Lungs and Cell Transport

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Name:   ______________________________ 

Title: Cell Transport – Respiratory Membrane 

The respiratory membrane of the lungs is located in the alveoli, small sacs that fill up with air when you breathe in. Approximately 300 million alveoli are in your two lungs. The average diameter of each alveolus is approximately 0.25. which is extremely small! The walls of the alveoli sacs are very thin. The walls are designed to be thin so that substances, like oxygen and carbon dioxide, can pass through them. Surrounding each alveolus is a network of capillaries. Capillaries are the smallest form of blood vessels. The capillaries are arranged so that air within the alveoli is separated only by a thin respiratory membrane. 

1. Where is the membrane located, specifically?     _______________________________________ 

1. How many alveoli can be found in your lungs?   ________________________________________ 

1. What are capillaries?  ____________________________________________________________ 

1. The picture on the right shows a capillary outside the alveoli. Review the picture. Which two gases are diffused across the respiratory membrane?   _________________________________ 

The factors that influence the rate of gas diffusion across the respiratory membrane include:  the thickness of the membrane, the surface area of the membrane, and the difference in concentration of the oxygen between the two sides of the membrane.  

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Respiratory Membrane Thickness   

Increasing the thickness of the respiratory membrane decreases the rate of diffusion. In healthy lungs, the respiratory membrane is 0.5-1.0 um thick, but the thickness can increase due to respiratory diseases. For example, in patients with pulmonary edema fluids accumulate in the alveoli, and gases must diffuse through a thicker than normal layer of fluid. COVID-19 effects lungs in much the same way, where lungs might become inflamed, making it tough for you to breathe. This can lead to pneumonia, an infection of the alveoli. This decreases the flow of oxygen into the body from the lungs. 

1. How thick is healthy respiratory membrane?   ______________________________  

1. What can cause respiratory membranes to thicken?   ________________________________  

1. Why do some Covid-19 patients have a difficult time getting enough oxygen into their body?   _____________________________________________________________________________   

Surface Area   

The total surface area of the respiratory membrane is approximately 70 m2 (nearly the area of one half of a tennis court) in a normal adult. The surface area of the respiratory membrane is decreased by several respiratory diseases, including emphysema and lung cancer (both can be caused by inhaling pollutants or smoking cigarettes). Even small decreases in the surface area affect the passage of gases, limiting the glow of oxygen. 

1. Describe the amount of respiratory membrane surface area in healthy adults.   ______________________________________________________________________   

1. How can respiratory diseases, such as emphysema, affect the surface area?   _____________________________________________________________________________   

Analysis – How does this relate to DIFFUSION? 

1. When you inhale, the most concentrated are of oxygen is the (highlight one) alveoli / capillaries. 

1. When you inhale, the least concentrated are of oxygen is the (highlight one) alveoli / capillaries. 

1. What must the oxygen pass through to get into your blood vessels?   ____________________________________________________________________________   

1. What could decrease the passage of oxygen into the bold vessels?   __________________________________________________________________________________   

1. Which process causes oxygen to flow from your lungs into your bloodstream?   _________________________________________________________________________________   

1. Explain how this reading proves to you the importance of diffusion.     ___________________________________________________________________________________