Lungs, Oxygen and Carbon Dioxide
Blood Vessels and Alveoli.
Surrounding the alveoli are tiny blood vessels or capillaries. This small blood vessels are structured as a
network and surround the alveoli. This is where oxygen enters the blood as it is transported along the breathing
Carbon dioxide gas or "exhaust" exchanges places with the oxygen and exits through blood entering the alveoli.
Carbon dioxide is then removed from the lungs. In order for our body to function properly, the oxygen and carbon
dioxide must both enter and exit through the blood at regular intervals.
The lungs have two sets of blood vessels. Blood vessels can be arteries or veins. A series of blood vessels
supplies the lung, while the other is charged with transporting oxygen from the lungs to the rest of the body,
passing through the heart.
The blood that has picked up oxygen from the lungs is pumped into the left side of the heart and transports this
oxygen-rich blood (called arterial blood) to the body. Once the blood has delivered oxygen to the cells of the body
(skin, organs, etc..) it brings it back into the right side of the heart. This is known as venous blood. Venous
blood contains large amounts of carbon dioxide and small amounts of oxygen. The venous blood continues its journey
to the lungs to eliminate carbon dioxide and pick up oxygen.
If the lungs are unable to receive enough oxygen or the passage of oxygen in the blood is blocked, the lung
tries to protect against oxygen deficiency by closing some of the blood vessels. The heart must then pump the same
amount of blood into a smaller number of blood vessels. Since the total amount of blood in the body is unchanged,
this causes additional stress for the heart. The stagnation of blood forces the heart to work harder and this often
causes an enlarged heart.