Lung Diseases

Fibrous tissue: Thick and not v. elastic (lungs are scarred etc)

Causes:

• Microscopic lung injury. NOT GENETIC (from dust, coal/rock particles, infection)- occurs in miners & quarrymen. Dust is usually trapped by mucus and cilia but if it penetrates alveoli there are no cilia to sweep particles away.
• Scarred alveolar epithelium, which becomes thickened and less elastic. Macrophages (big white blood cells) from the alveoli usually engulf particles then migrate between the cells of the alveoli lining into the lymphatic system. If there are large amounts of dust, macrophages stay in the connective tissue between the alveoli, stimulating the formation of fibrous tissue.

Symptoms:

• Shortness of breath, especially during exercise resulting from: Fibrous tissue occupies much of lung air space so less air taken in per breath (in extreme cases honeycomb lung: large spaces separated by fibrous tissue). Thickened alveolar epithelium (diffusion distance is greater & Oxygen diffusion rate decreases). Less elastic alveoli- volume of air in lungs decreases and reduces effective expulsion of air during expiration (leads to shall breathing).
• Chronic, dry cough (v. painful). Fibrous tissue obstructs bronchioles causing reflex action of coughing- no mucus so cough is 'dry'.
• Chest pain: From pressure & damage caused by fibrous mass and scarring.
• Weakness/tiredness: Reduced oxygen intake, reduced rate of respiration in cells, less energy/ATP available.

• Smoking (particularly 20 years +) -> Gradual, by the time of diagnosis it's too late and irreversible. Smoke stimulates white blood cells to release protease enzymes  -> breaks down...ELASTIN in the walls of the alveoli. Wont recoil properly (the alveoli) when stretched or really damaged (walls break down altogether). Lungs cannot exhale (expel) stale air effectively.
• Fick's Law: Diffusion gradient will be less, diffusion will be less rapid. Surface area is also reduced.

• Mucus in bronchiole: OBSTRUCTED.
• Enlarged alveoli: Walls between them break down.
• Fewer Capillaries: Can only exist on the walls of the alveoli.
• Normal bronchiole and alveoli: Large surface area.

• Coughing: Mucus in bronchiole
• Weak: Lack of oxygen
• Difficulty breathing: Lack of oxygen, less surface area in alveoli
• (Short of breath: rapid breathing).
• Blue lips/Nails: Short of oxygen
• Chronic cough = reflex action, not dry
• Inactive: Low oxygen levels.

Allergens e.g. dust mite faeces, pollen and animal fur cause the white blood cells on the linings of the bronchi and bronchioles to release a chemical called histamine. This is turn causes the following effects:

The lining of the airways becomes inflamed.

The goblet cells of the epithelial lining secrete larger quantities of mucus than normal.

Fluid leaves the capillaries and enters the airways.

The muscle surrounding the bronchioles contract and so constricts the airways.

Air enters the respiratory system from the nose and mouth and travels through the bronchial tubes. In an asthmatic person, the muscles of the bronchial tubes tighten and thicken, and the air passages become inflamed and mucus-filled, making it difficult for air to move. In a non-asthmatic person, the muscles around the bronchial tubes are relaxed and the tissue thin, allowing for easy airflow. 

• Difficulty in breathing
• A wheezing sound when breathing
• A tight feeling in the chest
• Coughing

Rate of diffusion is proportional to:

surface area x difference in concentration 

/diffusion difference

What would happen to rate of diffusion if:

I) Diffusion distance doubled: It would be halved (decrease)

II) Surface area tripled: It would triple (Increase)

III) Concentration difference halved: It would be halved (decrease)

Pulmonary (From the lungs) Tubercolosis/TB/consumption: Rod shaped bacteria

Pathogens: mycobacterium tubercolosis 

                 mycobacterium bovis (mainly cows)

Usually infect LUNGS (where they usually enter the body) but can infect any part of the body (in theory, but actually happens rarely)

Symptoms: Persistent cough

Tiredness

Loss of appetite

Weight loss

Fever: *

Coughing up blood: * Appear in later stages when it is more serious

• Air borne: droplets released by coughing, sneezing, talking, laughing etc.
• Bacteria survive in droplets (even dried) for several weeks
• Beware surfaces! Wash hands!
• Normally takes more than meeting someone in the street to become infected, frequent exposure to infected person.
• Spreads between: Family members, people in care homes/hostels, tube/underground, prisons, buses, aircraft. Crowded, damp, poorly ventilated areas. 
• From cows, milk CAN contain bacterium.
• Places where TB is common.
• People with reduced immunity more at risk: Elderly, babies, diabetics, post-transplant (immunosuppressant drugs), alcoholics, malnourished.

Infected people may show NO symptoms

Milk: Pasteurisation (72degrees 15 seconds) and sterilisation prevents this.

Bacteria live against most disinfectants, sunlight destroys them.

Once inhaled ->

Bacteria grow and divide in upper regions of lungs (good source of oxygen)

Immune system -> White blood cells build up infection & ingest bacteria.

Lymph nodes (drain lungs) inflame and enlarge PRIMARY INFECTION (usually children).

POST-PRIMARY TUBERCOLOSIS (usually adults) bacteria re-emerge to cause 2nd infection.

In upper regions of lungs not so controllable

Bacteria destroy lung tissue

Makes cavities, sometimes scar tissue

Coughs up blood with damaged tissue, without treatment -> fatal.

• Main method- Vaccination. All UK children tested for TB immunity. Those already immune- vaccination dangerous and unnecessary. Vaccine = weakened strain of Mycobacterium bovis (cattle).
• Better education (knowledge of needing to complete drugs courses)
• Less cramped and more housing
• More treatments
• Better health facilities close to everybody
• Good immune system: regular exercise, healthy balanced diet.

Drugs: Must be taken- 6-9 months Problem: Anti-resistant strains have developed.

Recent increase in many countries: HIV spread, development of drug-resistant forms, more living in cramped conditions, larger proportion of elderly. Also, increase in our air travel helps it spread.

If dangerous form develops, antibiotics and specialised drugs used. Can take up to 18 months.

When researching vaccine:

• Cost per dose
• Cost per treatment course
• How many doses needed
• Whether patient could administer treatment themselves.

Vaccine takes time to develop: Bacteria good at avoiding antibodies. New method: Protein in bacteria easily detected, body produces T cells.

For drug-resistant forms: 1st clinical trials for new TB vaccine in 80 years

Successful -> Surgeries by 2015. Used as booster for BCG, long lasting immunity.

BCG:

-Live but weakened form Mycobacterium bovis

-Active immunity: stimulates body's immune response -> produce antibodies. Remain in body to protect against actual M. bovis.

Only given to high risk groups: 

-Immigrants-> from countries with high cases of TB

-Infants less than one: living in an area of 40/100000 or higher or parents and grandparents from these areas.

Tissue mass (granuloma) formed in lung. Anaerobic tubercles. Contains dead bacteria & macrophages. Usually after 3-8 weeks lung tissue heals.