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Upper Limb Anatomy - Exam Answers

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Q1. Attachments of Rotator Cuff Muscles (3M)

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Q2. Attachments, Actions and Nerve Supply of Deltoid (3M)

• Origin (U-shaped):
  • Lateral 1/3 of clavicle (anterior part)
  • Acromion (middle part)
  • Spine of scapula (posterior part)
• Insertion: Deltoid tuberosity of the humerus (V-shaped impression on lateral shaft)

• Anterior fibres: Flexion and medial rotation of arm
• Middle fibres: Abduction of arm (primary abductor after supraspinatus initiates 0-15°)
• Posterior fibres: Extension and lateral rotation of arm

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Q3. Structures Under Cover of Deltoid Muscle

1. Shoulder joint (glenohumeral joint)
2. Subacromial (subdeltoid) bursa
3. Rotator cuff tendons (supraspinatus, infraspinatus, teres minor, subscapularis)
4. Tendon of long head of biceps brachii
5. Axillary nerve and posterior circumflex humeral vessels (passing through quadrangular space)
6. Greater and lesser tubercles of humerus
7. Intertubercular sulcus (bicipital groove)

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Q4. Attachment of Pectoralis Major Muscle (2M)

• Clavicular head: Medial half/anterior surface of clavicle
• Sternocostal head: Anterior surface of sternum + costal cartilages of ribs 1-6
• Small contribution from the aponeurosis of external oblique

• Lateral lip of intertubercular sulcus (bicipital groove) of humerus
• The tendon is folded on itself - clavicular fibres insert lower, sternocostal fibres insert higher (creating a twist)

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Q5. Attachments, Actions and Nerve Supply of Serratus Anterior (4M)

• Origin: Outer surfaces and superior borders of upper 8-9 ribs (by digitations)
• Insertion: Anterior (costal) surface of the medial border of scapula (the entire medial border and inferior angle)

1. Protracts scapula (pulls it forward around the thorax - essential for pushing/punching) - hence called "boxer's muscle"
2. Rotates the scapula so the glenoid faces superiorly - essential for raising arm above 90° (works with trapezius)
3. Holds the medial border of scapula against the thoracic wall

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Q6. Boundaries and Contents of Carpal Tunnel + Carpal Tunnel Syndrome

• Floor (posteriorly): Carpal bones (concave arch of carpus)
• Roof (anteriorly): Flexor retinaculum (transverse carpal ligament) - stretches between pisiform & hook of hamate (medially) and scaphoid tubercle & trapezium (laterally)

1. Median nerve
2. Flexor pollicis longus tendon (1)
3. Flexor digitorum superficialis tendons (4)
4. Flexor digitorum profundus tendons (4)

• Compression of the median nerve within the carpal tunnel
• Causes: tenosynovitis, pregnancy, hypothyroidism, rheumatoid arthritis, acromegaly
• Symptoms: Pain and tingling in lateral 3½ fingers, thenar wasting, weak opposition of thumb
• Positive Tinel's sign (tapping over wrist reproduces symptoms) and Phalen's test (wrist flexion for 60 sec reproduces symptoms)

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Q7. Nerve Supply and Actions of Interossei of Hand

• Nerve: Deep branch of ulnar nerve (C8, T1)
• Action: Abduction of fingers (DAB - Dorsal ABduct), also flex MCP joints and extend IP joints

• Nerve: Deep branch of ulnar nerve (C8, T1)
• Action: Adduction of fingers (PAD - Palmar ADduct), also flex MCP joints and extend IP joints

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Q8. Diagram and Explanation of Brachial Plexus (5M)

• Superior trunk: C5 + C6
• Middle trunk: C7 alone
• Inferior trunk: C8 + T1

• Lateral cord: Anterior divisions of superior + middle trunks
• Medial cord: Anterior division of inferior trunk
• Posterior cord: All 3 posterior divisions

• Musculocutaneous nerve (C5,6,7) - from lateral cord
• Ulnar nerve (C7,8,T1) - from medial cord
• Radial nerve (C5,6,7,8,T1) - from posterior cord
• Axillary nerve (C5,6) - from posterior cord
• Median nerve (C6,7,8,T1) - from both lateral AND medial cords

• Dorsal scapular nerve (C5)
• Long thoracic nerve (C5,6,7)
• Suprascapular nerve (C5,6) from superior trunk
• Nerve to subclavius (C5,6) from superior trunk

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Q9. Anatomical Basis of Deformity in Erb's Paralysis

• Deltoid (axillary nerve) - no abduction
• Biceps brachii (musculocutaneous) - no flexion, no supination
• Brachialis (musculocutaneous) - no flexion
• Supraspinatus/infraspinatus (suprascapular nerve) - no abduction/lateral rotation
• Subscapularis, teres major - unopposed, cause medial rotation

• Adduction (deltoid paralyzed, pectorals intact)
• Medial rotation (lateral rotators paralyzed, medial rotators intact)
• Extension at elbow (biceps/brachialis paralyzed)
• Pronation (supinator paralyzed, pronators intact)
• Hand/wrist relatively spared

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Q10. Pronation and Supination (2M)

• Muscles: Pronator teres (C6,7 - median nerve) and Pronator quadratus (C8,T1 - anterior interosseous nerve)
• Mechanism: Radius rotates over ulna, crossing it

• Muscles: Supinator (C6 - deep branch of radial nerve/posterior interosseous nerve) and Biceps brachii (C5,6 - musculocutaneous nerve)
• Biceps is the most powerful supinator, especially when elbow is flexed
• Mechanism: Radius uncrosses to lie parallel to ulna

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Q11. Median Nerve in Hand and Forearm (4M)

