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FIRST YEAR MBBS - HUMAN ANATOMY

UPPER LIMB - COMPLETE ANSWERS (7 Marks Each)

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Q1. Describe the Attachments of Rotator Cuff Muscles.

The Four Rotator Cuff Muscles (Mnemonic: SITS)

Diagram: Rotator Cuff Muscles

POSTERIOR VIEW:
                    Supraspinous fossa
                         |
             Supraspinatus -----> Greater tubercle (Superior facet)
             Infraspinatus -----> Greater tubercle (Middle facet)
             Teres Minor -------> Greater tubercle (Inferior facet)

ANTERIOR VIEW:
             Subscapular fossa
                    |
             Subscapularis -----> Lesser tubercle

              [Glenoid cavity]
              Humerus head surrounded by cuff tendons
              blending with joint capsule

How they form the cuff:

• The tendons of all four muscles blend with the fibrous capsule of the shoulder joint.
• Supraspinatus: covers superior aspect of joint capsule.
• Infraspinatus + Teres minor: cover posterior aspect.
• Subscapularis: covers anterior aspect.
• The inferior aspect has no cuff muscle (site of dislocation).

Clinical Significance:

• Rotator cuff tear: Most common in supraspinatus (avascular zone near insertion). Causes painful arc syndrome (60°-120° abduction).
• Subacromial impingement: Supraspinatus tendon compressed between greater tubercle and coracoacromial arch.

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Q2. Attachments, Actions and Nerve Supply of Deltoid Muscle.

Introduction:

ATTACHMENTS:

1. Clavicular part (anterior): Anterior surface and border of lateral one-third of clavicle.
2. Acromial part (middle): Lateral margin and superior surface of acromion process.
3. Spinous part (posterior): Lower lip of crest of spine of scapula, as far back as the deltoid tubercle.

• Deltoid tuberosity on the anterolateral surface of the shaft of humerus (V-shaped roughening at the junction of upper and middle thirds).

ACTIONS:

• The middle deltoid is the chief abductor of the arm (works with supraspinatus).
• It assists the rotator cuff muscles in stabilizing the shoulder joint.

NERVE SUPPLY:

• Axillary nerve (C5, C6) - posterior cord of brachial plexus.
• The nerve winds around the surgical neck of the humerus within the quadrilateral space.
• It pierces the deep surface of the deltoid to supply it.
• It also gives the upper lateral cutaneous nerve of arm (sensory - over badge area/regimental badge area).

Diagram: Deltoid Muscle

        Clavicle (lateral 1/3)
           |
   ________↓_______________
  |    Acromion              |
  |    Spine of Scapula      |
  |_________________________|
             |   |   |
         (3 heads merging)
             |
        Deltoid tuberosity
        (shaft of humerus)

Axillary nerve (C5,C6) - from posterior cord
   → enters via quadrilateral space
   → supplies deltoid & teres minor
   → gives upper lateral cutaneous nerve of arm

Structures Deep to (Under Cover of) Deltoid:

Clinical Note:

• Deltoid paralysis from axillary nerve injury (e.g., surgical neck fracture) causes inability to abduct arm between 15°-90°. Area of sensory loss: over lower deltoid ("badge area").

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Q3. Enumerate Structures Under Cover of Deltoid Muscle.

Structures Under Cover of Deltoid:

1. Head of humerus
2. Surgical neck of humerus
3. Greater tubercle of humerus
4. Shoulder (glenohumeral) joint

1. Supraspinatus (and its tendon)
2. Infraspinatus (and its tendon)
3. Teres minor (and its tendon)
4. Subscapularis (anteriorly)
5. Coracobrachialis (partially)
6. Short and long heads of biceps brachii (partially)

1. Subacromial bursa (subdeltoid bursa) - lies between the deltoid and supraspinatus; communicates with shoulder joint in 30% cases

1. Axillary nerve - winds around surgical neck in quadrilateral space, supplies deltoid and teres minor
2. Upper lateral cutaneous nerve of arm (terminal branch of axillary nerve)

1. Posterior circumflex humeral artery (from axillary artery, 3rd part) - accompanies axillary nerve
2. Anterior circumflex humeral artery (contributes to arterial anastomosis)
3. Deltoid branch of thoracoacromial artery (to anterior deltoid)

Diagram:

         DELTOID (Roof/Tent)
              ↓
   ┌──────────────────────────┐
   │ Supraspinatus tendon     │
   │ Shoulder joint capsule   │
   │ Surgical neck of humerus │
   │ Subacromial bursa        │
   │ Axillary nerve           │
   │ Post. circumflex hum. a. │
   └──────────────────────────┘

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Q4. Attachment of Pectoralis Major Muscle.

