S7) The Shoulder Flashcards
There are two types of muscles of the shoulder. Identify and describe them
- Extrinsic muscles originate from the torso and attach to the bones of the shoulder (clavicle, scapula or humerus)
- Intrinsic muscles originate from the scapula and/or clavicle and attach to the humerus
Identify the 6 intrinsic muscles of the shoulder
- Deltoid
- Teres major
- Supraspinatus
- Infraspinatus
- Subscapularis
- Teres minor
Describe the structure and function of the deltoid muscle
- Structure: consists of anterior, middle and posterior parts
- Action: shoulder flexion (anterior fibres), shoulder extension (posterior fibres), abduction 15-90o (middle fibres)
State the origin and attachment of the deltoid muscle
- Origin: scapula and clavicle
- Attachment: deltoid tuberosity on lateral surface of the humerus
What innervates the deltoid muscle?
Axillary nerve
Describe the structure and function of the teres major muscle
- Structure: forms inferior border of the quadrangular space
- Function: adduction, medial rotation
State the origin and attachment of the teres major muscle
- Origin: posterior surface of the inferior angle of the scapula
- Attachment: intertubercular groove of the humerus
What innervates the teres major muscle?
Lower subscapular nerve
What are the rotator cuff muscles and what do they do?
- The rotator cuff muscles are a group of four muscles that originate from the scapula and attach to the humeral head
- Collectively, the resting tone of these muscles acts to ‘pull’ the humeral head into the glenoid fossa stabilising the glenohumeral joint
Identify the 4 rotator cuff muscles
State the function of supraspinatus muscle
Abducts the arm 0-15° and assists deltoid for 15-90°
State the origin and attachment of the supraspinatus muscle
- Origin: supraspinous fossa of the scapula
- Attachment: greater tubercle of the humerus
What innervates the supraspinatus muscle?
Suprascapular nerve
State the function of the infraspinatus muscle
Lateral rotation
State the origin and attachment of the infraspinatus muscle
- Origin: infraspinous fossa of the scapula
- Attachment: greater tubercle of the humerus
What innervates the infraspinatus muscle?
Suprascapular nerve
State the function of the subscapularis muscle
Medial rotation
State the origin and attachment of the subscapularis muscle
- Origin: subscapular fossa on the costal surface of the scapula
- Attachment: lesser tubercle of the humerus
What innervates the subscapularis muscle?
Upper and lower subscapular nerves
State the function of the teres minor muscle
Lateral rotation
State the origin and attachment of the teres minor muscle
- Origin: posterior surface of the scapula
- Attachment: greater tubercle of the humerus
What innervates the teres minor muscle?
Axillary nerve
Where extrinsic muscles of the shoulder found?
Extrinsic muscles of the shoulder are located in the back aka. superficial back muscles
Which two muscles are in the superficial layer of the shoulder?
- Trapezius
- Latissimus Dorsi
Describe the structure and function of the trapezius muscle
- Structure: broad, flat and triangular muscle, most superficial of all the back muscles
- Function: elevate rotates scapula during abduction (upper fibres), retract scapula (middle fibres), pull scapula inferiorly (lower fibres)
State the origin and attachment of the trapezius muscle
- Origin: skull, nuchal ligament and the spinous processes of C7-T12
- Attachment: clavicle, acromion and the scapula spine
What innervates the trapezius muscle?
Accessory nerve
Describe the function of the lattismus dorsi
- Extension
- Adduction
- Medial rotation
State the origin and attachment of the lattismus dorsi
- Origin: spinous processes of T6-T12, iliac crest, thoracolumbar fascia and the inferior three ribs
- Attachment: intertubercular sulcus of the humerus
What innervates the lattismus dorsi?
Thoracodorsal nerve
Which three muscles are in the deep layer of the shoulder?
- Levator Scapulae
- Rhomboid major
- Rhomboid minor
Describe the structure and function of the levator scapulae
- Structure: small strap-like muscle
- Function: elevates the scapula
State the origin and attachment of the levator scapulae
- Origin: transverse processes of the C1-C4 vertebrae
- Attachment: medial border of the scapula
What innervates the levator scapulae?
Dorsal scapular nerve