Shoulder Muscles Anatomy Quiz

Shoulder Muscles

• Trapezius muscle has three sections (upper, middle, lower) with separate actions

  • Upper Trapezius originates from the base of the skull and inserts on the lateral clavicle and acromion. It elevates, rotates, and extends the scapula.
  • Middle Trapezius originates from the spinous processes of the upper thoracic vertebrae and inserts onto the scapular spine, and retracts the scapula.
  • Lower Trapezius originates from the spinous processes of the lower thoracic vertebrae and inserts onto the scapular spine. It depresses and rotates the scapula, and extends the neck.

• Deltoid muscle has three sections (anterior, middle, and posterior), each responsible for different arm movements.

  • The anterior deltoid originates from the clavicle and inserts on the deltoid tuberosity, and flexes, medially rotates, and horizontally adducts the arm.
  • The middle deltoid originates from the acromion and inserts on the deltoid tuberosity, and abducts the arm.
  • The posterior deltoid originates from the scapular spine and inserts on the deltoid tuberosity, and extends, laterally rotates, and horizontally abducts the arm.

• Teres Minor originates from the middle of the lateral scapular border and inserts on the inferior facet of the greater tubercle of the humerus, laterally rotates and extends the arm.

• Teres Major originates from the inferior angle of the scapula and inserts on the medial lip of the intertubercular sulcus of the humerus, adducts and medially rotates the arm.

• Rhomboid Major originates from the spinous processes of T2-5 and inserts on the medial border of the scapula, and retracts (draws back) and elevates the scapula.

• Rhomboid Minor originates from the spinous process of C7 and T1 and inserts on the medial border of the scapula, and retracts the scapula, rotating it downward.

• Latissimus Dorsi originates from the inferior 6 thoracic vertebrae, thoracolumbar fascia, and inferior 3 and 4 ribs, and inserts on the floor of the intertubercular sulcus of the humerus, and extends, adducts (draws together), and medially rotates the arm.

• Supraspinatus originates from the supraspinous fossa and inserts on the superior facet of the greater tubercle of the humerus. It abducts the arm (moves it away from the body).

• Infraspinatus originates from the infraspinous fossa of the scapula and inserts on the middle facet of the greater tubercle of the humerus, rotates the arm laterally.

• Subscapularis originates from the subscapular fossa and inserts on the lesser tubercle of the humerus, rotates the arm medially.

• Pectoralis Major originates from the medial clavicle, sternum, and oblique aponeurosis, and inserts on the lip of the intertubercular sulcus of the humerus, adducts and medially rotates the arm.

• Pectoralis Minor originates from the 3-5 ribs and costal cartilages, and inserts on the coracoid process of the scapula, and depresses the scapula.

Arm and Forearm Muscles

• Serratus Anterior Muscle is located on the sides of the chest,

  • originates from the upper 8 or 9 ribs
  • inserts on the anterior surface of the medial border of the scapula
  • Its action is to protract the scapula (draws it forward).

• Coracobrachialis muscle lies on the medial side of the upper arm,

  • originates from the tip of the coracoid process
  • inserts on the middle third of the medial shaft of the humerus.
  • and its action is to flex and adduct the arm.

• Biceps Brachii muscle originates from two points:

  • Short head: originates from the coracoid process of the scapula,
  • long head originates from the supraglenoid tubercle of the scapula,
  • and both heads insert on the tuberosity of the radius and fascia of the forearm.
  • The biceps flexes and supinates the forearm and flexes the arm at the elbow.

• Brachialis muscle is located on the front of the humerus,

  • originates from the distal half of the anterior surface of the humerus.
  • inserts on the coronoid process of the ulna and tuberosity of the ulna.
  • Its action is to flex the forearm at the elbow in all positions, including pronation.

• Triceps Brachii muscle has three heads and is the primary extensor of the forearm.

  • Long head: originates from the infraglenoid tubercle of the scapula,
  • Lateral head: originates from the posterior surface of the humerus, superior to the radial groove,
  • Medial head: originates from the posterior surface of the humerus, inferior to the radial groove.
  • All three heads insert onto the olecranon process of the ulna and the fascia of the forearm.

• Anconeus muscle on the back of the elbow,

  • originates from the lateral epicondyle of the humerus.
  • inserts on the lateral part of the olecranon process of the ulna and the posterior surface of the ulna.
  • It acts to extend the forearm.