Introduction:

ORIGIN (Three Heads):

INSERTION:

• Crest of the greater tubercle (lateral lip of bicipital groove) of the humerus.
• The insertion is a bilaminar tendon with a characteristic twist:
  • The clavicular head passes down and inserts into the lower part of the crest.
  • The sternocostal head passes up and inserts into the upper part (forming a U-shaped fold).
  • This twisted arrangement increases mechanical advantage.

Diagram: Pectoralis Major Attachments

                  Clavicle (medial half)
                        |
           Sternum -----+------ Clavicular head
           Ribs 2-6 ----+------ Sternocostal head
           Ext. oblique -+
                         \
                          \ (fan-shaped convergence)
                           \
                            → Crest of Greater Tubercle
                              (Lateral lip of bicipital groove)
                              BILAMINAR TWISTED TENDON

Nerve Supply:

• Medial pectoral nerve (C8, T1) - supplies mainly sternocostal head.
• Lateral pectoral nerve (C5, C6, C7) - supplies mainly clavicular head.

Actions:

• Adduction and medial rotation of arm.
• Clavicular head: flexion of arm.
• Sternocostal head: extension from flexed position.
• Accessory muscle of inspiration (if arm fixed).

Clinical Note:

• Pectoralis major forms the anterior fold of axilla.
• Assessed by asking patient to push hands on hips (adduction against resistance).

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Q5. Attachments, Actions and Nerve Supply of Serratus Anterior Muscle.

Introduction:

ORIGIN:

• Outer surfaces and superior borders of lateral aspects of ribs 1-8 (or 1-9).
• By 8 fleshy digitations that interdigitate with the digitations of the external oblique.

INSERTION:

1. Upper digitations (ribs 1, 2): Costal surface of superior angle of scapula.
2. Middle digitations (ribs 3, 4): Costal surface of medial border of scapula (along its length).
3. Lower digitations (ribs 5-8/9): Costal surface of inferior angle of scapula (most important - these pull the inferior angle forward and laterally).

NERVE SUPPLY:

• Long thoracic nerve (Nerve of Bell) - C5, C6, C7.
• Origin: arises from anterior rami of C5, C6, C7 in the neck.
• It runs down the superficial surface of serratus anterior on the thoracic wall.
• It is vulnerable to injury during mastectomy or axillary lymph node dissection.

ACTIONS:

Diagram: Serratus Anterior

         Scapula (medial border - costal surface)
         ↑
         |    Superior angle
         |    ←-------- ribs 1,2
         |    Medial border
         |    ←-------- ribs 3,4
         |    Inferior angle
         |    ←-------- ribs 5-8 (most powerful)
         |
     ──────────────────
     Ribs 1-8 (lateral surface - digitations)

Long thoracic nerve (C5,C6,C7) → runs on surface of muscle

Clinical Note: Winged Scapula

• Injury to long thoracic nerve (during mastectomy, axillary dissection, stab wounds) paralyzes serratus anterior.
• Results in winging of scapula: medial border of scapula protrudes posteriorly (especially when pushing against a wall).
• Patient cannot fully abduct arm above 90° (upward rotation of glenoid is impaired).

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Q6. Describe the Boundaries and Contents of Carpal Tunnel. Explain Carpal Tunnel Syndrome.

CARPAL TUNNEL - Definition:

BOUNDARIES:

CONTENTS (10 Structures):

NOTE:

• Flexor carpi radialis passes through a separate tunnel in the flexor retinaculum (not inside carpal tunnel proper).
• Palmaris longus lies superficial to the retinaculum.
• Ulnar nerve and vessels pass through Guyon's canal, not the carpal tunnel.

