Blood vessel and nerve development in the vertebrate embryo possess certain similarities in pattern and molecular guidance cues. To study the specific influence of shared guidance molecules on nervous and vascular development, an understanding of the normal neurovascular anatomy must be in place. The present study documents the pattern of nervous and vascular development in the Japanese quail hindlimb using immunohistochemistry and fluorescently labeled intravital injection combined with confocal and epifluorescent microscopy. The developmental patterns of major nerves and blood vessels of embryonic hindlimbs between stages E2.75 (HH18) and E6.0 (HH29) are described. By E2.75, the dorsal aortae have begun to fuse into a single vessel at the level of the hindlimb, and have completely fused by E3 (HH20). The posterior cardinal vein is formed at the level of the hindlimb by E3, as is the main artery of the early hindlimb, the ischiadic artery, as an offshoot of the dorsal aorta. Our data suggest that eight spinal segments, versus seven as reported by others (Tanaka and Landmesser, 1986a;Tyrrell et al., 1990), contribute to innervation of the quail hindlimb. Lumbosacral neurites reach the plexus region by E3.5 (HH21 & 22), pause for $24 hr, and then enter the hindlimb along with the ischiadic and crural arteries through shared foramina in the pelvic anlage. The degree of anterior-posterior spatial congruency between major nerves and blood vessels of the quail hindlimb was found to be highest medial to the pelvic girdle precursor, versus in the hindlimb proper. Anat Rec, 292:1559Rec, 292: -1568Rec, 292: , 2009. V V C 2009 Wiley-Liss, Inc.

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Blood vessel and nerve development in the vertebrate embryo possess certain similarities in pattern and molecular guidance cues. In order to study the specific influence of shared guidance molecules on nervous and vascular development, an understanding of normal neurovascular anatomy must be in place. The avian embryo is an excellent system for the study of neurovascular development and has traditionally focused on the chick and the quail forelimb. We have studied the pattern of nervous and vascular development in the quail hindlimb using immunohistochemistry and fluorescently labeled intravital injection combined with confocal and epifluorescent microscopy. The developmental patterns of major nerves and blood vessels of embryonic hindlimbs between the stages E2.75 and E6.5 are described. A high degree of spatial congruency was found between major nerves and blood vessels of the quail hindlimb. The spatial pattern of nervous development in the quail hindlimb was essentially identical to that of the chick, but was found to proceed at a slightly more rapid pace. This study provides the anatomical basis necessary for future studies examining the role of Sema3A on the congruency of nerves and blood vessels entering the embryonic hindlimb bud.