Biology 4.5 Lung Disease - Fibrosis, Asthma and Emphysema

To be efficient, gas exchange surface needs to be thin, have large surface area and be constantly ventilated.

Any factor that adversely affects one or more of these features reduces efficiency of gas exchange.

Pulmonary Fibrosis

Arises when scars form on epithelium of lungs, causing them to become irreversably thickened - linings of alveoli need to be thin, less efficient gas exchange as diffusion path is lengthened.

Volume of air lungs can contain has been reduced, elasticity of lungs reduced - expulsion of air relies on lungs springing back - Fibrosis makes it difficult to breath.

Effects of pulmonary fibrosis:

• Shortness of breath, especially when exercising = volume of air space within lungs being occupied by fibrous tissue, less air and less oxygen taken in each breath, thickened epithelium means slow diffusion through alveolar wall and into blood, loss of elasticity makes ventilating lungs difficult.
• Chronic, dry cough = fibrous tissue creates obstruction in airwars of lungs, body tries to remove by coughing, nothing is expelled so cough is "dry".
• Pain and discomfort in the chest = consequence of pressure and damage from fibrous tissue in the lungs and further damage and scarring from coughing.
• Weakness and fatigue = from reduced intake of oxygen into blood - release of energy from respiration…