When the limb buds are being formed in the 4-5th week they are permeated by a capillary network

  1. When the limb buds are being formed in the 4-5th week they are permeated by a capillary network

  2. 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.

  3. 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.

  4. 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.

  5. The axial artery of the upper limb persists as the subclavian, axillary and brachial trunks,

  6. 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.

  7. 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.