---

ANATOMY - FIRST YEAR MBBS

University Examination Answers

---

Q.1 - Describe the Attachments of Rotator Cuff Muscles [3 Marks]

Definition

The Four Rotator Cuff Muscles (Mnemonic: SITS)

Diagram

Actions of Rotator Cuff Muscles

• Supraspinatus: Initiates abduction (first 15 degrees); stabilizes humeral head
• Infraspinatus: Lateral (external) rotation of arm
• Teres Minor: Lateral rotation of arm; adduction
• Subscapularis: Medial (internal) rotation of arm

Clinical Significance

---

Q.2 - Attachments, Actions and Nerve Supply of Deltoid [3 Marks]

Attachments

Origin (From the "DeltACL" arch - Deltoid, Acromion, Clavicle, Lateral):

1. Anterior part: Anterior border and superior surface of the lateral 1/3 of the clavicle
2. Middle part: Lateral margin and superior surface of the acromion process of scapula
3. Posterior part: Inferior lip of the spine of the scapula

Insertion:

• Deltoid tuberosity - a V-shaped roughening on the mid-lateral aspect of the humerus (all three parts converge here)

Actions

Nerve Supply

• Axillary nerve (C5, C6) - from the posterior cord of the brachial plexus
• The axillary nerve winds around the surgical neck of humerus in the quadrangular space

Applied Anatomy

• Intramuscular injections are commonly given into the deltoid
• Fracture of the surgical neck of humerus or dislocation of shoulder can injure the axillary nerve, causing:
  • Paralysis of deltoid leading to loss of abduction of arm
  • Loss of sensation over the "Regimental badge" area (lateral aspect of upper arm)

---

Q.3 - Enumerate Structures Under Cover of Deltoid Muscle

Structures Deep to the Deltoid Muscle

1. Bones and Joints

• Upper end of humerus (greater tubercle, lesser tubercle)
• Shoulder (glenohumeral) joint

2. Muscles

• Supraspinatus muscle/tendon
• Infraspinatus muscle/tendon
• Teres minor muscle
• Subscapularis tendon (anteriorly)
• Coracobrachialis (partly)
• Short head of biceps brachii (partly)

3. Nerves

• Axillary nerve (with its anterior and posterior divisions; the anterior division supplies the anterior and middle parts of deltoid; posterior division supplies the posterior part and gives rise to the superior lateral cutaneous nerve of arm)
• Radial nerve (as it enters posterior compartment through triangular interval)
• Suprascapular nerve (passes to supraspinatus and infraspinatus)

4. Vessels

• Posterior circumflex humeral artery and vein (pass through the quadrangular space)
• Anterior circumflex humeral artery
• Suprascapular artery and vein
• Deltoid branch of thoracoacromial artery

5. Bursae

• Subacromial (subdeltoid) bursa - lies between deltoid and supraspinatus tendon. It reduces friction during shoulder movements.

6. Spaces

• Quadrangular space (bounded by teres minor above, teres major below, long head of triceps medially, surgical neck of humerus laterally) - transmits the axillary nerve and posterior circumflex humeral vessels

---

Q.4 - Attachment of Pectoralis Major Muscle [2 Marks]

Origin (TWO heads)

Insertion

• Both heads converge to form a bilaminar tendon that inserts into the lateral lip of the intertubercular sulcus (bicipital groove) of the humerus
• The tendon twists on itself: the clavicular part attaches inferiorly and the sternocostal part attaches superiorly

Nerve Supply

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

Actions

1. Adduction and medial rotation of the arm
2. Clavicular head: flexion of the arm (pulls arm forward)
3. Sternocostal head: extends the flexed arm
4. Accessory muscle of respiration (when arms are fixed)

Applied Anatomy

---

Q.5 - Attachments, Actions and Nerve Supply of Serratus Anterior Muscle [4 Marks]

Attachments

Origin:

• Lateral surfaces of the upper 8 or 9 ribs (ribs I to IX) by muscular slips, along with the fascia overlying the intercostal spaces

Insertion:

• Costal (anterior) surface of the medial border of the scapula, including the inferior angle

Diagram

Actions

1. Pulls the scapula forward (protraction) - important for reaching and punching movements
2. Rotates the scapula - tilts the glenoid fossa upward (critical for full arm elevation above 90°)
3. Holds the scapula firmly against the thoracic wall

Nerve Supply

• Long thoracic nerve (C5, C6, C7) - also called the "nerve of Bell"
• The long thoracic nerve descends from the roots of the brachial plexus, passes through the axillary inlet, and runs vertically down the medial wall of the axilla on the external surface of the serratus anterior, just deep to skin and subcutaneous fascia

Applied Anatomy - Winging of Scapula

• Stab wounds to the lateral chest
• Radical mastectomy (surgical damage)
• Carrying heavy loads on the shoulder

---

Q.6 - Boundaries, Contents of Carpal Tunnel and Carpal Tunnel Syndrome [4 Marks]

Definition

Boundaries

Contents (9 structures pass through the tunnel)

1. Median nerve (most important - the one compressed in CTS)
2. Flexor pollicis longus tendon (1 tendon, in its own synovial sheath)
3. Flexor digitorum superficialis tendons (4 tendons)
4. Flexor digitorum profundus tendons (4 tendons)

Carpal Tunnel Syndrome (CTS)

Definition

Causes of Compression

• Idiopathic (most common)
• Pregnancy (fluid retention)
• Rheumatoid arthritis (synovial thickening)
• Hypothyroidism (myxedema)
• Acromegaly
• Diabetes mellitus
• Repetitive wrist use (occupational)

Clinical Features

1. Sensory changes: Pain, tingling, numbness over the lateral 3½ digits (thumb, index, middle, and lateral half of ring finger) - the median nerve distribution in the hand
2. Night pain that wakes the patient (classic feature)
3. Motor changes: Weakness and wasting of thenar muscles (opponens pollicis, abductor pollicis brevis, lateral head of flexor pollicis brevis)
4. Ape thumb deformity (flattening of thenar eminence in chronic cases)

Special Tests

• Tinel's sign: Tapping over the carpal tunnel elicits tingling in the median nerve distribution
• Phalen's test: Full wrist flexion for 60 seconds reproduces symptoms

Treatment

• Conservative: Splinting (neutral position), NSAIDs, steroid injection
• Surgical: Carpal tunnel decompression (division of flexor retinaculum)

---

Q.7 - Nerve Supply and Actions of Interossei of the Hand [3 Marks]

The Interossei

Palmar Interossei (PAD - Palmar ADduct)

Dorsal Interossei (DAB - Dorsal ABduct)

Nerve Supply

Additional Actions of All Interossei

1. Flex the metacarpophalangeal (MCP) joints
2. Extend the interphalangeal (IP) joints - through their insertion into the extensor expansion

