Regional anatomy
Asking for Preferences
Reading File
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Reading File
Reading File
Reading File
Reading File
Reading File
Reading File
Reading File
Reading File
Loading Image
Finding Sources
Loading Image
Excellent - I have everything I need. Let me now compose the comprehensive Upper Limb Regional Anatomy study notes.
Upper Limb - Regional Anatomy (Exam Study Notes)
Source: Gray's Anatomy for Students
1. Overview and Bones
The upper limb is divided into five regions:
| Region | Key Bones |
|---|---|
| Shoulder girdle | Clavicle, scapula |
| Arm (brachium) | Humerus |
| Forearm (antebrachium) | Radius (lateral), Ulna (medial) |
| Wrist (carpus) | 8 carpal bones |
| Hand | 5 metacarpals + 14 phalanges |
Mnemonic for carpals (proximal to distal, lateral to medial):
- Proximal row: Scaphoid, Lunate, Triquetrum, Pisiform
- Distal row: Trapezium, Trapezoid, Capitate, Hamate
- "Some Lovers Try Positions That They Can't Handle"
2. Brachial Plexus
The most tested topic in upper limb anatomy.
Roots: Anterior rami of C5, C6, C7, C8, T1 - pass between anterior and middle scalene muscles, posterior to subclavian artery.
Schematic (Roots → Trunks → Divisions → Cords → Branches):
Trunks:
- Superior trunk = C5 + C6
- Middle trunk = C7 alone
- Inferior trunk = C8 + T1
Divisions: Each trunk divides into anterior and posterior divisions.
Cords (named by position relative to the 2nd part of the axillary artery):
- Lateral cord = anterior divisions of Superior + Middle trunks
- Medial cord = anterior division of Inferior trunk
- Posterior cord = all three posterior divisions
Key terminal branches:
| Cord | Terminal Nerves | Key Functions |
|---|---|---|
| Lateral | Musculocutaneous nerve, lateral root of median nerve | Arm flexors; forearm sensation |
| Medial | Ulnar nerve, medial root of median nerve | Intrinsic hand muscles; ring/little fingers |
| Posterior | Axillary nerve, radial nerve | Deltoid; all posterior compartment muscles |
The "M" over the axillary artery: The musculocutaneous nerve, lateral root of median nerve, median nerve, medial root of median nerve, and ulnar nerve form a visible M-shape over the 3rd part of the axillary artery - a landmark for identifying plexus components in surgery.
3. Axilla
The axilla is the gateway to the upper limb - a pyramidal space formed by the clavicle, scapula, upper thoracic wall, and humerus. It has four walls, an inlet (continuous with the neck), and a floor.
All major structures passing into/out of the upper limb pass through the axilla, including the axillary artery, axillary vein, and brachial plexus.
Key spaces in the posterior axillary wall:
- Quadrangular space: transmits axillary nerve + posterior circumflex humeral artery
- Triangular space: transmits circumflex scapular artery
- Triangular interval: transmits radial nerve + profunda brachii artery into the arm
4. Shoulder Region
Glenohumeral joint - ball-and-socket synovial joint, most mobile in body; least stable.
Rotator cuff muscles (SITS):
| Muscle | Action | Nerve |
|---|---|---|
| Supraspinatus | Abduction (initiates 0-15°) | Suprascapular (C5, C6) |
| Infraspinatus | Lateral rotation | Suprascapular (C5, C6) |
| Teres minor | Lateral rotation | Axillary (C5, C6) |
| Subscapularis | Medial rotation | Subscapular nerves (C5, C6) |
Axillary nerve exits the quadrangular space and innervates the deltoid and teres minor. It wraps around the surgical neck of the humerus - vulnerable in neck-of-humerus fractures and shoulder dislocations.
5. Arm (Humerus Region)
Two fascial compartments separated by medial and lateral intermuscular septa:
Anterior (flexor) compartment:
- Muscles: Biceps brachii, brachialis, coracobrachialis
- Nerve: Musculocutaneous nerve (C5, C6, C7)
- Biceps: long head from supraglenoid tubercle, short head from coracoid process → flexion + supination
- Brachialis: main elbow flexor (deep to biceps)
Posterior (extensor) compartment:
- Muscle: Triceps brachii (3 heads: long, medial, lateral)
- Nerve: Radial nerve (C7, C8)
- Radial nerve travels in the spiral groove (radial groove) of the humerus - vulnerable in mid-shaft humeral fractures → wrist drop (inability to extend wrist/fingers)
Main artery: Brachial artery (continuation of axillary) runs in the anterior compartment medial to the biceps tendon, bifurcating at the cubital fossa into radial and ulnar arteries.
6. Elbow Joint
- Hinge-type synovial joint allowing flexion/extension; also incorporates proximal radioulnar joint for pronation/supination
- Bones: Humerus (trochlea + capitulum) articulates with Ulna (trochlear notch) and Radius (head)
- Anular ligament of radius holds the radial head against the radial notch of the ulna; important in pronation/supination
- Fat pads lie over the olecranon, coronoid, and radial fossae - displacement ("sail sign") on X-ray indicates intra-articular effusion/fracture
- Medial (ulnar) collateral ligament & Lateral (radial) collateral ligament stabilize the joint
7. Forearm
Two compartments:
Anterior (Flexor) Compartment
Three layers, all mainly innervated by median nerve (except flexor carpi ulnaris + medial half of flexor digitorum profundus → ulnar nerve):
| Layer | Muscles |
|---|---|
| Superficial | Pronator teres, Flexor carpi radialis, Palmaris longus, Flexor carpi ulnaris |
| Intermediate | Flexor digitorum superficialis |
| Deep | Flexor digitorum profundus, Flexor pollicis longus, Pronator quadratus |
Posterior (Extensor) Compartment
All innervated by radial nerve (deep branch / posterior interosseous nerve):
| Layer | Muscles |
|---|---|
| Superficial | Brachioradialis, Extensor carpi radialis longus, ECRB, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris |
| Deep | Abductor pollicis longus, Extensor pollicis brevis, Extensor pollicis longus, Extensor indicis |
Note: Brachioradialis is innervated by the radial nerve before it divides (C5, C6) - flexes the elbow when forearm is in mid-pronation.
