Deltoid + Teres Major

Question 1

Give the Origin, Insertion, Innervation, Action, and Test of:

Teres Major

Answer 1

Origin:
Posterior surface of inferior angle of scapula (inferolateral third of scapula)

Insertion:
Medial lip of Intertubercular groove of humerus

Innervation:
Lower Subscapular Nerve (C6)

Action:

• Adducts + medially rotates arm
• Helps to extend arm from a flexed position
• Helps to stabilise humeral head in Glenoid cavity.

Test:
Ask patient to adduct and abducted arm against examiner resistance. If acting normally, can be visible + palpable on posterior axillary fold.

Question 2

Give the Origin, Insertion, Innervation, Action, and Test of:

Deltoid

Answer 2

Origin:
Lateral 1/3 of clavicle, Acromion, spine of scapula

Insertion:
Deltoid tuberosity of humerus

Innervation:
Axillary Nerve (C5,6)

Action:

• Clavicular (anterior) part - Assists pec. Major to flex and medially rotates arm.
• Acromial (middle) part - Abducts arm over 15 degrees and acts as a shunt muscle to prevent inferior displacement of humerus when carrying heavy load.
• Spinal (posterior) part - Assists latissimus Dorsi to extend arm. Also helps to laterally rotate arm.

Test:
Ask patient to abduct arm over 15 degrees against examiner resistance. If acting normally, muscle can be seen and palpated.