Vascular Growth in the Extraembryonic Mesoderm of Avian Embryos

The precursor of each definitive blood vessel is a capillary. During embryogenesis, the pattern of adult blood vessels is preformed by patterning at the capillary level. Under pathological conditions such as inflammation, collateralization in chronic ischemia, wound healing and tumor growth, capillary vessels precede the definitive newly formed blood vessels. Therefore, the mechanisms that are involved in the formation of capillary blood vessels are crucial for the development of a vascular system. Suitable models for studying capillary formation in vivo are rare, because in most newly vascularized tissues observation and interpretation of capillary growth are hampered by a complex spatial structure.