Diagram: Carpal Tunnel (Cross-Section)

         FLEXOR RETINACULUM (Roof)
    ________________________________
   |   FPL  |  FDS  |  FDS  |  FDP |
   |   (lat)|  (M,R)|  (I,L)|      |
   |        |  FDP (4)       |      |
   | Median |________________________________
   | nerve  ← lies laterally under retinaculum
   |________________________________________|
   Scaphoid  Trapezium  Capitate  Hamate (Floor/sides)

Key: FPL=Flexor Pollicis Longus, FDS=Flexor Digitorum Superficialis, FDP=Flexor Digitorum Profundus

CARPAL TUNNEL SYNDROME (CTS):

• Idiopathic (most common)
• Pregnancy, hypothyroidism, diabetes mellitus (fluid retention)
• Rheumatoid arthritis (tenosynovitis)
• Acromegaly
• Post-colles' fracture

• Burning pain and paraesthesia (tingling) in lateral three-and-a-half fingers (thumb, index, middle, lateral half of ring) - median nerve distribution.
• Pain worse at night (nocturnal pain - characteristic).
• Pain radiates up the forearm.
• Relief by hanging hand out of bed or "flick" sign.

• Wasting of thenar eminence (later stages).
• Weakness of thumb (opposition, abduction).
• Sensory loss over lateral 3½ digits (palm side).

• Tinel's sign: Tapping over carpal tunnel at wrist reproduces tingling in median nerve distribution.
• Phalen's test: Forced wrist flexion for 60 seconds reproduces symptoms.
• Reverse Phalen's test: Wrist extension worsens symptoms.

• Conservative: wrist splinting (neutral), corticosteroid injection, NSAIDs.
• Surgical: decompression by dividing flexor retinaculum (carpal tunnel release).

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Q7. Specify the Nerve Supply and Actions of Interossei of Hand.

INTEROSSEI - Introduction:

A. DORSAL INTEROSSEI (4 muscles)

• Origin: By two heads from adjacent sides of metacarpal bones (bipennate).
• Insertion: Into bases of proximal phalanges and extensor expansions.
  • 1st dorsal interosseous: Radial side of index finger (proximal phalanx + extensor expansion)
  • 2nd dorsal interosseous: Radial side of middle finger
  • 3rd dorsal interosseous: Ulnar side of middle finger
  • 4th dorsal interosseous: Ulnar side of ring finger

• Abduction of fingers away from axis of hand (middle finger as axis).
• Flexion of metacarpophalangeal joints.
• Extension of interphalangeal joints (via extensor expansion).

B. PALMAR INTEROSSEI (3 or 4 muscles - 3 according to BD Chaurasia)

• Origin: From the side of metacarpal shaft facing the axis of hand.
• Insertion: Base of proximal phalanx and extensor expansion of same finger.
  • 1st palmar interosseous: Ulnar side of index finger
  • 2nd palmar interosseous: Radial side of ring finger
  • 3rd palmar interosseous: Radial side of little finger

• Adduction of fingers toward axis (middle finger).
• Flexion of metacarpophalangeal joints.
• Extension of interphalangeal joints.

NERVE SUPPLY of ALL Interossei:

• Deep branch of ulnar nerve (C8, T1).
• All 7 interossei (4 dorsal + 3 palmar) are supplied by the deep branch of the ulnar nerve.

Diagram: Interossei of Hand

        INDEX   MIDDLE   RING   LITTLE
          |       |        |      |
     D1  D1↔D2  D2↔D3   D3↔D4
     (abduct)            (abduct)

Axis of hand = middle finger

DAB = Dorsal ABducts
PAD = Palmar ADducts

All supplied by: Deep branch of Ulnar nerve (C8, T1)

Combined action with Lumbricals:

• Both interossei and lumbricals together produce the "intrinsic-plus position": MCP flexion + IP extension.
• This is the position for writing ("pen grip").

