VAN 211: Veterinary Histology and Embryology (2+2)

CARDIO VASCULAR SYSTEM

• Both the blood vessels and blood cells arise from mesenchyme. The earliest formative tissue of this kind is the angioblast which differentiates in the mesodermal wall of the yolk sac where groups of angioblasts form the blood islands of Pander.
• Originally solid, these soon hollow out and in this process the peripheral cells become arranged as endothelium and central cells form blood cells. From the wall of the yolk sac, the blood vessels extend into the body of the embryo and spread into the different parts.