Extrinsic Muscles of the Shoudler Flashcards
What are the muscles of the shoulder associated with?
Movements of the upper limb
What do the muscles of the shoulder produce?
The characteristic shape of the shoulder
What can the muscles of the shoulder be divided into?
Extrinsic
Intrinsic
What are the extrinsic muscles of the shoulder?
Those that originate from the torso, and attach to the bones of the shoulder (clavicle, scapula or humerus)
What are the intrinsic muscles of the shoulder?
Those that originate form the scapula and/or clavicle, and attach to the humerus
Where are the extrinsic shoulder muscles located?
In the back
What are the extrinsic shoulder muscles organised into?
A superficial and deep layer
What are the superficial extrinsic shoulder muscles?
Trapezius
Latissimus dorsi
What is the most superficial of all the back muscles?
The trapezius
What shape is the trapezius?
Broad, flat, triangular
What do the muscles on each side of the trapezius form?
A trapezoid shape
What is the innervation of the trapezius?
Spinal accessory nerve (CN XI)
C3, C4 spinal fibres
What is the function of the spinal accessory nerve on the trapezius?
Motor functions
What is the function of the C3 and C4 spinal nerves on the trapezius?
Pain reception and proprioception
What is the arterial supply of the trapezius?
Transverse cervical artery
What is the action of the trapezius?
Descending part elevates and rotates during abduction of arm
Ascending part depresses
Middle part (or all parts together) retracts scapula
Descending and ascending parts together rotate glenoid cavity superiorly
What is the most common cause of accessory nerve damage?
Iatrogenic
What is meant by iatrogenic?
Due to a medical procedure
What medical procedure in particular can cause trauma to the accessory nerve?
Operations such as cervical lymph node biopsy or cannulation of the internal jugular vein
How is the accessory nerve tested?
Trapezius function can be assessed
How can trapezius function be assessed?
By asking the patient to shrug his/her shoulders
What are the other clinical features of accessory nerve damage?
Muscle wasting
Partial paralysis of sternocleidomastoid
Asymmetrical neckline
What happens to the fibres of the latissimus dorsi?
They converge into a tendon
What is the innervation of the latissimus dorsi?
Thoracodorsal nerve (C6-8)
What is the arterial supply of the latissimus dorsi?
Thoracodorsal artery
What is the action of the latissimus dorsi?
Extends, adducts, and medially rotates the humerus
Raises body towards arm during climbing
What are the deep extrinsic muscles of the shoulder?
The levator scapulae
Rhomboid minor
Rhomboid major
Where are the deep extrinsic muscles of the shoulder?
In the upper back, under the trapezius
What shape is the levator scapulae?
Small, strap-like
What is the innervation of the levator scapulae?
Dorsal scapular nerve (C4, C5) Cervical nerve (C3, C4)
What is the arterial supply of the levator scapulae?
Transverse cervical artery and ascending cervical artery
What is the action of the levator scapulae?
Elevates scapula and rotates its glenoid cavity inferiorly by rotating scapula
Where is the rhomboid minor situated relative to the rhomboid major?
Superiorly
What is the innervation of the rhomboid muscles?
Dorsal scapular nerve (C4, C5)
What is the action of the rhomboid muscles?
Retract scapula and rotate its glenoid cavity inferiorly
Fix scapula to thoracic wall
Draw a diagram illustrating the extrinsic muscle of the shoulder
Answer…
