What is the Function of the Circulatory System?

B. Schreiber

The function of the circulatory system is divided into two parts. It delivers nutrients to the cells of the body through the blood, which is pumped by the heart and carried to the tissues and cells through the blood vessels. Another function is carried out by the lymphatic and immune systems. The lymphatic system helps regulate the body's fluid composition, while the immune system also helps to rid the body of foreign organisms like bacteria.

The circulatory system.
The circulatory system.

The cardiovascular system can be divided into the heart, the blood, and the blood vessels. This system carries blood both away from the heart and back to it. The blood flowing away from the heart carries oxygen to the body's cells, and the returning blood carries carbon dioxide that is a waste product of the cells' activities. The heart is a muscular organ that keeps the blood in constant motion to support the life of the body.

A diagram showing different types of white blood cells.
A diagram showing different types of white blood cells.

There are three types of blood vessels. Arteries carry the oxygen-containing blood to all parts of the body. Veins complete the circle by return the blood containing carbon dioxide so that it can be exhaled. Capillaries are small blood vessels that connect the two at the level of organs and tissues. They both deliver oxygen to the tissues from the arteries and return carbon dioxide from it to the veins.

The structure of the aorta, part of the circulatory system.
The structure of the aorta, part of the circulatory system.

In addition to carrying oxygen and carbon dioxide, blood itself has many other functions. One of these is to deliver substances that are produced in specialized organs to other parts of the body. Blood is made of plasma, which is mostly water and a small amount of proteins, and formed elements in about equal parts. Formed elements include platelets and cells such as red and white blood cells.

A diagram showing the composition of a blood vessel.
A diagram showing the composition of a blood vessel.

The lymphatic vessels help maintain the balance of fluid in the body. They do this by collecting water that has escaped from the blood vessels, especially capillaries, and returning it to the cardiovascular system. Inside lymph vessels, this fluid is called lymph. Lymph nodes clean the lymph and sometimes become swollen in cases of infection.

A diagram of the human head and neck, including the blood vessels in red.
A diagram of the human head and neck, including the blood vessels in red.

Providing the body with immune defense is also a function of the circulatory system. The immune system is a division of the lymphatic system as a whole. Lymphocytes are immune cells that attack organisms like fungi and bacteria. Lymphoid organs, such as the spleen, also assist in the immune function, and lymphoid tissue helps the body fight infection in exposed areas like the respiratory system.

A person with visible blood vessels, which are part of the circulatory system.
A person with visible blood vessels, which are part of the circulatory system.

You might also Like

Readers Also Love

Discuss this Article

Post your comments
Login:
Forgot password?
Register: