Why did ancient Egyptians think that blood vessels contained air?

Ancient Egyptians believed that blood vessels contained air because they observed that the heartbeat and the pulse seemed to be connected to the movement of the body and its breath. They associated the flow of blood with vital life forces, including the breath, which they thought might travel through the blood vessels like air. This understanding was rooted in their broader views on the body, health, and the interplay of physical and spiritual elements in their medical practices. Their lack of advanced anatomical knowledge led to these misconceptions about the circulatory system.