Question

when we breathe there is an exchange of oxygen for carbon dioxide . Please explain how does diffusion work at the level of the alveoli and then explain how is drowning and pulmonary edema affect diffusion and how are they the same?

Answer 1

Respiratory system

The exchange of gases between the alveoli and the blood capillaries occur through diffusion .

?What is diffusion ?

It is a process driven by the difference in the concentration gradient .

Simple diffusion takes place at the alveoli level .

Gas molecules move from higher gradient to lower gradient without any ATP expenditure .

During inspiration ,our lungs gets filled with the air and the oxygen content in it is more than the blood capillaries .

This can be explained by the partial pressure .

Partial pressure is the measure of the presuure applied by individual components ina total mixture and hence the total pressure is the sum of PP of each component of it .

The amount of oxygen in the air we draw in is 20% and CO2 is 0.4 % . Therefore by applying Ficks law .

( FICKS LAW : Rate of diffusion is directly proportional to the surface area and the concentration difference and inversely proportional to the thickness of the membrane .)

In the lungs presence 300 million alveoli per lungs increases the surface area and due to the concentration gradient

The oxygen diffuses out of the alveoli into the blood capillaries and CO 2 from the blood into the alveoli in exchange .

PP of oxygen in the alveoli is 100 mmHg , in tissue it is 40 mmHg

PP of CO2 in the alveoli is 40 mmHg and tissue 45 mmHg.

? What happens during drowning ?

During drowning , the individual tries to hold his breathe and do rapid body movements . These activities can reduce the oxygen inthe blood but increase CO 2.

Our respiratory centre is more sensitive towards the amount of CO2 .

Since the perosn tries to hold the breathe , the presence of CO2 starts to build up in the blood .

The person experiences the hypercapnia , this may lead to death of the individual beacuse once he start to experience hypercapnia he will start losing consciousness .and becomes fatigue .

Then the individual will sometimes under the case of hyperventilation may intake a lot of water inside .

This water intake will cause pulmonary oedema laryngospasm

So when the water enters , larynx closes and prevents the entry of water ,therby the oxygen level in the blood falls drastically and the lungs fails to work .

? The pulmonary oedema is due to the presence of fluid aspirations in the air sacs alveoli .

This may be an outcome due to drowning (wet drowning )

During pulmonary oedema , it prevents the exchange of oxygen as there is no air but fluid is in the alveoli .

This cause impairment in the oxygen CO2 exchange and fails the respiratory system .

Both pulmonary oedema and drowning is smilar as hypoxia is the reason behind the mortality and morbidity of both .