Applied Anatomy

• Loss of precise pinch and grip
• Claw hand deformity (hyperextension at MCP and flexion at IP joints), primarily affecting ring and little fingers
• Loss of the "paper test" (cannot hold paper between fingers)

---

Q.8 - Draw and Explain the Diagram of Brachial Plexus [5 Marks]

Introduction

Diagram

Components (Mnemonic: Robert Taylor Drinks Cold Beer = Roots, Trunks, Divisions, Cords, Branches)

ROOTS (C5, C6, C7, C8, T1)

• Lie between the anterior scalene and middle scalene muscles
• Receive gray rami communicantes from the sympathetic trunk
• Branches from roots:
  • Dorsal scapular nerve (C5) - to rhomboids
  • Long thoracic nerve (C5, C6, C7) - to serratus anterior

TRUNKS (in the posterior triangle of neck)

• Branches from superior trunk: Suprascapular nerve (to supraspinatus + infraspinatus); Nerve to subclavius (C5, C6)

DIVISIONS (no branches)

• Each trunk divides into an anterior and a posterior division
• Anterior divisions supply flexor compartments
• Posterior divisions supply extensor compartments

CORDS (related to 2nd part of axillary artery)

BRANCHES (Terminal Nerves)

• Lateral pectoral nerve
• Musculocutaneous nerve
• Lateral root of median nerve

• Medial pectoral nerve
• Medial cutaneous nerve of arm
• Medial cutaneous nerve of forearm
• Ulnar nerve
• Medial root of median nerve

• Upper subscapular nerve
• Thoracodorsal nerve (to latissimus dorsi)
• Lower subscapular nerve
• Axillary nerve (C5, C6)
• Radial nerve (C5-T1) - largest branch of brachial plexus

---

Q.9 - Anatomical Basis of Deformity of Erb's Paralysis [4 Marks]

Definition

Mechanism of Injury

• In obstetric cases: Excessive separation of head and shoulder during difficult labor (traction on baby's neck)
• In adults: Fall of heavy weight on shoulder, motorcycle accident, or forcible depression of the shoulder

Muscles Affected (all supplied by C5, C6)

The Classic Deformity - "Waiter's Tip" / "Policeman Receiving a Tip" Position

Sensory Loss

Clinical Note

• The C5, C6 roots converge at Erb's point (just above the clavicle)
• Injury here results in the typical upper plexus palsy
• Distinguish from Klumpke's paralysis (C8, T1 injury) which causes claw hand and Horner's syndrome

---

Q.10 - Pronation and Supination [2 Marks]

Definitions

• Supination: Rotation of the forearm so that the palm faces anteriorly (palm up) or the radius lies parallel to the ulna
• Pronation: Rotation of the forearm so that the palm faces posteriorly (palm down) or the radius crosses over the ulna

Joints Involved

• Proximal radio-ulnar joint: Head of radius rotates within the anular ligament
• Distal radio-ulnar joint: Lower end of radius rotates around the lower end of the ulna

Muscles of Supination

Muscles of Pronation

Applied Points

• Biceps is the most powerful supinator - best felt when elbow is at 90°
• Fractures of the radius at different levels lead to specific deformities because different muscles pull the fragments in different directions based on their supinating/pronating effect

---

Q.11 - Median Nerve in the Hand and Forearm [4 Marks]

Root Value

Course

In the Forearm:

1. Enters the forearm by passing between the two heads of pronator teres
2. Passes deep to the fibrous arch of flexor digitorum superficialis
3. Gives off the anterior interosseous nerve - supplies flexor pollicis longus, lateral half of flexor digitorum profundus, and pronator quadratus
4. Descends between FDS and FDP
5. Emerges lateral to the tendon of FDS to the index finger at the wrist
6. Lies medial to flexor carpi radialis at the wrist (lateral to palmaris longus)

In the Hand:

1. Passes through the carpal tunnel deep to flexor retinaculum
2. Immediately distal to the retinaculum, it gives the palmar cutaneous branch (before entering carpal tunnel) and recurrent branch (motor to thenar muscles)

Branches in the Forearm

1. Articular branches to elbow joint
2. Muscular branches (to all superficial flexors except flexor carpi ulnaris):
   • Pronator teres
   • Flexor carpi radialis
   • Palmaris longus
   • Flexor digitorum superficialis
3. Anterior interosseous nerve: Flexor pollicis longus, lateral FDP (index/middle), pronator quadratus
4. Palmar cutaneous branch (lateral palm sensation)

Branches in the Hand

1. Recurrent (thenar) branch: Supplies the three thenar muscles - abductor pollicis brevis, opponens pollicis, and lateral head of flexor pollicis brevis
2. Palmar digital nerves (3½ digits - thumb, index, middle, lateral half of ring):
   • Digital nerves to thumb (both sides)
   • Digital nerves to index and middle fingers (both sides)
   • Digital nerve to lateral half of ring finger
   • These also supply the 1st and 2nd lumbricals

Muscles Supplied - Summary

Applied Anatomy - "Pope's Blessing" (Median Nerve Injury at Wrist)

• Loss of opposition, abduction of thumb
• Thenar wasting - "ape thumb deformity"
• Loss of sensation over lateral 3½ digits

---

Q.12 - Musculocutaneous Nerve [3 Marks]

Root Value and Origin

• Root value: C5, C6 (and sometimes C7)
• Arises from the lateral cord of the brachial plexus

Course

1. Arises in the axilla from the lateral cord
2. Pierces the coracobrachialis muscle (which it supplies)
3. Passes obliquely downward between biceps brachii (anteriorly) and brachialis (posteriorly), supplying both
4. Continues beyond the lateral border of biceps, at the level of the elbow, as the lateral cutaneous nerve of the forearm

Branches and Distribution

Motor Branches:

Sensory Branch:

• Lateral cutaneous nerve of the forearm: Supplies the lateral surface of the forearm on both its anterior and posterior aspects

Effects of Injury

• Weakness of flexion at the elbow (particularly with supination)
• Loss of the biceps jerk reflex (C5, C6)
• Sensory loss over the lateral forearm

---

Q.13 - Origin, Insertion and Distribution of Radial Nerve

Origin

• Arises from the posterior cord of the brachial plexus (C5, C6, C7, C8, and T1)
• It is the largest branch of the brachial plexus

Course

In the Axilla:

• Lies posterior to the axillary artery
• Passes with the profunda brachii artery into the posterior compartment of the arm through the triangular interval (bounded above by teres minor, below by teres major, and laterally by the shaft of humerus)

In the Arm (Radial Groove):

• Passes diagonally from medial to lateral in the radial groove (spiral groove) on the posterior aspect of the humerus, directly on bone
• Accompanied by the profunda brachii artery
• Passes through the lateral intermuscular septum to enter the anterior compartment
• Lies between brachialis and brachioradialis anterior to the lateral epicondyle

In the Cubital Fossa:

• Lies deep to brachioradialis at the level of the lateral epicondyle
• Divides into two terminal branches:

Terminal Branches

Distribution (Muscles Supplied)

In the Arm:

1. Triceps brachii (all three heads)
2. Anconeus
3. Brachioradialis
4. Extensor carpi radialis longus
5. Part of brachialis (lateral portion)

In the Forearm (via deep/posterior interosseous nerve):

1. Extensor carpi radialis brevis
2. Supinator
3. Extensor digitorum
4. Extensor digiti minimi
5. Extensor carpi ulnaris
6. Abductor pollicis longus
7. Extensor pollicis brevis
8. Extensor pollicis longus
9. Extensor indicis

Diagram

---

Q.14 - Root Value, Muscles Supplied and Clinical Anatomy of Radial Nerve

Root Value

Complete Summary of Muscles Supplied

Clinical Anatomy

1. Injury in the Axilla (Complete Radial Nerve Palsy)

• Cause: Crutch palsy, prolonged compression in axilla
• Deformity: Wrist drop + inability to extend fingers
• Triceps: Also paralyzed (distinguishes from radial groove injury)
• Sensory loss: Dorsum of hand

2. Injury in the Radial Groove (Most Common)

• Cause: Fracture of mid-shaft of humerus (most common), "Saturday night palsy" (compression against hard edge while intoxicated)
• Deformity: Wrist drop (loss of wrist extension), inability to extend fingers at MCP joints
• Triceps spared (its branches arise proximal to the groove)
• Sensory loss: Dorsum of hand (first dorsal webspace most reliable)

3. Posterior Interosseous Nerve Palsy (PIN palsy)

• Cause: Compression at fibrous arch of supinator (Arcade of Frohse), radial head fracture
• Deformity: Finger drop, no wrist drop (ECRL intact)
• No sensory loss (purely motor)

4. Superficial Radial Nerve Injury (Wartenberg's Syndrome)

• Purely sensory - pain/tingling over dorsal lateral hand

---

Q.15 - Parts, Course and Branches of the Axillary Artery [3 Marks]

Definition

Parts (divided by pectoralis minor into 3 parts)

Branches

1st Part (1 branch):

1. Superior thoracic artery: Supplies upper two intercostal spaces and pectoral muscles

2nd Part (2 branches):

1. Thoracoacromial artery: Divides into pectoral, acromial, deltoid, and clavicular branches
2. Lateral thoracic artery: Descends along the lateral border of pectoralis minor; supplies pectoral muscles and lateral breast; also sends branch to serratus anterior

3rd Part (3 branches):

1. Subscapular artery: Largest branch; divides into:
   • Circumflex scapular artery (anastomoses around scapula)
   • Thoracodorsal artery (to latissimus dorsi)
2. Anterior circumflex humeral artery: Passes anterior to surgical neck of humerus
3. Posterior circumflex humeral artery: Larger; passes through quadrangular space with axillary nerve around surgical neck of humerus; supplies deltoid and shoulder joint

Applied Anatomy

• The second part is surrounded by the three cords of the brachial plexus (lateral, medial, posterior) which are named by their position relative to this part
• Axillary artery aneurysm may compress the brachial plexus cords
• The anastomosis around the scapula (subscapular + suprascapular + dorsal scapular arteries) is clinically important - allows collateral circulation when the axillary artery is blocked

---

Q.16 - Cubital Fossa [7 Marks]

Definition

Boundaries

Diagram

Contents (from lateral to medial)

Roof Contents

• Venipuncture (blood tests, IV cannulation)
• Blood transfusion

Applied Anatomy

1. Brachial artery pulsation: Can be palpated in the cubital fossa for blood pressure measurement (with stethoscope over the brachial artery)
2. Venipuncture: Median cubital vein is the preferred site for IV access and blood sampling
3. Elbow dislocations/fractures: Can damage brachial artery or median nerve in this region
4. Entrapment syndromes: Pronator teres syndrome (median nerve compressed between heads of pronator teres)
5. Tennis elbow (lateral epicondylitis) involves the lateral boundary of the fossa

---

Q.17 - Axilla - Boundaries, Contents and Applied Anatomy [3 Marks]

Definition

Shape and Boundaries

Contents

1. Axillary Artery (and its branches)

2. Axillary Vein

3. Brachial Plexus

4. Lymph Nodes (5 groups)

5. Axillary Fat (fills all spaces)

6. Long Thoracic Nerve (on medial wall)

7. Intercostobrachial Nerve

Applied Anatomy

1. Breast Cancer and Lymphatics

• Approximately 75% of lymphatic drainage of the breast passes to axillary lymph nodes (primarily pectoral group)
• Sentinel lymph node biopsy and axillary dissection are performed for breast cancer staging
• Damage to long thoracic nerve during mastectomy causes winged scapula
• Damage to thoracodorsal nerve causes paralysis of latissimus dorsi

2. Quadrangular Space

• Bounded by: teres minor (above), teres major (below), long head of triceps (medial), surgical neck of humerus (lateral)
• Transmits: axillary nerve and posterior circumflex humeral artery
• Compression causes: deltoid weakness + loss of sensation over "badge area"

3. Axillary Artery Injury

• Penetrating or blunt trauma to the axilla can injure the axillary artery
• Rich anastomosis around the scapula allows collateral circulation

4. Axillary Vein Thrombosis

• Rare; causes swelling of the arm (effort thrombosis/Paget-Schroetter syndrome)
• Associated with repetitive overhead activities

---

References: All answers compiled from Gray's Anatomy for Students (4th ed.), S. Das Manual on Clinical Surgery (13th ed.), and General Anatomy and Musculoskeletal System - THIEME Atlas of Anatomy.

---

ANATOMY - FIRST YEAR MBBS

COMPLETE 7-MARK UNIVERSITY EXAM ANSWERS

---

---

Q.1 - Describe the Attachments of Rotator Cuff Muscles [7 Marks]

Introduction

The Four Rotator Cuff Muscles (Mnemonic: SITS)

1. Supraspinatus

2. Infraspinatus

3. Teres Minor

4. Subscapularis

Diagram

How the Rotator Cuff Stabilizes the Shoulder Joint

1. Compressing the humeral head into the glenoid
2. Counteracting the upward pull of the deltoid during abduction (supraspinatus creates a force couple with deltoid)
3. Creating a "compressive sling" around the joint

Summary Table

Applied Anatomy (Clinical Importance)

1. Rotator cuff tears: Most common in supraspinatus tendon (at its "critical zone" - 1 cm proximal to insertion, avascular watershed area). Caused by impingement under the acromion, degeneration, or trauma.
2. Painful arc syndrome: Pain at 60-120° of abduction due to supraspinatus impingement.
3. Supraspinatus test (empty can test): Arm at 90° abduction, 30° forward flexion, thumb pointing down - weakness suggests supraspinatus tear.
4. Subacromial bursitis: Inflammation of the bursa between the cuff and acromion commonly accompanies rotator cuff pathology.
5. Calcific tendinitis: Calcium deposits commonly form in the supraspinatus tendon.

