Keyword Definitions
• Mammary gland – Modified sweat gland, present in superficial fascia of chest wall.
• Axillary tail of Spence – Extension of breast into axilla, important in carcinoma spread.
• Cooper’s ligaments – Fibrous septa supporting breast tissue, tethered in malignancy.
• Retromammary space – Loose areolar plane between breast and pectoral fascia, allows mobility.
• Internal mammary artery – Provides medial blood supply to breast.
• Lateral thoracic artery – Provides lateral blood supply to breast.
• Nipple – Central pigmented projection, sensory innervation mainly from 4th intercostal nerve.
• Lobules – Functional units of breast, site of lactation.
• Lactiferous ducts – Drain lobules, open at nipple.
• Areola – Pigmented skin surrounding nipple, with Montgomery’s glands.
• Carcinoma breast – Malignancy spreading via lymphatics, often to axillary nodes.
Chapter: Anatomy / Thorax
Topic: Breast
Subtopic: Structure, Supply and Clinical Anatomy
Lead Question – 2013
All are true about mammary gland, except?
a) Is a modified sweat gland
b) Extends from 2nd to 6th rib vertically
c) Supplied by internal mammary artery
d) Nipple is supplied by 6th intercostal nerve
Explanation: The nipple is supplied by the 4th intercostal nerve, not the 6th. The breast is a modified sweat gland extending vertically from the 2nd to 6th rib. Blood supply is mainly by internal mammary and lateral thoracic arteries. Correct answer: (d). Clinical: Nipple sensation is important in surgeries.
Guessed Questions for NEET PG
1) Which nerve supplies the nipple?
a) 2nd intercostal nerve
b) 4th intercostal nerve
c) 6th intercostal nerve
d) Supraclavicular nerve
Explanation: The nipple is supplied by the 4th intercostal nerve, forming a key surface landmark. Correct answer: 4th intercostal nerve. Clinical: This landmark helps locate breast tissue during surgical incisions and reconstructive procedures.
2) Primary blood supply to the lateral portion of breast is from?
a) Internal mammary artery
b) Lateral thoracic artery
c) Subscapular artery
d) Thoracoacromial artery
Explanation: The lateral thoracic artery, a branch of the axillary artery, supplies the lateral breast. Correct answer: Lateral thoracic artery. Clinical: Preserved during mastectomy to maintain vascular supply for flaps.
3) Which statement about Cooper’s ligaments is true?
a) Are vascular structures
b) Are fibrous septa supporting breast
c) Connect nipple to areola only
d) Present only in lactating women
Explanation: Cooper’s ligaments are fibrous septa extending from skin to deep fascia, providing support. Correct answer: Fibrous septa. Clinical: In carcinoma, their contraction causes skin dimpling, a classic sign.
4) The axillary tail of Spence:
a) Lies in inframammary fold
b) Extends into axilla
c) Is absent in males
d) Has no clinical significance
Explanation: The axillary tail extends into the axilla and is clinically important as carcinoma often involves it. Correct answer: Extends into axilla. Clinical: Careful examination is essential in breast cancer screening.
5) Retromammary space allows:
a) Venous drainage
b) Lymphatic drainage
c) Free movement of breast
d) Attachment to skin
Explanation: Retromammary space is a plane of loose areolar tissue permitting free mobility of the breast over pectoral fascia. Correct answer: Free movement of breast. Clinical: Fixation of breast to chest wall indicates advanced carcinoma.
6) Which artery provides medial breast supply?
a) Axillary artery
b) Internal mammary artery
c) Subscapular artery
d) Thoracoacromial artery
Explanation: The internal mammary (internal thoracic) artery provides medial supply via perforating branches. Correct answer: Internal mammary artery. Clinical: In CABG, this artery is often harvested, affecting breast circulation.
7) Which lymph nodes are primarily involved in breast carcinoma spread?
a) Cervical
b) Axillary
c) Mediastinal
d) Inguinal
Explanation: Axillary lymph nodes are primary sites for metastatic spread from breast carcinoma. Correct answer: Axillary nodes. Clinical: Sentinel lymph node biopsy helps identify early spread and guides surgical treatment.
8) Which hormone is mainly responsible for breast milk ejection?
a) Prolactin
b) Estrogen
c) Oxytocin
d) Progesterone
Explanation: Oxytocin, released from posterior pituitary, causes contraction of myoepithelial cells for milk ejection. Correct answer: Oxytocin. Clinical: Suckling reflex stimulates oxytocin release, essential in lactation.
9) In carcinoma of breast, peau d’orange appearance is due to?
a) Blockage of veins
b) Blockage of lymphatics
c) Nerve involvement
d) Arterial spasm
Explanation: Obstruction of dermal lymphatics by carcinoma causes edema, producing skin thickening with dimpled “peau d’orange” appearance. Correct answer: Blockage of lymphatics. Clinical: Indicates locally advanced carcinoma.
10) A lactating mother develops mastitis, the most common causative organism is?
a) E. coli
b) Streptococcus
c) Staphylococcus aureus
d) Klebsiella
Explanation: Staphylococcus aureus is the commonest organism causing lactational mastitis through cracks in nipple. Correct answer: Staphylococcus aureus. Clinical: Treated with antibiotics and continued breastfeeding to prevent abscess formation.
Keyword Definitions
• Median nerve – Major nerve of forearm and hand, supplies palmar aspect of lateral 3½ fingers.
• Ulnar nerve – Supplies medial 1½ fingers and most intrinsic hand muscles.
• Radial nerve – Provides sensation to dorsum of hand and motor supply to extensor compartment.
• Digital nerves – Terminal branches of median and ulnar nerves, supplying fingers and nail beds.
• Nail bed – Specialized skin beneath nail plate, richly innervated for fine sensation.
• Palmar digital branches – Arise from median nerve, innervate palmar surfaces of lateral fingers.
• Dorsal digital branches – Arise from radial and ulnar nerves, supply dorsum of fingers.
• Clinical surface anatomy – Nail bed sensation is a key test in digital nerve injuries.
• Carpal tunnel – Narrow passage in wrist transmitting median nerve and tendons, site of compression.
• Sensory testing – Performed with pinprick or light touch to assess nerve integrity in trauma.
• Hand dominance – Important in recovery and surgical repair of nerve injuries.
