Heart Grows. The heart is such a remarkable organ that perhaps a few words about how it develops and grows are order. This is how it all begins. Within the first two weeks after conception a small tube begins to form in the tiny embryo or unborn baby. Believe it or not, this is the forerunner of all the blood vessels in the body.

A few embryonic blood cells also begin to float around within these tiny vessels. This is beginning of the bloodstream. From these early developments the entire circulatory system of the body will eventually form. As the little tube expands and grows, it begins to twist in a certain way, forming at first just one single chamber.

This is the beginning of the heart! Within this enlarging area a septum or dividing wall begins to grow, forming not two but four chambers. The two upper chambers are known as the left and right atrium {or auricle}, the two lower, as the left and right ventricles.

Normally there is no connection between the right and left sides of the heart after birth. But special doors or valves open between the atrium and ventricle on each side of the heart, so that the blood may only flow in one direction.

This whole mechanism is surprisingly simple, considering the enormous amount of work this embryonic heart must do. However, any failure in the development of the septum or valves may lead to some form of congenital heart disease.