📝 STANDARD DESCRIPTION:
Sequence (Ox):
Subclavian → Axillary → Brachial → Median → Palmar Common Digital II/III/IV → Proper Palmar Digital arteries.
• Axillary a. begins at first rib, lies in axillary space — chief vessel of the forelimb.
• Brachial a. = continuation along medial arm; gives off Deep Brachial → musculospiral groove.
• Median a. is the main continuation in the forearm (NOT radial like in humans!) — runs through carpal canal.
• Distally splits into common digital arteries that supply the cloven hoof.
Cephalic vein on cranial forearm = standard IV site in dog.
Jugular vein = main IV site in cattle/horse (not a forelimb vein, but commonly grouped clinically).
📚 DETAILED DESCRIPTION:
FORELIMB ARTERIAL HIGHWAY
Origin: The right forelimb artery arises from the brachiocephalic trunk (which also gives the right common carotid). The left forelimb artery arises directly from the aortic arch as the left subclavian artery.
1. Subclavian artery
Curves cranially over the first rib. Branches:
• Costocervical trunk (deep cervical + dorsal intercostal — to neck/withers)
• Vertebral artery (ascends through transverse foramina of cervical vertebrae to the brain)
• Internal thoracic artery (ventral chest wall, mammary chain)
• Superficial cervical artery (to shoulder muscles)
2. Axillary artery (continuation past first rib): chief vessel of limb. Branches: external thoracic, lateral thoracic (panniculus), subscapular (largest branch in cattle — supplies caudal shoulder & has the circumflex humeri).
3. Brachial artery on medial arm: gives off the deep brachial entering the musculospiral groove (with radial nerve), bicipital, collateral ulnar, and common interosseous.
4. Median artery = direct continuation in the forearm. Lies medial in the proximal forearm with the median nerve, then traverses the carpal canal deep to the flexor retinaculum.
5. Distal split: The median artery becomes the palmar common digital arteries (II, III, IV). These finally split at the fetlock into proper palmar (axial + abaxial) digital arteries that descend on each side of each claw and meet at the solar arch within P3 → supplies the corium of the hoof.
RADIAL ARTERY in cattle is small (vestigial) — opposite to humans where radial is dominant.
VENOUS RETURN: Mostly mirrors arteries (deep system) + a superficial system that includes:
• Cephalic vein — runs on the craniomedial forearm, crosses elbow medially, used for venepuncture in the dog (standard IV in puppies and small animals).
• Median cubital vein — bridges cephalic to brachial in the cubital fossa.
• Accessory cephalic vein dorsally over carpus.
// COMPARATIVE ANALYSIS
| OX |
Median artery dominant; radial vestigial. Cephalic + accessory cephalic prominent. Hoof corium fed by solar arch from proper palmar digitals. |
| HORSE |
Median artery is also dominant. Pulse routinely taken at facial artery at mandible (not forelimb). Distal limb: medial palmar digital artery used for diagnostic 'palmar digital block' pulse check. |
| DOG |
Cephalic vein is the routine IV site. Brachial pulse felt on medial elbow. Femoral pulse (hindlimb) commonly used for cardiac assessment. |
| FOWL |
Brachial artery main vessel. Wing veins (basilic / ulnar) used for venepuncture in birds (radiometacarpal anastomosis). |
CLINICAL RELEVANCE
Cephalic Venepuncture (Dog): Distal cranial forearm — most common IV site in small animal practice.
Jugular vein in large animals — clinically the practical 'forelimb-region' IV.
Hoof Pulse Examination (Horse): Increased digital pulse at the abaxial sesamoid → laminitis warning.
Aneurysm/Thrombosis of Brachial/Axillary Artery: Compression neuropathy of the median + musculocutaneous nerves due to Ansa Axillaris relationship.
