Lung Diseases

Pulmonary Fibrosis.

• Fibrosis is the formation of scar tissue in the lungs. This can be caused by an infection or exposure to dust or otehr substances like apspestos.
• Scar tiissue is thicker and less elastic than normal lung tissue.
• Sufferer's lungs are less able to expand and so cant hold as much air as normal - the tidal volume is reduced. It's also harder to force air out of the lungs due to loss of elacticity.
• There's a reduction in the rate of gaseous exchange - diffusion is slower across a thicker scarred membrane.
• Symptoms of fibrosis include shortness of breath, a dry cough, chest pain, fatigue & weakness.
• Fibrosis sufferers have a faster breathing rate than normal - to get enough air into tehir lungs to oxygenated their blood.

Asthma.

• Asthma is a respiratory condition where the airways become inflamed & irritated. These are often caused by allergic recactions to substances such as pollen & dust.
• During an asthma attack, the smooth muscle lining the bronchioles contract & a large amount of mucus is produced.
• This causes constriction of the airways, making it difficult for the sufferer to breathe properly. air flow in & out of the lungs is severly reduced, so less oxygen enters the alveoli & moves into a blood.
• Symptoms include, wheezing, a thight chest & shortness of breath. During an attack symptoms can come on very quickly. They can be relieved with drugs which cause the muscles to relax, opening up the airways. 

Emphysema.

• Emphysema is a lung disease caused by smoking or long-term exposure to air pollution - foreign partciles in the smoke become trapped in the alveoli.
• This causes inflamation, which attracts phagocytes to the area. The phagocytes produce an enzyme that breaks down the elsatin.
  Elastin helps the alevoli to return to its normal shape after inhaling & exhaling air.
• Loss of elastin means the alveoli can't recoil andto expel air as well, it remains trapped in the alveoli.
• It also leads to destruction of the alveoli walls, which reduces the surface area of the alveoli so the rate of gaseous exchange decreases.
• Symptoms of emphysema inculde shortnedd of breath & wheezing. People with emphysema have an increased breathing rate as they try to increase the amount of air reaching their lungs.