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When the limb buds are being formed in the 4-5th week they are permeated by a capillary network
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In the case of the arm is chiefly fed by the artery of the 7th cervical segment, while in the case of the leg bud the chief axial artery arises from a pelvic arterial plexus — soon connected with the internal iliac (hypogastric) artery.
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During the 6th week the main arteries of the limbs are being evolved from pathways in the primary capillary plexuses ; by the end of the 8th week, all the important arterial channels have been laid down.
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In each limb bud there is developed a main or axial artery, certain parts of which are suppressed in the 8th week while other accessory vessels are developed.
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The axial artery of the upper limb persists as the subclavian, axillary and brachial trunks,
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In the fore-arm the axial vessel is represented by the anterior (volar) interosseus, continued into the hand to give of the palmar interosseus vessels — the primary blood supply of the hand.
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On the extensor or dorsal aspect of the interosseus membrane of the fore-arm develops the dorsal interosseus artery of the fore-arm fed by branches of the axial artery which perforate at the proximal and distal ends of the membrane.