Chapter 7 - Circulation and shock

Aims of this chapter

  1. Become familiar with the anatomy of circulation.
  2. Appreciate what shock is and be aware of its different causes.
  3. Appreciate possible sites of internal bleeding and blood loss.
  4. Remember that blood can carry serious infections like HIV or hepatitis – use gloves when handling wounds or bleeding.


“Circulation” refers to the heart pumping oxygen blood around the body to help fuel the body’s organs and muscles with oxygen, as well as taking away carbon dioxide and other waste products to the lungs or kidneys to breathe out or dispose of in the urine.

The heart beating pumps blood through the muscular walled arteries under pressure – “blood pressure”. Arteries have a thick muscular wall to support this pressure and take blood away from the heart. Veins, however, have thin walls to collect blood under low pressure on its way back to the heart. The body’s organs depend on blood pressure to function normally. Hence, if the pressure in the system drops due to not enough blood being in the circulation through bleeding, or the heart not beating correctly, then the organs can fail to function normally. Evidence of the body’s organs not working correctly is known as “shock”.