---

---

Q.2 - Attachments, Actions and Nerve Supply of Deltoid [7 Marks]

Introduction

Attachments

Origin (broad, from three parts - the "DCA" arch: Deltoid, Clavicle, Acromion)

Insertion (all three parts converge)

Actions

Nerve Supply

• Axillary nerve (C5, C6) - from the posterior cord of the brachial plexus
• The axillary nerve winds around the surgical neck of the humerus within the quadrangular space
• The anterior branch of the axillary nerve supplies the anterior and middle parts; the posterior branch supplies the posterior part
• The posterior branch also gives rise to the superior lateral cutaneous nerve of the arm (sensory to the "regimental badge area")

Relations

• Deep to deltoid: Rotator cuff muscles, glenohumeral joint, subdeltoid/subacromial bursa, axillary nerve, posterior circumflex humeral vessels
• Superficial: Only skin and subcutaneous fascia
• Medial boundary: Pectoralis major (anterior axillary fold)

Applied Anatomy

1. IM Injections

2. Axillary Nerve Injury

• Fracture of the surgical neck of humerus (most common cause)
• Anterior dislocation of the shoulder (nerve is stretched)
• Compression from crutches (rarely)

• Paralysis of deltoid → loss of abduction of arm (patient cannot initiate abduction)
• Paralysis of teres minor
• Loss of sensation over the "Regimental badge" area (skin over the lower half of the deltoid)
• Deltoid wasting over time (flat shoulder contour)

3. Testing the Axillary Nerve

• Ask patient to abduct the arm against resistance
• Test sensation over the regimental badge area

4. Deltoid Tuberosity

---

---

Q.3 - Enumerate Structures Under Cover of Deltoid Muscle [7 Marks]

Introduction

Structures Deep to the Deltoid

A. Bones and Joints

1. Proximal end of the humerus:
   • Head of humerus (covered by joint capsule)
   • Greater tubercle (with the three facets for rotator cuff insertions)
   • Lesser tubercle
   • Surgical neck of humerus
   • Deltoid tuberosity (where deltoid inserts)
2. Glenohumeral (shoulder) joint - the synovial joint between the head of humerus and glenoid fossa of scapula
3. Lateral end of the clavicle and acromioclavicular joint (partially)

---

B. Muscles (Rotator Cuff and Others)

---

C. Nerves

---

D. Blood Vessels

---

E. Bursae

---

F. The Three Spaces in the Posterior Wall

1. Quadrangular Space

• Boundaries: Teres minor (above), teres major (below), surgical neck of humerus (lateral), long head of triceps (medial)
• Contents: Axillary nerve + posterior circumflex humeral artery and vein

2. Triangular Space

• Boundaries: Teres minor (above), teres major (below), long head of triceps (lateral)
• Contents: Circumflex scapular artery and vein

3. Triangular Interval

• Boundaries: Teres major (above), long head of triceps (medial), shaft of humerus (lateral)
• Contents: Radial nerve + profunda brachii artery

---

Applied Anatomy

1. Anterior approach to shoulder surgery (deltopectoral approach): Incision along the deltopectoral groove (where cephalic vein runs); the deltoid is retracted to expose the rotator cuff and joint
2. Quadrangular space syndrome: Compression of axillary nerve in the space causing weakness of deltoid and teres minor
3. Subacromial injection: Steroid injections given into the subacromial space for rotator cuff impingement and bursitis

---

---

Q.4 - Attachment of Pectoralis Major Muscle [7 Marks]

Introduction

Attachments

Origin - TWO Heads

1. Clavicular Head

• Anterior surface of the medial half of the clavicle
• Originates as a flat, thin fleshy sheet

2. Sternocostal (Sternal) Head

• Anterior surface of the sternum (manubrium + body) down to the level of the 6th or 7th costal cartilage
• Costal cartilages of ribs 1 to 6 (or 7)
• Aponeurosis of the external oblique muscle of the abdomen (the lower fibers form an "abdominal part")

Insertion

• Both heads converge on the humerus but form a bilaminar (two-layered) tendon:
  • The tendon inserts into the lateral lip of the intertubercular sulcus (bicipital groove) of the humerus
  • The clavicular head passes forward to form the anterior lamina and inserts into the lower part of the lateral lip
  • The sternocostal head twists 180° upon itself so its lower fibers become the posterior lamina and insert higher on the lateral lip
  • This twist means the muscle has a wide origin but a narrow, concentrated insertion

Diagram

Nerve Supply

Actions

Relations

• Superficially: Skin, subcutaneous fat, and deep fascia; nipple lies over the 4th intercostal space
• Deep to pectoralis major: Pectoralis minor, subclavius, clavipectoral fascia, axillary vessels, and brachial plexus
• Medially: Sternum and costal cartilages
• Laterally: Deltoid muscle (the deltopectoral groove contains the cephalic vein)

Applied Anatomy

1. Anterior Axillary Fold

2. Breast Anatomy and Cancer

• The breast overlies pectoralis major
• In breast cancer, the tumor may fix to the pectoralis major fascia (dimpling of skin) or the muscle itself
• Modified radical mastectomy preserves pectoralis major

3. Pectoralis Major Flap (Myocutaneous Flap)

• The pectoralis major is used as a workhorse flap in reconstructive surgery of the neck, oral cavity, and face
• Blood supply: Pectoral branch of thoracoacromial artery (dominant) + lateral thoracic artery (minor)

4. Pectoralis Major Rupture

• Rare injury; seen in weight lifters (bench press)
• The muscle tears at its humeral insertion
• The anterior axillary fold disappears and a gap is palpable

5. Nipple and Areola

---

---

Q.5 - Attachments, Actions and Nerve Supply of Serratus Anterior Muscle [7 Marks]

Introduction

Attachments

Origin

• Lateral surfaces and upper borders of the upper 8 or 9 ribs (ribs I to IX) by separate muscular slips
• Each slip arises from a separate rib
• The slips also arise from the fascia over the intercostal spaces
• The upper two slips interdigitate with slips of origin of pectoralis minor (ribs 3, 4, 5) and the lower slips interdigitate with external oblique

Insertion

• Upper 2 slips (from ribs I and II): Insert on the costal surface near the superior angle of the scapula
• Middle slips (from ribs II to IV): Insert along the costal surface of the medial border
• Lower 4-5 slips (from ribs V to IX): Insert on the costal surface of the inferior angle (the largest and most important part)

Diagram

Actions

Nerve Supply

The Long Thoracic Nerve (Nerve of Bell)

Applied Anatomy

Winging of Scapula (Winged Scapula)

1. Stabbing/penetrating wounds to the lateral chest wall
2. Radical mastectomy (nerve lies in the axillary fat and is vulnerable)
3. Carrying heavy bags on the shoulder
4. First rib resection for thoracic outlet syndrome
5. Viral neuritis (Parsonage-Turner syndrome)
6. Poorly positioned axiillary crutches

