Muscles of the Upper Limb Part 1

Question 1

What are the muscles of the chest?

Answer 1

1. Pectoralis Major
2. Pectoralis Minor
3. Serratus anterior
4. Deltoid

Question 2

Chest muscles - origin and insertion?

Answer 2

Pectoralis Major:
Origin - sternum & costal cartilages (sternal head), medial clavicle (clavicular head)
Insertion - Intertubular sulcus of the humerus

Pectoralis Minor:
Origin - 3rd-5th ribs
Insertion - Coracoid process of scapula

Serratus Anterior:
Origin - Ribs 1-8
Insertion - costal surface of the medial border of the scapula

Deltoid:
Origin - Lateral third of clavicle, acromon and spine of scaular
Insertion - Deltoid tuberosity on the lateral aspect of humerus

Question 3

Chest muscles - action and innervation?

Answer 3

Pectoralis Major: Function - Adducts and medially rotates the upper limb and draws the scapula anteroinferiorly. The clavicular head also acts individually to flex the upper limb.

Pectoralis Minor: Function - Stabilises the scapula by drawing it anteroinferiorly against the thoracic wall.

Serratus Anterior: Function - Rotates the scapula, allowing the arm to be raised over 90 degrees. It also protracts the scapula, holding it against the ribcage.

Question 4

What are the rotator cuff muscles?

Answer 4

1. Subscapularis
2. Supraspinatus
3. Infraspinatus
4. Teres Minor

Question 5

Rotator cuff muscles - origin and insertion?

Answer 5

Supraspinatus: Supraspinous fossa of scapula & inserts to greater tubercle of humerus.

Infraspinatus: Infraspinous fossa of the scapula & inserts to the greater tubercle of humerus.

Subscapularis: Subscapula fossa, on costal surface of scaula & inserts into the lesser tubercle of the humerus.

Teres Minor: Posterior surface fo scapula, adjacent to lateral border & inserts into greater tubercle of the humerus.

Question 6

Rotator cuff muscles - action and innervation?

Answer 6

Question 7

What are the muscles of the upper arm?

Answer 7

Anterior compartment (BBC):
1. Biceps brachii
2. Brachialis
3. Coracobrachialis

Posterior compartment
4. Triceps brachii

Question 7

Upper arm muscles - action and innervation?

Answer 7

Biceps brachii: Flexes arm at elbow & shoulder. Supination of forearm.
Musculocutaneous nerve.

Brachialis: Flexion at the elbow.
Musculocutaneous nerve (with contributions from radial nerve)

Coracobrachialis: Flexion of arm at the shoulder.
Musculocutaneous nerve.

Triceps: Extension of arm at the elbow.
Radial nerve.

Question 7

Upper arm muscles - origin & insertion?

Answer 7

Biceps: Long head from supraglenoid tubercle and short head from coracoid process of scapula.
Inserts radial tuberosity via bicipital aponeurosis (roof of cubital fossa).

Brachialis: Medial and lateral surfaces of humeral shaft.
Inserts ulnar tuberosity (just distal to elbow joint).

Coracobrachialis: Coracoid process of scapula.
Inserts to medial side of humeral shaft.

Triceps:
Long head - infraglenoid tubercle
Lateral head - humerus (superior to radial groove)
Medial head - humerus (inferior to radial groove)
All 3 heads converge into one tendon which inserts onto the olecranon of the ulna.