Upper Limb I - MEDIUM

Upper Limb Parts

• Includes the shoulder, axilla, arm, forearm, and hand

Pectoral Region and Back Muscles

• Muscles of the pectoral region and superficial/intermediate back layers move the upper limb and is considered in upper limb anatomy.
• The deep back muscles move the vertebral column and is considered with back anatomy.

Fascia of the Upper Limb

• Pectoral fascia covers the pectoral region and blends with the anterior abdominal wall fascia inferiorly.
• Axillary fascia is continuous with the pectoral fascia, forming the axilla's inferior wall.
• Clavipectoral fascia covers pectoralis minor, attaches to the clavicle superiorly, and is continuous with the axillary fascia laterally.
• Brachial fascia is the deep fascia of the arm. Forearm deep fascia is the antebrachial fascia.
• Antebrachial fascia thickens at the distal ulna and radius, forming flexor and extensor retinacula at the wrist's anterior and posterior aspects, respectively.
• Retinacula are continuous with the fascia of the hand.
• Palmar aponeurosis is the thickened central part of the palmar fascia.

Muscles of the Pectoral Region

• There are four muscles: Pectoralis major and minor, subclavius, and serratus anterior.
• Examines origin, insertion, innervation, and function.

Pectoralis Major

• Forms the anterior axillary fold.
• Clavicular head originates from the medial half of the clavicle.
• Sternocostal head originates from ribs 2-6.
• Inserts on the lateral lip of the intertubercular groove.
• Innervated by lateral and medial pectoral nerves (from lateral and medial cords, respectively).
• Adducts and medially rotates the arm; clavicular head assists in flexion and is the most powerful arm flexor.

Pectoralis Minor

• Originates from ribs 3-5.
• Inserts on the coracoid process.
• Innervated by the lateral and medial pectoral nerves (from the 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.
• Innervated by the nerve to the subclavius muscle (from the superior trunk).
• 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 and fixes the scapula against the thoracic wall.
• Inferior fibers raise the glenoid cavity and aid abduction above 90 degrees.

Clinical Note: Serratus Anterior Paralysis

• Long thoracic nerve injury from trauma or surgery can cause serratus anterior paralysis
• Patients cannot abduct the arm above 90 degrees
• The medial scapula border moves laterally/posteriorly away from the chest wall when raising the arm, creating a "winged scapula."

Superficial and Intermediate Back Muscles

• Classified into superficial posterior thoracoappendicular, deep posterior thoracoappendicular, and scapulohumeral groups.
• Includes trapezius, latissimus dorsi, levator scapulae, rhomboid muscles, deltoid, Teres major, and four rotator cuff muscles.

Trapezius

• Originates from the superior nuchal line, external occipital protuberance, and spinous processes of C7-T12 vertebrae.
• Inserts on lateral third of the clavicle (superior), acromion and spine of scapula (middle), base of scapular spine.
• Innervated by the accessory nerve (CN XI), with branches from the ventral rami of C3 and C4.
• Superior fibers elevate the scapula, middle fibers pull it medially, and inferior fibers depress/lower the shoulder.
• Superior and inferior Trapezius fibers also work together to superiorly rotate the scapula, assisting abduction above 90 degrees.

Clinical Note: Spinal Accessory Nerve Injury

• Injury to accessory nerve's spinal root causes head turning weakness on the opposite side (paralysis of SCM).
• Patients struggle to raise their shoulder and abduct arm above 90 degrees (trapezius paralysis).

Latissimus Dorsi

• Originates from spinous processes of inferior six thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3-4 ribs.
• Inserts on the intertubercular groove.
• Thoracodorsal nerve (branch of posterior cord) innervates it.
• Extends, adducts, and medially rotates the humerus (climbing muscle).

Clinical Note: Thoracodorsal Nerve Injury

• Thoracodorsal nerve damage may occur due to trauma or surgery
• Prevents raising the trunk during climbing, because of latissimus dorsi muscle dysfunction

Levator Scapula

• Originates from transverse processes of the first 3-4 vertebrae.
• Inserts on the superior part of the scapula's medial border.
• Innervated by dorsal scapular nerve.
• Elevates the scapula and tilts the glenoid cavity inferiorly.

Rhomboid Major and Minor

• Minor originates from the nuchal ligament and spinous process of C7 and T1 vertebrae.
• Major originates from the spinous process of T2-T5 vertebrae.
• They insert on the medial border of the scapula.
• Innervated by the dorsal scapular nerve.
• Pull the scapula medially and rotate it, depressing the glenoid cavity and assisting the serratus anterior in fixing the scapula against the thorax.