Chapter: Anatomy / Upper Limb
Topic: Hand
Subtopic: Nerve supply of digits and nail bed
Lead Question – 2013
The nerve supply of nail bed of index finger is?
a) Superficial br of radial nerve
b) Deep br of radial nerve
c) Median nerve
d) Ulnar nerve
Explanation: The nail bed of index finger is supplied by the palmar digital branches of the median nerve. The superficial branch of radial nerve supplies dorsum of hand but not the nail bed of index. Correct answer: (c) Median nerve. Clinical: Sensory loss here suggests median nerve injury.
Guessed Questions for NEET PG
1) Sensory loss over nail bed of middle finger indicates injury to?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: The nail bed of middle finger, like index, is innervated by the median nerve. Injury to the nerve proximal to wrist causes loss of sensation here. Correct answer: Median nerve. Clinical: Important in diagnosing carpal tunnel syndrome.
2) Which nerve supplies nail bed of little finger?
a) Radial nerve
b) Median nerve
c) Ulnar nerve
d) Musculocutaneous nerve
Explanation: The little finger is supplied by the palmar digital branches of the ulnar nerve. Correct answer: Ulnar nerve. Clinical: Injury to ulnar nerve in Guyon’s canal affects sensation of little finger.
3) Which nerve injury is suspected when thumb, index, and middle finger nail beds lose sensation?
a) Radial nerve
b) Median nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: Loss of sensation in thumb, index, and middle finger nail beds indicates median nerve injury. Correct answer: Median nerve. Clinical: Often seen in carpal tunnel syndrome and supracondylar fractures.
4) The superficial branch of radial nerve supplies?
a) Palmar surface of index finger
b) Dorsum of thumb
c) Nail bed of index finger
d) Palmaris brevis muscle
Explanation: The superficial branch of radial nerve supplies dorsum of thumb and hand but does not reach nail beds of index finger. Correct answer: Dorsum of thumb. Clinical: Injury leads to sensory deficit in dorsum of hand.
5) Injury at wrist producing loss of sensation in nail bed of ring finger (lateral half) indicates?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Posterior interosseous nerve
Explanation: The lateral half of ring finger is supplied by median nerve digital branches. Correct answer: Median nerve. Clinical: Important in mixed finger innervation assessment.
6) Which nerve supplies motor innervation to thenar muscles along with nail bed sensation of index finger?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Axillary nerve
Explanation: The median nerve supplies both thenar muscles (except adductor pollicis and deep head of FPB) and sensation of index finger nail bed. Correct answer: Median nerve. Clinical: Injury causes thenar atrophy and sensory loss.
7) A patient with carpal tunnel syndrome will typically complain of numbness over?
a) Little finger nail bed
b) Index and middle finger nail beds
c) Medial palm
d) Dorsum of hand
Explanation: Carpal tunnel compression of median nerve affects sensation over nail beds of thumb, index, middle, and radial half of ring finger. Correct answer: Index and middle finger nail beds. Clinical: Classic diagnostic sign.
8) Which nerve injury is tested by checking sensation at tip of little finger?
a) Median nerve
b) Radial nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: Sensation at tip of little finger is supplied by ulnar nerve digital branches. Correct answer: Ulnar nerve. Clinical: Simple bedside test to isolate ulnar nerve damage.
9) Which nerve provides sensory supply to dorsum of index finger proximal phalanx?
a) Ulnar nerve
b) Median nerve
c) Superficial radial nerve
d) Musculocutaneous nerve
Explanation: The dorsum of proximal index finger is supplied by superficial branch of radial nerve. Correct answer: Superficial radial nerve. Clinical: Differentiate radial vs median injury.
10) Following supracondylar fracture, patient develops loss of sensation in nail bed of index finger. Which nerve is likely injured?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: Supracondylar fracture often injures median nerve, causing sensory loss in index nail bed. Correct answer: Median nerve. Clinical: Needs urgent assessment due to risk of Volkmann’s ischemic contracture.
Keyword Definitions
• Anatomical snuff box – Triangular depression on lateral wrist, important surface landmark.
• Abductor pollicis longus (APL) – Forms lateral boundary of snuff box.
• Extensor pollicis brevis (EPB) – Lateral boundary with APL.
• Extensor pollicis longus (EPL) – Forms medial boundary.
• Extensor carpi ulnaris (ECU) – Not a boundary of snuff box, lies more medially.
• Radial artery – Runs through floor of snuff box, pulse palpable.
• Scaphoid bone – Floor of snuff box, common fracture site.
• Cephalic vein – Originates near snuff box region.
• Superficial branch of radial nerve – Crosses over snuff box, provides cutaneous innervation.
• Clinical importance – Site for palpating scaphoid fracture tenderness.
• Wrist injuries – Tenderness in snuff box suggests scaphoid fracture.
Chapter: Anatomy / Upper Limb
Topic: Wrist and Hand
Subtopic: Anatomical snuff box and relations
Lead Question – 2013
Boundaries of anatomical snuff box are all except
a) APL
b) EPL
c) EPB
d) ECU
Explanation: The anatomical snuff box is bounded laterally by abductor pollicis longus and extensor pollicis brevis, medially by extensor pollicis longus. Extensor carpi ulnaris is not a boundary. Correct answer: (d) ECU. Clinical: Snuff box tenderness is diagnostic of scaphoid fracture.
Guessed Questions for NEET PG
1) Which structure forms the floor of anatomical snuff box?
a) Capitate
b) Lunate
c) Scaphoid
d) Pisiform
Explanation: The scaphoid forms the main floor of the anatomical snuff box, along with trapezium. Correct answer: Scaphoid. Clinical: Scaphoid fractures are suspected if snuff box tenderness is present after a fall on an outstretched hand.
2) Which artery passes through anatomical snuff box?
a) Ulnar artery
b) Radial artery
c) Brachial artery
d) Interosseous artery
Explanation: The radial artery runs through the floor of the snuff box before entering the palm. Correct answer: Radial artery. Clinical: Radial pulse can be palpated here in lean individuals.
3) Injury to scaphoid bone presents with?
a) Swelling of thenar eminence
b) Pain in anatomical snuff box
c) Loss of thumb extension
d) Tingling of little finger
Explanation: Scaphoid fracture commonly presents with pain and tenderness in anatomical snuff box. Correct answer: Pain in anatomical snuff box. Clinical: Delayed diagnosis risks avascular necrosis of proximal scaphoid.