• At rest: The medial border of the scapula lifts off the chest wall, giving the appearance of a "wing"
• On pushing against a wall: The medial border and inferior angle protrude prominently backward
• On attempting to elevate the arm: Patient cannot raise arm above 90° (the scapula fails to rotate)

---

---

Q.6 - Boundaries and Contents of Carpal Tunnel. Explain Carpal Tunnel Syndrome [7 Marks]

Introduction

Boundaries of the Carpal Tunnel

Roof (Anterior)

• Flexor retinaculum (transverse carpal ligament) - a thick fibrous band, approximately 2-3 cm wide and 1-2 mm thick
• It is attached:
  • Medially: Pisiform and hook of hamate
  • Laterally: Scaphoid tubercle and ridge of trapezium

Floor and Sides (Posterior/Lateral/Medial)

• The concave arch formed by the carpal bones:
  • Lateral side: Scaphoid (tubercle) and Trapezium (ridge)
  • Medial side: Pisiform and Hook of hamate
  • Floor (deep): Capitate and Lunate

Contents of the Carpal Tunnel

Carpal Tunnel Syndrome (CTS)

Definition

Etiology (Causes of Increased Pressure)

Pathophysiology

1. Any condition that reduces the capacity of the tunnel or increases the volume of contents → increased pressure within the tunnel
2. Pressure impairs venous return → intraneural edema → further pressure
3. Ischemia of the median nerve → demyelination → sensory then motor changes
4. Chronic cases → axonal degeneration → wasting (irreversible)

Clinical Features

Symptoms (Sensory - earliest)

1. Pain, tingling (paresthesia), and numbness in the thumb, index finger, middle finger, and lateral half of ring finger (median nerve territory)
2. Nocturnal symptoms (waking at night with hand pain/tingling) - classic presenting symptom; due to venous stasis when lying flat
3. Relief of symptoms by hanging the arm out of bed or shaking the wrist

Signs (Motor - later)

1. Weakness of thenar muscles: Difficulty opposing thumb (pinching/gripping objects)
2. Wasting of thenar eminence - in chronic/severe cases
3. Ape thumb (simian) deformity: Thumb lies in the plane of the palm due to loss of opposition/abduction

Distribution of Sensory Loss

• The palmar cutaneous branch of the median nerve (which arises before entering the carpal tunnel and passes over the retinaculum) → sensation of the lateral part of the palm is PRESERVED in CTS

Special Clinical Tests

Investigations

1. Nerve conduction studies (NCS): Gold standard - shows slowing of conduction velocity at wrist
2. Electromyography (EMG): Shows denervation in thenar muscles in severe cases
3. Ultrasound: Shows enlarged median nerve at tunnel entrance

Treatment

---

---

Q.7 - Specify the Nerve Supply and Actions of Interossei of the Hand [7 Marks]

Introduction

Classification

Nerve Supply

• The deep branch of the ulnar nerve enters the hand by passing lateral to the pisiform, through the hypothenar muscles, and sweeps across the palm deep to the long flexor tendons to supply all interossei
• Root value: C8, T1

Palmar Interossei (4 muscles - PAD)

Dorsal Interossei (4 muscles - DAB)

Common Actions of ALL Interossei

1. Flexion of the metacarpophalangeal (MCP) joints - by their proximal attachment on the bases of proximal phalanges
2. Extension of the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints - by their distal attachment into the extensor (dorsal) expansion/hood

Insertion into Extensor Hood

• Pull the proximal phalanx into flexion at the MCP
• Through the hood, extend the IP joints
• This is the basis of the Bouchard test and the clinical hand position

Applied Anatomy

1. Froment's Sign (tests 1st dorsal interosseous / adductor pollicis)

• Ask the patient to hold a piece of paper between the thumb and index finger
• Normally, the adductor pollicis (ulnar nerve) holds it with the IP joints straight
• In ulnar nerve palsy: the patient compensates by flexing the IP joint of the thumb (using FPL - median nerve) = positive Froment's sign

2. Ulnar Nerve Palsy - Effects on Interossei

3. Rheumatoid Arthritis (RA)

• Synovitis causes stretching of the extensor hood
• Interossei may sublux, leading to boutonniere deformity (PIP flexion + DIP extension) or swan neck deformity (PIP hyperextension)

---

---

Q.8 - Draw and Explain the Diagram of Brachial Plexus [7 Marks]

Introduction

Diagrams

Components (Mnemonic: "Really Tired? Drink Cold Beer" = Roots, Trunks, Divisions, Cords, Branches)

---

1. ROOTS (5 Roots: C5, C6, C7, C8, T1)

• Located: Between the anterior scalene and middle scalene muscles in the neck (scalene triangle)
• Receive gray rami communicantes from the sympathetic trunk

Branches from Roots:

---

2. TRUNKS (3 Trunks)

Branches from Superior Trunk:

---

3. DIVISIONS (6 Divisions - NO branches arise)

• Anterior divisions = will ultimately supply FLEXOR compartments
• Posterior divisions = will supply EXTENSOR compartments

---

4. CORDS (3 Cords, named by relationship to the 2nd part of axillary artery)

Branches from Cords:

---

5. TERMINAL BRANCHES (5 Main Nerves)

Applied Anatomy - Brachial Plexus Injuries

---

---

Q.9 - Explain the Anatomical Basis of Deformity of Erb's Paralysis [7 Marks]

Introduction

Mechanism of Injury

In Neonates (Obstetric Erb's palsy):

• Difficult labor with shoulder dystocia
• Forceps traction on the head during shoulder presentation
• The shoulder is pushed down and the head pulled away - tearing C5, C6 roots

In Adults:

• Motorcycle accidents (fall on outstretched arm with head forced away)
• Fall from a horse (shoulder hits the ground, head forced sideways)
• Carrying heavy loads on shoulders
• Direct blow depressing the shoulder

Muscles Affected (C5 and C6 supplied muscles)

The Classic Deformity: "Waiter's Tip" / "Policeman Receiving a Tip"

Sensory Loss

• Over the lateral aspect of the upper arm (axillary nerve territory - C5)
• Over the lateral forearm (musculocutaneous nerve territory - C6)
• A strip along the radial side of the forearm and dorsum of hand

Reflexes Affected

• Biceps reflex (C5, C6): Absent
• Brachioradialis (supinator) reflex (C5, C6): Absent
• Triceps reflex (C7) and finger reflexes (C8) intact

Erb's Point

• The junction of C5 and C6 roots to form the upper trunk
• Located ~2-3 cm above the clavicle, posterior to the sternocleidomastoid
• Stimulation of this point (electrical or surgical) causes all the muscles listed above to respond

Differentiation from Klumpke's Palsy

Prognosis and Treatment

• Obstetric Erb's palsy: Most cases recover spontaneously within 3-6 months if nerve is neuropraxic (not avulsed)
• Physiotherapy to prevent contractures during recovery
• Surgical treatment (nerve grafting, neurolysis) if no improvement by 3-6 months
• Avulsion injuries (nerve pulled from spinal cord) are irreparable

---

---

Q.10 - Pronation and Supination [7 Marks]

Definitions

• Supination: Rotation of the forearm so the palm faces anteriorly (in anatomical position) or upward. The radius lies parallel to the ulna. The word "supination" comes from "supine" (lying on back).
• Pronation: Rotation of the forearm so the palm faces posteriorly or downward. The radius crosses obliquely over the ulna. "Prone" = face down.

