The Circulatory System: Blood Vessels

3 types of blood vessels Arteries  carry blood AWAY from heart (reminder tip: think “A” for Away) Veins  carry blood TO the heart Capillaries  network of tiny vessels within body tissues

What are some differences in structure between the 3 types of blood vessels? Why do they look different?

Arteries (Away from heart) Blood in arteries are under high pressure (pumped from the heart)  therefore walls are thick and elastic to withstand the pressure  most arteries carry oxygenated blood (except pulmonary arteries going to the lungs)

Veins (To the heart) There is less blood pressure & some veins have to fight gravity so they have valves to prevent backflow Walls are also thinner & are collapsible (less rigid shape) Most carry deoxygenated blood (except pulmonary veins coming back from the lungs)

Muscles help squeeze the blood in veins back to heart

Enlarged veins & dysfunctional valves due to continuous long-term standing or leg crossing

Varicose veins

Capillaries Walls are 1 cell thick  for efficient diffusion of gases Vessel is narrow (only 1 red blood cell can pass at a time)  slows blood flow down so gas exchange can happen

Heart  aorta  artery  arteriole  capillary  venule  vein  vena cava  Heart

Can you identify the 3 types of vessels in these cross sections?