Clinical Note:

• Ulnar nerve palsy causes loss of all interossei → clawing of ring and little fingers (more severe in little and ring due to loss of lumbricals to these two also).
• Froment's sign: Patient uses FPL to substitute for adductor pollicis (ulnar nerve palsy - flexes IP joint of thumb when gripping paper).

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Q8. Draw and Explain the Diagram of Brachial Plexus.

BRACHIAL PLEXUS - Introduction:

COMPONENTS: ROOTS - TRUNKS - DIVISIONS - CORDS - BRANCHES

BRACHIAL PLEXUS DIAGRAM (BD Chaurasia Style)

Roots:  C5  C6      C7      C8  T1
         \  /        |       \  /
Trunks: Upper      Middle    Lower
        (C5,6)      (C7)    (C8,T1)
          |           |         |
          A   P       A  P      A  P    (A=Anterior, P=Posterior)
Divisions: \  |       |  |      |  /
            \ |       |  |     / |
Cords:   Lateral  Posterior   Medial
         (C5,6,7)  (C5-T1)   (C8,T1)
             \        |      /

ROOTS (5 Roots):

• C5, C6, C7, C8, T1 (anterior rami)
• Pass between anterior and middle scalene muscles.

TRUNKS (3 Trunks):

DIVISIONS (6 Divisions):

• Each trunk divides into an anterior and posterior division (6 total).

CORDS (3 Cords):

BRANCHES:

• Nerve to serratus anterior (long thoracic nerve) - C5, C6, C7
• Nerve to rhomboids (dorsal scapular nerve) - C5
• Nerve to subclavius - C5, C6

• Suprascapular nerve (upper trunk) - C5, C6

Full Diagram (Simplified):

       C5─────┐
       C6─────┤ UPPER TRUNK ──── ant.div. ──┐
              |                post.div.──┐  |
       C7──── MIDDLE TRUNK ── ant.div. ──┼──┤→ LATERAL CORD → Musculocutaneous
                              post.div.──┼──┼┐   + Lat.root of Median N.
       C8─────┐                          |  |||
       T1─────┤ LOWER TRUNK ── ant.div.──┼──┼┘→ MEDIAL CORD → Ulnar N.
                              post.div.──┘  |    + Med.root of Median N.
                                            └──→ POSTERIOR CORD → Radial + Axillary N.

MEDIAN NERVE = Lateral root (C5,6,7) + Medial root (C8,T1)

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Q9. Explain the Anatomical Basis of Deformity of Erb's Paralysis.

DEFINITION:

ANATOMICAL BASIS OF ERB'S POINT:

• Located 2 cm above the clavicle at the junction of C5 and C6.
• At this point: anterior primary rami of C5 and C6 join to form the upper trunk.

CAUSES:

• Obstetric (most common): Excessive stretching of neck during delivery (shoulder dystocia, arm pulled over head).
• Adults: Motorcycle accidents (fall on neck + shoulder), direct blow.

MUSCLES PARALYSED (C5, C6 muscles):

THE CLASSIC DEFORMITY: "Waiter's Tip Position"

Diagram: Waiter's Tip / Porter's Tip Deformity

        Head
          |
          |  (neck laterally flexed opposite side at injury)
    ──────┤
          |
    Arm:  |──── Adducted (pectorals unopposed)
          |──── Medially rotated (subscapularis unopposed)
          |──── Elbow extended (triceps unopposed)
          |──── Forearm pronated (pronators unopposed)
          |──── Wrist flexed
          ↓
    APPEARANCE: Arm hangs limply at side, medially rotated,
    forearm pronated like a "WAITER EXPECTING A TIP"

Sensory Loss:

• Over regimental badge area (deltoid) - lateral cutaneous nerve of arm (C5).
• Along lateral forearm - lateral cutaneous nerve of forearm (C6).

Comparison: Erb's vs Klumpke's Palsy:

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Q10. Pronation and Supination.

DEFINITIONS:

• Supination: Rotation of forearm so that the palm faces anteriorly/upward (anatomical position). Radius and ulna are parallel.
• Pronation: Rotation of forearm so that the palm faces posteriorly/downward. Radius crosses over ulna.