Deltoid

• Originates from the lateral third of the clavicle, acromion scapula, and spine of scapula.
• Inserts on the deltoid tuberosity on the anterolateral humerus surface.
• Innervated by the axillary nerve (terminal branch of the posterior cord).
• Anterior deltoid fibers flex/medially rotate the arm and the middle deltoid fibers abduct the arm above 15 degrees (to 90 degress.)
• Posterior deltoid fibers extend/laterally rotate the deltoid.

Clinical Note: Axillary Nerve Injury

• Axillary nerve may be damaged following the fracture of the humerus, surgical neck, or dislocation of the shoulder joint.
• Denervation causes deltoid muscle atrophy; rounded shoulder contour fades.
• There is anesthesia (sensation loss) on the upper lateral arm part.* Deltoid muscle is a common site for intramuscular injection

Teres Major

• Forms posterior axillary fold.
• Originates from dorsal surface of inferior scapula angle.
• Inserts on medial lip of the intertubercular groove.
• Subscapular nerve from the posterior cord innervates.
• Adduction and medial rotation of the arm.

Rotator Cuff Muscles

• Teres minor, supraspinatus, infraspinatus, and subscapularis hold the humerus head in the glenoid cavity.
• All but supraspinatus are rotators of the humerus.

Teres Minor

• Originates from the superior part of the dorsal surface on the scapula's lateral border.
• Inserts on greater tubercle of the humerus (lower part).
• Innervated by the axillary nerve (terminal branch of the posterior cord).
• Laterally rotates the humerus.

Supraspinatus

• Originates from medial part of the supraspinous scapula fossa.
• Inserts on the greater tubercle of humerus (upper part).
• Suprascapular nerve from the superior trunk innervates it.
• Abducts humerus (starts abduction up to 15 degrees).

Infraspinatus

• Originates from the infraspinous fossa.
• Inserts on the greater tubercule (middle part).
• Suprascapular nerve (from the superior trunk) innervates.
• Lateral rotation of the humerus.

Subscapularis

• Origintes from the subscapular fossa.
• Inserts on the lesser tubercule.
• Subscapular nerve (from posterior cord) innervates.
• Medial rotation of the humerus.

Clinical Note: Rotator Cuff Injury

• Rotator cuff injury results from a fall on an abducted arm.
• Tenderness is around the greater tubercle with passive abduction of the arm about 45 degrees.
• Tendon tears may be seen in shoulder dislocations/forceful throwing (e.g., a third basemen who throws with force)
• Tendon tears cause a sharp pain for the patient, in the anterosuperior shoulder.

Muscles of the Arm

• There are four muscles in the arm (brachium).
• Three are in the anterior compartment and are flexors: Biceps brachii, brachialis, and coracobrachialis.
• One is in the posterior compartment and is an extensor: Triceps brachii.
• 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

• The short head originates from the tip of the coracoid process, with the long head originating from the supraglenoid tubercule.
• It inserts on the tuberosity of radius and deep fascia of the forearm through the bicipital aponeurosis.
• Innervated by the musculocutaneous nerve (from the lateral cord).
• A primary forearm supinator, it flexes the supinated forearm, with the long head aiding arm flexion.

Brachialis

• Originates from the distal half of the ant surface of the humerus.
• Inserts on the coronoid process and the tuberosity of the ulna.
• Innervated by the musculocutaneous nerve (from the lateral cord).
• Primary flexor of the forearm.

Coracobrachialis

• Originates from the tip of the coracoid process.
• Inserts on the middle third of the medial surface of the body of the humerus.
• Innervated by the musculocutaneous nerve.
• Helps with flexion and adduction of the arm.

Clinical Note: Musculocutaneous Nerve Injury

• Musculocutaneous nerve injury is uncommon and protected
• Paralysis of biceps brachii, corachobrachialis, and brachialis muscles occurs.
• Flexion and supination of forearm are greatly weakened but not lost.
• Loss of sensation occurs on the lateral forearm surfaces due to damage to the lateral antibrachial cutaneous nerve (continuation of the musculocutaneous nerve).
• Brachioradialis and supinator muscles are functioning (both supplied by the radial nerve).

Triceps Brachii

• Includes a long head: infraglenoid tubercule, Lateral head: post surface of the humerus, Medial head: post surface of humerus
• Proximal end of the olecranon
• innervated by the Radial nerve (from the posterior cord)
• A chief extensor of the forearm (long head aids in extension and adduction af the arm)

Anconeus

• Posterior part of the lateral epicondyle
• Lateral surface of olecranon and post surface of ulna at its superior part
• Radial nerve (from the posterior cord)
• Assist in triceps and fixes the elbow against flexion

Arm Spaces

• Two spaces defined at the upper arm.
  • Quadrangular and triangular spaces.

