Blood vessels

Blood vessels

Arteries and arterioles
1. Thick muscle to withstand high pressures
2. Blood carried at high pressures generated by the ventricular systole
3. Oxygenated blood
  1. Except pulmonary and umbilical arteries
4. Medium lumen
5. Elastic fibres to control pressure --> elastic recoil between contractions
Veins and venules
1. Thick collagen in the walls for support
2. Little elastic because they carry the blood at lower pressures
3. Valves in medium to large sized veins to prevent backflow
4. Carry deoxygenated blood except the pulmonary and umbilical ones
5. Smooth lining to allow the blood to flow easily
6. Large lumen
7. Muscle contraction squeezes them and forces the blood back towards the heart and the breathing movement of the chest pumps it back
Capillaries
1. One cell thick walls for small diffusion distances
2. Blood deoxygenates as it goes through the capillary
3. Smallest lumen to slow the flow of the blood right down and maximise the time for diffusion to occur
4. Erythrocytes have to go single-file to which increases the time available for exchange

Resource summary

	Created by Sara Bean almost 7 years ago