JOINTS INVOLVED:

1. Superior (proximal) radio-ulnar joint - pivot joint (head of radius in radial notch of ulna).
2. Inferior (distal) radio-ulnar joint - pivot joint (head of ulna in ulnar notch of radius).
3. Both joints act simultaneously (syndesmosis in middle too).

MUSCLES OF SUPINATION:

MUSCLES OF PRONATION:

Diagram: Pronation and Supination

SUPINATION:                    PRONATION:
    Thumb side up               Thumb side down
    Radius parallel to ulna     Radius crosses ulna
    
    Ulna                        Ulna
     |                           |
     |   Radius                  |    ┌─Radius
     |   (parallel)              |   /  (crossed)
     |                           |  /

    PALM FACES UP             PALM FACES DOWN

Axis of movement: Through head of radius (superior) + 
                  head of ulna (inferior)

Range of Motion:

• Supination: 0°-90° (can go to 90°)
• Pronation: 0°-85°

Clinical Note:

• "Screwdriver" principle: Supination is stronger than pronation (hence screws are right-handed).
• Biceps brachii is the most powerful supinator when elbow is flexed at 90°.
• "Pulled elbow" (Nursemaid's elbow): Radial head subluxes from annular ligament in children - causes sudden pronation with elbow extended.

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Q11. Median Nerve in Hand and Forearm.

MEDIAN NERVE - Origin:

• Formed by lateral root (C5,6,7 from lateral cord) and medial root (C8,T1 from medial cord) of brachial plexus.
• Forms a V (inverted) around the axillary artery.

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IN THE FOREARM:

1. Enters forearm by passing between the two heads of pronator teres (humeral head and ulnar head).
2. Passes deep to the fibrous arch of flexor digitorum superficialis.
3. Runs between FDS (anteriorly) and FDP (posteriorly) in the middle of forearm.
4. At the lower forearm, becomes superficial between FDS and flexor carpi radialis tendons.
5. Enters the palm via the carpal tunnel deep to the flexor retinaculum.

• Arises 5 cm above wrist, passes superficial to flexor retinaculum (NOT through carpal tunnel).
• Supplies skin of lateral part of palm.

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IN THE HAND:

• Exits carpal tunnel and immediately gives the recurrent (thenar) branch.

Diagram: Median Nerve in Forearm and Hand

AXILLA → ARM (no branches) → ELBOW → 

FOREARM:
    Pronator teres ←────────┐
    FCR, Palmaris longus ←──┤  Median nerve
    FDS ←───────────────────┤  (between FDS/FDP)
    FPL, lat. FDP, ←────────┤ (via AIN)
    Pronator quadratus ←────┘
    Palmar cutaneous branch ← above wrist (superficial to retinaculum)

CARPAL TUNNEL → HAND:
    Recurrent branch:
    - Abd.pollicis brevis
    - Opponens pollicis
    - Flex.poll.brevis (sup)
    
    1st, 2nd lumbricals
    
    Palmar digital nerves:
    → Both sides thumb
    → Both sides index
    → Both sides middle
    → Lat. half ring finger
    (= lateral 3½ fingers)

Median Nerve Injury Summary:

• "Hand of Benediction": Index + middle fingers remain extended (FDP lateral half + FDS for index/middle paralysed), ring and little finger flex (ulnar innervated FDP intact).
• Ape thumb deformity (Simian hand): Thumb falls into plane of palm (opposition lost, thenar wasting).

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Q12. Musculocutaneous Nerve.

ORIGIN:

• Terminal branch of the lateral cord of brachial plexus.
• Root value: C5, C6, C7.

COURSE:

1. Arises from the lateral cord in the axilla, lateral to axillary artery.
2. Pierces the coracobrachialis muscle (first structure it supplies).
3. Runs obliquely downward and laterally between biceps brachii (anterior) and brachialis (posterior).
4. Reaches the lateral side of the arm just above the elbow.
5. Pierces the deep fascia lateral to the biceps tendon.
6. Becomes the lateral cutaneous nerve of forearm (terminal cutaneous branch).

BRANCHES AND DISTRIBUTION:

• Lateral cutaneous nerve of forearm: Supplies skin of lateral surface of forearm (anterior and posterior), from elbow to the wrist.

