13) Cardiovascular and respiratory support

Blood circulates in the body through a network of vessels that begin and end at the heart, which is the circulatory pump. Actually the heart has two pumps, which work to coordinate with the lungs and vessels to keep blood moving, delivering nutrients and removing waste from tissue cells in the body.

The process starts in the lungs, where red blood cells are exposed in tiny capillaries to air containing oxygen and carbon dioxide. Red cells exchange carbon dioxide for fresh oxygen molecules and then flow to the heart where they are pumped through a network of artery vessels that transport the oxygenated blood throughout the body.

Plasma, which is primarily made of water, provides fluidity in the vessels to keep blood cells flowing. Along with oxygen carried by red cells, the plasma also delivers vital nutrients to the tissues of the body. When oxygen is release to the tissue cells, red blood cells pick up carbon dioxide waste and then travel back to the heart through a network of veins. The heart then pumps the carbonated blood to the lungs where red cells release the carbon dioxide in trade for fresh oxygen molecules in an endless cycle.

The kidneys and skin also play key roles in helping filter and eliminate waste from the blood. The average adult has five liters of blood in the circulatory system, which is circulated and filtered 24 to 36 times every day.