendon is compressed against the acromion, and this is when patients experience pain. An inflamed tendon may ultimately rupture.
What is Axillary lymph node metastasis?
Because lymph from the breast drains to the axillary lymph nodes, breast malignancy typically metastasises first to these nodes.
A malignant axillary node may be felt as a lump in the armpit and may be noticed before a mass in the breast itself.
How are Axillary lymph nodes detected and treated?
Axillary lymph nodes can be biopsied to assess whether or not breast malignancy has metastasised and can be removed as part of the patient’s treatment. Because they drain lymph from the upper limb, removal of the nodes can lead to fluid accumulation and swelling in the affected upper limb.
How are Axillary lymph nodes detected and treated?
Axillary lymph nodes can be biopsied to assess whether or not breast malignancy has metastasised and can be removed as part of the patient’s treatment. Because they drain lymph from the upper limb, removal of the nodes can lead to fluid accumulation and swelling in the affected upper limb.
What nerves are risked in Axillary lymph node metastasis?
Removing axillary lymph nodes potentially risks two nerves that are in close proximity to the axilla:
• The long thoracic nerve innervates serratus anterior and lies superficially on the surface of the muscles in the medial wall of the axilla. Injury to this nerve causes weakness or paralysis of serratus anterior.
• The thoracodorsal nerve to latissimus dorsi is also vulnerable to injury as it runs along the subscapularis muscle, which forms part of the posterior wall of the axilla.
What is a function of the long thoracic nerve?
One of the functions of this muscle is to hold the anterior border of the scapula flat against the posterior thoracic wall. If the muscle is paralysed, the anterior border lifts off the thoracic wall and the scapula appears to ‘stick out’. This is called a ‘winged scapula’.