4) Which tendon crosses the floor of snuff box?
a) Flexor carpi radialis
b) Extensor carpi radialis longus
c) Palmaris longus
d) Flexor digitorum profundus
Explanation: Extensor carpi radialis longus and brevis tendons form part of floor of anatomical snuff box. Correct answer: Extensor carpi radialis longus. Clinical: Palpable tendon aids in anatomical landmarking.
5) Which nerve crosses superficial to anatomical snuff box?
a) Ulnar nerve
b) Median nerve
c) Superficial radial nerve
d) Deep radial nerve
Explanation: The superficial branch of radial nerve crosses superficial to snuff box, supplying cutaneous sensation. Correct answer: Superficial radial nerve. Clinical: Injury causes numbness over dorsum of hand near thumb.
6) Which muscle tendon forms medial boundary of snuff box?
a) EPL
b) EPB
c) APL
d) ECU
Explanation: The medial boundary of the snuff box is formed by extensor pollicis longus tendon. Correct answer: EPL. Clinical: Prominent during thumb extension testing.
7) A patient with fall on outstretched hand and tenderness in snuff box most likely has?
a) Colles fracture
b) Scaphoid fracture
c) Hamate fracture
d) Lunate dislocation
Explanation: Snuff box tenderness is classic for scaphoid fracture. Correct answer: Scaphoid fracture. Clinical: Requires urgent immobilization to prevent avascular necrosis.
8) Which carpal bone is most prone to avascular necrosis after fracture?
a) Lunate
b) Pisiform
c) Scaphoid
d) Capitate
Explanation: The scaphoid bone is prone to avascular necrosis due to retrograde blood supply. Correct answer: Scaphoid. Clinical: Missed fractures can cause chronic wrist pain.
9) In wrist examination, tenderness in anatomical snuff box is tested to rule out?
a) Radial head fracture
b) Scaphoid fracture
c) Ulna styloid fracture
d) Capitate fracture
Explanation: Snuff box tenderness specifically indicates scaphoid fracture. Correct answer: Scaphoid fracture. Clinical: Common in young adults after fall on outstretched hand.
10) Which vein originates near anatomical snuff box?
a) Basilic vein
b) Cephalic vein
c) Median cubital vein
d) Radial vein
Explanation: The cephalic vein begins from venous plexus near the anatomical snuff box. Correct answer: Cephalic vein. Clinical: Important for venous access in upper limb procedures.
Keyword Definitions
• Pectoral region – The area on the anterior chest wall related to pectoral muscles.
• Pectoralis major – Large superficial chest muscle aiding arm adduction and medial rotation.
• Pectoralis minor – Lies deep to pectoralis major, attaches coracoid process to ribs.
• Subclavius – Small muscle beneath clavicle, stabilizes clavicle.
• Infraspinatus – Rotator cuff muscle of scapula, not part of pectoral region.
• Axilla – Space beneath pectoral region transmitting vessels and nerves.
• Thoracoacromial artery – Main arterial supply of pectoral region.
• Medial and lateral pectoral nerves – Innervation of pectoralis muscles.
• Clinical correlation – Trauma or surgery of chest may injure pectoral nerves.
• Rotator cuff – Group of muscles stabilizing shoulder joint, includes infraspinatus.
• Breast surgery relevance – Pectoralis muscles form bed of breast and are key in mastectomy.
Chapter: Anatomy / Upper Limb
Topic: Pectoral Region and Axilla
Subtopic: Muscles of pectoral region
Lead Question – 2013
Which of the following muscle is not in the pectoral region?
a) Pectoralis major
b) Infraspinatus
c) Pectoralis minor
d) Subclavius
Explanation: The pectoral region consists of pectoralis major, pectoralis minor, and subclavius. Infraspinatus is located on posterior aspect of scapula, part of rotator cuff, not pectoral region. Correct answer: (b) Infraspinatus. Clinical: Important to distinguish anterior chest muscles from posterior scapular muscles.
Guessed Questions for NEET PG
1) Which nerve supplies pectoralis major?
a) Thoracodorsal nerve
b) Medial and lateral pectoral nerves
c) Axillary nerve
d) Suprascapular nerve
Explanation: Pectoralis major is supplied by both medial and lateral pectoral nerves. Correct answer: Medial and lateral pectoral nerves. Clinical: Nerve injury may weaken adduction and medial rotation of arm.
2) Which structure lies deep to pectoralis minor?
a) Brachial plexus cords
b) Cephalic vein
c) Basilic vein
d) Ulnar nerve
Explanation: Pectoralis minor is a landmark for cords of brachial plexus and axillary vessels. Correct answer: Brachial plexus cords. Clinical: Used as a guide in axillary dissections.
3) Subclavius muscle function is?
a) Elevates scapula
b) Depresses clavicle
c) Flexes humerus
d) Extends arm
Explanation: Subclavius depresses and stabilizes the clavicle during shoulder movements. Correct answer: Depresses clavicle. Clinical: Provides protection to subclavian vessels during clavicular fracture.
4) Which artery mainly supplies pectoralis major?
a) Subclavian artery
b) Thoracoacromial artery
c) Radial artery
d) Subscapular artery
Explanation: The thoracoacromial artery, a branch of axillary artery, supplies pectoralis major. Correct answer: Thoracoacromial artery. Clinical: Important during reconstructive flap surgeries.
5) A breast carcinoma infiltrating deep fascia can involve which muscle first?
a) Serratus anterior
b) Pectoralis major
c) Infraspinatus
d) Latissimus dorsi
Explanation: Pectoralis major forms the bed of breast, hence infiltrated in advanced carcinoma. Correct answer: Pectoralis major. Clinical: Explains fixation of breast mass to chest wall.
6) Which muscle is part of rotator cuff but not pectoral region?
a) Subscapularis
b) Infraspinatus
c) Supraspinatus
d) Teres minor
Explanation: Infraspinatus is part of rotator cuff, not pectoral region. Correct answer: Infraspinatus. Clinical: Weakness causes loss of external rotation at shoulder.
