Anatomy 16 Flashcards
What is the clavicle?
Slender S shaped bone, collar bone
What does the clavicle articulate with?
Sternum medially (sternoclavicular joint)
Acromion of scapula laterally (acromioclavicular joint)
What types of joints are the sternoclavicular and acromioclavicular joint?
Synovial joints
What is the function of the clavicle?
Holds the limb away from the trunk so it can move freely
What is the scapula?
Flat bone with some bony projections, shoulder bone
What does the posterior surface of the scapula bear?
A ridge of bone called the spine which is easily palpable
What does the lateral end of the spine expand to form?
The acromion (shoulder blade)
What bones make up the pectoral girdle?
Clavicle
Scapula and attached muscles
What does the lateral aspect of the scapula contain?
Glenoid fossa - shallow fossa
What does the glenoid fossa articulate with?
Proximal humerus to form the shoulder joint
What is the name for the shoulder joint?
Glenohumeral joint
Why is the glenoid fossa a poor fit for the humerus?
It’s too shallow
What does the glenoid fossa being a poor fit for the humerus lead to?
Increases range of movement possible at the shoulder
But compromises the stability of the joint
What projections are found superior and inferior to the glenoid fossa?
Supraglenoid tubercle
Infraglenoid tubercle
What is the humerus?
Long bone of the arm
What does the head of the humerus articulate with?
Glenoid fossa
What is the name of the groove that the head of the humerus bears?
Anatomical neck
What projections of bones does the proximal humerus bear laterally?
Greater tubercle
Lesser tubercle - is a smaller anterior projection
What is the surgical neck region?
Region where the humerus bone becomes more narrow and continuous with the shaft
Why is the surgical neck region clinically important?
It is commonly fractured
The axillary nerve runs close to this region and can be injured by fractures of the surgical neck or dislocation of the humeral head
What is the deltoid tuberosity?
Slight protuberance on the upper lateral aspect of the humeral shaft - site of attachment for the deltoid muscle
What is the radial/spiral groove?
Marks the path of the radial nerve over the posterior aspect of the upper part of the humeral shaft
How can the radial nerve be injured?
Mid-shaft humeral fractures
What are the movements of the scapula?
Protraction
Retraction
Elevation
Depression
Rotation
Why is rotation of the scapula very important?
When raising the arm above the head, for every 2 degrees of abduction of the shoulder, the scapula rotates 1 degree
What determines the direction in which the scapula moves when the muscles contract?
Attachment points of the muscles
Orientation of the muscle fibres
What is the key muscle involved in protraction of the scapula?
Serratus anterior
What are the two large superficial muscles of the posterior pectoral girdle?
Trapezius
Latissimus dorsi
What does the latissimus dorsi attach to?
Anterior aspect of the proximal humerus
What are the 3 smaller, deeper muscles that attach the medial border of the scapula to the vertebral column?
Levator scapulae
Rhomboid major
Rhomboid minor
What movement does the trapezius execute?
Elevates, retracts, depresses and rotates the scapula
What movement does the latissimus dorsi execute?
Extends, adducts and medially rotates the humerus
What movement does the levator scapulae execute?
Elevates the scapula
What movement does the rhomboid major execute?
Retracts the scapula
What movement does the rhomboid minor execute?
Retracts the scapula
What are the origins of the trapezius?
Skull
Cervical and thoracic vertebrae
What are the insertions of the trapezius?
Clavicle
Scapula (spine and acromion)
What are the origins of the latissimus dorsi?
Lower thoracic vertebrae
What are the insertions of the latissimus dorsi?
Humerus - upper anterior
What are the origins of the levator scapulae?
Upper cervical vertebrae
What are the insertions of the levator scapulae?
Scapula - medial border
What are the origins of the rhomboid minor?
C7
T1
What is the insertion of the rhomboid minor?
Scapula - medial border
What is the origin of the rhomboid major?
Thoracic vertebrae
What is the insertion of the rhomboid major?
Scapula - medial border
What are the brachial plexus?
A complex network of nerves that innervate the upper limb
What is the trapezius innervated by?
CN 11 - Accessory nerve (specifically its spinal root)
What is the latissimus dorsi innervated by?
Thoracodorsal nerve - branch of the brachial plexus
What movements are possible at the shoulder joint?
Flexion
Extension
Abduction,
Adduction
Medial (internal) and lateral (external) rotation
Circumduction
What are the 6 muscles that attach the scapula to the humerus (scapulo-humeral muscles) ?
Deltoid
Supraspinatus
Infraspinatus
Subscapularis
Teres minor
Teres major
What are the rotator cuff muscles?
Supraspinatus
Infraspinatus,
Subscapularis
Teres minor
What is the deltoid?
Large muscle over the lateral aspect of the shoulder
What does the deltoid attach?
