The cardiovascular system is responsible for the distribution of all the substances an organism requires for life, such as oxygen, nutrients, hormones etc. throughout the body.  In simple terms, it consists of a pump, a “piping” system and a fluid transport medium. The function of the pump is carried out by the heart, the “piping” system consists of the blood vessels and the medium circulating within is the blood. Blood consists of a fluid component and various blood cells and is both a means of transport and an important part of the body’s immune system.

In a well-functioning cardiovascular system all tissues are well supplied with oxygen and nutrients. In order to assess the condition of the circulatory system, the mucous membranes of the mouth or the conjunctiva of the eye are examined; in a normal state of health they are pale pink and the capillary refill time is no longer than 2 seconds.