7) Injury to medial pectoral nerve causes weakness of?
a) Deltoid
b) Pectoralis minor
c) Latissimus dorsi
d) Teres major
Explanation: Medial pectoral nerve supplies pectoralis minor and part of pectoralis major. Correct answer: Pectoralis minor. Clinical: May weaken scapular protraction.
8) Which lymph nodes lie deep to pectoralis minor?
a) Apical
b) Central
c) Lateral
d) Subscapular
Explanation: Apical group of axillary lymph nodes lie deep to pectoralis minor. Correct answer: Apical. Clinical: Important in breast cancer spread and axillary clearance surgeries.
9) A patient with winging of scapula likely has injury to?
a) Medial pectoral nerve
b) Long thoracic nerve
c) Axillary nerve
d) Suprascapular nerve
Explanation: Winging of scapula occurs due to serratus anterior paralysis from long thoracic nerve injury. Correct answer: Long thoracic nerve. Clinical: Seen in radical mastectomy complications.
10) Which of the following is not a muscle of anterior axillary fold?
a) Pectoralis major
b) Pectoralis minor
c) Subclavius
d) Latissimus dorsi
Explanation: Anterior axillary fold is formed by lower border of pectoralis major. Latissimus dorsi forms posterior fold. Correct answer: Latissimus dorsi. Clinical: Used in surgical identification of axillary folds.
Keyword Definitions
• Palmaris longus – Superficial forearm flexor, often absent, inserts into palmar aponeurosis.
• Flexor carpi radialis (FCR) – Flexes and abducts wrist, arises from medial epicondyle.
• Lumbricals – Intrinsic hand muscles, unique as they originate from tendons of flexor digitorum profundus.
• Adductor pollicis – Adducts thumb, has oblique and transverse heads.
• Flexor digitorum profundus (FDP) – Deep flexor of digits, provides origin for lumbricals.
• Intrinsic hand muscles – Small muscles within hand responsible for fine motor control.
• Thenar muscles – Muscles at base of thumb aiding its opposition and movement.
• Carpal tunnel – Space in wrist transmitting flexor tendons and median nerve.
• Claw hand – Deformity due to ulnar nerve injury affecting lumbricals.
• Grip strength – Combination of extrinsic and intrinsic muscle function of hand.
• Clinical correlation – Lumbrical involvement critical in nerve injuries of hand.
Chapter: Anatomy / Upper Limb
Topic: Hand Muscles
Subtopic: Lumbricals and intrinsic muscles of hand
Lead Question – 2013
Which muscle originates from tendon of other muscle?
a) Palmaris longus
b) FCR
c) Lumbricals
d) Adductor pollicis
Explanation: Lumbricals are unique because they originate from the tendons of flexor digitorum profundus, unlike most muscles that arise from bone. They play a key role in flexion at MCP and extension at IP joints. Correct answer: (c) Lumbricals. Clinical: Paralysis leads to claw hand deformity.
Guessed Questions for NEET PG
1) Which nerve supplies the lateral two lumbricals?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Axillary nerve
Explanation: The lateral two lumbricals (1st and 2nd) are supplied by the median nerve. The medial two lumbricals (3rd and 4th) are supplied by the ulnar nerve. Correct answer: Median nerve. Clinical: Median nerve injury impairs fine finger movements.
2) Action of lumbricals is?
a) Flex MCP, extend IP
b) Extend MCP, flex IP
c) Extend both MCP and IP
d) Flex both MCP and IP
Explanation: Lumbricals flex the metacarpophalangeal joints and extend the interphalangeal joints simultaneously. Correct answer: Flex MCP, extend IP. Clinical: Important in coordinated writing and typing tasks.
3) Which head of adductor pollicis is supplied by ulnar nerve?
a) Oblique head
b) Transverse head
c) Both heads
d) Neither
Explanation: Both oblique and transverse heads of adductor pollicis are supplied by the deep branch of the ulnar nerve. Correct answer: Both heads. Clinical: Ulnar nerve palsy impairs thumb adduction (Froment’s sign).
4) Which intrinsic muscle of hand is absent in some individuals?
a) Lumbricals
b) Palmaris brevis
c) Palmaris longus
d) Adductor pollicis
Explanation: Palmaris longus is a forearm flexor, absent in 10–15% of population. Correct answer: Palmaris longus. Clinical: Often harvested for tendon graft surgeries without functional deficit.
5) Froment’s sign tests paralysis of?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Axillary nerve
Explanation: Froment’s sign is positive when a patient uses flexor pollicis longus instead of adductor pollicis due to ulnar nerve palsy. Correct answer: Ulnar nerve. Clinical: Seen in long-standing ulnar neuropathies.
6) Which muscle is called “writing muscle” of hand?
a) Interossei
b) Lumbricals
c) Adductor pollicis
d) Thenar muscles
Explanation: Lumbricals are called “writing muscles” as they help in flexion of MCP and extension of IP joints, enabling pencil grip. Correct answer: Lumbricals. Clinical: Loss leads to difficulty in writing and precision grip.
7) Which tendon passes through carpal tunnel?
a) Flexor digitorum superficialis
b) Palmaris longus
c) Extensor digitorum
d) Extensor pollicis longus
Explanation: Carpal tunnel contains flexor digitorum superficialis, profundus tendons, flexor pollicis longus tendon, and median nerve. Correct answer: Flexor digitorum superficialis. Clinical: Compression causes carpal tunnel syndrome.
8) A child presents with clawing of medial two fingers. Likely affected nerve?
a) Radial nerve
b) Ulnar nerve
c) Median nerve
d) Axillary nerve
Explanation: Ulnar nerve injury causes paralysis of medial two lumbricals, leading to clawing of ring and little fingers. Correct answer: Ulnar nerve. Clinical: Common in cubital tunnel syndrome.
9) Which lumbricals are bipennate?
a) First and second
b) Third and fourth
c) All four
d) None
Explanation: The first and second lumbricals are unipennate, while the third and fourth are bipennate. Correct answer: Third and fourth. Clinical: Helps in anatomical identification during dissections.
10) Loss of thumb opposition occurs in?
a) Median nerve injury
b) Ulnar nerve injury
c) Radial nerve injury
d) Musculocutaneous nerve injury
Explanation: Opposition of thumb is carried out by opponens pollicis, innervated by recurrent branch of median nerve. Correct answer: Median nerve injury. Clinical: Seen in carpal tunnel syndrome.
