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Chapter 9 Heat and Kinetic Theory -- Part 3
The gas exchange of oxygen into the blood and CO2 out of the blood is very fast.
The lungs are not fully emptied.
The table shows the composition of inspired and expired air.
Increased physical activity results in both faster and deeper breathing when the oxygen requirement increases.
70% of the air in the lungs is exchanged during deep breathing.
The oxygen needs of small animals may be completely satisfied through this channel, since only a small fraction of the oxygen required by large animals can be supplied through the skin.
The following considerations can be used to deduce this.
The mass of the animal is related to the energy consumption and the oxygen requirement.
The amount of oxygen flowing through the skin is determined by the surface area of the skin.
It's possible to estimate the maximum size of the animal that can get its oxygen from the skin.
Only small animals, such as insects, can rely on the transfer to get oxygen.
Frogs can get all the oxygen they need through their skin when the oxygen requirements of the animal are reduced to a very low value.
Some species of frog can be found at the bottom of the lakes in the winter.
This is an approximation.
There is a more detailed discussion.
The frog's body gets the required oxygen from the surrounding water.
The discussion neglected the size of the alveoli.
The alveoli's inner wall is covered in a thin layer of water.
The surface tension of this water layer reduces the surface.
The incoming air has to enter the alveoli to expand them.
Expanding the alveoli is similar to creating a bubble inside a liquid because they are embedded in a moist medium.
The walls of the alveolus are covered with plain water and the minimum pressure is required to open them.
The small alveoli can't open due to the incoming air at one atmosphere.
Breathing is possible by covering the alveolar water layer with surfactants.
The surface tension can be reduced by as much as a factor of 70 with the help of the surfactant molecule.
The lungs of premature infants don't produce enough of the stuff needed for breathing.
Artificial lung surfactants were developed in the 1980s and can now be used to treat Infant Respiratory Distress Syndrome.
The alveoli begin to produce their own surfactants when they are introduced into the lungs of the infant.
Frogs, snakes and lizards don't need lung surfactants for breathing.
The animals don't use energy to heat their bodies.
They need about a factor of ten less oxygen than warmblooded animals of the same size.
Cold-blooded animals can function with smaller lung surface area.
Lower pressure is needed to overcome surface tension in larger alveolus.
The majority of the human body gets its oxygen from the circulating blood.
The cells in the cornea receive oxygen from the surface layer of tear fluid.
The fact allows us to understand why most contact lens should not be worn during sleep.
The contact lens is fitted in a way that makes it work.
Fresh oxygen-rich tear fluid is brought under the lens by this rocking motion.
When people sleep, their eyes are deprived of oxygen because they don't blink.
This could result in a loss of transparency.
The stability of fish using air bladders is less than those using porous bones.
The gas equation is used to explain this phenomenon.
A scuba diver breathes air from a tank that has a pressure regulator that adjusts the pressure of the air in the tank to the ambient pressure.
The mean free path is 10-8 cm and the average speed of the molecule is 104 cm/sec.
The number of breaths per minute is calculated using the data in the text and Table 9.3.
The rate of oxygen dispersal through the skin is calculated by 7 m2.
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