The circulatory system is an extensive body system that is composed of three main parts--the heart, blood and blood vessels--which function together to transport nutrients, oxygen and water to cells and remove waste products such as carbon dioxide from the body.
Heart
The heart is the main organ of the circulatory system. The heart is the driving force responsible for pumping blood throughout the rest of the circulatory system. Without proper heart function, the other components involved cannot function as they should.
Blood
The heart pumps blood, the medium in which nutrients, water and oxygen are carried to the cells of the body. Blood is further broken down into four major components: red blood cells, white blood cells, platelets and plasma. Red blood cells are responsible for carrying oxygen from the lungs to various cells while white blood cells function to fight off germs and infection. The number of white blood cells the body produces is greatly increased when the body is under attack from an infection. Platelets are the portion of the blood that help stop bleeding during an injury. Platelets travel to the site of injury and form a "plug" that controls bleeding. These plugs are commonly referred to as scabs. The last portion of the blood, plasma, composes nearly half of blood volume and is liquid. Plasma is produced by the liver and is responsible for the actual transport of the blood cells mentioned above as well as other components.
Blood Vessels
There are three main types of blood vessels that each has a different function. Arteries are responsible for carrying blood away from the heart, veins carry blood back to the heart, and capillaries connect arteries and veins to one another. The blood vessels are the part of the circulatory system that resembles a highway system.
Blood Flow
Blood flow throughout the body is a continuous cycle that is directed by the heart. Blood is pumped from the left side of the heart into the arteries, which carry blood away from the heart. This blood contains oxygen and food for the body's cells. Oxygen and nutrients are delivered to the cells through the capillaries. The de-oxygenated blood travels back to the heart by way of veins, and the entire process begins again.
Blood Pressure
Blood pressure is the amount of pressure that pushes against the walls of the arteries when blood is transported. Blood pressure measurements vary throughout the day with body position and various activities. Higher blood pressure makes the heart work harder and puts extra stress on the arteries. Over time, arteries can weaken and the risk of stroke, heart attack and other health issues increases. Maintaining a healthy blood pressure is key to keeping the circulatory system healthy.
