Lymphatics, Dermatomes and Surface Anatomy

Superficial lymphatics:

• Accompany the superficial veins.
• The majority follow the basilic vein → drain into the cubital (supratrochlear) nodes (1–2 small nodes just above the medial epicondyle) → ascend to the axillary nodes (humeral/lateral group).
• A smaller lateral group follows the cephalic vein → mostly bypasses the cubital nodes → drains directly to the infraclavicular/deltopectoral nodes and then to the apical axillary nodes, though a few vessels may cross to join the axillary nodes lower down.

Deep lymphatics:

• Accompany the deep veins/arteries (radial, ulnar, brachial) directly to the axillary nodes (humeral/lateral group), generally without an intervening node group equivalent to the cubital nodes.

Cubital nodes:

• Located superficially, just above the medial epicondyle, along the basilic vein.
• Receive lymph from the medial forearm and hand (ulnar side); efferents drain to the axillary nodes.

Axillary node groups: Pectoral, subscapular, humeral, central, apical.

Drainage pathway (overall):

Digits/hand/forearm → superficial (basilic-associated) or deep lymphatics → cubital nodes (superficial pathway only) → axillary nodes (pectoral, subscapular, humeral groups) → central nodes → apical nodes → subclavian lymphatic trunk → venous system (right lymphatic duct or thoracic duct, depending on side).

Note: peripheral nerve cutaneous territories are distinct from dermatomes, the two overlap but do not correspond directly, since a dermatome reflects a single spinal segment's contribution while a peripheral nerve territory reflects a specific nerve's post-plexus distribution (often combining fibres from several segments).

Bony landmarks:

• Clavicle: entire length subcutaneous and palpable, S-shaped curve easily traced from sternum to acromion.
• Acromion: lateral tip of the scapular spine, forms the "point" of the shoulder.
• Coracoid process: palpable about 2–3 cm inferior to the lateral third of the clavicle, deep to the anterior deltoid.
• Scapular spine: palpable posteriorly, a useful reference point (its medial end lies roughly at the T3 vertebral spinous process level).
• Inferior angle of scapula: palpable posteriorly, typically at the level of the T7 spinous process/7th rib.
• Medial epicondyle: prominent medial bony point at the elbow; ulnar nerve palpable just posterior to it.
• Lateral epicondyle: prominent lateral bony point at the elbow; common extensor origin, site of tenderness in lateral epicondylitis ("tennis elbow").
• Olecranon: posterior point of the elbow; forms an equilateral triangle with the two epicondyles when the elbow is flexed to 90° (a useful check for elbow dislocation vs supracondylar fracture, since this relationship is preserved in fractures but disrupted in dislocations).
• Radial head: palpable in the lateral "soft spot" just distal to the lateral epicondyle; rotates under the palpating finger during pronation/supination.
• Radial styloid: distal lateral forearm, forms the proximal boundary of the anatomical snuffbox.
• Ulnar styloid: distal medial forearm, less prominent and slightly more proximal than the radial styloid.
• Anatomical snuffbox: visible depression on the radial dorsum of the wrist with the thumb extended; scaphoid tenderness here suggests fracture.

Muscle and tendon landmarks:

• Biceps tendon: palpable in the cubital fossa, lateral to the midline; useful guide to the underlying brachial artery (which lies just medial to it).
• Palmaris longus tendon: visible/palpable on the anterior wrist with wrist flexion and thumb-to-little-finger opposition (absent in some individuals).
• FCR and FCU tendons: palpable at the wrist, lateral and medial respectively to palmaris longus.
• Extensor tendons: visible on the dorsum of the wrist and hand with finger extension; EPL forms the medial border of the anatomical snuffbox.

Vascular landmarks:

• Brachial pulse: medial to the biceps tendon in the cubital fossa; standard site for blood pressure auscultation.
• Radial pulse: lateral wrist, between the radius and FCR tendon; the standard site for routine pulse palpation.
• Ulnar pulse: medial wrist, lateral to FCU tendon (less prominent, more variable than the radial pulse).
• Superficial veins: cephalic vein visible along the lateral forearm/arm and in the deltopectoral groove; basilic vein visible along the medial forearm/arm; median cubital vein visible/palpable crossing the cubital fossa (primary venepuncture site).