Muscles of Arm

Anterior Compartment

Biceps Brachii

Muscle	Origin	Insertion	Nerve Supply	Action
Biceps Brachii	Long head: §  A long tendon from supraglenoid tubercle within the shoulder joint Short head: §  A thick tendon from the tip of coracoids process of scapula	§  A strong tendon into rough part of radial tuberosity §  Bicipital apponeurosis with deep fascia of forearm	§  Musculo-cutaneous nerve	Both head: §  Strong supinator when the elbow is flexed §  Flexor of elbow Short head: §  Weak flexor of shoulder joint Long head: §  Help stabilize the head of humerus in the glenoid cavity

Coracobrachialis

Muscle	Origin	Insertion	Nerve Supply	Action
Coraco-brachialis	§  Coracoids process of scapula	§  Middle of medial border of humerus	§  Musculo-cutaneous nerve	§  Flexor of the arm §  Weak adductor of the arm

Brachialis

Muscle	Origin	Insertion	Nerve Supply	Action
Brachialis	§  Lower half of anteromedial & anterolateral surface of humerus	§  Ulna tuberosity & rough impression on the anterior surface of coronoid process of ulna	Medial part: §  Musculo-cutaneous nerve Lateral part: §  Radial nerve	§  Flexor of the elbow joint

Posterior Compartment

Triceps Brachii

Muscle	Origin	Insertion	Nerve Supply	Action
Triceps Brachii	Long head: §  Infraglenoid tubercle (extracapsular & extrasynovial) Lateral head: §  Upper third of humerus above the spiral groove Medial head: §  Posterior surface of lower half of humerus shaft below spiral groove	§  The 3 head fuse together in a common tendon & inserted into the posterior part of upper surface of olecranon process of ulna	§  Each head receives a separate branch from the radial nerve	§  It is a powerful extensor of elbow joint Long head: §  Stabilized of the shoulder joint

[Continue reading...]

Muscles of Scapular Region

Deltoid

Muscle	Origin	Insertion	Nerve Supply	Action
Deltoid	Anterior fiber: §  Lateral third of anterior border of clavicle Middle fiber: §  Lateral border of acromion process Posterior fiber §  Lower lip of the crest of the spine of scapula	§  Deltoid tuberosity of the humerus	§  Axillary nerve	Anterior fiber: §  Flexion & medial rotation of the arm Posterior fiber: §  Extension & lateral rotation of the arm Middle fiber: §  Abduction of the arm from 15 to 90 degree

Teres Major

Muscle	Origin	Insertion	Nerve Supply	Action
Teres Major	§  Lower 1/3 lateral border & inferior angle of scapula (dorsal surface)	§  Medial lip of the bicipital groove	§  Lower subscapular nerve (C5 & 6)	§  Extension, adduction & medial rotation of the arm

Rotator Cuff Muscles

Rotator Cuff Muscles

• The rotator cuff is the group of muscles and their tendons that acts to stabilize the shoulder. 
• the 4 muscles of rotator cuff are:

• Subscapularis
• Supraspinatus 
• Infraspinatus
• Teres Minor

Teres Minor

Muscle	Origin	Insertion	Nerve Supply	Action
Teres Minor	§  Upper 2/3 lateral border of scapula (dorsal surface)	§  Lower impression on the greater tuberosity	§  Axillary nerve (C5 & 6)	§  Adduction & lateral rotation of the arm §  Help to stabilize the shoulder

Subscapularis

Muscle	Origin	Insertion	Nerve Supply	Action
Subscapularis	§  Medial 2/3 of subscapular fossa	§  Lesser tuberosity of the humerus	§  Upper & lower subscapular nerve (C5 & 6)	§  Adduction & medial rotation of the arm §  Help to stabilize the shoulder

Supraspinatus

Muscle	Origin	Insertion	Nerve Supply	Action
Supraspinatus	§  Medial 2/3 of supraspinous fossa	§  Highest impression on the greater tuberosity	§  Suprascapular nerve	§  Initiate the abduction of the arm (from 0 to 15 degree) §  Help to stabilize the shoulder

Infraspinatus

Muscle	Origin	Insertion	Nerve Supply	Action
Infraspinatus	§  Medial 2/3 of infraspinous fossa	§  Middle impression on the greater tuberosity	§  Suprascapular nerve	§  Lateral rotation of the arm §  Help to stabilize the shoulder

[Continue reading...]

Muscles of Pectoral Region

Anterior Wall

Pectoralis Major

Muscle	Origin	Insertion	Nerve Supply	Action
Pectoralis Major	Clavicular head: §  Medial half of anterior border of clavicle §  Fibers pass downwards & laterally Sternocostal head: §  Half of anterior sternum §  upper 6 costal cartilage §  opponeurosis of external oblique	§  Bilaminar tendon into lateral lip of bicipital groove	§  Lateral pectoral nerves(C5, 6, 7) §  Medial pectoral nerves (C8, T1)	Both head: §  Adduct the arm & rotate it medially §  Muscle of respiration §  In climbing, draws body upwards Clavicular head: §  Flexion of the arm Sternocostal head: §  Extension of the arm

Pectoralis Minor

Muscle	Origin	Insertion	Nerve Supply	Action
Pectoralis Minor	§  3rd,  4th & 5th ribs, close to costalchondrial junction §  Fibers pass upwards & laterally	§  Medial border & upper surface of coracoids process	§  Medial pectoral nerve C8, T1	§  Draws the scapula downward & forward §  Depress shoulder §  If the shoulder is fixed, it elevates the ribs

Subclavius 

Muscle	Origin	Insertion	Nerve Supply	Action
Subclavius	§  upper surface of the 1st rib close to costal cartilage	§  Groove under surface of intermediate 3rd of clavicle	§  Nerve to subclavius C5, 6	§  Steady the clavicle in movement of shoulder girdle

Medial Wall

Seratus Anterior

Muscle	Origin	Insertion	Nerve Supply	Action
Seratus Anterior	§  8 fleshy digitations from corresponding outer surface of the upper 8 ribs §  1st digitations is from 1st & 2nd ribs	§  Ventral surface of superior & medial borders & inferior angle of scapula	§  Long thoracic nerve (nerve to seratus anterior) C5, 6, 7	§  Protect or pull the scapula forward §  Lower 5 digitations draw the lower angle of scapula forwards §  Raises the ribs in force inspiration

[Continue reading...]