Joints Involved

1. Proximal Radio-Ulnar Joint

• Type: Pivot (trochoidal) synovial joint
• Articulation: The head of radius rotates within the fibro-osseous ring formed by the radial notch of the ulna and the anular ligament
• The head of radius spins within this ring

2. Distal Radio-Ulnar Joint

• Type: Pivot synovial joint
• Articulation: The concave surface of the ulnar notch of the radius rotates around the head of the ulna
• The radius swings around the stationary ulna

Movement Summary

• Supination: Radius rotates laterally → becomes parallel to ulna
• Pronation: Lower end of radius rotates medially → crosses over the ulna

Muscles of Supination

Muscles of Pronation

Range of Movement

• Supination: 0° to approximately 85-90°
• Pronation: 0° to approximately 75-80°
• Combined range of ~170° at the radioulnar joints

The "Combined Movement" at the Elbow

• When making a fist and supinating against resistance (like using a screwdriver), the biceps does most of the work
• When gravity-assisted pronation is needed (putting a plate down), pronator quadratus acts

Applied Anatomy

1. Fractures and Deformity

2. Pronator Teres Syndrome

• Compression of the median nerve between the two heads of pronator teres
• Presents similarly to carpal tunnel syndrome but with forearm pain on resisted pronation
• Differentiated from CTS by the presence of forearm pain and absence of nocturnal symptoms

3. Posterior Interosseous Nerve (PIN) Compression

• The deep branch of the radial nerve passes through the two heads of the supinator (the "arcade of Frohse")
• Compression here causes weakness of finger extension without wrist drop (ECRL intact)

4. Clinical Test for Pronation/Supination

• Test with elbow fixed at 90° to eliminate shoulder rotation
• Note that the humerus must not rotate during the test (fix by pressing elbow against body)

5. Isolated Radial Head Fracture

• The most common elbow fracture in adults
• Causes painful limitation of pronation and supination
• Treated conservatively if undisplaced; radial head excision if comminuted

---

---

Q.11 - Median Nerve in the Hand and Forearm [7 Marks]

Root Value and Formation

• Root value: C6, C7, C8, T1 (sometimes C5)
• Formation: From the union of two roots:
  • Lateral root (C6, C7) from the lateral cord
  • Medial root (C8, T1) from the medial cord
  • These unite in front of (anterior to) the 3rd part of the axillary artery to form the median nerve

Course in the Arm

• Enters the arm at the inferior margin of teres major
• Initially lies lateral to the brachial artery in the proximal arm
• Crosses the brachial artery at mid-arm to lie medial to it in the distal arm
• No motor branches in the arm
• Enters the cubital fossa lying medial to the brachial artery

Course in the Forearm

1. Passes between the two heads of pronator teres (humeral head and ulnar head) - the first muscular branch here
2. Passes deep to the fibrous arch of flexor digitorum superficialis (FDS bridge)
3. Descends between FDS (superficially) and FDP + FPL (deep)
4. Gives off the anterior interosseous nerve (AIN) just below the elbow
5. About 5 cm above the wrist, the palmar cutaneous branch arises (passes superficial to the retinaculum - this branch is NOT compressed in CTS)
6. Crosses the wrist lying between the tendon of FDS (medially) and FCR (laterally), just lateral to palmaris longus

Branches in the Forearm

Direct Muscular Branches (all "surface" flexors except FCU and medial FDP):

Anterior Interosseous Nerve (AIN)

Palmar Cutaneous Branch

• Arises 5 cm above the wrist from the radial side of the median nerve
• Passes superficial (not through) the flexor retinaculum
• Supplies skin over the thenar eminence and lateral palm
• This branch is NOT compressed in carpal tunnel syndrome → sensory over lateral palm is preserved in CTS

Course in the Hand

1. Passes through the carpal tunnel (deep to the flexor retinaculum)
2. Immediately distal to the retinaculum it divides into:

Recurrent (Thenar) Branch (Motor - most important)

• Arises from the radial side of the median nerve just distal to the retinaculum
• Recurves back and enters the thenar eminence
• Supplies the three thenar muscles

Palmar Digital Nerves (Sensory + Motor to lumbricals)

Diagram (Course and Branches)

Summary: Complete Muscles Supplied

Applied Anatomy - Effects of Median Nerve Injury

High Lesion (at the elbow - e.g., supracondylar fracture in children):

• All forearm muscles (above) paralyzed
• "Pronator sign": Unable to pronate against resistance
• "Pen test": Cannot flex the DIP of index finger (FDP lateral half paralyzed) or IP of thumb (FPL paralyzed) - demonstrates AIN injury
• Loss of opposition of thumb
• Sensory loss over lateral 3½ digits and lateral palm
• "Pointing index" when making a fist (due to FDP lateral half paralysis)

Low Lesion (at the wrist - Carpal Tunnel Syndrome):

• Thenar wasting
• Loss of opposition of thumb
• "Ape thumb" or "simian thumb" deformity
• Sensory loss over lateral 3½ digits (NOT the lateral palm - palmar cutaneous branch is spared)
• Power of forearm flexors preserved

---

---

Q.12 - Musculocutaneous Nerve [7 Marks]

Introduction

Root Value

Origin

• Arises as the terminal branch of the lateral cord of the brachial plexus
• Originates in the axilla, at the level of the lower border of the pectoralis minor

Course

In the Axilla:

• Arises from the lateral cord of the brachial plexus
• Passes laterally, lying anterior to the axillary artery

In the Arm:

1. Pierces the coracobrachialis muscle (which it innervates as it passes through)
2. Passes obliquely downward between the biceps brachii (anteriorly) and the brachialis (posteriorly)
3. Supplies motor branches to biceps brachii and brachialis as it passes between them
4. Emerges at the lateral border of the biceps brachii tendon, just proximal to the elbow

Terminal Branch:

1. Passes through the deep fascia and continues as the lateral cutaneous nerve of the forearm

Diagram

Branches and Distribution

1. Branch to Coracobrachialis (C5, C6, C7)

• Arises as the nerve enters or pierces coracobrachialis
• Supplies the coracobrachialis muscle

2. Branches to Biceps Brachii (C5, C6)

• Several branches given off as the nerve passes between biceps and brachialis
• Supplies both heads of biceps brachii

