Upper Limb I - EASY

Muscles of the Upper Limb

• Upper limb includes the shoulder, axilla, arm, forearm, and hand.
• The pectoral region muscles and superficial/intermediate back muscles relate to upper limb movement, and are considered in this summary.
• The deep muscles of the back relate to vertebral column movements and are covered elsewhere.

Fascia of the Upper Limb

• Deep fascia of the pectoral region is known as pectoral fascia and blends with the anterior abdominal wall fascia inferiorly.
• The pectoral fascia continues as the axillary fascia, forming the axilla's inferior wall.
• Clavipectoral fascia covers the pectoralis minor, attaches to the clavicle superiorly, and joins the axillary fascia laterally.
• The deep fascia of the arm and forearm are called brachial fascia and antebrachial fascia respectively.
• The antebrachial fascia thickens distally at the ulna and radius ends.
• Anterior and posterior parts of the wrist have thickenings called the flexor retinaculum and the extensor retinaculum respectively.
• Retinacula are continuous with the hand's fascia.
• The palmar aponeurosis is the thickened central part of the palmar fascia of the hand.

Muscles of the Pectoral Region

• The region presents four muslces: Pectoralis major, Pectoralis minor, Subclavius, Serratus anterior.
• When the study guide refers to 'examining muscles', origin, insertation, innervation and function are considered, respectively.

Pectoralis Major

• Forms the anterior axillary fold.
• Clavicular head originates from medial clavicle half and sternocostal head originates from ribs 2-6.
• It inserts onto the lateral lip of the intertubercular groove.
• Innervated by lateral and medial pectoral nerves from lateral and medial cords respectively.
• It adducts and medially rotates the arm; the clavicular portion assists with flexion and being the most powerful flexor of the arm.

Pectoralis Minor

• Originates from ribs 3-5.
• Distal Insertion is the coracoid process.
• Innervated by lateral and medial pectoral nerves from lateral and medial cords respectively.
• Stabilizes the scapula by pulling it inferiorly and anteriorly.

Subclavius

• Originates from the first rib.
• Inserts on the middle part of the clavicle.
• Nerve to subclavius muscle (from the superior trunk) provides innervation.
• Stabilizes the clavicle during shoulder movements.

Serratus Anterior

• Originates from lateral parts of the first 8 ribs.
• Inserts on the anterior surface of the medial border of the scapula.
• Innervated by the long thoracic nerve (from the roots of the brachial plexus).
• Protracts the scapula and fixes it against the thoracic wall.
• The inferior fibers elevates the glenoid cavity
• Abduction above 90 degrees are possible

Clinical paralysis of the Serratus Anterior

• Injury to the long thoracic nerve during surgery of the axillary lymph nodes, or direct trauma may result in paralysis.
• Patients are unable to abduct the arm above 90 degrees.
• The medial border of the scapula moves laterally and posteriorly away from the chest wall, and is called "winged scapula" when extending the arm and pushing against a wall,

Superficial and Intermediate Layers of the Back Muscles

• Muscles of the superficial and intermediate back are classified as superficial posterior thoacoappendicular muscles, deep posterior thoracoapendicular, and scapulohumeral muscles.

Trapezius

• It originates from the superior nuchal line, external occipital protuberance, spinous processes of C7 to T12.
• Lateral Insertion is the clavicle 1/3 (sup), acromion, base of scapular spine.
• Accessory nerve (CN XI) and ventral rami of C3 and C4 provide innervation.
• Superior fibers elevate, middle fibers retract, and inferior fibers depress the scapula.
• Superior and inferior fibers perform superior rotation during abduction above 90 degrees.

Spinal Accessory Nerve Clinical Injuries

• Injury to the spinal root of the accessory nerve will cause paralysis of the SCM,.
• Paralysis of the SCM will result in weakness in turning the head to the opposite side against resistance.
• Paralysis of the trapezius muscle means patients are unable to raise the shoulder and prouce weakness in abducting the arm above 90 degrees.

Latissimus Dorsi

• Originates from the spinous processes of the inferior six thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3-4 ribs.
• Inserts onto the intertubercular groove.
• Thoracodorsal nerve (branch of the posterior cord) provides innervation.
• It extends, adducts, and medially rotates the humerus, and is known climbing muscle).

Thoracodorsal Nerve Clinical Points

• Damage to thoracodorsal nerve during surgery or after direct trauma may occur.
• Inability to raise the trunk when climbing results from dysfunction of the latissimus dorsi muscle.

Levator Scapula

• Transverse processes of the first 3-4 vertebrae provides the origin.
• Distal Insertation is superior part of the medial border of scapula.
• Dorsal scapular nerve provides innervation.
• It elevates the scapula and tilts the glenoid cavity inferiorly.

