Lung disease

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Pulmonary Ventilation- The amount of air taken into the lungs in 1 minute

PV= Tidal volume x ventilation rate

Tidal volume- volume of air in each breath (usually about 0.4dm3)

Ventilation rate- number of breaths per minute (about 15 breaths at resting)

So.. normal person at rest would have PV of about 0.4dm3 x 15mins = 6 dm3 min-1

Pulmonary Tuberculosis

- lung disease caused by Bacteria

Infection:

Immune system cells build wall around bacteria in lungs. This forms small, hard lumps (tubercles.)

Infected tissue in tubercles die. Gaseous exchange surface damaged so tidal volume decreased.

Also causes fibrosis- further reduces tidal volume.

If bacteria enters bloodstream they can spread to other parts of the body.

Symptoms:

Common symptoms include persistant cough, coughing up blood/mucus, chest pains, shortness of breath and fatigue.

Some may also have a fever.

Many lose weight due to reduction in appetitie.

Transmission:

Transmitted by droplet infection- infected person coughs/sneezes, tiny droplets of saliva/mucus containing bacteria released. If unaffected person breaths in droplets then bacteria are passed on.

More widespread in areas of poor hygeine and crowded conditions.

Can be prevented with BCG vaccine and treated with antibiotics.

Fibrosis

Formation of scar tissue in lungs. Can be result of infection or exposure to substances (e.g dust/asbestos.)

Scar tissue thicker & less elastic than normal lung tissue.

Means lungs less able to expand so can't hold as much air (tidal volume reduced.) Also harder to force air out.

Reduction in rate of gaseous exchange - diffusion slower across thicker scarred membrane.

Symptoms- shortness of breath, dry cough, chest pain, fatigue, weakness.

Faster breathing rate than normal to get enough air into lungs to oxygenate

Asthma

Respiratory condition- airways become inflamed/irritated. Usually due to allergic reaction to substances (e.g pollen/dust.)

During asthma attack, smooth muscles lining of bronchioles contract and large amount of mucus produced.

Causes constriction of airways making difficult for sufferer to breathe properly. Air flow in/out of lungs severely reduced so less oxygen enters alveoli and into blood.

Symptoms- wheezing, tight chest, shortness of breath. During an attack symptoms come on suddenly. Relieved by drugs (often inhalers) to relax muscles in bronchioles, opening up airways.

Emphysema

Lung disease caused by smoking or long-term exposure to air pollution- foreign particles in smoke (or air) become trapped in alveoli.

Causes inflamation which attracts phagocytes to area. These produce an enzyme that breaks down elastin (protein found in walls of alveoli.)

Elastin is elastic- helps alveoli return to normal shape after inhaling/exhaling air.

Loss of elastin means alveoli can't recoil to expel air as well (remains trapped in alveoli.)

Also leads to destruction of alveoli walls, reduces SA of alveoli so rate of gaseous exchange decreases.

Symptoms- Shortness of breath, wheezing. Increased breathing rate as they try to increase amount of air (containing oxygen) reaching their lungs.

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