Hi bebop2,
To put it simply, the heart relies on the alveoli for its supply of
oxygen. The alveoli is where the exchange of Oxygen (O2) and Carbon
Dioxide (CO2) between blood and air takes place, driven by the
difference in pressure between the alveoli and pulmonary capillary.
Carbon dioxide is carried by the blood from tissues to the alveoli,
where it is diffused and exhaled from the lungs. Oxygen is inhaled
into the lungs and is diffused at the alveoli into the blood. The
blood loses carbon dioxide and gains oxygen during this exchange.
There's a nice little diagram illustrating the exchange here:
Gas exchange schematic:
http://www.aero.ufl.edu/~uhk/GASX.jpg
The Respiratory System:
http://academic.wsc.edu/faculty/baengeb1/powerpoints/4rsp1.ppt
Lecture NotesRespiration I Jack Buchanan:
"The respiratory system works with the cardiovascular system to
extract oxygen from air in the lungs, to transport it to the tissues
bound to hemoglobin in red blood cells, and via diffusion and the
bicarbonate system to deliver C02 from the tissue to the lungs where
it is transported to the alveoli to be removed via expiration.
Respiration can be divided into 3 basic steps:
1. Pulmonary ventilation--The mechanics of respiration. The entry of
air into the lungs (inspiration) and the outflow of air from the lungs
(expiration).
2. External (pulmonary) respiration--The exchange of gases between the
air spaces of the lungs and blood in pulmonary capillaries. The blood
gains oxygen and loses CO2 in this process.
3. Internal (tissue) respiration. The exchange of gases between blood
in small capillaries and tissue cells. The blood loses oxygen and
gains CO2."
http://memphis.mecca.org/bme/lifescience/respiration.html
Lecture 19: Respiration: Gas Exchange in Alveoli:
"The Alveoli are Designed for Rapid Gas Exchange
* After branching repeatedly the bronchioles enlarge into millions of
alveolar sacs
* This arrangement produces an enormous surface are for gas exchange
* Each alveolus is surrounded by a net of capillaries
* Alveolar cells are thin squamous epithelium; endothelial cells
lining capillaries are also thin
* The diffusion distance from gas in the alveoli to blood cells in the
capillaries is very short
* Blood takes about 1 second to pass through the lung capillaries
* In this time the blood becomes nearly 100% saturated with oxygen and
loses its excess CO2"
http://members.aol.com/Bio50/LecNotes/lecnot19.html
I hope this helps. If you have any questions, please post a
clarification request before rating my answer.
Thank you,
hummer
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