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Bronchioles: They are a series of branching subdivisions of bronchi. The walls of
bronchioles are made of muscle lined with epithelial cells. This muscle is important as the
muscle allows the wall to constrict so they can control the flow of air in and out of the
Alveoli: they are air sacs, with the diameter of between 100m to 300m, at the end of the
bronchioles. They contain some collagen and elastic fibre and they are lined with epithelial
cells.…read more

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Pulmonary ventilation is the total volume of air that is moved into the lungs during one
minute. We use a measure called pulmonary ventilation which is used to measure how much
air is taken in and out of the lung in a given time.
The equation we use is:
Pulmonary ventilation (dm min ) = tidal volume(dm ) X ventilation rate (min )
Tidal wave is the volume of air normally taken in at each breath when the body is at rest.…read more

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Diffusion of gases between the blood and the alveoli is very rapid because the red blood
cells are slowed as they pass through pulmonary capillaries which allows more time for
diffusion. The alveoli and pulmonary capillaries have a very large surface area. The walls of
alveoli and capillaries are very thin so short pathway for diffusion.
The blood flow through the pulmonary capillaries maintains a concentration gradient.…read more

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Drugs can also be used to prevent it but the problem with the drugs is that they have to be
taken for a long time for about 69 months.
Regardless of all this there has been a recent increase in TB in many developed countries.
The reasons are people living in rough conditions, large proportion of elderly people in the
population and the spread of HIV.
Pulmonary fibrosis:
This disease occurs when the epithelial cells of the lung become thickened.…read more


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