In chickens, embryonic development begins upon egg formation and lasts for 21 days of incubation until hatching. The CAM is an extraembryonic membrane that serves a critical role in acid-base balance, gaseous exchange, calcium solubilization, and antimicrobial protection. Comparative proteomic analyses of CAM at two developmental stages (ED12 and ED19), in comparison to the proteome of embryonic blood serum, revealed protein groups that are relatively or highly specific to the CAM. The specific CAM functions include gaseous exchange, Ca2+ transport, vasculature development, and protection against pathogen invasion. Overall, our results highlight the structure-function relationship of the CAM protein constituents that potentially could expand its biomedical applications.