Which structure contains deoxygenated blood?
Pulmonary veins
Pulmonary arteries
Left atrium
Aorta
Left ventricle
Which of the following is true of arteries?
Arteries lack an endothelial layer
The walls of arteries and veins are about the same thickness in a given tissue
Their thick walls are due entirely to the bulk of elastic fibers in the middle layer
Vein walls are thicker than arteries because veins must pump blood up from the lower body
Their walls are thick and muscular compared with veins
