Blood Supply and Venous Drainage

Subclavian artery → axillary artery → brachial artery → radial artery + ulnar artery → superficial and deep palmar arches → digital arteries.

Subclavian artery: arises from the brachiocephalic trunk (right) or directly from the aortic arch (left); becomes the axillary artery at the outer border of the 1st rib.
Axillary artery: three parts relative to pectoralis minor; becomes the brachial artery at the lower border of teres major.
Brachial artery: descends the medial arm; branches include profunda brachii, superior and inferior ulnar collateral arteries; divides into radial and ulnar arteries at the neck of the radius, just below the elbow.
Radial artery: passes deep to brachioradialis, becomes superficial and palpable at the wrist (classic pulse site), crosses the floor of the anatomical snuffbox, passes between the two heads of the first dorsal interosseous to enter the palm and form the deep palmar arch.
Ulnar artery: larger of the two terminal branches; passes deep to pronator teres and FDS, gives off the common interosseous artery, runs with the ulnar nerve through Guyon canal to form the superficial palmar arch.
Palmar arches: give rise to the common and proper palmar digital arteries, supplying the fingers.

Level	Key Branches
Axillary artery	Superior thoracic, thoracoacromial, lateral thoracic, subscapular, anterior/posterior circumflex humeral
Brachial artery	Profunda brachii, superior ulnar collateral, inferior ulnar collateral
Radial artery	Radial recurrent, palmar carpal branch, superficial palmar branch, dorsal carpal branch, princeps pollicis, radialis indicis
Ulnar artery	Ulnar recurrent (anterior/posterior), common interosseous (→ anterior + posterior interosseous), palmar carpal branch, dorsal carpal branch, deep palmar branch

Axillary artery is surrounded by the cords of the brachial plexus (2nd part).
Brachial artery is crossed anteriorly by the median nerve around mid-arm and lies within the bicipital groove; in the cubital fossa it lies medial to the biceps tendon, lateral to the median nerve.
Radial artery is a useful surface landmark deep to brachioradialis proximally, and lies lateral to FCR tendon distally.
Ulnar artery runs medial to the ulnar nerve in the distal forearm and through Guyon canal.

Scapular anastomosis (around the scapula):

Formed by the suprascapular artery and transverse cervical (cervicodorsal) artery, both from the subclavian artery/thyrocervical trunk (entering from above), connecting with the circumflex scapular artery (a branch of the subscapular artery, from the axillary artery) and the dorsal scapular artery.
Provides collateral circulation if the axillary artery is occluded or must be ligated between the origin of the subscapular artery and the take-off of the suprascapular/transverse cervical arteries proximally, blood can flow retrograde through the scapular anastomosis to refill the distal axillary/brachial artery.

Elbow (cubital) anastomosis:

Formed by four pairs of vessels meeting around the elbow: radial collateral and middle collateral arteries (from profunda brachii) meeting the radial recurrent and interosseous recurrent arteries; superior and inferior ulnar collateral arteries (from brachial artery) meeting the anterior and posterior ulnar recurrent arteries.
Provides collateral flow around the elbow joint, important if the brachial artery is compromised near the elbow (e.g., supracondylar fracture), though this collateral supply is often insufficient to fully protect the forearm from ischaemia if the brachial artery is acutely occluded, hence the clinical urgency of supracondylar fractures with vascular compromise.

Carpal anastomoses:

Palmar and dorsal carpal arches, formed by carpal branches of the radial and ulnar arteries (and contributions from the anterior/posterior interosseous arteries), encircling the wrist and providing collateral flow to the carpus and proximal hand.

Superficial palmar arch:

Formed predominantly by the ulnar artery, completed on the lateral side by the superficial palmar branch of the radial artery (variable completion, may be completed by other branches).
Lies at the level of the distal border of the extended thumb, superficial to the long flexor tendons.
Gives rise to three common palmar digital arteries (which each split into two proper palmar digital arteries) supplying the medial 3½ digits; the thumb and radial side of the index finger are supplied separately by princeps pollicis and radialis indicis from the deep arch/radial artery directly.

Deep palmar arch:

Formed predominantly by the radial artery, completed on the medial side by the deep palmar branch of the ulnar artery.
Lies deeper, at the level of the bases of the metacarpals, deep to the long flexor tendons, on the interossei.
Gives rise to palmar metacarpal arteries, which anastomose with the common palmar digital arteries; also gives princeps pollicis (to the thumb) and radialis indicis (to the radial side of the index finger).

Vein	Origin	Course	Termination
Dorsal venous network	Dorsum of the hand	Drains fingers via dorsal digital veins	Feeds into cephalic and basilic veins
Cephalic vein	Lateral end of the dorsal venous network	Ascends the lateral forearm and arm, through the deltopectoral groove/triangle	Axillary vein (piercing clavipectoral fascia)
Basilic vein	Medial end of the dorsal venous network	Ascends the medial forearm, then medial arm; pierces deep fascia in the mid-arm	Joins the brachial venae comitantes to form the axillary vein
Median cubital vein	Connects cephalic and basilic veins	Runs obliquely across the roof of the cubital fossa, superficial to the bicipital aponeurosis	Drains into either vein
Median antebrachial (median) vein	Palmar venous plexus	Ascends the anterior forearm, between cephalic and basilic systems	Variable: may join the basilic vein or the median cubital vein

Radial veins and ulnar veins: paired venae comitantes accompanying the respective arteries in the forearm.
Brachial veins: paired venae comitantes accompanying the brachial artery; join the basilic vein to form the axillary vein.
Axillary vein: single vein, formed at the lower border of teres major; lies anteromedial to the axillary artery; receives the cephalic vein and tributaries corresponding to the arterial branches.
Subclavian vein: continuation of the axillary vein at the outer border of the 1st rib; joins the internal jugular vein to form the brachiocephalic vein.

Venepuncture: Median cubital vein is the standard site, superficial, relatively fixed in position by the underlying bicipital aponeurosis (which also protects the brachial artery and median nerve beneath it), and generally well-tolerated.
IV access: Dorsal venous network and forearm veins (cephalic, basilic tributaries) are common peripheral sites; basilic vein is frequently used for PICC line (peripherally inserted central catheter) insertion due to its relatively straight course into the axillary/subclavian vein.
Central venous anatomical relationships: The subclavian vein (via infraclavicular approach) and internal jugular vein are common sites for central venous catheter placement; the subclavian vein lies anterior to the subclavian artery and is separated from it by anterior scalene muscle, relevant to avoiding arterial puncture during central line placement; the axillary/subclavian venous junction area is close to the thoracic duct (left) and the phrenic nerve, relevant to iatrogenic injury risk during central access procedures.

Arterial Supply