Vascular myelopathy later in this article. However, TIAs can result from emboli in calcific aortic disease and aortic coarctation. Spinal arteriovenous malformations (AVMs, or angiomatous malformations) are congenital (from birth) abnormalities of blood vessels. Arteries that directly communicate with veins bypass the capillary network (which has not yet developed) and thus creates a shunt. AVMs appear as a mass of convoluted, dilated vessels. In regards to the spinal cord, they are usually located in the thoracolumbar region (between the thoracic and lumbar regions, 60% of the time), as opposed to the upper thoracic (20%) and cervical regions (approximately 15%). Cervical malformations arise
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