3. Branches to Brachialis (C5, C6)

• Branches given to the bulk of the brachialis as the nerve descends
• Note: The lateral part of brachialis is also supplied by the radial nerve (C6) - the only flexor supplied by the radial nerve

4. Articular Branch

• Small branches to the elbow joint

5. Lateral Cutaneous Nerve of the Forearm (sensory terminal)

• Passes through the deep fascia lateral to the biceps tendon at the elbow
• Divides into anterior and posterior branches:
  • Anterior branch: Supplies the anterior (volar) surface of the lateral forearm as far as the thenar eminence
  • Posterior branch: Supplies the posterior (dorsal) surface of the lateral forearm

Summary of Muscles Supplied

Sensory Distribution

Applied Anatomy

1. Injury to Musculocutaneous Nerve

• Penetrating injuries to the arm
• Dislocation of the shoulder (rare)
• Violent arm movement in sports (arm wrestling injury)
• Compression from prolonged hyperabduction (surgery)

• Weakness of elbow flexion (brachialis, biceps) - particularly with the forearm supinated
• Loss of supination (biceps is the main supinator)
• Loss of biceps reflex (C5, C6) - important clinical sign
• Sensory loss over the lateral forearm (lateral cutaneous nerve of forearm)
• The coracobrachialis is paralyzed (but clinically not noticed much)

2. Clinical Testing

• Motor: Flex elbow against resistance with forearm supinated (biceps); flex elbow in mid-prone position (brachialis)
• Reflex: Biceps jerk (C5, C6) will be absent
• Sensory: Test the lateral forearm

3. Distinction from C5-C6 Root Lesion

4. Coracobrachialis as a Landmark

---

---

Q.13 - Specify the Origin, Insertion and Distribution of Radial Nerve [7 Marks]

Root Value and Origin

• Root value: C5, C6, C7, C8, T1
• Origin: Arises as the terminal branch of the posterior cord of the brachial plexus
• It is the largest branch of the brachial plexus and the principal nerve of the extensor compartments

Course and Distribution

1. In the Axilla

• Lies posterior to the axillary artery
• Passes with the profunda brachii artery toward the triangular interval

2. In the Arm - Posterior Compartment

• Lies in the radial groove (spiral groove) on the posterior surface of the humerus - in direct contact with bone
• Accompanied by the profunda brachii artery
• Travels diagonally from medial to lateral

3. At the Lateral Epicondyle

4. Superficial Branch (Purely Sensory)

• Passes deep to brachioradialis, descending lateral to the radial artery
• Emerges at the wrist between brachioradialis and ECRL, winds around the radius
• Supplies: Skin of the dorsal lateral hand, dorsum of lateral 3½ digits (proximal phalanges and parts of middle phalanges of thumb, index, middle, lateral ring fingers)
• The first dorsal webspace (between thumb and index) is the most consistent area

5. Deep Branch = Posterior Interosseous Nerve (PIN)

• Winds around the neck of the radius between the two heads of the supinator muscle (passing through the "Arcade of Frohse" - the fibrous arch of the supinator)
• Enters the posterior compartment of the forearm
• Supplies all muscles of the posterior forearm:

Diagram

Complete Summary of Distribution

Motor Distribution:

Sensory Distribution:

---

---

Q.14 - Describe Root Value, Muscles Supplied and Clinical Anatomy of Radial Nerve [7 Marks]

Root Value

Muscles Supplied (Complete List)

Clinical Anatomy - Sites of Injury

Site 1: In the Axilla (High radial nerve injury)

Site 2: In the Radial (Spiral) Groove - Most Common Site

Wrist Drop - The Classic Deformity

Site 3: Posterior Interosseous Nerve (PIN) Palsy - At the Elbow

Site 4: Superficial Radial Nerve Injury (Wartenberg's Syndrome)

Summary Table of Radial Nerve Injuries

Clinical Testing

1. Motor: Ask patient to extend wrist and fingers against resistance
2. Reflex: Triceps jerk (C7), brachioradialis (C5-C6)
3. Sensory: Test first dorsal webspace (most consistent area of radial nerve sensory territory)
4. Tinel's sign: Tap over the radial groove for nerve regeneration

---

---

Q.15 - Specify the Parts, Course and Branches of the Axillary Artery [7 Marks]

Introduction

Course

Parts (Divided by Pectoralis Minor)

Branches in Detail

First Part: 1 Branch

• Passes medially between pectoralis major and minor
• Supplies: Upper two intercostal spaces, pectoralis major and minor muscles

---

Second Part: 2 Branches

• Short trunk that pierces the clavipectoral fascia just medial to the pectoralis minor
• Immediately divides into 4 branches:

• Descends along the lateral border of pectoralis minor
• Accompanies the long thoracic nerve
• Supplies: Pectoralis major and minor, serratus anterior, lateral breast (important in breast surgery)
• Larger in females (supplies lateral mammary branches)

---

Third Part: 3 Branches

• Descends along the lateral border of subscapularis
• Divides almost immediately into:

• Passes anteriorly around the surgical neck of the humerus
• Anastomoses with the posterior circumflex humeral artery
• Smaller of the two circumflex humeral arteries
• Supplies: Anterior capsule of shoulder joint; tendon of long head of biceps in bicipital groove

• Much larger; passes through the quadrangular space with the axillary nerve
• Winds around the posterior surgical neck of the humerus
• Anastomoses with the anterior circumflex humeral artery
• Supplies: Deltoid (major supply), glenohumeral joint capsule, teres minor, head of humerus

Relations of the Axillary Artery

Applied Anatomy

1. Scapular Anastomosis

• Provides collateral circulation when axillary artery is ligated
• Allows the hand to remain viable even when the axillary artery is occluded proximal to the subscapular artery origin

2. Axillary Artery Injury

• Penetrating trauma (stab, gunshot wounds) or severe shoulder dislocation
• Vascular surgeon must be involved early
• Collateral anastomosis may not be sufficient in acute occlusion

3. Surgical Importance

• In breast surgery (mastectomy, axillary clearance): The lateral thoracic, subscapular, and thoracodorsal arteries are all encountered
• The thoracodorsal artery is the pedicle for the latissimus dorsi flap - one of the most widely used reconstructive flaps

4. Thoracodorsal Artery Flap

• Reliable pedicle for latissimus dorsi myocutaneous flap
• Used in breast reconstruction, head and neck reconstruction

---

---

Q.16 - Cubital Fossa [7 Marks]

Introduction

Boundaries

Diagram

Contents (Lateral to Medial - mnemonic: "TAN" = Tendon, Artery, Nerve)

• The radial nerve and its terminal branches lie just outside the lateral boundary (beneath brachioradialis), not truly within the fossa - the radial nerve divides into:
  • Superficial branch: Continues deep to brachioradialis
  • Deep branch (PIN): Enters supinator
• The ulnar nerve does NOT pass through the cubital fossa - it passes posterior to the medial epicondyle (in the cubital tunnel)

