Anatomy - The Posterior Upper Limb Flashcards
Name the 5 superficial back muscles.
- Trapezius 2. Latissimus dorsi 3. Leavator scapuli superioris 4. Rhomboid minor 5. Rhomboid major
What is the innervation of trapezius?
Cn 11 - accessory
What is the action of trapezius?
Elevates the scapula and rotates it during abduction of the arm.
Which rhomboid muscle lies most superiorly?
Rhomboid minor lies superior to major.
Name the 4 rotator cuff muscles.
- Supraspinatus 2. Infraspinatus 3. Subscapularis 4. Teres minor
What is the function of the rotator cuff muscles?
To give the shoulder joint additional stability.
Where do the rotator cuff muscles originate from and insert?
Origin: scapula, insertion: humeral head.
Why can posterior dislocation of the shoulder result in deltoid weakness and numb skin above the deltoid tendon?
Because it can stretch the axillary nerve.
What is the insertion of deltoid?
Deltoid tuberosity of the humerus.
What is the function of deltoid?
To abduct, flex and extend the arm.
Name the 4 rotator cuff muscles.
- Supraspinatus. 2. Infraspinatus. 3. Teres minor. 4. Subscapularis.
What is the function of the rotator cuff muscles?
To stabilise the shoulder joint.
What is the action of supraspinatus?
Abduction.
What is the action of infraspinatus?
External rotation.
What is the action of teres minor?
External rotation.
What is the action of subscapularis?
Internal rotation.
What is the innervation of the deltoid muscle?
Axillary nerve.
What is the insertion of the deltoid muscle?
Deltoid tuberosity of humerus.
What is the action of deltoid?
Abduction of the arm!
What type of muscles fibres make up deltoid?
Multi-pennate fibres - these fibres are powerful.
What is the function of latissiums dorsi?
Adduction!
What is the action of triceps?
Extension of the forearm.
What is the axilla?
An area underneath the shoulder joint at the junction between the upper limb and thorax.
What structures form the apex of the axilla?
The first rib, clavicle and scapula.
What structures form the medial wall of the axilla?
Serratus anterior, ribs and intercostal spaces.
What structures form the lateral wall of the axilla?
Upper humerus, biceps brachii and coracobrachialis muscle.
What structures form the anterior wall of the axilla?
Pectoralis major and minor.
What structures form the posterior wall of the axilla?
Latissimus dorsi, teres major and subscapularis.
What structures form the base of the axilla?
Skin and deep fascia.
Name 5 things contained within the axilla.
- Fat. 2. Lymph nodes. 3. Axillary artery. 4. Axillary vein. 5. Brachial plexus.
What is the clinical relevance of a frozen shoulder?
- the tendon of supraspinatus passes through a tight gap between the humerus and acromion
- if inflamed it will be painful for the patient to raise their arm past a short distance
- if the arm is raised further there is no pain as the swollen area has passed through the gap
- it is described as the painful arch
What is the clinical relevance of axillary nerve palsy?
- axillary nerve runs along the neck of the humerus
- can be damaged by dislocation of the shoulder or fracture of the humerus neck
- paralysis of the deltoid and numbness on the lateral arm
What is the clinical relevance of radial nerve palsy?
“Saturday night palsy”
- the radial nerve runs in the spiral groove directly against the humerus
- easily damaged by fracture of the humerus of direct pressure (sleeping on it)
Which muscles are responsible for the abduction of the shoulder?
- Initiation is supraspinatus and then it is assisted by deltoid.
- Rotation of the scapula is by trapezius.
Describe the movements of the scapula and humerus during abduction of the shoulder?
- Supraspinatus initiates abduction and after 10-15 degrees it is assisted by deltoid.
- As the arm rises the humerus externally rotates to keep the articular surfaces in contact.
- At full abduction (upper limb vertically above the head) the humerus has externally rotated 90 degrees.
- For every 2 degrees of abduction at the glenohumeral joint the scapula rotates by 1 degree over the thoracic wall.
- In full abduction (upper limb vertically above the head) the scapula is rotated so that the glenoid points upwards by 60 degrees.
Which nerve supplies trapezius?
Spinal accessory nerve (cranial nerve XI)
Which nerve is damaged by a posterior dislocation of the shoulder and what sensory and motor loss is experienced?
Axillary nerve; sensory loss in skin over the insertion of deltoid muscle and paralysis of deltoid.
What structures stabilise the shoulder joint?
The rotator cuff muscles; supraspinatus, infraspinatus, teres minor and subscapularis.
Which bony parts of the shoulder girdle lie subcutaneously and can be palpated easily?
Manubrium sternum, clavicle, spine of the scapula and acromium.
Will “Saturday night palsy” result in a weakness of triceps, explain your answer?
- No.
- Saturday night palsy is loss of function of the radial nerve as it runs against the mid-shaft of the humerus in the spiral groove.
- Although the posterior compartment of the arm, which is formed by triceps, is supplied by the radial nerve the branches leave the nerve before the spiral groove.
