- In a fetus, the heart will be the first organ that is functional.
-Before the heart can start fully developing during the third week, symmetrical groups of cells, the cardiogenic mesoderm cells, have to move from different parts of the body and come together.
-During the third week of the gestation period, the two halves of the heart join together to form a two-chambered heart.
-This fusion that occurs during the third week is when the heart starts to beat.
-Since at this time the brain has not fully formed yet, the heart is able to beat due to the fact that the cardiac muscles do not rely on stimulation from the nervous system.
-When the heart starts to beat during the third week, rapid change begins. The tissue starts adjusting itself into three chambers because the left and the right atria are split.
-During the fourth week of the gestation period, the septum that divides the left and right atria finishes developing.
-The left and right atria stay open to each other through an opening in the septum, the foramen ovale. This allows the fetus to breathe as it does not use the lungs, until it is out of the womb which is when the foramen ovale closes.
-During the seventh week of the gestation period, the septum in the ventricles of the heart is formed, so now the heart has four chambers because the pulmonary artery and aorta are positioned correctly.
-After birth, the pulmonary artery delivers deoxygenated blood from the heart to the lungs, and the aorta delivers oxygenated blood to the heart from the body.
| The fully formed heart |
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