Diagram: Musculocutaneous Nerve

     LATERAL CORD (C5,C6,C7)
              |
              ↓
     Axilla → pierces CORACOBRACHIALIS
              |
              ↓
     Between BICEPS (ant.) and BRACHIALIS (post.)
              |
         Supplies: BICEPS BRACHII
         Supplies: BRACHIALIS
              |
              ↓ (pierces deep fascia lateral to biceps tendon)
     LATERAL CUTANEOUS NERVE OF FOREARM
     (supplies lateral forearm skin)

Actions of muscles supplied:

• Coracobrachialis: Flexion and adduction of arm at shoulder.
• Biceps brachii: Flexion of elbow, supination of forearm, flexion at shoulder (long head - maintains humeral head in glenoid).
• Brachialis: Pure flexor of elbow (workhorse of elbow flexion).

Clinical Notes:

• Isolated musculocutaneous nerve injury is uncommon.
• Causes: penetrating injury in axilla, shoulder dislocation, heavy backpacking ("rucksack palsy" - though usually brachial plexus).
• Effects of injury:
  • Weakness of elbow flexion and supination.
  • Loss of biceps jerk reflex.
  • Sensory loss over lateral forearm.
• The nerve may occasionally have communications with the median nerve (variant).

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Q13. Specify Origin, Insertion and Distribution of Radial Nerve.

RADIAL NERVE - Origin:

• Largest terminal branch of the posterior cord of brachial plexus.
• Root value: C5, C6, C7, C8, (T1) - all roots of brachial plexus.

COURSE AND DISTRIBUTION:

• Lies posterior to axillary artery.
• Gives branches: posterior cutaneous nerve of arm, nerve to long head of triceps.
• Passes between long head of triceps (medially) and the humerus.

• Winds around the spiral groove (radial groove) of the humerus with the profunda brachii artery.
• Courses from medial-posterior to lateral-anterior.

• Lies between brachialis medially and brachioradialis laterally ("radial tunnel" area).
• Divides into superficial and deep branches just in front of lateral epicondyle.

• Sensory only.
• Runs under brachioradialis in forearm.
• Emerges at lower forearm laterally.
• Supplies dorsal skin of lateral 3½ fingers (proximal phalanges only; distal phalanges by median nerve).

• Motor only (after giving radial nerve branches in forearm).
• Passes between superficial and deep heads of supinator muscle (arcade of Frohse).
• Winds around lateral aspect of radius.
• Enters posterior compartment of forearm.
• Supplies all extensors in posterior compartment:

Diagram: Distribution of Radial Nerve

POSTERIOR CORD
     |
 RADIAL NERVE (C5-C8,T1)
     |
     ├── Axilla: to triceps (long head), post. cut. n. of arm
     |
     ├── Spiral groove of humerus: triceps (med+lat heads), brachioradialis, ECRL
     |
     ├── Cubital fossa: DIVIDES
     |        |                     |
     |   SUPERFICIAL BR.        DEEP BR. (PIN)
     |   (sensory)              through supinator
     |   dorsal lat 3½ fingers  to all extensors

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

ROOT VALUE:

MUSCLES SUPPLIED (Complete List):

1. Triceps brachii (all 3 heads - extension at elbow)
2. Anconeus (extension at elbow)
3. Brachioradialis (flexion at elbow in midprone position)
4. Extensor carpi radialis longus (wrist extension + radial deviation)

CLINICAL ANATOMY - Sites of Injury:

• Compression by crutch or "Saturday night palsy" (also at arm level - sleep on chair).
• All muscles paralysed.
• Wrist drop + finger drop + triceps paralysis + loss of reflexes.
• Sensory loss over posterior arm, forearm, and dorsal hand.

• Radial nerve injured in spiral groove by midshaft humeral fracture.
• Triceps is SPARED (branches given before spiral groove).
• Classic wrist drop: Inability to extend wrist and fingers.
• Sensory loss over anatomical snuffbox area (dorsal hand, lateral 3½ fingers - proximal phalanges).
• Triceps reflex present; brachioradialis reflex lost.

