The circulatory system has evolved over time from simple diffusion through cells, in the early evolution of animals, to a complex network of blood vessels that reach all parts of the human body.

When did circulatory systems evolve?

When these functions arose in evolution

Then, around 540 million to 510 million years ago, an ancestral vertebrate evolved a closed vascular system, with blood pumping through vessels lined by endothelium.

Why does the circulatory system develop first?

When an embryo is made up of only a very few cells, each cell can get the nutrients it needs directly from its surroundings. ... Thus, the first organ system to develop is the heart, blood and circulatory system, so that nutrients and waste can be transported throughout the growing embryo.