Rhomboid Major and Minor

• Minor: Nuchal ligament and spinous processes of C7 and T1 vertebrae
• Major: Spinous processes of T2-T5 vertebrae provide the origin
• Distal Insertation is the Medial border of the scapula.
• Dorsal scapular nerve provides innervation.
• Acts to Pull the scapula medially and rotates it to depress the the glenoid cavity.
  • The serratus anterior is assisted in fixing the scapula against the thorax.

Deltoid Muscle

• Lateral Origin is third of clavicle, acromion and spine of scapula.
• Deltoid tuberosity on the anterolateral surface of the humerus provides the insertion
• Axillary nerve (terminal branch of the posterior cord) provides innervation
• Anterior fibers flex and medially rotate the arm.
  • Middle fibers abduct the arm above 15 degrees, up to 90 degrees.
  • Posterior fibers extend and laterally rotate the arm.

Axillary Nerve Clinical Injuries

• Axillary nerve may be damaged following the fracture of the proximal end and surgical neck of the humerus, as well as dislocation of the shoulder joint
• In cases of denervation where the deltoid muscle undergoes atrophy and its rounded contour of the shoulder disappears it can be used for diagnosis
• Anaesthesia (loss of sensation) on a small area around the upper lateral part of the arm usually indicates a problem
• Deltoid muscle is a common site for intramuscular injections

Teres Major Muscle

• Forms the posterior axillary fold.
• Originates from the dorsal surface of the inferior angle of the scapula.
• Inserts onto the medial lip of the intertubercular groove.
• Subscapular nerve (from the posterior cord) provides innervation.
• Adduction and medial rotation of the arm result from usage.

Rotator Cuff muscles

• These muscles include teres minor, supraspinatus, infraspinatus, and subscapularis.
• Holds head of humerus in glenoid cavity
• Except for supraspinatus, all are rotators of the humerus.

Teres Minor

• It originates from the superior part of the dorsal surface of the lateral border of the scapula.
• Greater tubercule of humerus (lower part) is insertion.
• The axillary nerve (terminal branch of the posterior cord) provides innervation.
• The action is laterally rotating the humerus.

Supraspinatus

• Its origin is the medial part of the supraspinous fossa of scapula.
• Greater tubercule of humerus (upper part) insertion
• Suprascapular nerve (from the superior trunk) provides innervation
• The Abduction of the humerus (starts up to 15 degrees) is the action

Infraspinatus

• The entire infraspinous fossa provides the origin
• Greater tubercule (middle part) is the destination.
• Suprascapular nerve (from the superior trunk) innervates this muscle.
• Lateral rotation of the humerus

Subscapularis

• Subscapular fossa origin.
• Lesser tubercule is insertion
• Subscapular nerve (from posterior cord) innervates
• Medial rotation of the humerus

Rotator cuff injuries

• Injury often results from a fall on the outstretched hand with the arm abducted which manifests as Aching pain.
• Tenderness around the greater tubercle with passive abduction of the arm about 45 degrees is a clue
• Tears of the tendons may be seen in shoulder dislocations.
• Tears of the tendons cause a sharp pain in the anterosuperior part of the shoulder.

Muscles of the Arm

• There are four muscles in the arm (brachium).
• Three are in the anterior compartment consisting of Biceps brachii, brachialis and coracobrachialis, they are flexors
• One is in the posterior compartment (Triceps brachii), it is extensor
• The anconeus muscle lies at the posterior aspect of the elbow and it is a small muscle, essentially is part of the triceps brachii muscle

Biceps Brachii

• Origin is short head: tip of coracoid process, Long head: supraglenoid tubercule
• Tuberosity of radius, deep fascia of the forearm is inseration.
• The musculocutaneous nerve (from the lateral cord) innervates
• it is the primary supinator of the forearm (powerful especially in flexion - turning a screw,

Brachialis

• Distal attachment is half of the anterior surface of the humerus.
• The process and tuberosity of the ulna (coronoid) is its target.
• Musculocutaneous nerve (lateral cord of the brachial plexus) innervates this muscle.
• Actions include Flexes forearm.

Coracobrachialis

• It originates at the tip of the coracoid process.
• The middle third of the medial surface of the body is its target.
• The musculocutaneous muscle provides innervation.
• Helps in flexion and adduction of the arm result from usage.

Musculocutaneous Nerve Clinical Facts

• Is an uncommo site due to is protected location.
• Injury causes the paralysis of biceps brachii, corachobrachialis and brachialis muscles.
• Flexion and supination of the forearm are greatly weakened but not lost.
  • This is because brachioradialis and supinator muscles are still fuctioning since both are supplied by the radial nerve
• Loss of sensation on the lateral surface of the forearm will be observed
• Lateral antebrachial cutaneous nerve (continuation of the musculocutaneous nerve) damage causes this

Triceps Brachii

• The origin of the long head is in the infraglenoid tubercule
• The Lateral Attachment is post surface of the humerus
• The Medial Connectionis the post surface of the humerus
• Proximal end of the olecranon provides its destination
• Radial nerve (from the posterior cord) innervates
• Chief action includes extension of the forearm.
  • Long head aids in extension and adduction af the arm