• At or below radial head (fracture head of radius, lipoma, arcade of Frohse compression).
• No wrist drop (ECRL spared - supraepicondylar).
• Finger drop (cannot extend fingers at MCP).
• Wrist deviates radially (ECRL intact, ECU paralysed).
• No sensory loss (PIN is purely motor).

• At wrist (tight watch band, de Quervain's surgery).
• Sensory loss only over dorsal lateral hand.
• No motor loss.

Diagram: Wrist Drop

       Wrist: ─────┐  NORMAL position
                   │
       Wrist drop: ──────── (gravity - no wrist extensors)
                            ← Cannot extend wrist
                            ← Finger drop (cannot extend at MCP)
                            ← Thumb cannot be extended/abducted

Signs: Loss of brachioradialis jerk
       Sensory: anatomical snuffbox + dorsal lateral hand

Key Clinical Points:

• Wrist drop is the hallmark of radial nerve palsy.
• Triceps is usually SPARED in shaft of humerus fractures.
• Most humeral shaft fractures with radial nerve injury recover spontaneously (neurapraxia).

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Q15. Specify the Parts, Course and Branches of the Axillary Artery.

DEFINITION:

PARTS (3 Parts - Divided by Pectoralis Minor):

• 1st Part: From lateral border of rib I to upper border of pectoralis minor.
• 2nd Part: Behind pectoralis minor.
• 3rd Part: From lower border of pectoralis minor to lower border of teres major.

RELATIONS:

• Surrounded by the three cords of brachial plexus (lateral, medial, posterior cords), hence the name.
• Axillary vein is medial.

BRANCHES (3-2-3 Rule):

Diagram: Axillary Artery and Branches

SUBCLAVIAN ARTERY
      |
      | (crosses lat. border of rib I)
      ↓
─────────────────────────────────────────
1st PART:  ──────────────────── Superior thoracic a.
      |
Pectoralis Minor (posterior relation)
      |
─────────────────────────────────────────
2nd PART:  ──────────────────── Thoracoacromial a.
           ──────────────────── Lateral thoracic a.
      |
─────────────────────────────────────────
3rd PART:  ──────────────────── Subscapular a.
                                 ├── Thoracodorsal a.
                                 └── Circumflex scapular a.
           ──────────────────── Ant. circumflex humeral a.
           ──────────────────── Post. circumflex humeral a.
      |
      | (crosses lower border teres major)
      ↓
BRACHIAL ARTERY

Mnemonic: "Send The Lord's Souls Above Palms"
(Superior thoracic, Thoracoacromial, Lateral thoracic, 
Subscapular, Anterior circumflex, Posterior circumflex)

Clinical Notes:

• Axillary artery can be compressed against the humerus for emergency bleeding control.
• Axillary artery aneurysm may compress cords of brachial plexus.
• In shoulder dislocation, the anterior circumflex humeral artery or the axillary artery itself may be injured.
• The posterior circumflex humeral artery accompanies the axillary nerve through the quadrilateral space.

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Q16. Cubital Fossa.

DEFINITION:

BOUNDARIES:

CONTENTS (Medial to Lateral: TAN):

Roof Contents:

• Median cubital vein - connects cephalic to basilic vein (important for intravenous access and venepuncture).
• Medial and lateral cutaneous nerves of forearm.
• Cephalic and basilic veins.

Diagram: Cubital Fossa

         Lateral epicondyle    Medial epicondyle
                  |                  |
                  |←─── BASE ───────→|
                  |                  |
     Brachioradialis ←────────────────────→ Pronator Teres
     (lateral wall)                         (medial wall)
                  \                  /
                   \                /
                    ──────APEX──────

CONTENTS (deep, lateral to medial):
   Radial n.  Biceps tendon  Brachial a.  Median n.
   (under brachioradialis)

ROOF: Deep fascia + Bicipital aponeurosis + skin
FLOOR: Brachialis + Supinator

SUPERFICIAL (in roof): Median cubital vein, cutaneous nerves

Applied Anatomy:

1. Venepuncture: Median cubital vein in cubital fossa roof is the standard site for IV cannulation, blood sampling. The bicipital aponeurosis protects the brachial artery and median nerve from inadvertent puncture.
2. Blood pressure measurement: Brachial artery in cubital fossa is the site for auscultation (Korotkoff sounds).
3. Brachial artery injury: Results in Volkmann's ischaemia → compartment syndrome → Volkmann's ischaemic contracture (flexion deformity of forearm and hand).
4. Biceps tendon rupture: Palpable gap in cubital fossa.
5. Radial nerve entrapment in radial tunnel (lateral to cubital fossa) can cause lateral epicondylitis-like pain.

