system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
The specialized group of mesenchymal cells that aggregate to form blood islands centrally and primitive blood vessels peripherally are called
assistant
The correct answer is  The angioblasts are the mesenchymal cells that form blood vessels in embryonic development, as well as embryonic blood cells.