Keyword Definitions
• Profunda brachii artery – Deep artery of arm, branch of brachial artery, runs in spiral groove.
• Spiral groove – Shallow groove on posterior humerus, occupied by radial nerve and profunda brachii artery.
• Radial nerve – Continuation of posterior cord of brachial plexus, supplies extensor compartment.
• Ulnar nerve – Arises from medial cord, passes behind medial epicondyle, supplies intrinsic hand muscles.
• Median nerve – Formed from medial and lateral cords, passes through carpal tunnel, major flexor nerve.
• Humeral shaft fracture – Common injury damaging radial nerve in spiral groove.
• Wrist drop – Clinical sign of radial nerve injury, due to loss of extensor muscle function.
• Saturday night palsy – Radial nerve compression neuropathy in spiral groove.
• Deep brachial artery – Synonym for profunda brachii artery, accompanies radial nerve.
• Extensor compartment – Muscles of posterior arm and forearm controlled by radial nerve.
• Clinical correlation – Spiral groove relation important in fractures and compressive neuropathies.
Chapter: Anatomy / Upper Limb
Topic: Arm and Brachial Plexus
Subtopic: Radial nerve and profunda brachii artery in spiral groove
Lead Question – 2013
Nerve running along with profunda brachii artery, in spiral groove?
a) Ulnar
b) Median
c) Radial
d) None
Explanation: The radial nerve runs along with the profunda brachii artery in the spiral groove of the humerus. This relationship is clinically significant as humeral shaft fractures can injure both structures. Correct answer: (c) Radial. Clinical: Injury causes wrist drop and sensory loss over dorsum of hand.
Guessed Questions for NEET PG
1) A mid-shaft fracture of humerus most commonly injures?
a) Median nerve
b) Radial nerve
c) Ulnar nerve
d) Musculocutaneous nerve
Explanation: Mid-shaft humeral fractures frequently damage the radial nerve as it lies in the spiral groove. Correct answer: Radial nerve. Clinical: Presents with wrist drop and loss of finger extension.
2) Which muscle is first affected in radial nerve palsy at spiral groove?
a) Triceps
b) Anconeus
c) Brachioradialis
d) Extensor carpi radialis longus
Explanation: Triceps is spared in spiral groove lesions. Brachioradialis and wrist extensors are first affected. Correct answer: Brachioradialis. Clinical: Weak elbow flexion in mid-pronation position.
3) Saturday night palsy refers to?
a) Ulnar nerve compression
b) Radial nerve compression
c) Median nerve compression
d) Axillary nerve compression
Explanation: Saturday night palsy occurs when prolonged compression damages the radial nerve in spiral groove during deep sleep or intoxication. Correct answer: Radial nerve compression. Clinical: Wrist drop with sensory loss.
4) Sensory loss in radial nerve injury at spiral groove involves?
a) Thenar eminence
b) Dorsum of first web space
c) Medial forearm
d) Palmar little finger
Explanation: Spiral groove injury spares triceps but causes sensory loss over dorsum of hand, particularly first web space. Correct answer: Dorsum of first web space. Clinical: Important diagnostic clue.
5) Which branch of radial nerve supplies triceps?
a) Posterior cutaneous nerve
b) Muscular branches
c) Deep branch
d) Superficial branch
Explanation: Muscular branches of radial nerve supply triceps before entering spiral groove. Correct answer: Muscular branches. Clinical: Triceps preserved in spiral groove lesions.
6) Which artery is at risk with humeral shaft fracture along with radial nerve?
a) Brachial artery
b) Profunda brachii artery
c) Radial artery
d) Ulnar artery
Explanation: Profunda brachii artery accompanies radial nerve in spiral groove, making it vulnerable in shaft fractures. Correct answer: Profunda brachii artery. Clinical: Bleeding complicates fracture management.
7) Which test best detects radial nerve palsy?
a) Asking patient to oppose thumb
b) Asking patient to extend wrist
c) Asking patient to flex DIP of index
d) Asking patient to abduct little finger
Explanation: Wrist extension is controlled by radial nerve. In palsy, patient cannot extend wrist, producing wrist drop. Correct answer: Wrist extension test. Clinical: Pathognomonic finding.
8) Wrist drop occurs due to paralysis of?
a) Flexor muscles
b) Extensor muscles
c) Pronator muscles
d) Intrinsic hand muscles
Explanation: Radial nerve injury paralyzes extensor muscles of forearm, causing wrist drop. Correct answer: Extensor muscles. Clinical: Patient presents with inability to extend wrist and fingers.
9) Which part of triceps is usually spared in spiral groove lesion?
a) Long head
b) Lateral head
c) Medial head
d) All heads affected
Explanation: Radial nerve supplies long and lateral heads of triceps before entering spiral groove, hence spared. Medial head may be affected. Correct answer: Long and lateral heads spared. Clinical: Partial triceps weakness only.
10) In radial nerve injury, supination is preserved due to action of?
a) Biceps brachii
b) Supinator
c) Pronator teres
d) Brachialis
Explanation: Supination is performed by supinator (radial nerve) and biceps brachii (musculocutaneous nerve). Even if radial nerve is injured, biceps maintains supination. Correct answer: Biceps brachii. Clinical: Supination relatively preserved in palsy.
Keyword Definitions
• Dual nerve supply – Muscle receiving motor innervation from two different nerves.
• Subscapularis – Supplied by upper and lower subscapular nerves.
• Pectoralis major – Supplied by medial and lateral pectoral nerves.
• Pronator teres – Supplied by median nerve only.
• Flexor digitorum profundus – Medial half by ulnar nerve, lateral half by anterior interosseous branch of median nerve.
• Brachial plexus – Network of nerves supplying upper limb, roots C5–T1.
• Median nerve – Formed by medial and lateral cords, supplies most forearm flexors.
• Ulnar nerve – Arises from medial cord, supplies intrinsic hand muscles and medial FDP.
• Subscapular nerves – Branches of posterior cord, innervate subscapularis.
• Clinical correlation – Knowledge of dual supply important in nerve lesions and recovery.
