Anatomy and Physiology of the Cardiopulmonary and Respiratory System.

Prior to administering cardiopulmonary resuscitation (CPR) candidates are taught about the anatomy and physiology of the cardiopulmonary and respiratory system. In all rescues, candidates must check for the airway, breathing, and circulation of victims. However, prior to checking, monitoring, or maintaining those priorities candidates must have a good understanding of the human body’s cardiopulmonary system. This page will focus on the anatomy and physiology of the ABC which stand for airway, breathing, and circulation.


The airway is referred to as parts of the respiratory system that connect the lungs to the atmosphere from the outside world.  Included in the airway are the nose, mouth, pharynx, larynx, and trachea. Candidates will learn to open the airway for adult, child, and infant victims.


Breathing is the exchange of air between the lungs and the outside world. In the “breathing section” participants will learn about how air passes through the nose, mouth, pharynx, larynx, trachea, bronchi, and bronchioles. When air passes through these passages it enters the lung tissues (alveoli). This is where the exchange of oxygen and carbon dioxide occurs in the body. Breathing is mostly controlled automatically through the “respiratory control center” within the central nervous system. The air that people breathe in is approximately 21 percent oxygen and the air we breath out is 16% oxygen. Even with this 5% difference in oxygen content “mouth-to-mouth” resuscitation is still extremely effective at administering oxygen into a victim’s lungs.


The circulatory system includes the heart, arteries, capillaries, and veins in which blood flows continuously.  The circulatory system circulates oxygen and carbon dioxide throughout the body. The heart works as two pumps, divided into left and right, which work simultaneously and circulates the oxygen-enriched or carbon dioxide-filled blood throughout the body. It sends the blood throughout the body and into the lungs for oxygenation. Blood that is oxygen-depleted is slightly darker and flows centrally through veins back to the heart.

Candidates need to have a basic understanding of the components mentioned above. This will help participants better understand how effective and efficient CPR can promote recovery and preserve the vital organs of the body. Without this basic understanding of the Anatomy and Physiology of the Cardiopulmonary respiratory system, participants may struggle with basic concepts of CPR.