At the 8 mm crown-rump length (CRL) stage, the subclavian artery, a continuation of the seventh intersegmental artery, crosses the lateral margin of the first rib and continues as the axillary artery (Rodríguez-Niedenführ et al. 2001a, b). The axillary artery extends through the posterior axillary fold and continues as the brachial artery after passing the inferior border of the teres major tendon in the 11 mm CRL stage (Rodríguez-Niedenführ et al. 2001a, b). From the 11 to 14 mm CRL stages, the brachial artery descends the upper limb, pierces the entepicondylar foramen, and continues as the interosseous artery, supplying the embryonic forearm before regressing (Rodríguez-Niedenführ et al. 2001a, b). A well-developed brachial artery can be observed from the 14 to 17 mm CRL stage, and defined structures corresponding to the ulnar, median, and interosseous arteries can be identified (Rodríguez-Niedenführ et al. 2001a, b). By the 23 mm CRL stage, the interosseous and median arteries have regressed. The definitive adult arterial morphology can now be visualized, in which the ulnar and newly formed radial artery branches descend the forearm to supply the hand.