Gas ExchangeThe Respiratory System and Smoking

The lung

The Lung

A thoracic chest cavitySurrounded by pleural membranesEnclose an airtight spaceSmall quantity of fluid for friction free

movement and prevention of desiccationVentilation of the lung conducted by the

movement of diaphragm/ ribs

Trachea A tube leading from the throat

to the lung Has cartilage to keep in open,

allow friction free movement and prevent the trachea from collapsing – arranged in C-shape rings

Has goblet cells which produces mucus

Has smooth muscle on the endothelium

Has cilia to sweep up the mucus Is not the site of gas exchange

Bronchus

There are two bronchi at the base of the trachea

Has cartilage in irregular blocksHas goblet cellsHas smooth muscle cellsHas cilia, and still not the site of gas

exchange

Bronchioles

Branches off from bronchusSurrounded by smooth musclesCan contract or relax to control amount of air

going inE.g.. Relaxes during exercise for more flow of

airNo cartilage – flexibility

Alveoli

Air sacs in the lungSite of gas exchangeThe walls – contain elastic fiber – stretch and

recoil respectively when breathing in and outHas thin wall – 0.5 micrometerPressed close against bloodcapillaries

Alveoli

A concentration gradient is always maintained where carbon dioxide would move in through the lung where there is lower concentration of CO2

Oxygen would move into capillaries where there is lower concentration of oxygen

Constant inhalation/ exhalation s well as blood flow keep this concentration gradient going

Warming/ Cleaning Air

Air flowing in is warmed to body temperature – to prevent desiccation

Particles of 5 – 10 micrometer will be caught by nasal hair

Mucus (made of mucin droplets which are glycoproteins) produced by goblet cells will capture dust, pollen grains, fungal spores, pathogens

Mucus produced by goblet cells – which has an enlarged upper part contain a mucin droplet and the rest of the cell slender like a stem

Warming/ Cleaning Air

Mucous gland also produces mucus from under the epithelium cell

Sulfur dioxide/ nitrogen dioxide can combine with mucus to form acidic solution – this may irritate the lining

Between goblets – ciliated cells 0 continuously beating the mucus up at 1cm/min

The mucus reaches the top of the trachea – it is swallowed down the esophagus – the pathogens destroyed by stomach acid

Macrophages also patrol the airway

Smoking

Smokes contain Tar/ Nicotine/ Carbon monoxide

CO and Nicotine damage the cardiovascular system

Tar/ Carcinogens damage the gas exchange system

Tobacco Smoking

Tar: mixture of compounds – settle in the airways – can lead to obstructive diseases

Tar contains carcinogens – can lead to lung cancer

Passive smoking is caused from side stream smoke (the burning tip) which is 85% of the smoke compared o the rest which is mainstream (mouth piece)

Lung DiseasesAir flows in the depth of the lung is slowAllowing some particles to settleMay be airborne infectionsCOPD (Chronic Obstructive Pulmonary

Diseases) are non infectious and can be caused by pollution and tobacco smoke

Chronic Bronchitis

Tar in cigarettes – cause mucus glands/ goblets to mutate and enlarge

Cilia are destroyed by tarMore production of mucusMucus accumulates in bronchiolesSmokers will attempt to cough them out

Chronic Bronchitis

The epithelium soon are replaced by scar tissue which due to its large size narrow the airway

Causes difficulty in breathingMucus allow for accumulation of bacteria

such as one that causes pneumoniaThis may lead to inflammation and more

narrowingPhlegm may be produced

Emphysema

Inflammation stimulates phagocytes to line the airway

To reach the airway, the phagocyte uses elastin (enzyme) to destroy alveoli and to make pathway

Alveoli can not expandThe bronchioles collapse and alveoli burstThis leads to less surface area and less

capillary and less oxygen absorbed

Emphysema

Loss of elastin – difficult to move air out – make it hard to refresh air in the lung – the air becomes stagnant

Blood is not oxygenatedBlood vessels in the lung become more

resistant 0 stimulating enlargement of right side of the heart

Lung Cancer

Tar can react with DNA in epithelial cells – or through breakdown products

Causes development of tumorCancer spreads through bronchial epithelium –

into the lymphatic and to the rest of the bodyTake 20 – 30 years to developTissue damage can lead to coughing bloodDifficulty in breathing / chest pain

Lung Cancer

Bronchoscopy, Chemotherapy, CT scan can detect lung cancers

Lung cancers are usually discovered when they are advanced

Effects on the Cardiovascular system

Nicotine:absorbed very readily by the bloodStimulates nervous system to reduce diameter

of blood vesselsRelease more adrenalineBlood pressure increases – less blood flow to

extremities Increases risks of blood clotting