AND FETAL CIRCULATION
The heart raises from a little group of special cells located in the
embryological region which will become the chest. During the first four
weeks of pregnancy this cells grow until they form a tube called the
primitive heart tube. It is constituted of four segment: the seno-atrium
which forms the atria, the primitive ventricle which forms the left
ventricle, the heart bulb which forms the right ventricle and the truncus
arteriosus which forms the aorta and the pulmonary artery. In the primitive
heart tube the blood arrives in the senoatrium, travel through the tube
and go out through the truncus arteriosus.
Embryological development of the heart. A. Primitive heart tube stage.
The senoatrium (SA) will give right and left atrium; the primitive ventricle
(V) is the precursor of left ventricle; the bulbous cordis (BC) will
give the right ventricle; the truncus arteriosus (TA) will branch into
aorta (A) and pulmonary artery (P). B. C. D. Successive stages of the
development up to an heart with 4 cavities-.
During the next step the primitive heart tube coils up in a handle giving
two atria and two ventricles. The right atrium connects to right ventricle
through the tricuspid valve, left atrium connects to the left ventricle
through the mitral valve. Contemporaneously are formed the atrial and
the ventricular septum. The truncus arteriosus branches into aorta and
pulmonary artery which connect respectively to the left and right ventricle
. At ten weeks the heart is completely formed and functional and during
the rest of the pregnancy it will grow to supply the demand of developing