8. Carpal Tunnel & Wrist
The carpal tunnel is formed by the carpal bones posteriorly and the flexor retinaculum anteriorly.
Contents of the carpal tunnel (9 tendons + 1 nerve):
- Flexor digitorum superficialis (4 tendons)
- Flexor digitorum profundus (4 tendons)
- Flexor pollicis longus (1 tendon)
- Median nerve
The ulnar nerve and artery pass OUTSIDE the carpal tunnel, through Guyon's canal.
Carpal tunnel syndrome: Compression of the median nerve → pain/paresthesia in the lateral 3½ digits, thenar wasting, weak opposition of thumb.
9. Hand
Palmar Arches
| Arch | Source | Location |
|---|---|---|
| Superficial palmar arch | Mainly ulnar artery + radial superficial branch | Superficial to long flexor tendons |
| Deep palmar arch | Mainly radial artery + ulnar deep branch | Deep to long flexor tendons, over metacarpals |
Allen's test checks adequacy of anastomosis between radial and ulnar arteries.
Nerves of the Hand
| Nerve | Sensory | Motor |
|---|---|---|
| Median | Lateral 3½ fingers (palmar), distal dorsal tips of these fingers | Thenar muscles (LOAF: Lateral 2 lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis) |
| Ulnar | Medial 1½ fingers (both surfaces) | All other intrinsic hand muscles (interossei, medial 2 lumbricals, hypothenar, adductor pollicis) |
| Radial (superficial branch) | Dorsum of lateral 3½ fingers (proximal) | None in hand |
Thenar vs. Hypothenar Eminences
- Thenar (base of thumb): median nerve - abductor pollicis brevis, opponens pollicis, flexor pollicis brevis
- Hypothenar (base of little finger): ulnar nerve - abductor digiti minimi, flexor digiti minimi, opponens digiti minimi
Anatomical Snuffbox
- Lateral border: Tendons of APL + EPB
- Medial border: Tendon of EPL
- Floor: Scaphoid + trapezium
- Contents: Radial artery (pulse palpable here), terminal branches of superficial radial nerve, origin of cephalic vein
- Clinical: Tenderness in snuffbox = scaphoid fracture until proven otherwise
10. Key Clinical Nerve Injuries
| Nerve | Injury Site | Deformity | Muscle Loss |
|---|---|---|---|
| Radial nerve | Spiral groove (mid-shaft humerus) | Wrist drop | Cannot extend wrist/fingers |
| Median nerve | Carpal tunnel | "Ape hand" (thenar wasting) | No thumb opposition |
| Ulnar nerve | Medial epicondyle (elbow) | "Claw hand" (medial 2 fingers) | Intrinsic hand muscles |
| Axillary nerve | Surgical neck of humerus | Rounded shoulder | Deltoid paralysis |
| Musculocutaneous nerve | Axilla | Weak elbow flexion | Biceps/brachialis |
Brachial plexus injuries:
- Erb's palsy (upper trunk C5-C6): "Waiter's tip" deformity - arm adducted, medially rotated, forearm pronated. Caused by forceful neck-shoulder separation (difficult delivery, motorcycle fall)
- Klumpke's palsy (lower trunk C8-T1): Intrinsic hand muscle paralysis + claw hand. May include Horner syndrome if T1 sympathetic fibers involved
11. Superficial Veins
| Vein | Course |
|---|---|
| Cephalic vein | Originates from lateral dorsal venous network → anatomical snuffbox → lateral forearm → deltopectoral groove → drains into axillary vein |
| Basilic vein | Medial dorsal network → medial forearm → pierces deep fascia → drains into brachial vein → forms axillary vein |
| Median cubital vein | Connects cephalic and basilic at the cubital fossa - standard IV access site |
Quick-Reference Summary Table
| Region | Key Nerve | Key Artery | High-Yield Clinical |
|---|---|---|---|
| Shoulder | Axillary (C5-C6) | Posterior circumflex humeral | Rotator cuff tears, shoulder dislocation |
| Arm | Musculocutaneous (ant), Radial (post) | Brachial | Radial nerve palsy - wrist drop |
| Elbow | Median, Radial, Ulnar | Brachial bifurcation | Lateral epicondylitis ("tennis elbow") |
| Forearm | Median (ant), Radial (post), Ulnar (FCU, FDP) | Radial + Ulnar | Pronator syndrome |
| Wrist/Carpal tunnel | Median | Radial artery | Carpal tunnel syndrome |
| Hand | Median (lateral), Ulnar (medial) | Superficial + deep palmar arches | Scaphoid fracture, dupuytren's, mallet finger |
Gray's Anatomy for Students, Chapter 7 - Upper Limb
This is a shared conversation. Sign in to Orris to start your own chat.