A Pessimist's Blood Type is Always B-Negative

By ensuring disease fighting measures and stable homoeostasis the circulatory is absolutely necessary but why and how? 

The multiple litres of blood are comprised of platelets, red blood cells, plasma and white blood cells. As well lymph runs through the circulatory system, it assists in cleaning unwanted materials from the body.

The circulatory system
is an umbrella system
to three body systems
that work together.

The circulatory system itself is an umbrella of sorts for the cardiovascular (heart), pulmonary (lungs), and systemic (arteries, veins, coronary and portal vessels). 

The cardiovascular system is at the heart of the circulatory system (haha get it the heart because it is the heart) as it pumps blood throughout the entire body. Arteries transfer oxygen full blood away from the heart to the rest of the body and ensure stationary cells receive the oxygen and nutrition they require. 

The aorta is the largest artery from the heart and goes through the neck (after receiving oxygen from the lungs: pulmonary flow) and branches out through the body into smaller arteries and then into very small arterial and then to capillaries where the newly oxygenated red blood cells provide oxygen to the cells. The body's stationary cells accept oxygen and various nutrients from passing red blood cells when the oxygen and nutrients diffuse from the plasma surrounding the red blood cells to the interstitial fluid surrounding stationary cells throughout the body.

Once the cells receive the nutrient or oxygen they require the waste (including carbon dioxide) is dumped into venules that go backwards and end up going to the Inferior Venae Cavae (Bottom section of the body) or Superior Venae Cavae (Head, arms)that converge and bring all the blood back to the heart. From the two Venae Cavae the blood goes into the ventricles of the heart where the blood get re-oxygenated by the capillaries that go to the alveoli in the lungs. This is called the pulmonary system. The capillaries bring in the groceries (oxygen) and throw out the trash (carbon dioxide).

 
Major Organ:

Heart: The heart's walls are made of muscle that is able to pump blood from the left ventricle out of the aorta when the heart beats (muscle contracts). The heart has two atriums, left and right where the blood enters the heart from the lungs (left atrium) or from the Venae Cavae (right atrium) The heart's ventricles are kind of storage spaces where the blood stays in between heart beats when it is pumped out of either the pullmnory artery (right side, re-oxygenation) or the aorta (left side, oxygenated blood throughout the body). The heart itself has its own set of arteries and veins called the coronary system and eventually the blood from this system feeds into the right and left ventricle as well.