Blood vessel Blood vessel The blood vessels are the part of the circulatory system, and microcirculation, that transports blood throughout the human body. These vessels are designed to transport nutrients and oxygen to the tissues of the body. They also take waste and carbon dioxide and carry them away from the tissues and back to the heart. Blood vessels are needed to sustain life as all of the body’s tissues rely on their functionality.There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals
Blood islands plasma, beginning 3 weeks after fertilization. Blood formation inside the embryo proper begins around 5 weeks after fertilization in the liver, and at the twelfth week in the spleen, red bone marrow and thymus. Blood islands have been seen in the area vasculosa in the vitelline veins and arteries, and in the dorsal aorta. Blood islands Blood islands are structures around the developing embryo which lead to many different parts of the circulatory system. Blood islands arise external to the developing embryo on the umbilical vesicle, allantois, connecting stalk and chorion. They are also known as Pander's islands or Wolff's