The circulatory system

The circulatory system is our body’s transport system for two fluids, namely, blood and lymph.

For the purposes of first aid we will focus on the transport of blood, also known as the cardiovascular system.

This system consists of the heart and blood vessels, which supply our body, and in particular, our vital organs such as the brain and heart, with blood containing oxygen and nutrients to keep them healthy.

Our heart is a hollow muscular pump, about the size of your fist, with two pairs of chambers. These chambers collect blood flowing back from our body after depositing the oxygen and nutrients, before being pumped back to the lungs to collect more oxygen so that the cycle of transportation can continue.

The adult heart beats approximately 60 – 80 times every minute and pumps approximately six litres of blood around our body every minute.

The blood vessels within this system are:

• Arteries
  Deliver oxygenated blood from the heart to the body, with the exception of the pulmonary artery which carries deoxygenated blood from the heart to the lungs
• Veins
  Carry the de-oxygenated blood back to the heart
• Capillaries
  Much smaller vessels that form a link between the arteries, veins and body tissue to allow the transfer of oxygen and nutrients to the body and the waste products to be removed

Blood is made up of:

• Plasma
  The fluid component of the blood of which 90% is water
• Platelets
  Help to block the blood flow by clotting
• Red cells
  Transport the oxygen via the haemoglobin
• White cells
  Manufacture antibodies and fight infection and bacteria