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		Embryonic limb bud culture in media Kate Yoder Early in embryonic development, the region of the chick embryo which is determined to form a limb first differentiates from the rest of the embryo1. The next step in the formation of the actual limb (wing or leg) is the development of the limb region into a specific set of functional tissues through the interactions of several proteins, or morphogenesis. Morphogenesis of the vertebrate limb occurs similarly in all tetrapods. This similarity is marked by growth in three dimensions which are along the proximal-distal, anterior-posterior, and dorsal-ventral axes. By the sixth day, the limb bud possesses all the necessary signals to continue growth of the limb in culture and is visible as a process on the embryo with distinct axes. As development continues, the basic limb structure arises out of the limb bud as skin, cartilage, and skeletal muscle. As the embryo matures, the cartilage will turn into bone, thus getting closer to fulfilling the fate which began in the early embryo. In addition to differentiating into basic structure, the limbs differentiate from each other. This differentiation is determined by the interaction of several chemicals and growth factors. As a result, a wing is not the same as the leg. The consequence of normal limb development in the chick embryo are the legs and wings necessary for the organism's survival.