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Q17. Axilla - Boundaries, Contents and Applied Anatomy.

DEFINITION:

BOUNDARIES (4 Walls + Apex + Base):

• Bounded by: posterior surface of clavicle (anteriorly) + superior border of scapula (posteriorly) + lateral border of rib I (medially).
• Through the apex pass: axillary vessels, brachial plexus trunks.

• Skin, superficial fascia, and axillary fascia between the anterior and posterior folds.
• Covered by coarse axillary hair.

Diagram: Axilla (Walls)

                 APEX (Inlet)
                    ↑
          ┌─────────────────────┐
 Anterior │ Pect. Major         │ Posterior
 Wall     │ Pect. Minor         │ Wall
          │ Subclavius          │ Subscapularis
          │                     │ Teres Major
          │                     │ Lat. Dorsi
          └─────────────────────┘
 Medial wall: Serratus ant. on ribs
 Lateral wall: Bicipital groove (humerus)
                    ↓
                  BASE (Floor)
              Skin + Axillary fascia

[Pyramidal space - apex directed upward toward neck]

CONTENTS of Axilla:

• Divided into 3 parts by pectoralis minor.
• 6 branches (1+2+3): Superior thoracic, Thoracoacromial, Lateral thoracic, Subscapular, Ant. and Post. circumflex humeral.

• Medial to axillary artery.
• Begins at lower border of teres major.
• Receives cephalic vein and tributaries.
• Becomes subclavian vein at lateral border of rib I.

• In axilla: the cords and their terminal branches.
• Lateral cord (C5,6,7): musculocutaneous nerve + lateral root of median nerve + lateral pectoral nerve.
• Medial cord (C8,T1): ulnar nerve + medial root of median nerve + medial cutaneous nerves + medial pectoral nerve.
• Posterior cord (C5-T1): axillary nerve + radial nerve + subscapular nerves + thoracodorsal nerve.

• Axillary sheath (prolongation of prevertebral fascia enclosing artery, vein, cords).
• Axillary fat (fills space).
• Tail of Spence (axillary tail of breast - extends into axilla).
• Long thoracic nerve (on serratus anterior).
• Intercostobrachial nerve (T2 lateral cutaneous branch).

APPLIED ANATOMY:

1. Breast cancer and axillary lymph nodes:
   • Lymph from lateral breast drains to axillary nodes (especially anterior/pectoral group).
   • Sentinel node biopsy and axillary clearance are done in breast cancer staging.
   • Injury to long thoracic nerve during axillary clearance → winging of scapula.
   • Injury to thoracodorsal nerve → weakness of latissimus dorsi.
   • Injury to intercostobrachial nerve (T2) → sensory loss over medial upper arm.
2. Axillary nerve injury (surgical neck of humerus fracture or shoulder dislocation):
   • Loss of deltoid action (abduction 15°-90°).
   • Loss of sensation over badge area.
3. Brachial plexus injury:
   • Penetrating injuries in axilla can damage cords.
   • Pancoast tumor invades lower trunk (Klumpke's type lesion + Horner syndrome).
4. Axillary artery aneurysm or injury:
   • Can compress brachial plexus cords.
   • Injury in shoulder dislocation.
5. Crutch palsy:
   • Pressure on axillary contents from ill-fitting crutch → brachial plexus (posterior cord) compression → wrist drop.
6. Axillary vein thrombosis:
   • Paget-Schroetter syndrome: effort thrombosis of axillary vein in young athletes.

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KEY DIAGRAMS SUMMARY (For Exam Use)

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QUICK REVISION MNEMONICS

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