Question

In which phylum, blood vessel are first formed

Answer 1

Answer:

Vasculogenesis is the formation of a vascular network from mesodermal progenitor cells. It requires differentiation of endothelial cells from hemangioblasts and then organization into a primary capillary network.

Explanation:

i hope you like my answer ☺..................

Answer 2

As far as blood vessels are concerned one should make note that there are two types of circulation Closed and open based on whether blood vessels are being used or not(sequenced Sentence). It is evident that close vascular system makes the use of blood vessels and the phylums which use closed vascular system are:
1.Annelida
2.Chordata