Overview
This lecture provides a comprehensive overview of the anatomy of the upper limb and thorax, focusing on bones, joints, muscles, nerves, vessels, surface markings, and clinical correlations essential for medical students.
Parts & Bones of Upper Limb
- Upper limb consists of shoulder region (clavicle, scapula), arm (humerus), forearm (radius, ulna), and hand (carpals, metacarpals, phalanges).
- Clavicle: only long bone lying horizontally, first to ossify, no medullary cavity, transmits limb weight to axial skeleton.
- Scapula: thin triangular bone with two surfaces, three borders, three angles; site of many muscle attachments.
- Humerus: longest bone of upper limb, has anatomical and surgical neck, closely related to axillary, radial, and ulnar nerves.
- Radius (lateral) and ulna (medial) form forearm; radius rotates over ulna during pronation/supination.
- Carpal bones (8), metacarpals (5), and phalanges (14) make up the hand; the thumb has only 2 phalanges.
Muscles, Fascia, and Attachments
- Muscles are grouped regionally: pectoral (pectoral major/minor, subclavius, serratus anterior), scapular (deltoid, rotator cuff), arm (biceps, triceps, brachialis, coracobrachialis), forearm, and intrinsic hand muscles.
- Fasciae include deep fascia, flexor and extensor retinacula, and specialized structures in hand (palmar aponeurosis, fibrous sheaths).
- Key muscle actions: pectoralis major (adduction, medial rotation), deltoid (abduction), biceps (supination, flexion), triceps (extension).
Arteries, Veins, Nerves, and Lymphatics
- Arterial supply: subclavian → axillary → brachial → radial & ulnar arteries → palmar arches.
- Venous drainage: cephalic (lateral), basilic (medial), median cubital vein (venipuncture site).
- Main nerves: brachial plexus branches include musculocutaneous, median, ulnar, radial, and axillary nerves; knowledge of their course and motor/sensory supply is key for clinical neurology.
- Lymphatic drainage primarily to axillary lymph nodes, especially relevant in breast cancer.
Joints & Movements
- Major joints: shoulder (ball and socket), elbow (hinge), wrist (ellipsoid), carpometacarpal (thumb: saddle), interphalangeal (hinge).
- Movements: pronation/supination at forearm, opposition at thumb, abduction/adduction at digits; axis for finger abduction/adduction passes through the third finger.
Surface and Radiological Anatomy
- Important landmarks: clavicle, scapular spine, deltoid tuberosity, medial/lateral epicondyles, styloid processes, anatomical snuffbox.
- Surface markings aid in procedures (e.g., venipuncture, nerve blocks, arterial pulse palpation).
- Recognize normal and pathological features on radiographs (AP and lateral views).
Clinical Correlations
- Common injuries: clavicle fracture, humerus midshaft (radial nerve damage → wrist drop), supracondylar fracture (median nerve injury), Colles fracture (distal radius).
- Clinical syndromes: Erb’s palsy (upper trunk brachial plexus), winged scapula (serratus anterior/long thoracic nerve), carpal tunnel syndrome (median nerve).
- Breast cancer spreads to axillary nodes; knowledge of lymphatic drainage is crucial.
- Knowledge of referred pain and physical signs (e.g., referred cardiac pain to arm, apex beat location) is essential.
Key Terms & Definitions
- Brachial Plexus — Network of nerves supplying the upper limb (C5–T1).
- Flexor Retinaculum — Fibrous band over carpal tunnel, median nerve passes deep to it.
- Anatomical Snuffbox — Depression at wrist bounded by thumb extensors, site of scaphoid palpation.
- Dermatome — Area of skin supplied by a single spinal nerve.
- Carpal Tunnel Syndrome — Compression neuropathy of the median nerve at the wrist.
- Lymphatic Drainage — Pathways that carry lymph to lymph nodes, important for metastasis.
Action Items / Next Steps
- Review diagrams of bones, joints, and muscle attachments.
- Practice surface landmark identification on self and peers.
- Study clinical cases related to nerve injuries and common fractures.
- Work through MCQs and viva questions provided in the text.
- Revise nerve supply and actions of upper limb muscles for practical exams.