What is the cardiovascular system?

The cardiovascular system, also called the circulatory system, is an organ system that allows blood to circulate throughout the body and supply cells with the needed nutrients and oxygen, as well as remove carbon dioxide and other waste products. Without the cardiovascular system, the body would be unable to fight off diseases and infections or maintain a stable internal environment (such as regulated temperature and fluid balance within the body).

The cardiovascular system is a closed system of vessels (blood vessels) which allow blood to flow quickly and efficiently from the heart to every area of the body and back again. There are two main components in the human body: the systemic circulation loop and the pulmonary circulation loop. Each of these components is formed by the arteries, capillaries and veins.

Arteries are blood vessels that are formed by elastic tissue and muscle fibers. They receive blood from the heart, the muscle that works as a real blood pump. Their elastic tissues allow them to stretch and contain any pressure from the heart. Arterioles are narrower blood vessels that branch off the ends of arteries and carry blood to capillaries. Capillaries are tubes formed from thin walls which carry blood very close to the cells of the bodily tissues in order to exchange nutrients, gases and waste products. They convey blood to smaller blood vessels, called venules, which converge to form the veins that carry blood back to the heart.

In cases of systemic circulation, blood coming from the lungs, rich in oxygen and nutrients, is pumped from the left ventricle (one of the four chambers of the heart in which the blood flows through) within the aorta, which then distributes it to the rest of the body. Once waste products are removed from body tissues, deoxygenated blood is returned to the right atrium (one of the four chambers of the heart).

Pulmonary circulation, on the other hand, forms a closed circuit between the heart and lungs and starts in the right ventricle, where carbon dioxide enriched blood is collected from the right atrium, transported through the tricuspid valve and pumped into the pulmonary artery. This is divided into two branches, called the capillaries, which collect oxygen at the level of the alveoli. The oxygenated blood is then conveyed in vessels and flown up into the pulmonary veins, which then enter the right atrium of the heart, into the right ventricle and through the mitral valve.


What function does the cardiovascular system serve?

The cardiovascular system has three main functions:

  • to deliver oxygen and nutrients to all organs, tissues and cells of the body
  • to remove carbon dioxide and waste matter
  • to protect the body against foreign microbes and toxins.


It is also used to convey important components of the immune system (white blood cells) and other molecules (such as hormones) that carry out different functions in the body and help deliver or expel any nutrient, gases, waste products, and messages throughout the body, as needed, through a dense network. Clotting mechanisms are also present and protect the body from blood loss after an injury.