Roof Contents (Superficial Layer)

Bicipital Aponeurosis

• A flat fibrous expansion from the medial aspect of the biceps tendon
• Passes medially and distally to blend with the deep fascia of the forearm
• Covers and protects the brachial artery and median nerve anteriorly
• Used as a guide during vascular surgery (divide the aponeurosis to access the brachial artery)
• The sharp medial edge of the bicipital aponeurosis can be palpated

Applied Anatomy

1. Blood Pressure Measurement

• The sphygmomanometer cuff is applied to the arm
• The stethoscope is placed over the brachial artery in the cubital fossa
• Korotkoff sounds are heard here

2. Venipuncture and IV Cannulation

• Blood sampling
• IV cannulation
• Blood transfusion
• Cardiac catheterization (older technique)

3. Elbow Dislocations and Fractures

• The sharp distal fragment may injure the brachial artery → ischemia to the forearm
• The median nerve (anterior interosseous branch) may be injured
• The radial nerve may be injured
• Volkmann's ischemic contracture results from unrecognized arterial injury → forearm compartment syndrome → fibrosis → flexion contracture of wrist and fingers

4. Entrapment Syndromes

• Pronator teres syndrome: Compression of the median nerve between the two heads of pronator teres as it exits the cubital fossa → pain in the forearm + weakness of FPL and FDP
• Anterior interosseous nerve syndrome: AIN compressed after it branches from the median nerve → weakness of FPL + lateral FDP + pronator quadratus

5. Branchial Aneurysm

• Traumatic pseudoaneurysm of the brachial artery can develop in the cubital fossa after arterial puncture
• Presents as a pulsatile swelling with a bruit

6. Surgical Access

• The Henry approach (anterior approach to the forearm) begins at the cubital fossa
• The brachioradialis-FCR interval is exploited after identifying the key structures of the fossa

---

---

Q.17 - Axilla - Boundaries, Contents and Applied Anatomy [7 Marks]

Introduction

Shape

• 1 apex (inlet - superior)
• 4 walls (anterior, posterior, medial, lateral)
• 1 base (floor - inferior)

Boundaries

Apex (Axillary Inlet)

• Directed upward, medially, and posteriorly
• The margins of the inlet are entirely bony:
  • Anterior: Posterior surface of the clavicle
  • Posterior: Superior border of the scapula to the coracoid process
  • Medially: Lateral border of rib I
• The apex communicates with the root of the neck (posterior triangle)

Anterior Wall

Posterior Wall

Medial Wall

• Serratus anterior muscle (overlying ribs 1-4 and intercostal spaces)
• Upper part of thoracic wall

Lateral Wall (Narrowest Wall)

• Intertubercular sulcus (bicipital groove) of the humerus
• Formed by the convergence of the anterior and posterior walls on the humerus

Floor (Base)

• Formed by the axillary fascia (continuation of clavipectoral fascia and pectoral/latissimus fascia)
• Covered by skin bearing axillary hair
• The skin of the floor forms the "armpit"

Diagram

Contents of the Axilla

1. Axillary Artery (and its 6 branches)

• Continuation of the subclavian artery from the lateral border of rib I
• Becomes the brachial artery at the inferior border of teres major
• Divided into 3 parts by pectoralis minor (see Q.15)

2. Axillary Vein

• Formed by the union of the brachial veins + basilic vein at the lower border of teres major
• Lies medial and anterior to the axillary artery
• Becomes the subclavian vein at the lateral border of rib I
• Tributaries: Cephalic vein + veins accompanying the 6 arterial branches

3. Brachial Plexus (Cords and Terminal Branches)

• The three cords surround the second part of the axillary artery:
  • Lateral cord (C5, C6, C7): Lateral to artery
  • Medial cord (C8, T1): Medial to artery
  • Posterior cord (C5-T1): Posterior to artery
• Terminal branches arise in the distal axilla

4. Axillary Lymph Nodes (5 Groups)

• Level I: Below/lateral to pectoralis minor
• Level II: Behind pectoralis minor (including the central group)
• Level III: Above/medial to pectoralis minor (apical group)

5. Other Contents

Applied Anatomy

1. Breast Cancer and the Axilla

• Approximately 75% of breast lymphatic drainage goes to the axillary nodes (primarily Level I - pectoral group)
• 25% drains to the internal mammary chain
• Sentinel lymph node biopsy (SLNB): The first lymph node to receive drainage from the tumor is identified and biopsied; if negative, formal axillary dissection can be avoided
• Axillary node dissection: Removal of Level I-III nodes; staging procedure
• Complications of axillary dissection:
  • Long thoracic nerve injury → winged scapula
  • Thoracodorsal nerve injury → paralysis of latissimus dorsi
  • Axillary vein injury → upper limb lymphedema (chronic arm swelling)

2. Winged Scapula

• Injury to the long thoracic nerve (C5, C6, C7) during axillary surgery
• Serratus anterior is paralyzed
• Medial border of scapula wings away from the chest wall on pushing

3. Quadrangular Space Syndrome

• Compression of the axillary nerve and posterior circumflex humeral artery in the quadrangular space (bounded by teres minor, teres major, long head of triceps, surgical neck of humerus)
• Causes: Hypertrophied muscles, fibrous bands, shoulder overuse
• Symptoms: Deltoid weakness, dull aching shoulder pain, loss of sensation over "badge area"

4. Axillary Vein Thrombosis

• "Effort thrombosis" or Paget-Schroetter syndrome
• Caused by repetitive overhead activities (swimmers, baseball pitchers, weight lifters)
• Presents with sudden arm swelling, heaviness, and pain
• Treated with anticoagulation or thrombolysis

5. Crutch Palsy

• Compression of the radial nerve (or whole posterior cord) in the axilla from poorly fitted axillary crutches
• Causes radial nerve injury at the axillary level (highest possible level)
• All muscles including triceps are paralyzed

6. Axillary Dissection and Lymphedema

• Disruption of lymphatic channels during axillary clearance → chronic lymphedema of the upper limb
• The arm becomes chronically swollen and there is a risk of recurrent cellulitis
• Prevented by sentinel node biopsy technique

---

Reference: All answers compiled from Gray's Anatomy for Students, 4th Edition (Drake, Vogl, Mitchell), S. Das Manual of Clinical Surgery, 13th Edition, General Anatomy and Musculoskeletal System - THIEME Atlas of Anatomy, and Gray's Anatomy, 41st Edition. Source: Medical Textbook Library (Orris).

---

• Introduction (0.5 mark): Define the topic in 1-2 sentences
• Main body with subheadings (5 marks): Use tables, numbered lists, and organized subheadings. Examiners look for completeness.
• Diagram (1 mark): Even a simple labeled diagram earns a mark
• Applied/Clinical anatomy (0.5-1 mark): Always add 2-3 clinical points at the end - this differentiates good answers