• Muscle palsy – Weakness pattern helps localize lesion to specific nerve or part of plexus.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus and Muscle Innervation
Subtopic: Dual nerve supply of upper limb muscles
Lead Question – 2013
All of the following muscles have dual nerve supply except?
a) Subscapularis
b) Pectoralis major
c) Pronator teres
d) Flexor digitorum profundus
Explanation: Subscapularis has dual supply (upper and lower subscapular nerves). Pectoralis major has dual supply (medial and lateral pectoral nerves). FDP has dual supply (median and ulnar nerves). Pronator teres has single supply (median nerve). Correct answer: (c) Pronator teres. Clinical: Isolated median injury can paralyze pronator teres completely.
Guessed Questions for NEET PG
1) Which muscle among the following is supplied by both ulnar and median nerves?
a) Flexor pollicis longus
b) Flexor carpi radialis
c) Flexor digitorum profundus
d) Pronator quadratus
Explanation: Flexor digitorum profundus has dual supply – medial half by ulnar, lateral half by anterior interosseous (median). Correct answer: FDP. Clinical: Explains partial preservation in isolated lesions.
2) Subscapularis is supplied by?
a) Upper and lower subscapular nerves
b) Thoracodorsal nerve
c) Lateral pectoral nerve
d) Axillary nerve
Explanation: Subscapularis is innervated by both upper and lower subscapular nerves from posterior cord. Correct answer: Upper and lower subscapular nerves. Clinical: Injury leads to weak internal rotation.
3) Which muscle receives innervation from both medial and lateral pectoral nerves?
a) Pectoralis major
b) Pectoralis minor
c) Subclavius
d) Serratus anterior
Explanation: Pectoralis major is supplied by medial and lateral pectoral nerves. Correct answer: Pectoralis major. Clinical: Paralysis leads to weak adduction and internal rotation.
4) A patient with ulnar nerve lesion at wrist retains partial flexion of DIP of ring finger due to?
a) Median nerve supply
b) Radial nerve supply
c) Musculocutaneous nerve supply
d) Axillary nerve supply
Explanation: Lateral half of FDP (index and middle fingers) supplied by median, medial half (ring and little fingers) by ulnar. Correct answer: Median nerve supply. Clinical: Explains incomplete loss in ulnar palsy.
5) Which of the following has single nerve supply?
a) FDP
b) Pectoralis major
c) Pronator teres
d) Subscapularis
Explanation: Pronator teres is solely supplied by median nerve. Others have dual innervation. Correct answer: Pronator teres. Clinical: Useful in lesion localization.
6) Which nerve supplies medial half of flexor digitorum profundus?
a) Ulnar
b) Median
c) Radial
d) Musculocutaneous
Explanation: Medial half (ring and little fingers) of FDP is innervated by ulnar nerve. Correct answer: Ulnar nerve. Clinical: Explains weakness of DIP flexion in ulnar palsy.
7) Damage to lateral pectoral nerve causes weakness in?
a) Shoulder abduction
b) Arm adduction
c) Elbow flexion
d) Wrist extension
Explanation: Lateral pectoral nerve innervates pectoralis major, main action is adduction and internal rotation of arm. Correct answer: Arm adduction. Clinical: Loss of powerful adduction in lesion.
8) A patient with lesion of posterior cord affecting both upper and lower subscapular nerves shows weakness in?
a) Internal rotation
b) External rotation
c) Abduction
d) Supination
Explanation: Subscapularis performs internal rotation of humerus, supplied by both upper and lower subscapular nerves. Correct answer: Internal rotation. Clinical: Shoulder stability is also reduced.
9) Median nerve injury at elbow spares which of the following?
a) Pronator teres
b) Flexor digitorum profundus (medial half)
c) Flexor digitorum superficialis
d) Flexor pollicis longus
Explanation: Medial half of FDP is supplied by ulnar nerve, hence spared in median nerve injury at elbow. Correct answer: FDP (medial half). Clinical: Explains partial preservation of finger flexion.
10) Which of the following combinations represent dual innervation correctly?
a) FDP – Median & Ulnar
b) Pectoralis major – Medial & Lateral pectoral
c) Subscapularis – Upper & Lower subscapular
d) All of the above
Explanation: All mentioned muscles are examples of dual innervation. Correct answer: All of the above. Clinical: Important for understanding muscle function in partial nerve injuries.
Keyword Definitions
• Superficial anterior compartment of forearm – Contains five muscles: pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis.
• FDS – Flexor digitorum superficialis, a superficial flexor of fingers.
• FCR – Flexor carpi radialis, wrist flexor and abductor.
• Palmaris longus – Weak wrist flexor, absent in 10-15% individuals.
• FPL – Flexor pollicis longus, belongs to deep compartment, flexes thumb.
• Median nerve – Supplies most superficial anterior forearm muscles.
• Ulnar nerve – Supplies flexor carpi ulnaris and medial half of FDP.
• Brachial artery – Main arterial supply of forearm, divides into radial and ulnar.
• Clinical correlation – Superficial muscles are commonly involved in tendinitis and occupational overuse syndromes.
• Compartment syndrome – Increased pressure in forearm compartments can damage muscles and nerves.
• Pronator teres syndrome – Median nerve entrapment by pronator teres in superficial compartment.
Chapter: Anatomy / Upper Limb
Topic: Forearm Muscles
Subtopic: Superficial anterior compartment of forearm
Lead Question – 2013
Which of the following is not the muscle of superficial anterior compartment of forearm?
a) FDS
b) FPL
c) FCR
d) Palmaris longus
Explanation: The superficial anterior compartment includes pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. Flexor pollicis longus is a deep compartment muscle. Correct answer: (b) FPL. Clinical: FPL is important in thumb flexion and tested in anterior interosseous nerve palsy.
Guessed Questions for NEET PG
1) Which of the following is a superficial flexor of forearm?
a) Pronator teres
b) Flexor pollicis longus
c) Flexor digitorum profundus
d) Supinator
Explanation: Pronator teres belongs to superficial anterior compartment. FPL and FDP are deep flexors, supinator belongs to posterior compartment. Correct answer: Pronator teres. Clinical: Median nerve may be compressed between its two heads.
2) Which superficial anterior forearm muscle is most frequently absent in population?
a) FCR
b) FCU
c) Palmaris longus
d) Pronator teres
Explanation: Palmaris longus is absent in about 10–15% of individuals. Correct answer: Palmaris longus. Clinical: Its tendon is used in reconstructive tendon graft surgeries without functional deficit.
