Abstract

The concept of usage trophy (troph – Development y – The process of) and disuse atrophy has evidenced again and again that functionality directs anatomy in all biological systems

When we consider the foetal adjustment of various systems at birth especially the circulatory system once the umbilical cord is ligated, the placental circulation stops. Blood flow through umbilical vein ceases causing contraction of ductus venosus within one to three hours after the birth. The systemic vascular resistance increases as the pressure in the LA (left atrium), LV (left ventricle) and aorta increases.