Shoulder Flashcards
Name the 6 muscles of the scapulohumeral group (Intrinsic shoulder muscles)
Deltoid, teres major, and the four rotator cuff muscles (supraspinatus, infraspinatus, supscapularis and teres minor).
Differentiate between extrinsic and intrinsic muscles of the shoulder
Extrinsic - originate from the torso, and attach to the bones of the shoulder (clavicle, scapula or humerus).
Intrinsic – originate from the scapula and/or clavicle, and attach to the humerus.
What are the attachments of the Deltoid muscle?
Originates from the scapula and clavicle, and attaches to the deltoid tuberosity on the lateral surface of the humerus.
What nerve innervates the deltoid?
Axillary
What are the actions of the deltoid?
The anterior fibres flex the arm at the shoulder.
The posterior fibres extend the arm at the shoulder.
The middle fibres are the major abductor of the arm – it takes over from the supraspinatus, which abducts the first 15 degrees.
Attachments of teres major
Originates from the posterior surface of the inferior angle of the scapula. It attaches to the intertubecular groove of the humerus.
Innervation of teres major
Lower subscapular nerve.
Actions of teres major
Adducts at the shoulder and medially rotates the arm.
Supraspinatus - innervation & actions
Innervation: Suprascapular nerve.
Actions: Abducts the arm 0-15o, and assists deltoid for 15-90o
Infraspinatus innervation and action
Innervation: Suprascapular nerve.
Actions: Laterally rotates the arm.
Subscapularis - innervation & action
Innervation: Upper and lower subscapular nerves.
Actions: Medially rotates the arm.
Teres minor - innervation & action
Innervation: Axillary nerve.
Actions: Laterally rotates the arm.
What are the two extrinsic muscles of the shoulder?
the trapezius and latissimus dorsi.
What is the innervation of the trapezius?
Motor innervation is from the accessory nerve. It also receives proprioceptor fibres from C3 and C4 spinal nerves.
Actions of the trapezius
The upper fibres of the trapezius elevates the scapula and rotates it during abduction of the arm.
The middle fibres retract the scapula and the lower fibres pull the scapula inferiorly.
