• Blood vessels are most noticeable in the arms.Image by Flickr.com, courtesy of Colin Davis
  
  

Artery

• Arterial walls are muscular in nature, allowing them to contract and expand in order to direct oxygenated blood flow away from the heart. The pulmonary artery is the only artery to transport blood other than oxygenated blood.
  
  

Arteriole

• The arterioles serve as a catalyst for blood between the arteries and the capillaries. They work much like the arteries and are the main vessels for regulating blood pressure and flow.
  
  

Capillary

• Capillaries appear in most body organs and tissues and are sometimes visible on the skin surface. Unlike other vessels, they do not transport blood but rather deliver the components found in blood that organs and tissues need, while also removing waste from surrounding cells.
  
  

Venule

• Venules begin the blood's journey back to the heart, as they drain the blood from capillaries and transport it to veins.
  
  

Vein

• Almost the exact opposite of arteries, veins have thick, non-elastic walls that carry deoxygenated blood back to the heart.