• Enters between the two heads of pronator teres
• Runs between FDS (superficially) and FDP (deeply)
• Gives off the anterior interosseous nerve (supplies FPL, lateral half of FDP, pronator quadratus)
• Enters hand through carpal tunnel

• All flexors EXCEPT FCU and medial half of FDP (those are ulnar)
• Pronator teres, FCR, Palmaris longus, FDS, FPL, lateral FDP, pronator quadratus

• Recurrent (thenar) branch: Supplies 3 thenar muscles - Abductor pollicis brevis, Flexor pollicis brevis (superficial head), Opponens pollicis
• Digital branches: 1st and 2nd lumbricals
• Sensory: Lateral 3½ fingers (palmar surface) + dorsal tips of same fingers

• Loss of opposition and abduction of thumb
• Thenar wasting
• Loss of sensation in lateral 3½ fingers

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Q12. Musculocutaneous Nerve (3M)

• Pierces coracobrachialis muscle
• Passes between biceps brachii (anteriorly) and brachialis (posteriorly)
• Exits lateral to biceps tendon at elbow as the lateral cutaneous nerve of the forearm

1. Coracobrachialis (C6, C7)
2. Biceps brachii (C5, C6) - flexion and supination
3. Brachialis (C5, C6) - main flexor of the elbow

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Q13. Origin, Insertion and Distribution of Radial Nerve

• Enters arm posterior to brachial artery
• Winds in the radial groove (spiral groove) of humerus with profunda brachii artery
• Passes through lateral intermuscular septum to enter anterior compartment
• Enters cubital fossa between brachialis and brachioradialis

• In arm: Triceps brachii, brachioradialis, ECRL, part of brachialis
• In forearm (via deep branch / posterior interosseous nerve): ECRB, supinator, EDC, EDM, ECU, APL, EPL, EPB, EIP
• Superficial branch (sensory): Dorsum of lateral 3½ fingers (proximal phalanges only)

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Q14. Root Value, Muscles Supplied and Clinical Anatomy of Radial Nerve

1. Injury in axilla (Saturday night palsy, crutch palsy): All muscles paralyzed - loss of triceps + wrist/finger extensors. Sensory loss over posterior arm, forearm, dorsum of hand.
2. Injury in radial groove (midshaft humerus fracture): Triceps spared (branch arises before the groove), but wrist drop (loss of wrist extensors), loss of supination. Wrist drop is the classic sign.
3. Injury at lateral epicondyle / posterior interosseous nerve: Finger drop without wrist drop (ECRL spared). No sensory loss (pure motor).

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Q15. Parts, Course and Branches of Axillary Artery (3M)

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Q16. Cubital Fossa (7M)

• Superiorly (base): Imaginary horizontal line between medial and lateral epicondyles of humerus
• Medially: Pronator teres (medial epicondyle origin)
• Laterally: Brachioradialis (lateral supraepicondylar ridge)
• Floor: Brachialis muscle (mainly) and supinator
• Roof: Deep fascia + skin, reinforced by bicipital aponeurosis

1. Radial nerve - under brachioradialis lip, divides into superficial and deep branches (not strictly "inside")
2. Tendon of biceps brachii - central, inserts into radial tuberosity
3. Brachial artery - bifurcates into radial and ulnar arteries at the apex
4. Median nerve - most medial, exits by passing between heads of pronator teres

• Site for venepuncture (median cubital vein in roof)
• Brachial artery palpation / blood pressure measurement
• Site for elbow joint aspiration

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Q17. Axilla - Boundaries, Contents and Applied Anatomy (3M)

1. Axillary artery (and its 6 branches)
2. Axillary vein
3. Brachial plexus (cords and branches)
4. Axillary lymph nodes (5 groups: anterior/pectoral, posterior/subscapular, lateral, central, apical)
5. Long thoracic nerve (on medial wall)
6. Intercostobrachial nerve
7. Axillary fat and loose connective tissue

• Axillary lymph nodes are surgically important in breast cancer - they receive 75% of breast lymph drainage. Axillary clearance is part of breast cancer surgery; it risks damage to the long thoracic nerve (winged scapula) and thoracodorsal nerve (loss of latissimus dorsi)
• Crutch palsy (radial nerve compression in axilla) - wrist drop
• Brachial plexus injuries - occur at inlet of axilla
• Axillary vein thrombosis - can result from hyperabduction

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All answers based on Gray's Anatomy for Students (Elsevier). Good luck with your exam!All 17 questions are covered above with exam-ready answers. Here is a quick orientation to help you use the notes:

• Q16 (Cubital fossa - 7M): Memorize boundaries, contents in order (lateral to medial), and the mnemonic "Really Need Beer More"
• Q8 (Brachial plexus - 5M): Learn the diagram - Roots (C5-T1) → Trunks (Superior/Middle/Inferior) → Divisions → Cords (Lateral/Medial/Posterior) → Terminal nerves (M.U.R.A.M.)
• Q5 (Serratus anterior - 4M): Origin on ribs, insertion on medial border of scapula, long thoracic nerve C5,6,7, winged scapula
• Q11 (Median nerve - 4M): Two-compartment answer - forearm muscles + hand muscles (LOAF: Lumbricals 1&2, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis)

• Rotator cuff: SITS
• Cubital fossa contents: Really Need Beer More (Radial, biceps tendon, Brachial artery, Median nerve - lateral to medial)
• Interossei: PAD (Palmar = ADduct) and DAB (Dorsal = ABduct)
• Brachial plexus terminal nerves: M.U.R.A.M. (Musculocutaneous, Ulnar, Radial, Axillary, Median)