Attaches the humerus to the lateral part of the clavicle and to the spine of the scapula
What is the deltoid tuberosity?
The landmark at which the deltoid inserts onto the humerus
What do the anterior and posterior fibres of deltoid contribute to?
Flexion and extension of the shoulder
Does the deltoid initiate abduction?
No, another muscle initiates the first 20 degrees (or so) of abduction before deltoid takes over
What is the deltoid innervated by?
Axillary nerve - major branch of the brachial plexus
What can injury to the axillary nerve lead to?
Atrophy and weakness (or even paralysis) of deltoid
Where does the teres major arise from?
Posterior aspect of the scapula
What does the teres major insert onto?
Anterior aspect of the humerus
Where do the Supraspinatus, infraspinatus and teres minor originate from?
Posterior surface of the scapula
Where do the Supraspinatus, infraspinatus and teres minor insert onto?
The greater tubercle
What do the tendons of the Supraspinatus, infraspinatus and teres minor fuse with?
The fibrous capsule that surrounds the shoulder joint
What is the quadrilateral space?
Square-shaped space bounded by:
teres minor above,
teres major below,
the long head of triceps medially,
the surgical neck of the humerus laterally.
What nerve runs through the quadrilateral space?
Axillary nerve - to enter the posterior scapula region and innervate the deltoid and teres minor
What does the subscapularis originate from?
Anterior surface of the scapula
What does the subscapularis insert onto?
Lesser tubercle of the humerus
Why is the supraspinatus clinically important?
It travels under the acromion, and the tendon can become inflamed and pinched between the acromion and humerus during movements of the shoulder.
This is called impingement and the typical finding on examination of the patient is a ‘painful arc’.
What structures contribute to the stability of the shoulder?
- a rim of fibrocartilage around the margin of the glenoid fossa – the glenoid labrum – deepens the shallow fossa and aids stability
- the capsule is reinforced by ligaments
- the tendon of biceps brachii, which lies in the anterior arm, also reinforces the joint
What does intermuscular septa do?
Separates the arm into anterior and posterior compartments
What compartment of the arm does the triceps brachii lie in?
Posterior compartment
What do the muscle bellies of the triceps converge via?
A common tendon onto a single insertion point – the olecranon of the ulna
What are the names of the 3 muscle bellies/heads of the the triceps?
Long head
Lateral head
Medial head
Where does the long head of the triceps originate from?
Infraglenoid tubercle of the scapula.
It is the most medial part of triceps.
Where does the lateral head of the triceps originate from?
Posterior humerus, proximal to the radial groove
Where does the medial head of the triceps originate from?
Posterior humerus, distal to the radial groove
Which of the heads of the triceps contribute to the extension of the shoulder joint?
Long head
What are the 3 parts of the triceps innervated by?
Radial nerve - major terminal branch of the brachial plexus
Where is the radial nerve located?
It winds around the posterior aspect of the humerus in the radial (spiral) groove between the medial and lateral heads of the triceps
What is adhesive capulitis?
‘Frozen shoulder’
The main symptoms of this condition are pain and stiffness in the shoulder.
The capsule of the joint becomes inflamed, stiff and tight. Adhesions may develop.
What type of people is Adhesive capsulitis most likely sen in?
Middle-aged people, and is more common in women and people with diabetes, but the cause is not understood.
What is the cure for adhesive capulitis?
No cure, and supportive treatment with physiotherapy is the main treatment
How long does it take for adhesive capsulitis to resolve?
Up to 3 years
How can the rotator cuff be injured?
Acute trauma or repetitive use
What happens if the supraspinatus tendon becomes injured and inflamed?
May become impinged between the acromion and the humeral head, as the space here is small
What is a ‘painful arc’?
When the inflamed tendon is compressed against the acromion
What happens in the dislocation of the shoulder?
The humeral head moves out of the glenoid fossa
What type of dislocation of the shoulder is more common?
Anterior dislocation
What is anterior dislocation of the shoulder often caused by?
Blunt force trauma
What is posterior dislocation of the shoulder associated with?
Vigorous muscle contraction, such as an epileptic seizure
What can both types of shoulder dislocation injure?
The axillary nerve
What can the axillary nerve be injured by?
Fractures in the region of the surgical neck or dislocation of the shoulder joint
What do the motor fibres of the axillary nerve innervate?
Deltoid
Teres minor
What do the sensory fibres of the axillary nerve innervate?
A patch of skin over the upper lateral arm
What can injury to the axillary nerve result in?
Weakness or paralysis of deltoid
What does weakness or paralysis of the deltoid present functionally as?
Difficulty abducting the shoulder - and altered sensation or numbness over the upper lateral arm
What can cause injury to the radial nerve?
Fractures of the humeral shaft
What can injury to the radial nerve lead to?
Weakness or paralysis of the muscles that are innervated by the radial nerve ‘downstream’ of the point at which the nerve is injured
