Contraction of the SA node sets the tempo for the entire heart. Arteries and veins are distinguished by the direction in which they carry blood. Arteries carry blood away from the heart and with the exception of the pulmonary artery carry oxygenated blood. Veins carry blood twoard the heart and with the exception of the pulmonary veins carry deoxygenated blood. Blood pressure Force of blood against arterial walls.
Distinguish thoroughfare capillaries versus true capillaries.