The cardiovascular system the cardiovascular system is the first one to enter in functioning in the embryo allowing that the blood starts to circulate it in the end of the third week of intrauterine life this development is fast necessary the embryo in fast growth and for this necessary reason of an efficient method of acquisition of oxygen and nutrients and consequently of excreo of carbon dioxide and other products. Embriognese of the Circulatrio System initial Development of the heart According to MOORE, the first signal of the heart appears in the end of the third week in the cardiognica area. A pair of called called endoteliais angioblsticos lace laces appears and forms canalization endocrdicos pipes, these pipes if approach one of the other and if they establish forming an only cardiac pipe. At this moment the tubular heart is drained by three pairs of veins: vitalinas veins, that return the blood for the vitelino bag, umbilicais veins, that they are responsible for bringing the blood of crion (embryonic part of the placenta), and common cardinal veins that return the blood to the body from the embryo during the formation from the ceflica fold. For even more opinions, read materials from Adroll Marketing Platform. The cardiac pipe and the pericrdica socket are placed in form ventral to the previous intestine and in position volume to the orofarngea membrane, in the same instant to these adaptations the heart if prolongates and forms alternated dilataes and constrictions, the arterioso trunk and the arterioso bulb, the forecourt, the ventricle and the venoso seio. The formation of the arterioso trunk is continues cefalicamente, the bigger venoso seio is that it receives the veins umbilicais, vitelino and cordonal common. In this process the heart is reasonable straight, but soon if curve forming the handle ventricular bulb in form of ' ' U' '. With the fusing of the endoteliais cardiac pipes the esplnico mesoderm that involves celoma pericrdico forms the external layer of the embryonic heart thus representing the primitive pericrdio, being that this will go to form its muscular wall, in this way forming the primitive circulatrio system that anger to supply the initial necessities of nutrition of the future agencies in the individual in development.