Quadrangular Spaces (humerotricipital space)

• Bounded by humerus laterally, long head of triceps medially, teres major inferiorly, teres minor superiorly.
• Transmits the axillary nerve,posterior circumflex humeral artery and vein.

Triangular Space (scapulotricipital space)

• Bounded by the long head of triceps laterally, teres major inferiorly,and teres minor superiorly.
• Transmits the circumflex scapular artery and vein.

Muscles of the Forearm

• Deep forearm fascia and interosseous (radius and ulna) separate forearm into anterior and posterior compartments
• Typically, anterior compartment muscles are flexors/pronators innervated by median nerve
• Typically, posterior compartment muscles are extensors/supinators innervated by radial nerve - Except brachioradialis, exception that lies in the posterior compartment but acts only as a flexor muscle.

Anterior Compartment

• Muscles are arranged in three layers.
• Originate from the medial epicondyle from a common tendon from common flexor origin.
• Tendons, that insert into bone of the hand, but mostly pass deep to the flexor retinaculum.

Superficial layer:

• Pronator teres
• Flexor carpi radialis
• Flexor carpi ulnaris
• Palmaris longus

Intermediate Layer:

• Flexor digitorum superficialis

Deep layer:

• Flexor digitorum profundus
• Flexor pollicis longus
• Pronator quadratus

Pronator Teres:

• Ulnar head-coronoid process Humeral head-common flexor origin
• Lateral surface of the radius
• Median nerve innervation
• Pronates and flexes the forearm

Flexor Carpi Radialis:

• Common flexor origin
• Base of the 2nd metacarpal bone (the tendon acts as reference to the radial artery(lateral to it))
• Median nerve
• Flexes and abducts the hand

Flexor Carpi Ulnaris:

• Common flexor tendon and upper part of posterior aspect of the ulna
• Base of the fifth metacarpal bone
• Ulnar nerve innervation
• Flexion and adduction of the hand

Palmaris Longus:

• Common flexor tendon and superior part of the post aspect
• Palmar aponeurosis (long tendon acts as a guide for the median nerve (lateral to it at the wrist))
• Median nerve innervation
• Flexes the hand and tenses the palmar aponeurosis

Flexor Digitorum Superficialis

• Common flexor tendon, coronoid process of ulna
• Around the wrist (4 tendons insert to the palmar aspects of the middle phalanges of the 2nd to 5th fingers)
• Median nerve
• Flexes the middle phalanges (action to flex the joints like metacarpphalyngeal and wrist )

Flexor digitorum profundus

• Anterior surface of ulna and interosessous membrane
• 4 tendons insert to the palmar aspect of the base of the distal phalanges of the (2nd to 5th fingers)
• Tendons pass through the tendinous openings of the flexor digitorum.
• nerve distribution:
• Medial part: Ulnar neve *,,Lateral part: Median nerve *(2 nerves distributed to the mucle)
• Flexes the distal phalanges of (2-5th fingers) (*Flexes the joint like metcarpophalyngeal and wrist joints in the action)

Flexor pollicis longus

• Anterior, upper of radius, interosseous membrane in the area
• inserts to the palmar surface (thumb).
• Median nerve action
• Flexes the thump

Pronator quadratus

• Distal area on the ant aspect
• Distal area on the ant surface of the radius
• Median nerve: innervation
• Pronates the forearm

Posterior Compartment

• Typically all muscles are inervated by the the radial never.
• Except two insertion: All pass deep to the extensor retinaculum

Superficial layer

• Brachioradials
• Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris

Deep layer

• Supinator
• Abductor pollicis longus
• Extensor pollicis longus
• Extensor pollicis brevis
• Extensor indicis

Brachioradialis

• Ridge: Lateral Supracondylar.
• End: on dist of radius (lateral exterior)
• Radial never innveration
• flexes area

Extensor Carpi Radialis Longus

• Ridge: Lateral Supracondylar
• Dorsal to two Metacrpals
• Radial nerve
• handExtention and Abduction

Extensor carpi radialis brevis

•  Extensor Common origin
  

•  Dorsel aspect of base of the 3rd metacarpal
  

•  Radial nerve
  

• Hand Extention and Abduction

Extensor digitorum

•  Common for Extensor origin
  

•   Expansions: Extensor (Digts the four Medial in infira:vide)
  

•  Radial nerve innervation
  

•    hand:the,joints metacarpophalyngea|