scapulohumeral (intrinsic shoulder) muscles

Question 1

Answer 1

Deltoid

• *proximal attachment**: lateral third of clavicle; acromion and spine of scapula
• *distal attachment** : deltoid tuberosity of humerus
• *main action**: clavicular (anterior) part flexes and medially rotates shoulder joint; acromial (middle) part abducts shoulder joint; spinal (posterior) part extends and laterally rotates shoulder joint
• *innervation**: axillary nerve (C5,C6)
• three headed multipenate, fibres that insert on a tendon from multiple directions.
• clavicular (anterior), acromial (middle), spinal (posterior) parts that can act separately or as a whole. all three together contract to abduct shoulder

Question 2

Answer 2

Supraspinatus

Proximal attachment: supraspinous fossa of scapula

distal attachment: superior facet of greater tubercle of humerus

main action: initiates and assists deltoid in abduction of shoulder joint and acts with other rotator cuff muscles

innervation: supra scapular nerve ( C4, C5, C6)

-initiates and assists the deltoid in the first 15 degrees of abduction of the arm

Question 3

Answer 3

Infraspinatus

proximal attachment: infraspinous fossa of scapula

distal attachment: middle facet of greater tubercle of humorous

main action: laterally rotate shoulder joint; help hold humeral head in glenoid cavity of scapula

innervation: supra scapular nerve (C5,C6)

Question 4

Answer 4

Teres minor

proximal attachment: middle part of lateral border of scapula

distal attachment: inferior facet of greater tubercle of humerus

main action: laterally rotate shoulder joint; help hold humeral head in glenoid cavity of scapula

innervation: axillary nerve (C5, C6)

Question 5

Answer 5

Teres major

proximal attachment: inferior part of lateral border of scapula and posterior surface of inferior angle of scapula

distal attachment: inter tubercular sulcus of humerus

main action: adducts and medially rotates shoulder joint

innervation: lower sub scapular nerve (C5, C6)

Question 6

Answer 6

Subscapularis

proximal attachment: subscapular fossa (most of anterior surface of scapula)

distal attachment: lesser tubercle of humerus

main action: medially rotates and adducts shoulder joint; helps hold humeral head in glenoid cavity

innervation: upper and lower subscapular nerves (C5,C6,C7)

Question 7

rotator cuff muscles

Answer 7

supraspinatus, infraspinatus, teres minor, subscapularis

• SITS muscles
• Rotator cuff muscles because they form a musculotendinous rotator cuff around the glenohumeral joint