Back to: Basic CPR/AED & First Aid
Heart
Our heart beats 100,000 times a day, pushing 5,000 gallons of blood through our body every 24 hours. It delivers oxygen and nutrient-rich blood to our tissues and carries away waste.
The heart is a muscular organ roughly the size of a closed fist. It sits in the chest, slightly to the left of center.
As the heart contracts, it pumps blood around the body. It carries deoxygenated blood to the lungs where it loads up with oxygen and unloads carbon dioxide, a waste product of metabolism.
The heart, blood, and blood vessels combined are referred to as the circulatory system. An average human has around 5 liters (8 pints) of blood, which is constantly pumped throughout the body.
Lungs
The human body contains two lungs, of which one is positioned on the left side of the chest cavity and the other on the right side. The right lung is separated into three divisions or lobes, while the left lung contains two lobes. Each lung is surrounded by a two-layered membrane lining (pleura) that attaches the lungs to the chest cavity. The membrane layers of the pleura are separated by a space filled with fluid.
The lungs are organs of the respiratory system that allow us to take in and expel air. In the breathing process, the lungs take in oxygen from the air through inhalation. Carbon dioxide produced by cellular respiration is in turn released through exhalation. The lungs are also closely associated with the cardiovascular system as they are the sites for gas exchange between the air and the blood.
