Respiratory System Theme 1

What occurs in emphysema?

Alveoli become larger as a result of smoking breaking down their walls, increasing their SA/V ratio so gas exchange less efficient

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What occurs in fibrosis?

Walls if lung tissue are thickened, increasing the diffusion pathway so gas exchange reduced

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What occurs in cystic fibrosis?

Genetic condition causing excess muscous that is thick and viscous; leads to infection as cilia can't sweep mucous. Large increase in resistance so lungs work harder to ventilate (damaging their tissues).

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What occurs in boronchitis?

Infection irritates and inflames the bronchi, causing them to produce more mucous. The body tries to shift the extra mucous by coughing, which damages the lung tissues.

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What is COPD?

Chronic obstructive pulmonary disease (as in emphysema and bronchitis) where their is a difficulty breathing - expiring especially - as the airways are narrowed and airflow is reduced

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What forms the upper respiratory tract? What is its function?

Pharynx, larynx, vocal cords and nasal cavity. Shape of nose conchae slows the air flow by making it turbulent, so cilia trap more pathogens/debris. Warms and humidifies the air so alveoli not damaged (don't dry out). Also functions in vocalisation.

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What forms the lower respiratory tract? What is its function?

Trachea, bronchi, bronchioles and alveoli; they function to allow conduction through the airways, regulate air flow and stabilise the conducting airways (all for efficient gas exchange).

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What is the function of the cartilage rings of the trachea?

Incomplete U shaped cartilage so portective and prevent collapse whilst still allowing oesophagus to expand in peristalsis

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What causes bronchoconstriction?

Ouurs via local vasoconstrictors like histamine and the sympathetic nervous system (when nor-adrenaline binds to Beta-2 receptors)

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What causes bronchodilation?

Occurs when more CO2 returning to lungs (higher plasma PCO2). Parasympathetic nervous system causes Ach release, which binds to M3 receptors.

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What is the role of the bronchial circulation?

Brochial arteries supply additional oxygenated blood to the smooth muscle of the bronchioles - lungs still function without it. Bronchial veins remove most deoxygenated blood the smooth muscle creates, but not all (so some enters pulmonary veins).

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What is the role of the goblet cells lining the airways?

Produce mucous so continuous layer formed along tract

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How are alveoli adapted for gas exchange?

Only one layer thick, side facing capillaries leaky (for gas echange) whilst supporting side is robust and distensible (collagen IV allows expansion/retraction), have macrophages at their surface and a dense capillary network

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Describe type I pneumocytes

Larger, squamous and rounded so adapted to gas exchange. Fused to the endothelial cell layer of capillaries at the basal membrane (and have a thin cytoplasm layer) to provide a short diffusion difference.

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Describe type II pneumocytes

Smaller (still rounded), release surfactant (has two lipid arms that anneal) which reduce the surface tension to prevent alveolar collapse, especially in smaller alvoeoli

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Describe Wiebel's model of the bronchial tree

Generation 0 at trachea, then conductive zone (where trachea-->bronchi-->bronchioles-->terminal bronchioles) to generation 16. Transitional zone from generations 17-19 (increase in alveolation in respiratory brooncholes where walls rough).

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Respiratory System Theme 1

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