The main purpose of the cardiovascular system is transportation, explains Paul A. Iaizzo, Ph.D., Director for Education at the University of Minnesota's Lillehei Heart Institute. The components of this organ system -- the heart, the blood vessels, the blood and the lymphatic system -- function together to rapidly move molecules between cells inside the body, the surface of the body, and specialized organs and tissues. The underlying purpose of all this movement is the exchange of substances between the body and the external environment and between various parts of the body.
Oxygen Delivery
The blood absorbs oxygen in the lungs and the cardiovascular system, then distributes the oxygen-rich blood to cells in different parts of the body. Red blood cells, or erythrocytes, serve to transport the oxygen in the blood. Twenty major arteries route the oxygen-carrying blood out into the body. Along the way, they branch out into smaller arterioles, which in turn branch out into very small vessels called capillaries. Almost every cell in the human body is close to one or more capillaries, notes Professor Iaizzo, author and editor of the "Handbook of Cardiac Anatomy, Physiology, and Devices." The transfer of oxygen from the red blood cells to the other cells of the body takes place at the level of the capillaries.
Waste Removal
At the same time that oxygen passes from the capillaries to the cell, another transfer of materials takes place in the opposite direction: the by-products of cellular metabolism pass from the cells into the blood. These products include carbon dioxide and lactic acid. The circulatory system's veins carry the blood with those waste products back towards the heart, the lungs, the liver and the kidneys. The lungs expel the carbon dioxide back out into the external environment, and the liver and kidneys filter out other wastes, and these are then ejected from the body.
Synthesis and Regulation of Hormones
The purpose of cardiovascular system goes beyond pumping blood. The heart itself produces several hormones, including atrial natriuretic peptide. That hormone acts to increase blood volume and the total output of blood by the heart. Certain receptors connected with the heart help to regulate the amount of antidiuretic hormone by the pituitary gland. That hormone affects the amount of water that the kidneys lose.
References
- "Cardiovascular Physiology Concepts"; Richard E. Klabunde; 2004
- "Handbook of Cardiac Anatomy, Physiology, and Devices"; Paul A. Iaizzo, Editor; 2009
- American Heart Association: Heart, How It Works
- Texas Heart Institute Heart Information Center: Anatomy of the Cardiovascular System
- Merck Manuals: Organ Systems