3) Which muscle is supplied by ulnar nerve among superficial flexors?
a) FCR
b) FCU
c) Palmaris longus
d) Pronator teres
Explanation: Flexor carpi ulnaris is the only superficial flexor supplied by the ulnar nerve. Others are supplied by median nerve. Correct answer: FCU. Clinical: Weak wrist flexion and ulnar deviation occur in lesions.
4) A patient unable to flex PIP joints of fingers likely has paralysis of?
a) FDP
b) FDS
c) FPL
d) FCU
Explanation: Flexor digitorum superficialis flexes proximal interphalangeal joints. Correct answer: FDS. Clinical: Median nerve lesions at elbow impair this function.
5) Which muscle originates from common flexor origin on medial epicondyle?
a) Palmaris longus
b) Pronator teres
c) FCR
d) All of the above
Explanation: All superficial flexors except FDS deep head arise from medial epicondyle via common flexor origin. Correct answer: All of the above. Clinical: Overuse may cause medial epicondylitis (golfer’s elbow).
6) Flexor pollicis longus is supplied by?
a) Median nerve (anterior interosseous branch)
b) Ulnar nerve
c) Radial nerve
d) Posterior interosseous nerve
Explanation: FPL is innervated by anterior interosseous branch of median nerve. Correct answer: Median nerve (AIN). Clinical: AIN palsy causes inability to make “OK” sign due to FPL weakness.
7) Which superficial flexor muscle is involved in carpal tunnel syndrome symptoms due to tendinopathy?
a) FDS
b) FCR
c) FCU
d) Pronator teres
Explanation: Flexor digitorum superficialis tendons pass through carpal tunnel and may contribute to compression. Correct answer: FDS. Clinical: CTS presents with numbness, tingling in lateral fingers.
8) Median nerve lies deep to which superficial muscle at wrist?
a) FCU
b) FCR
c) Palmaris longus
d) Pronator teres
Explanation: Palmaris longus tendon lies superficial to median nerve at wrist. Correct answer: Palmaris longus. Clinical: Median nerve blocks may be guided by this relation.
9) Which superficial forearm muscle flexes and abducts the wrist?
a) FCR
b) FCU
c) Palmaris longus
d) FDS
Explanation: Flexor carpi radialis flexes wrist and abducts it towards radial side. Correct answer: FCR. Clinical: FCR tendon is palpable in radial wrist and used for arterial cannulation landmark.
10) In anterior compartment syndrome, which superficial muscle is most vulnerable due to location?
a) Pronator teres
b) FCR
c) FCU
d) FDS
Explanation: Flexor digitorum superficialis, being central and bulky, is commonly affected in increased compartment pressure. Correct answer: FDS. Clinical: Early decompression prevents ischemic contracture (Volkmann’s).
Keyword Definitions
• Midpalmar space – Deep fascial space of hand located beneath central compartment, communicates with forearm via carpal tunnel.
• Lumbricals – Four small intrinsic hand muscles arising from flexor digitorum profundus tendons.
• FDP – Flexor digitorum profundus, flexes distal interphalangeal joints.
• Thenar space – Fascial space near thumb, separated from midpalmar space by septum.
• Hand compartments – Thenar, hypothenar, adductor, central, interosseous compartments.
• Clinical correlation – Midpalmar abscess can spread to forearm through carpal tunnel.
• Carpal tunnel – Passage for FDP, FDS tendons, FPL tendon, and median nerve.
• Infection spread – From finger pulp to midpalmar space via lumbrical canals.
• Surgical drainage – Important in treating deep palmar space infections.
• Lumbrical canal – Interval through which lumbrical muscles enter palm from FDP.
• Interossei – Intrinsic hand muscles not part of midpalmar space content.
Chapter: Anatomy / Upper Limb
Topic: Hand
Subtopic: Midpalmar Space
Lead Question – 2013
Contents of midpalmar space are all except
a) 2nd lumbrical
b) FDP of 3rd finger
c) 1st lumbrical
d) FDP of 4th finger
Explanation: Midpalmar space contains medial three lumbricals and flexor digitorum profundus tendons of middle, ring, and little fingers. The 1st lumbrical belongs to thenar space, not midpalmar. Correct answer: (c) 1st lumbrical. Clinical: Midpalmar abscess can cause swelling in central palm and requires careful surgical drainage.
Guessed Questions for NEET PG
1) Which lumbrical muscle lies in thenar space?
a) 1st lumbrical
b) 2nd lumbrical
c) 3rd lumbrical
d) 4th lumbrical
Explanation: The 1st lumbrical lies in thenar space along with FPL tendon. Others lie in midpalmar space. Correct answer: 1st lumbrical. Clinical: Swelling of thenar space may compromise thumb movements.
2) Infection from the index finger pulp may spread to?
a) Thenar space
b) Midpalmar space
c) Hypothenar space
d) Dorsum of hand
Explanation: Lumbrical canal of index finger connects pulp with thenar space. Correct answer: Thenar space. Clinical: Early drainage is essential to preserve thumb function.
3) Which tendon passes through carpal tunnel and continues into midpalmar space?
a) FPL
b) FDP
c) Extensor digitorum
d) Palmaris longus
Explanation: Flexor digitorum profundus tendons pass through carpal tunnel and form part of midpalmar space contents. Correct answer: FDP. Clinical: Infections may spread from palm to forearm via carpal tunnel.
4) Midpalmar space infection presents with swelling in which region?
a) Thenar eminence
b) Hypothenar eminence
c) Central palm
d) Dorsal web space
Explanation: Midpalmar space infections typically cause fullness in central palm. Correct answer: Central palm. Clinical: Deep abscess requires surgical drainage through palmar incision.
5) Which of the following is not a boundary of midpalmar space?
a) Palmar aponeurosis
b) Metacarpals of index finger
c) Interossei muscles
d) Flexor pollicis longus
Explanation: FPL belongs to thenar space, not boundary of midpalmar space. Correct answer: FPL. Clinical: Differentiating compartments is crucial in infection management.
6) Which lumbricals are supplied by ulnar nerve?
a) 1st and 2nd
b) 3rd and 4th
c) All four
d) None
Explanation: The 3rd and 4th lumbricals are supplied by the deep branch of ulnar nerve. Correct answer: 3rd and 4th. Clinical: Ulnar nerve injury affects fine grip due to lumbrical paralysis.
