Muscles of the arm and shoulder

Question 1

Deltoid muscle

Answer 1

3 parts:
-Clavicular (anterior)
-acromial (posterior) - acromion of scapula
-spinal part (posterior) - spine of scapula

3 parts converge to insertion point which is the deltoid tuberosity found on lateral surface of shaft of humerus

• innervated by axillary nerve

Question 2

Rotator cuff muscles

Answer 2

4 muscles
Posteriorly:
-Supraspinatus
-Infraspinatus
-teres minor
Anteriorly:
-Subscapularis

Originare from scapula and insert at the humerus
-Medial and lateral rotation of arm at shoulder joint.

-Supraspinatus originates at supraspinous fossa inserts at greater tubercle of humerus.
-innervated by suprascapular nerve which arises from superior trunk of brachial plexus.

-infraspinatus muscle originates from infraspinous fossa and inserts at greater tubercle of humerus.
-innervated by suprascapular nerve

-Teres minor originates from infraspinius fossa and lateral border of scapula. Inserts at greater tubercle of humerus.
- innervated by axillary nerve

-Subscapularis muscle originates from subscapular fossa and inserts at lesser tubercle of humerus
-Innervated by upper and lower subscapular nerve.

Question 3

Teres major

Answer 3

Origin - interior angle of scapula
-Inserts at the crest of the lesser tubercle of the humerus.
-Innervated by subscapular nerve

Question 4

Pectoralis major

Answer 4

Found in Pectoral region

3 parts:
-Clavicular part
-Sternocostal part
-Abdominal part

insert at the crest of the greater tubercle of the humerus

innervated by 2 nerves:
- medial and lateral pectoral nerves which are direct branches of the brachial plexus

Question 5

Muscle of the arm - Lats

Answer 5

Latissimus dorsi:
-Originates from spinous processes T7 to T12, iliac crest, thoracolumbar fascia and the ninth to twelfth ribs.
-Inserts at intertubercular sulcus of the humerus.
-Innervated by the thoracodorsal nerve.

Question 6

Muscles of the arm - Coracobrachialis

Answer 6

Coracobrachialis muscle:
-Originates from coracoid process of the scapula and inserts at anteromedial surface of the humerus.
-Innervated by the musculocutaneous nerve.

Question 7

Muscles of the arm - Biceps

Answer 7

Biceps brachii muscle:
-2 heads
- Long head originates from the supraglenoid tubercle of the scapula and short head from the coracoid process of scapula.
-Inserts at radial tuberosity
-Innervated by musculocutaneous nerve

Question 8

Muscles of the arm - triceps

Answer 8

3 heads

Long head: infraglenoid tubercle of scapula;
Lateral head: posterior surface of humerus, superior to radial groove;
Medial head: posterior surface of humerus, inferior to radial groove

Insertion
Proximal end of olecranon process of ulna and fascia of forearm

Action
Chief extensor of forearm; long head steadies head of abducted humerus

Innervation
Radial nerve (C6, C7, C8)

Arterial supply
Branches of deep brachial artery

Question 9

Muscles of the forearm (posterior)- Brachioradialis

Answer 9

• Originates from lateral supercondylar ridge of humerus and lateral intermuscular septum
  -Inserts styloid process of radius

Function:
Flexion of forearm when semi-pronated

-Only primary flexor muscle in posterior compartment.