7) Patient with midpalmar space infection is unable to flex distal phalanx of ring finger. Which tendon is affected?
a) FDS
b) FDP
c) FPL
d) Extensor indicis
Explanation: FDP of ring finger passes through midpalmar space, infection can impair its function. Correct answer: FDP. Clinical: This indicates deep involvement requiring urgent drainage.
8) Which muscle group borders the midpalmar space dorsally?
a) Palmaris brevis
b) Interossei
c) Thenar muscles
d) Hypothenar muscles
Explanation: Interossei muscles form dorsal boundary of midpalmar space. Correct answer: Interossei. Clinical: Infection here can spread to intermetacarpal spaces.
9) Midpalmar space communicates with forearm via?
a) Anatomical snuffbox
b) Carpal tunnel
c) Guyon’s canal
d) Radial bursa
Explanation: Midpalmar space communicates proximally through carpal tunnel with forearm. Correct answer: Carpal tunnel. Clinical: Explains spread of deep hand infections to forearm flexor sheath.
10) Which space is affected in a patient unable to oppose thumb with swelling near 1st web space?
a) Midpalmar space
b) Thenar space
c) Hypothenar space
d) Dorsal space
Explanation: Thenar space infection affects thumb opposition and causes swelling near first web space. Correct answer: Thenar space. Clinical: Misdiagnosis may lead to permanent disability of thumb.
Keyword Definitions
• Axillary nerve – Branch of posterior cord of brachial plexus, supplies deltoid and teres minor.
• Quadrangular space – Anatomical space transmitting axillary nerve and posterior circumflex humeral artery.
• Deltoid paralysis – Clinical feature of axillary nerve injury, causing loss of shoulder abduction.
• Humeral surgical neck – Common fracture site leading to axillary nerve damage.
• Circumflex humeral arteries – Branches of axillary artery encircling humerus.
• Teres minor – Rotator cuff muscle innervated by axillary nerve.
• Shoulder dislocation – Can injure axillary nerve.
• Posterior circumflex humeral artery – Runs with axillary nerve in quadrangular space.
• Clinical test – Abduction and sensation over regimental badge area for axillary nerve integrity.
• Brachial plexus – Nerve network supplying upper limb.
• Surgical relevance – Axillary nerve at risk during deltoid intramuscular injections.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Axillary Nerve and Vessels
Lead Question – 2013
Axillary nerve is accompanied by which artery?
a) Axillary
b) Subscapular
c) Anterior circumflex humeral
d) Posterior circumflex humeral
Explanation: Axillary nerve passes through the quadrangular space along with the posterior circumflex humeral artery. This anatomical relationship is clinically important during humeral neck fractures or shoulder dislocations. Correct answer: (d) Posterior circumflex humeral artery. Clinical: Injury leads to deltoid weakness and sensory loss over regimental badge area.
Guessed Questions for NEET PG
1) Which space transmits axillary nerve and posterior circumflex humeral artery?
a) Triangular space
b) Quadrangular space
c) Cubital fossa
d) Axilla
Explanation: Axillary nerve and posterior circumflex humeral artery pass through quadrangular space. Correct answer: Quadrangular space. Clinical: Compression here can cause axillary neuropathy.
2) Fracture of surgical neck of humerus most likely injures?
a) Radial nerve
b) Axillary nerve
c) Median nerve
d) Ulnar nerve
Explanation: Surgical neck fracture endangers axillary nerve and posterior circumflex humeral artery. Correct answer: Axillary nerve. Clinical: Presents with deltoid atrophy and shoulder abduction weakness.
3) Which muscle is NOT supplied by axillary nerve?
a) Deltoid
b) Teres minor
c) Teres major
d) Skin over regimental badge
Explanation: Teres major is supplied by subscapular nerve, not axillary nerve. Correct answer: Teres major. Clinical: Differentiates axillary nerve palsy from broader plexus injury.
4) Loss of sensation over regimental badge area indicates injury to?
a) Radial nerve
b) Axillary nerve
c) Suprascapular nerve
d) Musculocutaneous nerve
Explanation: Axillary nerve injury causes sensory deficit over regimental badge area. Correct answer: Axillary nerve. Clinical: Pathognomonic for axillary neuropathy.
5) Which rotator cuff muscle is innervated by axillary nerve?
a) Supraspinatus
b) Infraspinatus
c) Teres minor
d) Subscapularis
Explanation: Teres minor is the only rotator cuff muscle supplied by axillary nerve. Correct answer: Teres minor. Clinical: Weakness in external rotation occurs in axillary nerve injury.
6) During deltoid intramuscular injection, which nerve is at risk?
a) Radial nerve
b) Median nerve
c) Axillary nerve
d) Musculocutaneous nerve
Explanation: Axillary nerve runs deep to deltoid; incorrect needle placement may injure it. Correct answer: Axillary nerve. Clinical: Presents with deltoid weakness.
7) Posterior circumflex humeral artery is a branch of?
a) Brachial artery
b) Axillary artery
c) Subclavian artery
d) Radial artery
Explanation: Posterior circumflex humeral artery arises from the 3rd part of axillary artery. Correct answer: Axillary artery. Clinical: Injured in humeral neck fractures.
8) Which movement is most affected in axillary nerve injury?
a) Elbow flexion
b) Shoulder abduction
c) Wrist extension
d) Thumb opposition
Explanation: Deltoid paralysis impairs shoulder abduction beyond 15 degrees. Correct answer: Shoulder abduction. Clinical: Differentiates from supraspinatus injury which initiates abduction.
9) Which clinical test best evaluates axillary nerve function?
a) Flexion of elbow
b) Abduction of shoulder against resistance
c) Extension of wrist
d) Pronation of forearm
Explanation: Abduction of shoulder against resistance tests deltoid function supplied by axillary nerve. Correct answer: Shoulder abduction against resistance. Clinical: Standard examination method.
10) Anterior dislocation of shoulder commonly injures?
a) Radial nerve
b) Axillary nerve
c) Median nerve
d) Ulnar nerve
Explanation: Axillary nerve lies close to shoulder joint and is frequently injured in anterior dislocation. Correct answer: Axillary nerve. Clinical: Presents with deltoid atrophy and regimental badge anesthesia.